I have much experience with 350's but I'm planning my first 454 rebuild. I know they are two seperate beasts but I'm wondering if some of the same principals apply.
For example, when designing 350's I know I can add a hole point to my compression ratio if I am installing Aluminum heads because of the added heat disipation. Does this apply to the 454 also? What compression ratio can I run with aluminum heads for a streetable but potent engine. I only want to bore it as required and no stroke change. I"m looking at cams and intake manifolds and generally trying to think things through but the first constant has to be compression ratio.
any info would be appreciated


[Modified by Strike3, 12:30 AM 2/16/2003]

 

The same rules apply to BB's as to SB's. However, due to the larger bore they are slightly more detonation prone, and so you should set compression about 1/2 ratio lower than a comparable SB.

 

So many things play a part in what compression ratio you choose and there is a limited number of pistons available. I started out with 11.25 but the cam drained so much off that I never had a problem and that was with iron heads. You need to run more compression with aluminum heads to equal cast iron. Also you can adjust compression with decking the block and milling the heads including head gasket choice.
Good luck

 

I'd think 10:1 would be a safe and potent compression ratio for an aluminum headed street Rat. A lot of the rest of the setup is going to depend on what intake your going to run and a large part of that choice is stock or aftermarket hood, not a whole lot fits under the stock hood.

:cheers:
Pat Kunz

 

Actually if I had aluminum heads I'd probably run around 11:1 compression ratio. If you compare equal cast iron heads and aluminum heads, you need to run almost a point higher compression ratio to get the same performance out of an aluminum head. The reason being is heat dissipation, aluminum dissipates heat much better than an iron head....when dealing with combustion chambers that is NOT what you want. I'm running around 10.5:1 compression with my motor with iron heads and don't have any problems with detonation. I think my 294 solid lifter cam helps bleed of some compression too.

 

As Bence mentioned cam is a big factor here as well, especially concerning dynamic compression, which can have as much to do with detonation problems as anything. Normally large duration cams have enough overlap that dynamic compression is fairly low at low RPM's so detonation isn't a problem, but throw a low duration cam into the same engine and it may become a problem. I said 10:1 becouse it's pretty safe with just about any cam unless you go for a really big cam and it's not so high that a low duration cam would have much of a detonation problem with it either. I guess what we really need to know is what's your goals and budget and what you want to do with the hood.

:cheers:
Pat Kunz

 

Thanks one-and all for the excellent input. I never thought much about the hood, but since this one is not a NCRS restoration, I feel OK about some high L88 type hood or something.
As for as Budget, my approch has always been to decide on the correct combination of parts for what I want to accomplish, then go for it, even if I have to save nicholes and dimes for awhile.
Intended use? Right now, I'm thinking this would not be a daily driver (probably couldn't afford to keep gas in it) but rather something to injoy on special weekends and those Vette cruses that pop up occasionally. Oh yhea! and maybe once or twice down the local drag strip to see what she can do, but nothing to be considered as an ultimate drag machine (just for fun and excitement). For the cruses, I would be looking for reliability & durability (and show-off ability). It would be nice if it had a nict throty lope and good low end torque, but not so much lope or hi idle speed that I would be uncomfortable sitting at a trafic light with an auto trans in "D".
I'm thinking a good dual plane intake, aluminum heads, tuned headers with an "H" pipe, something like a Demon with about 1000 cfm range and a roller cam.
Opinions on components to accomplish this greatly appreciated. Thanks again!

Bill :confused:

 

Unless you have a pretty heavily modified 454...1000cfm is overkill. My 454 with some heavily ported heads, bigger 2.19/1.88 valves and a 294 solid flat tappet cam .595/.595 lift, 248 Duration @ .050". I'm running an 850cfm Holley double pumper and it gets the motor fuel just fine. I'm also running about 10.5:1 compression.

So I would say unless you are running 11:1 or higher, huge R-Port heads, and a hefty solid lifter cam....1000cfm is too much.

 

If you want your low end torque then stay with Oval port heads, a mild cam (something in the 280 range), roller would be unnescessary and added expense, a good hydraulic grind would work as long as you plan keeping the rpm under 6000. A weiand Stealth or RPM air gap intake. a vacuum secondary carb in the 780-850 range. 10.25-10.5:1 compression range should keep it 93 octane friendly. 1 7/8 -2" primary headers with 2.5" exhaust with crossover, and go with something like a 3.55-3.73 gear. This combination should make for a Rat with very impressive midrange with both good top end and low end and be very driveable and low maintenance that can be taken on the highway without spinning too many rpm's. It won't be the fastest thing on the street or track but it will hold it's own very well and be very driveable in daily situations, and most importantly it should be able to do great smoke shows with an abundance of low and midrange torque. Well these are my thoughts on it anyway.

:cheers:
Pat Kunz