Howdy (This is my first post so if it's in the wrong section or has some other problem, please let me know...) I am having a current struggle with a connection between Aluminum Heads and Compression... I have a gen 4 454 with this cam (https://www.summitracing.com/parts/cca-cl11-600-4) and I have a set of these heads (https://www.skipwhiteperformance.co...port-aluminum-heads-assem-bbc-oval-272_90010/) My concern is that on the website for those heads it says "These heads are not suitable on 396, 427 or 454 engines that have compression below 10.5:1" which I've never heard of before, My 454 has a 4.31 bore with the stock 4 inch stroke making for a ~8.2:1 CR, which is clearly a lot less than the 10.5:1 it's calling for, my main question is Why would they ask for a higher CR and what would happen if I just kept it as is?
Pro comp not so good , maybe the translation didn’t work. Perhaps some design issues, they will work at lower compression but there may be some combustion issues? Try Fred White instead of Skip , just saying .
So I was looking at that and called the company, which is based in America and they told me a couple of things... They said they buy the assembled heads and they go over them and clean up the machine work and install all new valve train (their parts are listed on the website) and they talk about Fred and how he isn't involved with the company anymore, it seems like skip white performance is in every way other than name the company that took over his business.... But back to the point- There should be no "minimum compression ratio" for the heads and running something more like 8.3:1 would be okay, right? I appreciate the feedback
https://www.holley.com/products/fue...sniper_4bbl_tbi_kits/sniper_efi/parts/550-511 https://www.jegs.com/i/Edelbrock/350/7161/10002/-1 *Hopeful smile* -- This is my first time doing anything engine build related so I'm hoping to not butcher it... it doesn't have to be perfect, it just has to run...
Yes, you can build an engine from a collection of parts and it will run. The question is how well for your intended purpose. Few engines are perfect, but you need to have a planned use and then assemble a collection of parts that will all compliment each other. Usually the first step is picking a desired CR based on fuel and intended use. And for a street driven engine, bigger can be better to a point, but you can have too much CR, too big of a cam, too big of a carb, and heads that have the potential to flow too much. If you look at most cam sites many grinds have a minimum CR. For the carb to meter correctly you need a certain air flow speed. So yes, the parts all have to work together. And that's true for a mild daily driver, or an all out race engine. As a young man it took me a bit of time to learn that. I would do a bit more research before spending more money.
i may be wrong in this but from what i understand is all aftermarket aluminum heads for the big block are the rectangle port heads. may be needing the compression to benefit from the port size.
These are oval port heads. They have pretty big chambers, too. It will probably make more power over the full RPM range than it would with stock heads. It probably won't make as much power as it would if you also put some different pistons in there.
I think until you compute your actual CR with the new heads and current pistons you really don't know where you are at
I drove around a 7.5:1 LS-7 for a few years with a single 4bbl on it, it ran ok, but not spectacularly. It worked better with the blower on it. But yeah, you can build it low compression and be OK. If it's a mostly stock truck 454 short block, it would end up around 8.2 compression.
Alloy transmits heat better than iron. Heat lost is energy lost. One article said the loss is equivalent to 1 point of compression, so it was suggested to go 1 higher. So..it seems you will have as much power as you would have with 7.2 iron heads. You may do a little better if the alloy heads have design features that improve power over the design of the iron heads. An article some years ago about Japanese experiments with ceramic coated combustion chambers & piston tops that traps most heat where it can be used show big increase in HP and reduced the needed radiator capacity to a quart and the same for oil capacity. Of course that wouldn't work on the street because most drivers don't check fluid levels.
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