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BBC 454 build questions

Just collecting parts for now...
So here is an intake I have...
Should I use it or sell it and get an aftermarket alloy airgap or such?
Its from 1968 390HP quadrajet chevelle or Camaro I believe , as the casting number is 3931067...

IMG_2821.jpg


IMG_1.jpg
 
Here are my 781 heads..
IMG_2906.jpg


IMG_2907.jpg


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Here is some pics of a set of used, but near perfect TRW forged pistons I have... I think the are 30 over so might work... Thoughts anyone?

IMG_2892e.jpg

IMG_2902e.jpg
 
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Those are TRW forged pistons domed pistons (.030" oversized) and you want to stay away from the domed pistons. You want a flat top piston. The dome actually hinders flame propagation and will make less power than a piston with less compression.
 
Ok, thanks.
I thought with the open chamber design of the 781 heads I would need that, but proves how much I know!
What about the intake?
 
4X4HIGH said:
Those are TRW forged pistons domed pistons (.030" oversized) and you want to stay away from the domed pistons. You want a flat top piston. The dome actually hinders flame propagation and will make less power than a piston with less compression.
Click to expand...

In a sbc yes but you will have 7.8 to one compression with a ft and a 118 combustion chamber in a 454. Big blocks all require domes to get any kind of compression unless you use shrouded bathtub close chambers or build big like a 496. I have a 7.8 compression bbc and it runs good but if your building for power I would push it up a bit. Those pistons will be fine, if you don't use them mail them to me. Intake will be fine.
 
80' 427 said:
In a sbc yes but you will have 7.8 to one compression with a ft and a 118 combustion chamber in a 454. Big blocks all require domes to get any kind of compression unless you use shrouded bathtub close chambers or build big like a 496. I have a 7.8 compression bbc and it runs good but if your building for power I would push it up a bit. Those pistons will be fine, if you don't use them mail them to me. Intake will be fine.
Click to expand...

I will argue that point since i built Gregs 496 with 781 heads and flat top pistons and i was right at 9.3:1 CR. The "build big" comment is just rediculous because going with the larger bore does not increase compression ratio hardly at all.
 
4X4HIGH said:
I will argue that point since i built Gregs 496 with 781 heads and flat top pistons and i was right at 9.3:1 CR. The "build big" comment is just rediculous because going with the larger bore does not increase compression ratio hardly at all.
Click to expand...

What deck height? I meant big meaning stroked etc. Not just a 454. My friend is building a 496 right now and with a 118 cc head, flattops, 0 deck, .039 head gasket with a 4.370 bore, 4.31 cylinder bore, 4.25 stroke I get 8.7 to one. With a 454 instead I get 8.0 to 1 with it being .02 in the hole (what I have). I am sure you are using a better calculator but I am using this one.

http://www.kb-silvolite.com/calc.php?action=comp

I do believe a big dome will kill power but a small dome like that will add to homogenization of the cylinder much like a dish. I had 50cc domes in my 427 to start and moved to a 30cc dome to allow pump gas. So you are saying if I put in flat tops dropping compression I would make more power?
 
I use the same calculator that you're using. Not all flat top pistons are created equal though. The valve relief will affect piston volume CC's obviously. IIRC i used Probe pistons in Gregs 496 stroker and it was zero decked and i did get the head chambers down aroud 116cc's IIRC and that put me right at 9.3:1

Yes, getting rid of a domed piston even though it will reduce compression can make more power.
 
Just for fun...
In case anyone forgets... Dont run too long with the stock Nylon covered Cam drive...
Or this happens...
CamGearE.jpg

CamGear1E.jpg


Which does this....
ValleyE.jpg

PushRodsE.jpg

On disembeled looks like this...:eek1:
PRCamE.jpg
 
4X4HIGH said:
I use the same calculator that you're using. Not all flat top pistons are created equal though. The valve relief will affect piston volume CC's obviously. IIRC i used Probe pistons in Gregs 496 stroker and it was zero decked and i did get the head chambers down aroud 116cc's IIRC and that put me right at 9.3:1

Yes, getting rid of a domed piston even though it will reduce compression can make more power.
Click to expand...

So the 660 flywheel horsepower I make with my 427 will be more at 8 to 1 than at 10? Ah no. I agree trucks shouldn't have crazy compression but mild domes will increase power. Those little domes won't change much in that astro dome of a combustion chamber. I would be more worried about quench than the domes. I still only get 8.9 to one with 116 and a 3 cc valve relief. It doesn't matter but a 118cc head on a 454 and a ft NOT decked gives you 7.8-8.0 to one and I think thats a bit low. I am working on limiting my advance so I can run more int to pick up the bottomend a bit. Need to go use my buddies dist machine.
 
80' 427 said:
So the 660 flywheel horsepower I make with my 427 will be more at 8 to 1 than at 10? Ah no. I agree trucks shouldn't have crazy compression but mild domes will increase power. Those little domes won't change much in that astro dome of a combustion chamber. I would be more worried about quench than the domes. I still only get 8.9 to one with 116 and a 3 cc valve relief. It doesn't matter but a 118cc head on a 454 and a ft NOT decked gives you 7.8-8.0 to one and I think thats a bit low. I am working on limiting my advance so I can run more int to pick up the bottomend a bit. Need to go use my buddies dist machine.
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Compression makes little difference in HP/TQ numbers. Cam and heads are where the HP/TQ is made. I have my knowledge from 22 years of hands on professional experience as an automotive machinist. You are going to believe what you want so it's no use in me trying to convince you otherwise so i'm done with the thread. :rolleyes:
 
4X4HIGH said:
Compression makes little difference in HP/TQ numbers. Cam and heads are where the HP/TQ is made. I have my knowledge from 22 years of hands on professional experience as an automotive machinist. You are going to believe what you want so it's no use in me trying to convince you otherwise so i'm done with the thread. :rolleyes:
Click to expand...

I wasn't really trying to argue that much just discuss. I kinda wish you were closer so we could have beer and cuss and discuss. I don't have 22 years but I have done a few things. I currently just built a 450hp 2bbl 355 for our dirt car that cost $1200. Last year I had a 380 hp 9 to 1 383 with a stock intake and rochester 2bbl. I have spent a huge amount of time on the chassis dyno testing and retesting. I bought a flow bench this year and I am saving for a engine dyno. I am not a machinest, just a stupid service manager at the gm garage. But I spend most days thinking about quench, volumetric effency, compression ratios, air flow, how cylinder pressure is effected by displacement/airflow and cam design, carb flow at different depressions, etc.

You can pm me if you want and we can b.s. via email.
 
Ok, so back to my questions, LOL!
Should I sell the pistons?
Should I sell the intake?
How expensive is it to put the bigger valves into the 781 head?
 
My opinion only, others will disagree. I like the intake for a cheap "for now" intake. I would consider a future upgrade but its a easy change. I would like to see the numbers off the pistons but "I" think it will be just fine with them as long as it puts you in the 8.5-9 to one compression range. Here in nebraska is would be $500-$600 to have a set of ovals opened to bigger valves with the parts included. Of course it depends on how badly worn out the heads are. If they need guides and such it would be toward the top of that.
 
Oh and I have a friend building a ft 496 with 781 but is leaving the valves small. I have a peanut port 454 with 8 to 1 a intake headers and rv cam (speed pro 204/214). We are both going to chassis dyno our trucks before truck pulling them.
 
80' 427 said:
I would like to see the numbers off the pistons but "I" think it will be just fine with them as long as it puts you in the 8.5-9 to one compression range.
Click to expand...

Numbers as in part number? If you want a part number it is easily seen as L2300 +.030"
 
I didn't look sorry just saw the domes. I will dig out my trusty speedpro catalog and see whats I see.
 
Yes, my buddy said they were from a 427.
I was thinking that the 427 was destroked... or is it a smaller bore?
 
KeyBlazer said:
Yes, my buddy said they were from a 427.
I was thinking that the 427 was destroked... or is it a smaller bore?
Click to expand...

427 and 454 both have a 4.250" bore but the 427 has a 3.76" stroke and the 454 has a 4" stroke. If you try using those piston in a 454 block with the 454 crank the pistons will sit .120" down the bore from a theoretic zero deck.
 
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