The edelbrock performer rpm alluminum heads,performer manifold intake and edelbrock 750 carb.from the stock g heads.how much of a difference will they this upgrade make on my 455,right now its stock other than a mild cam upgrade.i would rather go with the rpm intake but don't know if there's enough room under the hood .

 

I'd venture to say, that you won't gain much of anything.

The problem with G headed engines is the fact that they have 7.8:1 compression.

Take that Head money you are saving, and buy yourself a nice set of pistons first.

 

Since when? Isn't the compression ratio 8.5:1?

 

So which one is it

 

guess i will investigate that,thanks.so if the moter was borded 40 Over,don't it have bigger pistons anyway .
it was rebuilt before i got it.

 

Since 1971.

Bore=4.125
stroke=4.25
rod length=6.735
HG bore=4.25
HG thickness= .015
deck height=10.625
top of 1st ring to piston top =.025
Head chamber= 81cc
piston dish=40cc
piston to deck=.025
8.15:1 compression ratio.

With a .042 fel-pro head gasket in place of the factory shim gasket= 7.84:1

 

It has bigger diameter pistons, but the dish could be just as bad.
Also, aftermarket pistons have a wider piston to deck clearance.
If those new pistons sit deeper in the bore,
say, at .050, and you still have a 40cc dish,
Your compression ratio drops even lower to 7.56:1

 

I don't get this HP question, I see it here over and over again, if you look I bet there are at least 3 of them listed on this sight right now, is there some magical equation somewhere that I have missed that tells what HP increase you will get from whatever oddball combo comes down the road?
Sorry don't mean to be a dick but this is a dumb question.

 

Lol,guess u are one

 

I took your statement to mean that an untouched as it left the factory original had 7.84:1 compression which it did not. I see your point that the claimed compression is higher than the actual compression & the point you were making is that upon rebuild the compression would drop further because of the lack of thin head gaskets.


Carry on.

 

You nailed it buddy. It's unfortunate for certain.

 

Thanks for the input,final sugestions

 

Drive it, and enjoy it. I wouldn't put a cam bigger than 220 duration @ .050 in it.
It's just an old torquey gas hog, not a race engine.
Save up 7 grand and build yourself a different monster on the side if your goal is to go fast.

 

Lol,I'm winning races so opinions are like swiss cheese.

 

Great! I'll give big chief a call and see if we can get you a t.v. spot. Sounds like a real list shaker.

Or did you mean bracket races?

 

Another post which I find incomprehensible.

Translations?

- Eric

 

I'm guessing he's saying that opinions are full of holes?

 

Is there a way to get shim gaskets still?

 

KODA smitty sells em mj proformance. Also to the op do your homework it seems you want someone to agree on your hp figure which imo you need to truly know what you have to get a figure. Even then you need the proper running gear to back it up you can have 400 hp but if you don't have the right converter and rear gear etc etc etc then it will under perform .

 

That's too funny. I love that show (Street Outlaws) but it's not on enough. There are some seriously fast cars on it. I don`t agree with street racing (anymore) though.