454 efficiency - Maximum CR

Propane, Butane, LPG, GPL, C3H8, C4H10
storm
Posts: 551
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Location: NSW, Australia

Re: 454 efficiency - Maximum CR

Post by storm » Mon Dec 25, 2017 1:01 am

On a decent load bearing dyno part throttle testing isn't as difficult or time wasting as some may think. Most performance videos do just do WOT dyno pulls but I'm pretty sure most reputable tuning shops will do part throttle testing as well.

Yes heads play a very important part in part throttle and transient efficiency. In my experience, admittedly much less than many on SpeedTalk, a small head vs a slightly larger (I highlighted that video because of the size of the heads used) head won't make much of a difference if air speed for the size of the port remains high. When air speed drops so does part throttle and transient efficiency, and also WOT torque and power. With all else being equal a smaller head will have a higher air speed and higher low rpm torque but heads need to be sized for the engines intended operating range and a head can strangle an engine (I used the example of the VW boxer 4 in a previous post) if it is to small for the intended usage.

I must admit I am starting to like the idea behind the Vortec head. If what I have been reading is correct their design makes them a great candidate for a low to mid rpm engine. They already have hardened seats, a good combustion chamber design, good flow for the size of the port, and don't have a problem with being up to 50 years old like some Mark IV heads do.
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burbfixer
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Re: 454 efficiency - Maximum CR

Post by burbfixer » Mon Dec 25, 2017 1:44 am

One challenge with the L29 Vortec 454 heads is getting the compression up to the 11:1 range we've been discussing. The engine is rated supposedly 9:1 stock, and some gains could be made with milling/gaskets, but I doubt it would be anywhere near that much. The shape of the chamber will interfere with a normal piston dome. I need to do some research on that. They also have a swirl ramp built in to the intake port bowl.

gottago
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Re: 454 efficiency - Maximum CR

Post by gottago » Mon Dec 25, 2017 2:40 pm

Always a good idea to try and match up the parts that go into making the entire combo first on paper. One little thing like the availability of high compression pistons for one head but not another can be a deal breaker. I went for a ride in a dually bbc vortec this past week. It was a tower, 13 mpg gasoline. Fellow claims he can get as high as 15 with very gentle driving. Not the greatest power, but not bad for what it was. I'd keep looking for what piston is available for the vortec head.. just a quick look... not sure it will work but 10:1 with a 118cc head should be a little over 11:1 with a 98cc (vortec) head. Will respond better in a few days..
https://www.summitracing.com/parts/slp- ... /year/1998

gottago
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Re: 454 efficiency - Maximum CR

Post by gottago » Wed Dec 27, 2017 1:45 pm

The cam dyno simulation I posted was an example of what you would have to do to get a broad car like power band from a small peanut port head in a bbc. Just showing its possible by using an extra 20% ex duration. But there is a downside to just making what you have work as opposed to selecting the parts that would make things work right. Of course we don't all have the desired bottomless wallet to go with it but there are still options. The vortec takes a roller cam right? That opens things up a bit too. A nice basic cam profile that will work for high compression lpg is probably sitting right on a shelf somewhere. What are the stock vortec cam specs?

I'm away from home for awhile so don't have part numbers but the 3 dial msd timing control unit I use was an old model replaced by digital stuff now. You can set initial timing, then rpm where timing curve kicks in, then how fast it kicks in. Works great to get an unusual combo dialed in. Afterwards you can read the numbers off a timing light and likely mimic the results with conventional springs and weights. The one dial unit has its place too, just have to interpret the results a bit differently in your mind and tailor whatever dizzy you have accordingly.

I' ll leave the link to a very basic online dyno program. It is good for showing the results and direction of changes but not to be taken as gospel on the actual numbers. Takes a bit to input the info if not familiar with using these sort of programs but once you get there not bad for a free program. There are much better and someone with one would probably run your final combo through for a small fee. Meantime this gets you in the ball park. The vortec head with the roller cam etc looks pretty good.. Easier than dealing with the peanut port head and ft cam if you can get the compression to fall in line. Milling and using a thin head shim with a torque cam gets you to what compression? Benefit of lower lift shows up here too, ptv clearance. Balance flow with duration and lift..

http://www.colorado4x4.org/vbb/showthre ... e-Download

burbfixer
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Re: 454 efficiency - Maximum CR

Post by burbfixer » Mon Jan 22, 2018 1:22 am

Hey gents...
Been tied up with life, and then this website seemed to be down too so I haven't on for a while...
storm,
I was re-reading your Dec 24 post. You made an interesting comment pertaining to port velocity : "a small head vs a slightly larger head will not make much difference if air speed remains high". That caused me to remember something I experienced vividly with my 396. My experience is limited too, but I would tend to agree with your statement, and here's why:
When I first got my 396 back in the day, it was a stock 350hp chevelle engine with 10.25cr, stock 214/218, 461/480, 115lsa cam, stock iron high rise 'Holley' intake and stock exhaust manifolds. I put it in a 2wd 69 chev pickup with a th400 and 3.73 gears, and ran it on propane. It didn't last long because the exhaust valves recessed, but before that happened I loved the way that engine ran. I liked to play with this impressive 'torque surge' thing it would do. You could really feel it when you drove away from a stop light normally then right after the 1-2 upshift added another 1/4 to 1/3 throttle. The rpm was no more than 2000-2500, but I remember vividly how it would press you really hard back in the seat! Torque to weight ratio is what I was feeling, but here's the point : that engine was making plenty torque for the job at a fairly low rpm with oval ports that were something like 250 cc - bigger than anything I'm considering for my current 454 build. For comparison, that port volume on a 396 is like a 220 cc port on a 350 - pretty much racing territory, isn't it? Makes me wonder if maybe it's a mistake to place too much emphasis on the importance of needing very small ports to have enough velocity for a fun daily driver....
As a side note, but relevant to this thread, when the stock small chamber heads went bad, I put some 454 heads on with similar size ports, but substantially larger chambers - about 20cc bigger. The engine ran fine, but that fun torque surge went away with that 1.5 or so points of compression loss. In other words, compression loss made a big, very noticeable difference in low rpm part throttle torque, but a fairly large port size had great low rpm part throttle torque when the compression was there. I never tried smaller port heads on that motor, so who knows, they may have made it even more torquey, but your comments still helped me remember what I had experienced back then but forgotten. So thank-you! That helps me further prioritize things with my current build.

gottago,
The L29 vortec cam is a roller, 204/209, .480/.483 and I think a 118 (!) lsa from the info I've gathered.
I've also been playing with some numbers in a compresssion calculator. It looks like the heads would need to be milled .100 or more to get the chamber down in the 80-83 cc range. That gets it to mid 10's for compression with a .022 gasket. I have no idea yet if it's practical or even possible to mill that much, but if so, it might be cheaper and easier than digging into the shortblock for a piston change. A dome piston can apparently be used if the vane in the chamber is clearanced for it, but I'd rather not go that route. I worry a bit that use of a dome piston might adversely affect the way the efficient heart shaped chamber is designed to work??
Also, thanks for the link. I couldn't seem to get it to download though - need to try it again.

storm
Posts: 551
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Location: NSW, Australia

Re: 454 efficiency - Maximum CR

Post by storm » Wed Jan 24, 2018 5:09 am

Welcome back

Port velocity is directly related to a couple of things, 1. Engine size, 2. Stroke. Mix and match them well and you'll have a killer street combination.

2 engines of the same family, e.g 305 and 400 SBC, fitted with the same heads will have different port velocities purely because of the size difference. The 400 sucks in more air so the port velocity will be higher simply because of the larger capacity providing greater vacuum on the intake stroke. Apparently 305 heads are highly sought after in the US on larger build because of this fact. Problem with this is the 305 is also a small valve from what I remember.

2 engines of similar size, e.g. 427 and 428 FE Ford BB fitted with the exact same heads will have different port velocities purely because of the stroke difference. The 427 (it was actually a 425 or something like that) had a shorter stroke so it could rev higher while the 428 had a 5mm longer stroke which gave it more low down torque. Basically the 427 was a race engine and the 428 was a luxo barge torque monster. Fit the exact same heads and the 427 will need higher rpm to achieve the same port velocities the 428 would at lower rpm.
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: 200
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Location: British Columbia Canada

Re: 454 efficiency - Maximum CR

Post by gottago » Fri Feb 02, 2018 9:57 pm

Makes me wonder if maybe it's a mistake to place too much emphasis on the importance of needing very small ports to have enough velocity for a fun daily driver....
As a side note, but relevant to this thread, when the stock small chamber heads went bad, I put some 454 heads on with similar size ports, but substantially larger chambers - about 20cc bigger. The engine ran fine, but that fun torque surge went away with that 1.5 or so points of compression loss. In other words, compression loss made a big, very noticeable difference in low rpm part throttle torque, but a fairly large port size had great low rpm part throttle torque when the compression was there.
Bingo! Compression with propane is #1. Port size is still important to rev range and response but secondary to what compression will do for you. As noted burb, that last 1.5 increase in compression ratio is where propane really works its best. Sure you need to pay extra attention to cooling and timing but when it all comes together, it is pretty sweet. Power and mileage with 25% off the base price of regular gasoline. Its worth striving for.

Sorry not sure why the previous links aren't working. There was a piston advertised on summit that was close to the desired comp ratio. I'll see if I can find it again if you aren't able to mill to where you need to be.

burbfixer
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Joined: Mon Nov 06, 2017 10:07 am

Re: 454 efficiency - Maximum CR

Post by burbfixer » Sun Feb 11, 2018 9:49 pm

Here's something I've wondered about, and it relates to what we've been discussing.

Propane vapor occupies a greater volume of the intake charge. It was awhile back that I researched this, but I never did find a definite answer to exactly how much more, but compared to gasoline 'mist' from a carburetor, I believe it's several percent (5-8%??). This may mean that one should theoretically use a larger intake port (including the intake manifold ports) to help offset the air (oxygen) volume loss (and power potential) of a propane engine build. Combined with optimizing compression for the fuel and camming the engine appropriately, it might help one achieve gasoline performance (or better) from this fuel we all love.

If my thinking on this is correct, it would make a stronger case for using a bit larger volume 'airflow components'. For example, larger intake port volumes, perhaps an Rpm 'air gap' style manifold as opposed to a smaller one, twin mixers to feed it all, etc... And it would also help explain the lower rpm torque gains seen in a combo like gottago's when he went to a tunnel ram - a much larger intake system.

Anyone agree/disagree?

storm
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Re: 454 efficiency - Maximum CR

Post by storm » Sun Feb 11, 2018 10:08 pm

If petrol was "atomised" thoroughly you would find it would "take up more space" that it does already. LPG already being a vapour (in mixer systems as it enters the mixer) is already "atomised" mixing with the air stream, and cannot fall out of suspension like petrol can (and does with certain combinations). 1 droplet of liquid LPG expands something like 270 times its size during vapourisation, I don't know the number for petrol but it would be a similarly large number.

A larger port will not bring about any more benefit for all engine combinations if LPG is used. The total airflow through the port isn't, and should never be, the deciding variable simply because a large port on a small engine will not (as already explained in a different post) have the air speed required to make good torque and, as a byproduct, power at usable rpm.
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
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Location: British Columbia Canada

Re: 454 efficiency - Maximum CR

Post by gottago » Mon Feb 12, 2018 1:17 pm

If my thinking on this is correct, it would make a stronger case for using a bit larger volume 'airflow components'. For example, larger intake port volumes, perhaps an Rpm 'air gap' style manifold as opposed to a smaller one, twin mixers to feed it all, etc... And it would also help explain the lower rpm torque gains seen in a combo like gottago's when he went to a tunnel ram - a much larger intake system.
Keep in mind I run a very high compression, a mid/long duration low lift cam, and a smallish set of heads that is known to make torque. The runner size of the head did not change when I changed intake manifolds. The new bigger longer intake runner filled and maybe rammed the fuel charge through the head passage making everything work much more efficiently, maxing head flow. I'd run several other manifold combos previously through these same heads including a smallish dual plane. Low end was quite nice but ran out in mid upper rev range. Almost seemed to be choking itself off way too soon for a performance sbc. Determine the rev range you want and no need to go too big or too small.

The airgap might be a good choice.. Speedway dual carb to one 4bbl adapter on top, progressive linkage. In regard the compression again. If milling heads as much as what was indicated, the intake should be milled to match as well. Remember, a cam can be used to raise compression too along with the head mods if you decide to go that way. Might be enough without having to change pistons?

burbfixer
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Re: 454 efficiency - Maximum CR

Post by burbfixer » Tue Feb 13, 2018 1:22 am

Hmm. I think I didn't explain my theory very well.
I understand velocity is important, and going to a very large port isn't the best idea for a street driver, no matter what fuel is used. What I meant was maybe a bit more volume in the port might be a good thing to allow 'room' for a mixture that simply takes up more space because the fuel is already a vapor. And I understand gasoline would do exactly the same thing - occupy a greater volume - if it were a true vapor mixture in the intake tract.

Maybe I'm completely out of line, and there's zero advantage whatsoever to a bit larger intake port with propane. Compression aside, I'm just trying to understand why relatively large ports worked as well as they did on my old engine. As I said, maybe smaller ports like the vortec (235ish) or the peanut (200ish) would have made more torque yet, assuming compression remained the same. Guess I'll never know.... Just thought I'd throw the theory out there & see what you guys thought!

Admittedly, it's probably oversimplifying things a bit to only talk about cc volume when discussing ports.. They say port shape, cross section, etc, etc, are all important factors too, and affect velocity, but I know very little about these things.

The effect of plenum volume is also something I have very little real understanding about, but from what I gather, the best running propane engines have large plenums. (gottago's tunnel ram must have a huge plenum!). Maybe the larger volume that our mixture occupies is the reason propane likes the bigger plenums....

I'll hopefully have some time soon to check into the head milling and/or the feasability of dome pistons with the L29 Vortec heads. I'll be sure to share what I find once I do. It's funny, I have 2 454's sitting in the garage now, the peanut port genV and the l29vortec. They both have advantages and disadvantages.... I'd really like to try them both. I do have 2 Suburbans, a winter beater & my other nicer one...... Maybe they'll both get a big block!

gottago
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Re: 454 efficiency - Maximum CR

Post by gottago » Tue Feb 13, 2018 1:29 pm

It would be nice to be able to test all the different parameters and combinations of parts we think of and talk about. Unfortunately it is a fair bit of work and doesn't usually work out that way. I try to get people talking about what they've done and the results they experienced when I run into someone with a new propane powered ride. Everyone agrees with increasing compression but it gets a little foggier after that. I've run carb spacers up to 2" thick to increase plenum volume on a low rise intake and that seemed to help somewhat. I know someone who runs with huge head ports on a high compression/ smallish cam, smallish intake combo. No lack of response there. It ran out too quickly in rpm so cam was retarded. Surprisingly it picked up right across the board, low rpm to high. A said, my heads are relatively small in port size and the intake large. The opposite of his. It has no lack of response either. So go figure...

I'll be using a large single plane intake on another build this year. I suspect its more the plenum volume than port size that effects the performance the most with propane as long everything is in the ballpark. Compression trumps it all though imo and can make almost any match of parts work at some rpm. Last year a sbc with lowish compression and small ports got a short duration 108 lsa solid cam. No other changes. It turned into a quite responsive little street driver. Never did get the mileage numbers from him but he was happy with the power difference.

It is commonly said that you can use a tighter spread cam to crutch a poorer flowing head. If you really have a 118 lsa stock cam, that leaves a lot of room if you wish to use a different cam to change compression and port flow. You have two burbs, maybe one doesn't need as big fuel mileage numbers as the other? Or a turbo on one like dayzed in the other thread and drop compression instead. Options, options... Either way, glad you come back to share your experiences.

storm
Posts: 551
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Re: 454 efficiency - Maximum CR

Post by storm » Tue Feb 13, 2018 2:06 pm

burbfixer wrote:
Tue Feb 13, 2018 1:22 am
Hmm. I think I didn't explain my theory very well.
I understand velocity is important, and going to a very large port isn't the best idea for a street driver, no matter what fuel is used. What I meant was maybe a bit more volume in the port might be a good thing to allow 'room' for a mixture that simply takes up more space because the fuel is already a vapor. And I understand gasoline would do exactly the same thing - occupy a greater volume - if it were a true vapor mixture in the intake tract.
No you explained it adequately enough. What I was trying to say is the fuel being used doesn't matter it is all part of the air stream in a carb/mixer system (and even in a port fuel injected system). Bigger volume heads wont perform better for LPG for the reason you think, they may perform better because LPG is already fully atomised but not because LPG takes up more volume.
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: 200
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Location: British Columbia Canada

Re: 454 efficiency - Maximum CR

Post by gottago » Wed Apr 04, 2018 12:48 pm

Just thought this post from another burb driver had some interesting points in regard cam choice. Its on gasoline but the tq hp range is near what was being sought here.
How many stock pick-up trucks hit 5000rpms on a regular basis?

I built a 400SBC with 9.5 compression, 305 #601's I think on the heads, dished KB pistons, 5.56 rods, and a 390 BGN 4-bbl carb with pretty rare 2 stage power valves ( they really work ). It was in a 1989 Suburban that I drove back and forth to Charlotte as my Serdi Service vehicle. It made over 500ft/# RWTQ and about 325RWHP @ 4500rpm. From red light to red light it would keep up with most 5.0 Mustangs and Z-28's it was a blast to drive. It had a Reed hydraulic cam in it that was 214-224@.050 on a 106 lobe separation .390/.410 lift. I installed the cam with the intake on 96 and the thing ran like a top for almost 250,000 miles. I kept a log book on that truck for every mile I ran for tax purposes and it got 20-21mpg on the hiway and 18mpg around town.

I would still have it today but it was stolen from my shop while I was at Talladega. They caught the thiefs about 5 years later on an ATF / DEA deal, I did get about $50K worth of tools and tool boxes back but the truck was long gone. The group of them got 20+ years no parole ( cause of the guns and drugs ).

If I built that same engine today and put a 4L80E behind it she might get 25mpg, especially with the better 16" Michelin XPS ribs I run on my truck now. They run at 90psi and give a great ride and the old Kelly Springfields ran only 35psi, there is about 2-3 mpg right there.

I agree with most everything you guys have said about tuning and cold air and all the rest, but I also know there are huge gains to be made in advancing any camshaft, and if it does kill power and you want it back you just have to go bigger on you .050" duration to get it back. Basing power production on advancing and retarding a camshaft is just not knowing where the proper intake and exhaust event need to be.

Folks that have never tried it just don't know.

burbfixer
Posts: 14
Joined: Mon Nov 06, 2017 10:07 am

Re: 454 efficiency - Maximum CR

Post by burbfixer » Sun Apr 22, 2018 8:31 pm

Hey, thanks for the info - very interesting!
Been stripping down my L29 big block and found some issues, but nothing I can't deal with. Might take a bit longer than I hoped to get it in the vehicle, but at least we're finally making progress.

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