454 efficiency - Maximum CR

Propane, Butane, LPG, GPL, C3H8, C4H10
gottago
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Re: 454 efficiency - Maximum CR

Post by gottago » Sat Dec 16, 2017 3:21 pm

A bit of a general theoretical discussion is beneficial to everyone. Lots of good points to consider. Knowing what didn't work for some is as important as knowing what does work. There are lots of tradeoffs and not everyone wants the exact same thing. In regard crewcab's combo.. He is apparently using a reverse split cam. That changes things considerably in many ways including timing requirements.. On speedtalk forum, Mike Jones, (camking) described how a non split cam profile will up the midrange power at the expense of the upper rpm. The reverse split takes that theory a little further. Note.. this is in a smaller cu in 6 cyl..
custom ground Oregon Cams 260I / 248E .440 / 437
What is applicable to one engine size may not be suitable for another. It is of interest and is beneficial to understand the fundamentals behind this sort of thing though. This one was opposite of the usual split duration cam profiles. You could tailor each in different ways to perform differently in various weight and gearing combinations. It does help to know what you want out of it before even choosing an engine for the application but that's not always that easy.

Once you decide, whats best for weight and gearing.. in this case a bbc 454 you can tailor to suit. Some of the offbeat cam choices are interesting and are worth running in a dyno simulation program. Heads intake etc can be matched up in the same way.. There are various ways to shift that torque curve around a bit and some ways will likely produce better fuel mileage than others.

Do pay attention to the lift side of the cam, the dyno programs are quite good in that regard also. If 50 thou less lift only looses 5hp at peak, that could also be a 5 mpg gain right there. Smaller ports and valves work nicely with higher compression in the lower and midrange again benefitting fuel mileage. The port velocity thing.. If you can't use cam lift to put power where you want, you can still feed in with duration being mindful that will raise and lower combustion chamber pressures too. They need to stay up for fuel mileage. LSA does play a big role in how the combo will feel. LSA is just a number derived from the opening / close points of the valves so can be looked at/ discussed from the individual points or the end result.

I've run lsa from 104/ 108/ 110/ 112/ and 114 .. Of course duration and lift will change how each acts and then you have split or non/ and varying lifts in to ex..

They all have their benefits and drawbacks.. Knowing what you want and knowing what you will get from each is very important. Guessing wrong and putting up with a doggy fuel guzzler isn't the way to go.. Well worth talking it through drawing on all the real life examples you can find.


gottago
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Re: 454 efficiency - Maximum CR

Post by gottago » Sun Dec 17, 2017 12:30 pm

The heads pistons and cam intake close point should be looked at all together as a complete system. The bbc just by virtue of its size will produce torque quite easily. My experience with a 104 lsa camshaft in a high compression sbc showed me how easy you can get neck snapping low end torque. Responsive is an understatement. I can hardly imagine that sort of cam in a 454. The 108 lsa cams I have been around, real good power wise and street driveable but were down on fuel mileage. The 110 lsa was a decent compromise. Power was pretty good and mileage was down but still reasonable. The 112 lsa was where I saw gains in fuel mileage both with a bbf, sbf, and the sbc. I've had two 114 lsa cars in the past and the mileage was very good. Power dropped into a bit doggy range at low rpm partly due gearing and compression. Mid range power was good and highway mileage was best. I'd like to do a bit more testing in that range someday but I think compression needs to be way up to make that work with propane.. The upper # lsa cams soften the low end rpm power and make things driveable. A big block may like that. Too much duration would make that too high of a rever though and put the power out of the useable range. A small duration retarded on a 112 or 114 lsa may get the best mileage. I accidentally retarded a small 114 lsa cam on a sbf and was amazed at the mileage. Lost too much low end for its intended purpose though in a small block.

So burb's thoughts on his cam around 220@50 112 lsa is probably a good starting point to do some figuring from.. If a few more particulars on heads, pistons, dcr, etc were figured in to a dyno program.., I think that would provide the best outcome. I ended up running my 377 sbc cam in a retarded position contrary to what I thought, but which matched results with what a dyno program had predicted. I gained faith in using that tool more so than most any other means. You can play with and sort out many combinations of parts and cams without buying a thing. Wish I had of caught onto that a bit earlier.

ps.. these cams was just my own experience and observations.. Not saying that any of these combinations were properly optimised or that they couldn't be made to work better. Cam splits, lifts, lsa, durations, and install points all have a bearing. I didn't try them all.
Last edited by gottago on Mon Dec 18, 2017 4:11 pm, edited 1 time in total.

storm
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Re: 454 efficiency - Maximum CR

Post by storm » Mon Dec 18, 2017 12:49 am

gottago wrote:
Sun Dec 17, 2017 12:30 pm
So burb's thoughts on his cam around 220@50 112 lsa is probably a good starting point to do some figuring from.
In my experience an LSA of around 112 produces the flatest torque curve but not necessarily the highest torque.
Fuel flow requirements calculations viewtopic.php?f=5&t=1638

gottago
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Re: 454 efficiency - Maximum CR

Post by gottago » Mon Dec 18, 2017 4:04 pm

The question then becomes, is the amount of torque produced by the suggested cam installed in a high compression bbc suited to the vehicle and to what the driver wants? Wide lsa is the easiest way to get a wider power band without increasing duration to the point where the idle gets lumpy and fuel mileage disappears. A broader typical car like power as opposed the tractor type all in torque at lower rpm. Going to have to generate some preliminary numbers to work with. Parts are likely to be off the shelf items for cost and availability so one may as well design around that. A small piston dome, closed chamber heads, cylinders bored out, tight quench, and a cam that will keep the cylinder pressure where it needs to be.

Builders choice...The vortec head seems a good compromise for both power and mileage. The little peanut may be acceptable too with a fuel mileage bias.. ???

storm
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Re: 454 efficiency - Maximum CR

Post by storm » Mon Dec 18, 2017 4:32 pm

gottago wrote:
Mon Dec 18, 2017 4:04 pm
Builders choice...The vortec head seems a good compromise for both power and mileage. The little peanut may be acceptable too with a fuel mileage bias.. ???
I, personally, wouldn't use a peanut port head. Why? when the Chev 6.2 & 6.5 V8 diesel heads have bigger ports for engine that were designed to run low RPM (Idle-3500) and for years the oval port head did an excellent job on low rpm street engines (petrol) the only advantage that I can see the peanut ports having is a forced rpm limit through intake restriction (early VW flat fours suffered this and couldn't get over 100kmh) and potentially better fuel consumption if the driver didn't keep their foot down trying to keep the speed up. I don't know enough about the Vortec heads to comment on them.
Fuel flow requirements calculations viewtopic.php?f=5&t=1638

gottago
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Re: 454 efficiency - Maximum CR

Post by gottago » Mon Dec 18, 2017 5:29 pm

The peanut port is probably too mileage oriented. Maybe suited for an ultra low rpm application. The vortecs have decent reviews from the street performance guys. I have only used them in small blocks but they have a fairly good fast burn closed chamber and the ports flow well into mid range at least. Would take a larger valve than the peanut and would likely clean up nicely with a bit of port polish work. The old oval ports may be worth consideration too but I'm not familiar at all with them. In addition I believe there is a possibility that a tunnel ram may be sitting on the chosen heads. Have to check parts match and availability for each too.

storm
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Re: 454 efficiency - Maximum CR

Post by storm » Mon Dec 18, 2017 6:07 pm

There are oval port tunnel rams around, the Edelbrock 7115 is an example but they are matched to certain head types such as early or late but not both. Manifolds like these work well with LPG but aren't great for petrol.
Fuel flow requirements calculations viewtopic.php?f=5&t=1638

gottago
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Re: 454 efficiency - Maximum CR

Post by gottago » Tue Dec 19, 2017 12:27 pm

The bbc is one engine that I have no experience with. Been doing some reading though and do plan on one in the not too distant future. I really like the vortec heads on the small blocks but will have to research how they respond on the bb. The more modern fast burn chambers seem to be the way to go if you are able to keep the compression up. I haven't heard of too many bbc guys raving about their fuel mileage. Burb and his 396 at 18mpg on propane was as good as I've heard. Add 50 cu. in. though and could be a different story..

A few things that pop up in regard the 454 that need be taken into account for cam selection. Apparently they suffer from shrouding more than most so they like the bores opened up as much as possible. The standard valve size isn't that much bigger than a performance sbc but needs to feed 20% more cubes on the bbc.. This is partially why D Vizard says to tighten the lsa on the bbc. In a straight performance build for max torque you could go as low as a 106 lsa.

storm
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Re: 454 efficiency - Maximum CR

Post by storm » Tue Dec 19, 2017 7:21 pm

I've been doing some reading on BBC Vortec heads. From what I can tell they are between peanut and oval port in intake size and can be made to flow quite well. The exhaust is better designed so it flows less volume but faster which is good for torque as it evacuates the cylinder more efficiently. Vortec heads will require a different cam design because of this. They are for Mark V & VI BBC engines so they are metric and have different rocker design, neither of which is an issue but does need to be taken into account. The Edelbrock tunnel ram manifold I mentioned in my previous post probably wouldn't fit these heads and I'm not sure there are any that are made for them.

Vizard did alot of experimenting on BBC engines. At one stage he was boring them off centre so the heads were not shrouded. I don't have the stats but there was some improvement.
Fuel flow requirements calculations viewtopic.php?f=5&t=1638

gottago
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Re: 454 efficiency - Maximum CR

Post by gottago » Tue Dec 19, 2017 9:24 pm

When you have an engineering department like GM, the newer parts models should definitely be looked at. I'll have to do some reading up but if the bbc vortecs do as well as the sbc, they are in the running imo. They can produce power and mileage. How much would the cam specs need to differ? I'll do some looking around for a tunnel ram style intake.

storm
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Re: 454 efficiency - Maximum CR

Post by storm » Tue Dec 19, 2017 9:53 pm

Traditional BBC exhaust ports are to big compared to the intake so the cams are smaller on the exhaust side than an engine whose intake/exhaust flow % are better. The exhaust side of the cam for the Vortec would possibly need to have a longer duration than traditional BBC cams to take advantage of the better air speed of the Vortec's exhaust.

If you take a look at this link http://www.nastyz28.com/bbcmenu.php you'll see that most traditional BBC cams are equal in lift and .050 duration on Intake and Exhaust.
This link http://www.chevelles.com/forums/18-engi ... 6-cam.html indicates Mark V & VI come with more duration on the exhaust.
Fuel flow requirements calculations viewtopic.php?f=5&t=1638

gottago
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Re: 454 efficiency - Maximum CR

Post by gottago » Wed Dec 20, 2017 2:19 pm

That is a good start point for looking at the vortecs. The way the factory did things was all for a reason. Meanwhile, over on the speedtalk forum as of late, a list of links to camshaft design factors. Old and new... Some interesting points including on the split duration /ex flow theory.. ...
This was an interesting article on a bbc cam swap with dyno results.. Its not always the smallest cam that increases low end torque. I would imagine the fuel mileage suffered on this one though..
http://www.superchevy.com/how-to/engine ... -cam-swap/
Not only did the cam swap net an additional 52 horsepower (peak-to-peak), but the gains exceeded 80 hp higher in the rev range. Even better than the big peak gains was the fact that the cam swap improved power through the entire rev range. Equipped with the new cam, torque production from the 454 now exceeded 500 lb-ft.
The vortecs do not seem to do for the bbc what they did for the sbc. A little porting cam make a big difference on most heads. Back to the lowly peanut port.. For fuel mileage considerations and being that this is mainly for lower rpm use, the peanut has some benefits.. Port velocity at very low rpm for one.. Ported, they may be the best of both worlds at the cheapest price..
This article explores the peanut head etc and shows results from a few cam choices. Says to treat it like the old Pontiac 455.
http://garage.grumpysperformance.com/in ... ombo.2900/

Quote from one peanut port head user..
What no one understands, the smaller ports do not really 'restrict' flow... they increase velocity.... all the better for mid-rpm pulls....


Its not quite that simple but theoretically you can work with this. 5,000 rpm is probably about it but that may be OK with a high geared setup.
The oval port tunnel rams can be modified to fit this head..

There are many examples of what others have done with the 454 and the peanut heads to draw from. Not many are posting fuel mileage from their combos though.. Lots of numbers available to use and run through a dyno program.. Most of the big power boys are using the 108 lsa cams..
454 bbc 111 lsa.JPG
If I knew how to attach a photo.. this is a 111 lsa hyd roller cam with moderate duration and low lift.. Fairly retarded position.. I do not know what torque # is too much or not enough at given rpm.. Note hp is very low at low rpm.. How would that feel in a heavy high geared vehicle?

storm
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Re: 454 efficiency - Maximum CR

Post by storm » Wed Dec 20, 2017 11:47 pm

There is quite a big difference between the Pontiac 455 and the BBC. The major difference is the stroke with the Pontiac 455 having a 4.21" stroke and the Chev 454 having a 4" stroke. Pontiacs were never designed to rev, unless of course we start discussing the Trans Am 303 with a 2.840" stroke, but were designed to be very streetable and produce mountain moving torque for their size at very low revs.

I don't have my Pontiac info available at the moment, it is packed away cause I am moving at the end of January, but even the head design of the Pontiac is different to other traditional American V8s. The Pontiac has a 30 degree valve seat for excellent low lift flow but it really hurts high lift flow. On the other hand peanut port heads have a small port to produce good air speed rather than produce alot of flow.

As for choosing heads watch this video I think you'll find it interesting https://www.youtube.com/watch?v=p1w8OU_8-JM
Fuel flow requirements calculations viewtopic.php?f=5&t=1638

gottago
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Re: 454 efficiency - Maximum CR

Post by gottago » Thu Dec 21, 2017 1:03 am

Oh I'm a believer.. The fuel mileage side of things rarely gets mentioned in tests like that. Too bad, its another deciding factor. 5mpg more over the course of 100,000 miles = xxx
Anyways, looks quite possible to get the power in the ball park, just need the fuel mileage to fall in line. In the cam example I left above, the intake is only running at .485 valve lift on a 111 lsa . That would help mileage but I have no idea what that mileage number would actually be. This chart is with 11.3 static compression, ported peanut heads, a tunnel ram and dual 4's. One more thing, the exhaust duration has to be 20 degrees more than the intake to get this sort of torque curve.. Note it stays above 460 ft lbs from 2000, rpm to 5500 rpm. Try to get that from a small block. It may suit a lighter vehicle, I'm not sure. Anyway, there is promise..

burbfixer
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Re: 454 efficiency - Maximum CR

Post by burbfixer » Sun Dec 24, 2017 11:21 pm

Wow, great discussion everyone!
I just complicated the hell out of my plans tho. Strolled thru my nearest Pick n Pull recently and (holy crap!) found a 212km '97 Vortec 454. I'd never seen any brand big block in that yard before, but I was back the minute they opened the next day to pull it! So now I have both a complete Gen V and Gen IV sitting in the garage. Lots more options now...

BigBlockMopar,
Ask anything you like, no worries about hijack. We're after similar things with our builds I think.

storm
Funny you post a link to that vid... it's the same one that prompted my "Steve Brule for President.." thread over on Speedtalk. I think your taking note of that video proves we have similar opinions about what defines a really good engine combo. Of course, no stock head should be compared to anything from AFR, but the take-away for me was smaller can be better for a street vehicle, and Brule even commented on part throttle, which almost never happens in connection with dyno testing. Love those Pontiacs! Totally have a soft spot for the old 70's and early 80's Firebirds and Camaros.

gottago
Thanks for posting that simulation result. It's a little down on power at 11,000 rpm, otherwise looks really good though! :) Which dyno sim program do you use? You do have a bit of a different take on cam lift than I've ever considered before. I've always thought of lift as a 'get as much as you can' type deal - really, the simplest of the cam parameters to choose. Maybe I was wrong..... In the example you gave, why the 20 degrees of extra exhaust duration? That seems to be a huge departure from the single pattern (or close to it) cams we've been discussing.

One thing I like about your approach is the attention to tuning. I've never adjusted cam timing in any of my combos before, and may never get to, but tuning your advance curve with dials is exactly what I'd love to do. Never heard of the 3 dial setup though...it sounds ideal. Msd makes a single dial part that I would like, but now I'm curious about that part you mentioned. I've been shopping for a wideband setup too, but haven't bought one yet. Right now I just do mixtures at the leanest 'good power' setting, and I've modified the cone in the air gas valve in my 425 mixer to run a bit leaner. I've played with my timing curve quite a bit, and like you, have a pretty aggressive setting in there now.

The way I will approach my current project is to see how a simple,fairly traditional combo turns out if compression is optimized for propane. For me, a good intake manifold (likely with 2 mixers) and a free flowing exhaust with long tube headers are a given - I think you have to take care of those things first to get meaningfull results from any other changes. Initially at least, and in order to really learn the most, I think I should install a cam that isn't a major departure from 'normal' for the intended use. Once those choices are made, and the engine is what it is, then I'll tune it as best I can and see where I'm at.
Last edited by burbfixer on Mon Dec 25, 2017 1:33 am, edited 2 times in total.

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