Camshaft for sbc on propane

Propane, Butane, LPG, GPL, C3H8, C4H10
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robin_chevelle
Posts: 4
Joined: Wed Nov 16, 2016 11:44 am
Location: the Netherlands

Camshaft for sbc on propane

Post by robin_chevelle »

Can someone give me a good direction, advice or just join the discussion about a camshaft for a sbc on Propane?
What does propane like??

The details:
400sbc stock crank, rods and pistons.
aluminum cylinder heads 65cc chambers (2.020 in. Intake valve and 1.600 in. Exhaust valve.) angle plug heads with 180 or 190cc intake runners. I don’t know, to long ago that I bought them.
9,5 to 1 compression.
1 5/8 long tube headers.
MSD ignition
edelbrock performer rpm air-gap intake.
I took the gasoline carb completely off, and stuffed an Impco 425 on a holley 750 baseplate. I know it´s only 460 cfm, so it comes up short on top.
Octane is 105 AKI.
maximum rpm?? Maybe 4750 if it gets that far with only 460cfm.. (but if it can it's most unlikely I ever push it that far).


th 350 transmission, stock/factory converter (I think about 1400 stall?).
3.07 open rear end.
255/70 R15 rear tires 29,06 inch wheel diameter.
Turns 3200 rpm on the high way with 85mph.
And 1900 rpm driving local from town to town with 50 mph.

The car... well it's a: Chevy G20 Van – 1977 – curb weight 4300Lbs. But it’s all about the engine.

It’s used as weekend driver, for holiday and high-way driving (85 mph).
Sometimes I use it to transport a motorcycle or hauling car parts and maybe 3 times a year to pull a small trailer.


Camshaft for the 400 engine.
I bought a camshaft with the heads from Chris Straub, but that was when I did not wanted to run the engine on Propane. I think the cam card is lost when I moved to my new home. But I thought it was something like: 209/216 .050, .450" lift. From his advice this camshaft was for good torque in this engine.

I asked many company´s for a propane cam and the timing is different.
Lunati 213/219 @050 .454/.468 112LSA 60101LK
Melling 204/214 @050 .420/.438 112LSA CL-MTC-1
Schneider 204/204 @050 .420/.420 114LSA 32056
Jonescams 208/210 @050 .449/.450 111LSA H66299-67300-111 and add 1.6 rocker ratio
Crane gasoline 204/216 @050 .427/.454 112LSA 113902
Crane propane 204/204 @050 .427/.427 112LSA 11H00048 and add 1.6 rocker ratio
Comp 210/218 @050 .447/.462 111LSA X4254H
Comp 203/212 @050 .429/.438 110LSA 246PE

At Jonescams and Schneider they both say they have experience in propane engines. But both give a very different cam advice… What do you think?
Just trying to get some opinions on dual, single or even reverse pattern cam's for a propane application.
'70 Chevelle SS396 - 4L80e - 3.55 - gasoline
'77 G20 Van - 350ci - th350 - 3.07 - propane

storm
Posts: 665
Joined: Wed Jan 10, 2007 10:10 pm
Location: NSW, Australia

Re: Camshaft for sbc on propane

Post by storm »

First up take a look at this page to work out your engine revs. Be honest with volumetric efficiency %.

Second, someone like C3H8 may pipe in but from my experience you really don't need to change cams for LPG. The cam opens and closes the valves to allow air/fuel mixture in and is designed to maximise the amount of air/fuel mixture for a given engine usage. It really doesn't know about fuels. At a basic level the larger the number @50 the higher the rev range is so the cam needs to match things like the intake, You have a dual plane air gap so the intake is designed for slightly higher revs than an ordinary dual plane.

I, personally, don't like single pattern cams for old tech V8s the exhaust flow really needs a longer duration exhaust compared to intake simply to get all the exhaust gas out of the cylinder. Single pattern cams are great for race engines where the engine builder has made sure the exhaust flow can keep up with intake flow.

If you just want to use the engine as a normal daily driver then stick with a cam spec close to daily driver factory cams. If you want a little bit better performance then move up to something in the low 200s duration @50. To know what LSA to choose alot more information is required on the heads but I'd stick with something like 112 based on the limited information given.
Every job is a self-portrait of the person who did it. Autograph your work with excellence.

Fuel flow requirements calculations viewtopic.php?f=5&t=1638

robin_chevelle
Posts: 4
Joined: Wed Nov 16, 2016 11:44 am
Location: the Netherlands

Re: Camshaft for sbc on propane

Post by robin_chevelle »

thanks for you reply.
volumetric efficiency: 400ci, 75%, 4750rpm = 412 to 536 cfm.
somewhere between 4500 and 4750 will be max. rpm.

I need to change the camshaft in the engine, don't know what's in it now. And because I need to buy one, I want to use this opportunity to buy the best cam for the application.

I understand your point of view. But propane compared to gasoline the energy content is 74%
You are using the engine coolant temp. to convert the liquad propane to gas form, this causes a higher air/gas temp.
The propane and air (fuel mixture) does not cool down when it goes into the engine. Not like normal gasoline, vapour is liquid that has been forced to vapourise. The cooling effect of liquid petrol droplets is not present with LPG and the total heat is released more quickly. There is no temperature drop and the fuel/air mix enters the combustion chamber at ambient temperature or slightly higher due to the heating while passing through the induction system.

That is why I thought the theory can be true that a low rpm, high torque propane V8 engine does have a advantage from more intake duration and a 114LSA. The burnt mixture is the same as gasoline, peak flame temperature of propane at 3614 F is only 23 F or less than 1% higher than gasoline. The exhaust can stay the same duration, then you get a single pattern or a reverse pattern camshaft. As a additional bonus you have a higher cylinder pressure, more efficiency, less waste of fuel by the wider LSA.
If.... If the real world can be compared with this theory. :?: (just trying to get some different point of views here).
'70 Chevelle SS396 - 4L80e - 3.55 - gasoline
'77 G20 Van - 350ci - th350 - 3.07 - propane

storm
Posts: 665
Joined: Wed Jan 10, 2007 10:10 pm
Location: NSW, Australia

Re: Camshaft for sbc on propane

Post by storm »

Let's break this down into simple sections
robin_chevelle wrote:thanks for you reply.
You're welcome
robin_chevelle wrote:volumetric efficiency: 400ci, 75%, 4750rpm = 412 to 536 cfm.
somewhere between 4500 and 4750 will be max. rpm.
Good
robin_chevelle wrote:I need to change the camshaft in the engine, don't know what's in it now. And because I need to buy one, I want to use this opportunity to buy the best cam for the application.
You don't know what's in it now but you know you need to change it? Seems a bit premature to me. You could work out the cam timing of the current cam with it in the engine if you wanted to know what its specs are.
robin_chevelle wrote:I understand your point of view. But propane compared to gasoline the energy content is 74%
You are using the engine coolant temp. to convert the liquad propane to gas form, this causes a higher air/gas temp.
The propane and air (fuel mixture) does not cool down when it goes into the engine. Not like normal gasoline, vapour is liquid that has been forced to vapourise. The cooling effect of liquid petrol droplets is not present with LPG and the total heat is released more quickly. There is no temperature drop and the fuel/air mix enters the combustion chamber at ambient temperature or slightly higher due to the heating while passing through the induction system.
I'm very well aware of the properties of LPG. You need to remember propane is already a gas mixed in with the air which unlike petrol means less energy is required to make it a combustible mixture. The BTU of LPG is lower than petrol but on a per BTU basis LPG is more efficient than petrol during the combustion cycle simply because it is already mixed in. I'm not sure the comment "vapour is liquid that has been forced to vapourise" is really all that accurate in most cases of LPG usage in the automotive field. In its natural form LPG is a vapour that is forced into liquid form. In normal usage LPG is kept as a liquid in a pressure container. It is pumped under pressure into that container from another pressure container. You let it out of that pressure container it will vapourise on it own. In automotive use the pressure is actually being regulated by the regulator (also called a convertor). LPG expands something like 230 times its own "size" when released from a pressure container and that is simply by opening the tap and releasing it into the atmosphere (not something I recommend).

Petrol droplets in the intake system are a recipe for disaster. Petrol should atomise meaning you should not see droplets. If you have droplets your intake system is not functioning at best or poorly designed at worst. Droplets lead to pooling of fuel and erratic air fuel mixtures. It also means you are consuming more fuel than required and you will foul your spark plugs quickly. Last but not least droplets of fuel do not ignite very well. What you have described is only a little short of flooding.
robin_chevelle wrote:That is why I thought the theory can be true that a low rpm, high torque propane V8 engine does have a advantage from more intake duration and a 114LSA. The burnt mixture is the same as gasoline, peak flame temperature of propane at 3614 F is only 23 F or less than 1% higher than gasoline. The exhaust can stay the same duration, then you get a single pattern or a reverse pattern camshaft. As a additional bonus you have a higher cylinder pressure, more efficiency, less waste of fuel by the wider LSA.
It seems as though you have already made up your mind. Anyway you neglected to mention the difference in ignition timing between LPG and petrol and its effect on cylinder pressures.
robin_chevelle wrote:If.... If the real world can be compared with this theory. :?: (just trying to get some different point of views here).
Theory is great but each engine combination is different. An airgap manifold is not really designed for a maximum of 4700 rpm, a 400 chev is a torque motor (long stroke low revs) which suits the Impco quite well for size. If you want more power you need more revs (HP = Torque x RPM ÷ 5252) so to suit the airgap you need a bigger mixer.

A bigger LSA makes overlap smaller effectively limiting the exhaust scavenging process meaning you will leave residual exhaust gasses in the cylinder. Residual gases has the same effect as EGR. EGR is only meant to operate when the engine is producing vacuum, residual gases caused through a lack of exhaust scavenging cause an EGR effect at all times.

Increasing the intake duration, or reducing the exhaust duration which ever way you prefer to look at it, also means less opportunity to scavenge exhaust. Having a larger intake duration than exhaust duration (if the exhaust is not as efficient as it should be) will limit the amount of intake flow simply because the exhaust has not been allowed to escape the cylinder. As I said theory is great but theory applied poorly ends up with an engine that runs at less than its potential given the parts is is built with.

Here's an article for you to read on Lobe Separation Angles and the effects they have http://www.superchevy.com/how-to/engine ... ance-test/

You started this topic with
robin_chevelle wrote:Can someone give me a good direction, advice or just join the discussion about a camshaft for a sbc on Propane?
What does propane like??
I gave you advice gained from practical experience with traditional US style V8s. I can't do more than that.
Every job is a self-portrait of the person who did it. Autograph your work with excellence.

Fuel flow requirements calculations viewtopic.php?f=5&t=1638

franz
Posts: 1201
Joined: Thu Oct 07, 2004 7:57 pm
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Contact:

Re: Camshaft for sbc on propane

Post by franz »

Now, THAT is what I call a really decent discussion! ! ! !

Lets assume for a second that your current camshaft may indeed be worn out (not that uncommon on older small block Chevy's). As I state in my book and from years of work on engines, I prefer a little more lift rather than duration, to increase airflow. Increased lift does incur the piston to valve problem but hopefully you have that worked out already. If you just really want an camshaft that gives a rumpty rump idle, there are some of those too.

Its really difficult to chose a camshaft for someone else, since everyone has their own exact desires and engine specifications. Please be careful when choosing a cam, and dont full victim of putting the biggest one that will fit. Cams really dont make more power until you get up in the RPM range (3600 rpm plus).

Not too long ago, a close friend of mine changed the cam in his FOX body Mustang with a 5.0. It has already been converted to a Holley carb and mechanical ignition. He gained about 25 bhp but lost 4 mpg and low speed drivability went into the trash. He was using stock heads and stock original shorty headers. He then put on a set of Edelbrock heads and Hooker mid length headers, no other changes. Horsepower increased 50 bhp and he regained the lost mileage. The engine also smoothed out. As luck would have it, the cam and distributor gear didnt like each other and after about 1000 miles, it quit running. He replaced the cam with one with a less aggressive profile and didnt lose any power but gained a lot of low speed drivability. Airflow is airflow, it really doesnt matter how it gets into the engine. These improvements helped to eliminate OEM shortcomings. If I had my choice, headers first followed by heads, then cam.

storm
Posts: 665
Joined: Wed Jan 10, 2007 10:10 pm
Location: NSW, Australia

Re: Camshaft for sbc on propane

Post by storm »

To make an educated cam choice the purchaser, or the person choosing it, really needs to know the airflow specs of the intake and exhaust system. You also need to know what the engine will be used for.

We now this engine will not really get high revs but we don't know what heads are on it nor their airflow specs.

These are the cams that Edelbrock recommends for the manifold http://www.edelbrock.com/automotive/mc/ ... y-sb.shtml
2102 duration @ 50 = 201/214 lift .420/.442 @ the valves LSA 112 degrees Intake C/L 107 degrees.
2103 duration @ 50 = 214/214 lift .442/.442 @ the valves LSA 112 degrees Intake C/L 107 degrees.

To me LPG camshafts are like lures sold to people wanting to go fishing. Most lures don't do anything except catch people (because they fell for the marketing hype) who want to go fishing likewise most camshafts advertised for LPG don't do anything that other camshafts do. Yes LPG is different but its not that different that the engines cam requirements are different.
Every job is a self-portrait of the person who did it. Autograph your work with excellence.

Fuel flow requirements calculations viewtopic.php?f=5&t=1638

robin_chevelle
Posts: 4
Joined: Wed Nov 16, 2016 11:44 am
Location: the Netherlands

Re: Camshaft for sbc on propane

Post by robin_chevelle »

Thank you for the response. Really not trying to push this dilemma one way or the other and I certainly dit not already have made up my mind. :wink:

Like Franz said: "Lets assume for a second that your current camshaft may indeed be worn out"
Just for the discussion about a propane camshaft, for a 400ci sbc that needs torque.

robin_chevelle wrote:I understand your point of view. But propane compared to gasoline the energy content is 74%
You are using the engine coolant temp. to convert the liquad propane to gas form, this causes a higher air/gas temp.
The propane and air (fuel mixture) does not cool down when it goes into the engine. Not like normal gasoline, vapour is liquid that has been forced to vapourise. The cooling effect of liquid petrol droplets is not present with LPG and the total heat is released more quickly. There is no temperature drop and the fuel/air mix enters the combustion chamber at ambient temperature or slightly higher due to the heating while passing through the induction system.
storm wrote:I'm very well aware of the properties of LPG. You need to remember propane is already a gas mixed in with the air which unlike petrol means less energy is required to make it a combustible mixture. The BTU of LPG is lower than petrol but on a per BTU basis LPG is more efficient than petrol during the combustion cycle simply because it is already mixed in. I'm not sure the comment "vapour is liquid that has been forced to vapourise" is really all that accurate in most cases of LPG usage in the automotive field. In its natural form LPG is a vapour that is forced into liquid form. In normal usage LPG is kept as a liquid in a pressure container. It is pumped under pressure into that container from another pressure container. You let it out of that pressure container it will vapourise on it own. In automotive use the pressure is actually being regulated by the regulator (also called a convertor). LPG expands something like 230 times its own "size" when released from a pressure container and that is simply by opening the tap and releasing it into the atmosphere (not something I recommend).

Petrol droplets in the intake system are a recipe for disaster. Petrol should atomise meaning you should not see droplets. If you have droplets your intake system is not functioning at best or poorly designed at worst. Droplets lead to pooling of fuel and erratic air fuel mixtures. It also means you are consuming more fuel than required and you will foul your spark plugs quickly. Last but not least droplets of fuel do not ignite very well. What you have described is only a little short of flooding.
Yes you are on the point of flooding the engine. I agree. But I wanted to discuss the point that gasoline/air mixture is cooler when it goes into the engine then propane/air mixture. And, when you see how much pure fuel your accelerator pump, pumps into the intake.... that should vapourise very quickly, when it does the air/mix temp. drops.

robin_chevelle wrote:That is why I thought the theory can be true that a low rpm, high torque propane V8 engine does have a advantage from more intake duration and a 114LSA. The burnt mixture is the same as gasoline, peak flame temperature of propane at 3614 F is only 23 F or less than 1% higher than gasoline. The exhaust can stay the same duration, then you get a single pattern or a reverse pattern camshaft. As a additional bonus you have a higher cylinder pressure, more efficiency, less waste of fuel by the wider LSA.
storm wrote:Anyway you neglected to mention the difference in ignition timing between LPG and petrol and its effect on cylinder pressures.
Can you explain what the difference in ignition timing is? I did not neglected, I just don't know the exact reason why you need to recurve your ignition, what's the exact difference and why?


robin_chevelle wrote:If.... If the real world can be compared with this theory. :?: (just trying to get some different point of views here).
storm wrote:Theory is great but each engine combination is different. An airgap manifold is not really designed for a maximum of 4700 rpm, a 400 chev is a torque motor (long stroke low revs) which suits the Impco quite well for size. If you want more power you need more revs (HP = Torque x RPM ÷ 5252) so to suit the airgap you need a bigger mixer.
I can agree with that. Do you know (or have a idea) why there are people that claim they have more torque even low in the rpm range with a single plane? Because a single plane is designed for high rpm. I thought it is because they have a large open plenum and propane likes the extra room.
storm wrote:A bigger LSA makes overlap smaller effectively limiting the exhaust scavenging process meaning you will leave residual exhaust gasses in the cylinder. Residual gases has the same effect as EGR. EGR is only meant to operate when the engine is producing vacuum, residual gases caused through a lack of exhaust scavenging cause an EGR effect at all times.

Increasing the intake duration, or reducing the exhaust duration which ever way you prefer to look at it, also means less opportunity to scavenge exhaust. Having a larger intake duration than exhaust duration (if the exhaust is not as efficient as it should be) will limit the amount of intake flow simply because the exhaust has not been allowed to escape the cylinder. As I said theory is great but theory applied poorly ends up with an engine that runs at less than its potential given the parts is is built with.

Here's an article for you to read on Lobe Separation Angles and the effects they have http://www.superchevy.com/how-to/engine ... ance-test/
Yes a bigger LSA makes overlap smaller and does limit the scavenging, scavenging helps getting the cylinders empty. But when? When is there profit (in what rpm range)?

As far as I know the smaller LSA ensures a higher fuel consumption, less vacuum at low rpm
It can result in a minimal blow back that contaminates the fresh mixture (very, very far caught, I know).
A smaller LSA does have more peak power and sometimes more peak torque. But at what rpm?
I don't care about torque at 4000 rpm and power at 5000 rpm (or higher).
A wider LSA brings the torque curve down, improves Idle rpm and vacuum.
Who drives a heavy car on the street in daily traffic in that rpm range? That's for me (personally the question).
I try to get a maximum and flat torque curve from 1500 to 3100 rpm.
franz wrote:Now, THAT is what I call a really decent discussion! ! ! !
Thank you.

franz wrote:Lets assume for a second that your current camshaft may indeed be worn out (not that uncommon on older small block Chevy's). As I state in my book and from years of work on engines, I prefer a little more lift rather than duration, to increase airflow. Increased lift does incur the piston to valve problem but hopefully you have that worked out already. If you just really want an camshaft that gives a rumpty rump idle, there are some of those too.
I think that is why a lot of companies do advice 1.6 rockers (at least on intake side).
franz wrote:Its really difficult to chose a camshaft for someone else, since everyone has their own exact desires and engine specifications. Please be careful when choosing a cam, and dont full victim of putting the biggest one that will fit. Cams really dont make more power until you get up in the RPM range (3600 rpm plus).
That's my point, the engine will be most it's live below 3600 rpm. I'm looking for maximum torque from 1500 to 3100 rpm.
franz wrote:Not too long ago, a close friend of mine changed the cam in his FOX body Mustang with a 5.0. It has already been converted to a Holley carb and mechanical ignition. He gained about 25 bhp but lost 4 mpg and low speed drivability went into the trash. He was using stock heads and stock original shorty headers. He then put on a set of Edelbrock heads and Hooker mid length headers, no other changes. Horsepower increased 50 bhp and he regained the lost mileage. The engine also smoothed out. As luck would have it, the cam and distributor gear didnt like each other and after about 1000 miles, it quit running. He replaced the cam with one with a less aggressive profile and didnt lose any power but gained a lot of low speed drivability. Airflow is airflow, it really doesnt matter how it gets into the engine. These improvements helped to eliminate OEM shortcomings. If I had my choice, headers first followed by heads, then cam.
I'm trying to get the flow numbers from the heads to see if that helps us anything in this discussion.
storm wrote:To make an educated cam choice the purchaser, or the person choosing it, really needs to know the airflow specs of the intake and exhaust system. You also need to know what the engine will be used for.
I'm going to try to get those as soon as possible.

We now this engine will not really get high revs but we don't know what heads are on it nor their airflow specs.
I'm going to try to get those as soon as possible.
storm wrote: These are the cams that Edelbrock recommends for the manifold http://www.edelbrock.com/automotive/mc/ ... y-sb.shtml
2102 duration @ 50 = 201/214 lift .420/.442 @ the valves LSA 112 degrees Intake C/L 107 degrees.
2103 duration @ 50 = 214/214 lift .442/.442 @ the valves LSA 112 degrees Intake C/L 107 degrees.

To me LPG camshafts are like lures sold to people wanting to go fishing. Most lures don't do anything except catch people (because they fell for the marketing hype) who want to go fishing likewise most camshafts advertised for LPG don't do anything that other camshafts do. Yes LPG is different but its not that different that the engines cam requirements are different.
Yes I can confirm that, that's also why I still don't know which way to go. :?:

Some of the latest advices:
208/208 @050 .440/.440 116LSA use 1.6 rockers on intake side.
Yes 116LSA..... company said they have much experience with propane.....
210/208 @050 .500/.480 114LSA also a company that said they have propane experiance.
208/210 @050 .449/.450 111LSA a company that does a lot of government propane cars.
'70 Chevelle SS396 - 4L80e - 3.55 - gasoline
'77 G20 Van - 350ci - th350 - 3.07 - propane

storm
Posts: 665
Joined: Wed Jan 10, 2007 10:10 pm
Location: NSW, Australia

Re: Camshaft for sbc on propane

Post by storm »

robin_chevelle wrote:Thank you for the response. Really not trying to push this dilemma one way or the other and I certainly dit not already have made up my mind. :wink:
I don't see this as a dilemma, I see this as someone who asked for advice and has been given it only to come back with wrong information and use it for a reason to go one particular way.
robin_chevelle wrote:Yes you are on the point of flooding the engine. I agree. But I wanted to discuss the point that gasoline/air mixture is cooler when it goes into the engine then propane/air mixture. And, when you see how much pure fuel your accelerator pump, pumps into the intake.... that should vapourise very quickly, when it does the air/mix temp. drops.
I think we need to define advice-discuss-give good direction. If you want a discussion great I'm all in for that but my initial response is advice-direction based on personal experience. Your responses after your OP have not been about advice, infact they have attempted to refute advice which is fine but gets a bit tiring when the person initially asked for it.
robin_chevelle wrote:Can you explain what the difference in ignition timing is? I did not neglected, I just don't know the exact reason why you need to recurve your ignition, what's the exact difference and why?
Read this http://www.acl.com.au/web/acl00056.nsf/ ... enDocument
robin_chevelle wrote:I can agree with that. Do you know (or have a idea) why there are people that claim they have more torque even low in the rpm range with a single plane? Because a single plane is designed for high rpm. I thought it is because they have a large open plenum and propane likes the extra room.
With what fuel? how long are the runners? what are the operating conditions? what are the engine specs? I can't comment on all claims but in general long runners, which some(not all) single plane manifolds have compare to dual planes, create more torque.
robin_chevelle wrote:Yes a bigger LSA makes overlap smaller and does limit the scavenging, scavenging helps getting the cylinders empty. But when? When is there profit (in what rpm range)?

As far as I know the smaller LSA ensures a higher fuel consumption, less vacuum at low rpm
It can result in a minimal blow back that contaminates the fresh mixture (very, very far caught, I know).
A smaller LSA does have more peak power and sometimes more peak torque. But at what rpm?
I don't care about torque at 4000 rpm and power at 5000 rpm (or higher).
A wider LSA brings the torque curve down, improves Idle rpm and vacuum.
Who drives a heavy car on the street in daily traffic in that rpm range? That's for me (personally the question).
I try to get a maximum and flat torque curve from 1500 to 3100 rpm.
Did you read the article? the answer to your question was in it. The large LSA cam had less power throughout the usable rev range of the engine (a 406 Chev).

From the article
Our dyno figures bear this out. The 406 made more low-end torque with the 107 LSA cam, regardless of the intake manifold it was wearing, and held its own at higher rpm. In the same vein, the dual-plane equipped 406 had better results with the 107 LSA cam. "The dual-plane reacted to lobe separation almost exactly as it would to a smaller camshaft," said Godbold.

The 113 LSA cam, on the other hand, made less power everywhere and especially fell on its face with the single-plane intake. "I'm not totally sure if the reason is simply a result of the shorter runner length with a single-plane, or if you could trace it back to the common plenum," Godbold observed. "However, I do know for certain that single-plane manifolds have always run best with tighter lobe separation camshafts."
A good discussion happens when all involved are actively working to make the discussion happen. I ask you to show your evidence so we can discuss it.
Every job is a self-portrait of the person who did it. Autograph your work with excellence.

Fuel flow requirements calculations viewtopic.php?f=5&t=1638

robin_chevelle
Posts: 4
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Location: the Netherlands

Re: Camshaft for sbc on propane

Post by robin_chevelle »

storm wrote:
robin_chevelle wrote:Thank you for the response. Really not trying to push this dilemma one way or the other and I certainly dit not already have made up my mind. :wink:
I don't see this as a dilemma, I see this as someone who asked for advice and has been given it only to come back with wrong information and use it for a reason to go one particular way.
I want to go the right way, whatever it is. Just want confirmation what the wrong information is and more important why it's wrong.. Should be great to have a topic online that gives no room for misinterpretation, don't you think? There is already so much contradicting info online about propane.
Don't you find it strange that 2 reputable companies that both say they have a lot of propane experience give such a different advice? Because I do and that is what makes me wonder why, what, how, does it affect torque/mpg/driveability.

First company:
208/210 @050 .449/.450 111LSA use 1.6 rockers on intake side don't use a shorter exhaust duration, it will increase exhaust temp, and that's bad with propane.

Next company:
208/208 @050 .440/.440 116LSA use 1.6 rockers on intake side. get as much lift as you can, should have amazing torque from idle to 4500 and cruise nicely with hi vacuum at part throttle.

That is what they said.


If I understand what you're saying, (just for now, picking between those 2) it's go with the first one.
And it's not that different because the fuel is propane and the mixer cfm is only 460cfm.


storm wrote:
robin_chevelle wrote:Can you explain what the difference in ignition timing is? I did not neglected, I just don't know the exact reason why you need to recurve your ignition, what's the exact difference and why?
Read this http://www.acl.com.au/web/acl00056.nsf/ ... enDocument
Thank you, that's helpful.

storm wrote:
robin_chevelle wrote:I can agree with that. Do you know (or have a idea) why there are people that claim they have more torque even low in the rpm range with a single plane? Because a single plane is designed for high rpm. I thought it is because they have a large open plenum and propane likes the extra room.
With what fuel? how long are the runners? what are the operating conditions? what are the engine specs? I can't comment on all claims but in general long runners, which some(not all) single plane manifolds have compare to dual planes, create more torque.
I meant with propane. You are right, without all engine specs you can't say much about it except what you stated about runner length.
storm wrote:
robin_chevelle wrote:Yes a bigger LSA makes overlap smaller and does limit the scavenging, scavenging helps getting the cylinders empty. But when? When is there profit (in what rpm range)?

As far as I know the smaller LSA ensures a higher fuel consumption, less vacuum at low rpm
It can result in a minimal blow back that contaminates the fresh mixture (very, very far caught, I know).
A smaller LSA does have more peak power and sometimes more peak torque. But at what rpm?
I don't care about torque at 4000 rpm and power at 5000 rpm (or higher).
A wider LSA brings the torque curve down, improves Idle rpm and vacuum.
Who drives a heavy car on the street in daily traffic in that rpm range? That's for me (personally the question).
I try to get a maximum and flat torque curve from 1500 to 3100 rpm.
Did you read the article? the answer to your question was in it. The large LSA cam had less power throughout the usable rev range of the engine (a 406 Chev).

From the article
Our dyno figures bear this out. The 406 made more low-end torque with the 107 LSA cam, regardless of the intake manifold it was wearing, and held its own at higher rpm. In the same vein, the dual-plane equipped 406 had better results with the 107 LSA cam. "The dual-plane reacted to lobe separation almost exactly as it would to a smaller camshaft," said Godbold.

The 113 LSA cam, on the other hand, made less power everywhere and especially fell on its face with the single-plane intake. "I'm not totally sure if the reason is simply a result of the shorter runner length with a single-plane, or if you could trace it back to the common plenum," Godbold observed. "However, I do know for certain that single-plane manifolds have always run best with tighter lobe separation camshafts."
Yes I did read the article. What do they call low-end torque? Most dyno pulls do not begin at 1500 rpm and they are looking at numbers below 6000 rpm. When I read it, I'm thinking they are looking at numbers from 3000 to 6000 rpm.
You are saying that it does not matter and this science can be used through the complete rpm range, also with propane?

storm wrote:A good discussion happens when all involved are actively working to make the discussion happen. I ask you to show your evidence so we can discuss it.
I don't have evidence about propane.
Only from my 396 bbc on gasoline. I've got the Lunati 60202 in it.
rpm air-gap intake, holley 750 vac.sec., mid-lenght headers, 9.0-1 compression, stock heads.

Behind it is a 4L80e and 3.55 gear. With the converter in lock-up I drive 50mph with 1600 rpm. (a speed that I drive a lot from town to town).

The cam is 219/227 @050 .530/.542 112LSA and advertised as: 1400-5800rpm.

Personally, for my taste it's too big! Yes it runs great, sounds good, vacuum is perfect, even mpg is okay. But it's sluggish down low. It runs perfect and is really awake from 1800rpm and up (with or with-out the coverter in lock-up).

The other evidence I have is only 2-stroke experience. (15 years).
One of them a 50cc 2 stroke, runs max. 16500rpm. RPM range begins at 13000, does have 20HP at rear wheel.
'70 Chevelle SS396 - 4L80e - 3.55 - gasoline
'77 G20 Van - 350ci - th350 - 3.07 - propane

storm
Posts: 665
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Re: Camshaft for sbc on propane

Post by storm »

robin_chevelle wrote:I want to go the right way, whatever it is. Just want confirmation what the wrong information is and more important why it's wrong.. Should be great to have a topic online that gives no room for misinterpretation, don't you think? There is already so much contradicting info online about propane.
Yes there is and that is why there are sites for that deal with LPG where questions like this have been asked viewtopic.php?t=626
search.php?keywords=cam&terms=all&autho ... mit=Search
search.php?keywords=camshaft&terms=all& ... mit=Search
robin_chevelle wrote:Don't you find it strange that 2 reputable companies that both say they have a lot of propane experience give such a different advice? Because I do and that is what makes me wonder why, what, how, does it affect torque/mpg/driveability.
I am sure the business' you have communicated with have good intentions but they are business' and their primary goal is to sell products and make money. I once asked a reputable business why their suspension would be better for my 4wd and they couldn't answer the question. The reply I got was a mixture of giggles and negative comments about competitors that told me nothing about why their suspension was the better choice.
robin_chevelle wrote:First company:
208/210 @050 .449/.450 111LSA use 1.6 rockers on intake side don't use a shorter exhaust duration, it will increase exhaust temp, and that's bad with propane.
2 degrees difference in duration isn't much. Why say don't use a shorter duration exhaust yet use 1.6 rockers on the intake only?
robin_chevelle wrote:Next company:
208/208 @050 .440/.440 116LSA use 1.6 rockers on intake side. get as much lift as you can, should have amazing torque from idle to 4500 and cruise nicely with hi vacuum at part throttle.
Yet evidences provided on a 400 says wider LSA lowers all outputs in all streetable revs.
robin_chevelle wrote:That is what they said.
They are selling you a product.
robin_chevelle wrote:If I understand what you're saying, (just for now, picking between those 2) it's go with the first one.
I wouldn't go with either.
robin_chevelle wrote:And it's not that different because the fuel is propane and the mixer cfm is only 460cfm.
I don't understand the point here.
robin_chevelle wrote:Thank you, that's helpful.
So now you know ignition requirements are different for Petrol and LPG and ignition timing is a major factor in determining combustion pressures how are you going to use that information?
robin_chevelle wrote:I meant with propane. You are right, without all engine specs you can't say much about it except what you stated about runner length.
So we are in the middle of a guess and a hard place then because we don't have any real evidence to comment on.
robin_chevelle wrote:Yes I did read the article. What do they call low-end torque? Most dyno pulls do not begin at 1500 rpm and they are looking at numbers below 6000 rpm. When I read it, I'm thinking they are looking at numbers from 3000 to 6000 rpm.
Most? The article stated the 113 LSA cam was lower on all outputs compared to the other cams but may be better over 6000 rpm.
robin_chevelle wrote:You are saying that it does not matter and this science can be used through the complete rpm range, also with propane?
Is this a statement or a question? You start this by telling me what I am saying then you end it with a question mark. What I am saying is you have asked a question about camshaft choice based on information you believe to be true, yet don't provide where you got it from, and concentrate solely on the properties of LPG while totally ignoring the engine itself. If you want a recommendation on cam specs provide a full mapping of the heads flow specs and we may be able to help you out.
robin_chevelle wrote:I don't have evidence about propane.
LPG is a fuel like E85 is a fuel like Diesel is a fuel like Petrol is a fuel like Ethanol is a fuel. A camshaft helps an engine breath, it opens and closes the valves to provide a usable rev range tailored to the engines design. Forget about the marketing hype about LPG camshafts it is designed to make money on specifically designed cams when normal engine cams will do just as well.

To finish this post, the crux of what I am saying is choose a cam that suits the rev range of the engine as well as the heads flow specs. I prefer a larger (and not just 2 degrees larger) exhaust duration @50 thou lift because traditional US style V8s exhaust do not flow as well as they should. I wouldn't be buying a cam just because someone told me it is for LPG.
Last edited by storm on Sun Nov 20, 2016 5:56 pm, edited 1 time in total.
Every job is a self-portrait of the person who did it. Autograph your work with excellence.

Fuel flow requirements calculations viewtopic.php?f=5&t=1638

gottago
Posts: 205
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Re: Camshaft for sbc on propane

Post by gottago »

RC ..I've run a couple of 400 sbc on propane. Had a brother who used one in a load hauler for years. We use to run the recommended wide spread cams but in rv grinds with higher lift. That helped but still suffered a bit at the low end. You can tighten the spread and still not increase the overlap by dropping the duration to match the desired rpm level. That will concentrate max torque into a narrower band which can be at very low rpm but the upper end will suffer. You could go as low as a 109 lsa imo with those heads and intake valve size. D Vizard etc have done lots of dyno testing on which lsa will produce most power. You have to interpret a bit to figure out how to apply that to propane and make it work in a more streetable application but the fundamentals still apply imo.

As you said about your 396 it lacks down low and only begins to come on at 1800 plus. You interpret that it is too big of a cam but it is partially the spread causing that. I've even run a 104 lsa cam in a 377 (destroked 400) on propane. Huge torque, radically out doing the 112 spread cams but suffering a bit too much at the upper end.

As far as the choices you list, I'd lean towards the 111 lsa. Would probably like a slightly longer exhaust duration but its getting in the ball park. The 116 spread cam would be ridiculous to drive without a turbo imo. I rode in a 408 sbf yesterday with a 111 spread cam very small duration. It was a 12:1 motor with aluminum heads 2.08 intake valve mind you but was an extremely nice combination. Cam was retarded 4 degrees to even out the powerband from being overly torquey down low. Runs cool and very reliable. He gets 18- 20 mpg 411 gears and od trans.. just adding my two bits from personal experience.. Good luck,

storm
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Re: Camshaft for sbc on propane

Post by storm »

Here's a little rundown on the different aspects of cam design and their effects on engine performance.

Lift: Lift allows the valves to open and the engine to breath in (intake) or push out (exhaust) air. Lift should correspond to the airflow profile of the corresponding port to maximise intake/exhaust flow.

Duration: Cam duration directly affects the amount of time an engine has to breath in (intake) or push out (exhaust) the air it consumes. The smaller the duration the less air ingested or exhausted. More duration less efficient idle, less idle vacuum. Less duration more efficient idle, more idle vacuum. More duration, assuming same LSA, more overlap. Less duration lower operational rev range, more duration higher operational rev range.

Overlap: Valve overlap directly affects the ability of the engine to breath in (intake) or push out (exhaust) the air it consumes. The exhaust cycle assists the engine to breath in fresh air by causing a pressure wave that sucks in fresh air. This pressure wave effectively evacuates the exhaust from the engine and also drags fresh air through into the exhaust. The higher the overlap the more fresh air flows out through the exhaust (this is wasted fresh air). Higher overlap also causes the engine to idle less efficiently with less vacuum. Smaller overlap enables the engine to idle more efficiently with higher vacuum.

LSA (Lobe Seperation Angle): With everything else being equal a tight (numerically small e.g. 108) LSA enables the engine to produce more torque at lower rpm but produces less idle vacuum (it also creates more overlap which is probably the link to lower idle vacuum). A loose (numerically high e.g. 116) LSA creates less overlap but moves the operational peak of the engine to higher revs.

LC (Lobe Centreline): LC directly affects cylinder pressure, especially on the intake stroke. With all else being equal an Intake LC that is to early wont allow the engine to breath in as much fresh air as it is capable of. Likewise an Intake LC that is to late can potentially push incoming air back into the intake. An Exhaust LC that is to early shuts the exhaust valve early stopping the evacuation of exhaust and subsequent dragging in of fresh air through the intake. Likewise an Exhaust LC that is to late doesn't provide enough time for the exhaust to escape and produce the pressure wave that draws in fresh air.

Other considerations when choosing a cam are;
Valve size: the larger the cylinder for the size of the valve more duration is required to fill the cylinder. A cam that will let a 305 fill completely will not fill a 427 if the valve sizes are the same size.
Intake-Exhaust (flow) ratio: Street engines (N/A) usually require an Intake-Exhaust (flow) ratio of about 75%. If the exhaust ports do not flow well enough to reach this more exhaust duration is required to compensate.

All of these things, except lift, produce competing effects on an engines operation, because of this the ideal cam does not exist for any engine.
You have to weigh the benefits of duration vs overlap vs LSA vs LCL to come up with a cam profile that matches what you want from an engine.
Every job is a self-portrait of the person who did it. Autograph your work with excellence.

Fuel flow requirements calculations viewtopic.php?f=5&t=1638

gottago
Posts: 205
Joined: Thu May 24, 2012 7:39 pm
Location: British Columbia Canada

Re: Camshaft for sbc on propane

Post by gottago »

We have the compression ratio (static) heads seem to be a decent match for the desired rpm. Intake could be ok for the application. The 111 lsa cam would push it fairly well. Heat wouldn't be an issue even with the short exhaust duration imo. Its not a bad starting point to figure from. Put it in at a 104 icl. any desktop dyno guys out here? All the other variables come into play from there to tailor it as well as can be. Head flow numbers/ dcr per cam choice/ lobe intensity etc.. It can get fairly complicated the further you get into it but this isn't an all out race application looking for that last 10th second.

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