Randel '86

I was looking at getting a pair of Edelbrock Performer RPM heads (64 cc) and some TRW pistons for my 355. TRW says I will be getting about 11.89:1 CR with that setup. I don't think my bottom end will have any problem handeling that at all? and what about pump gas? I have heard on 92 octane you can run up about 12:1 CR, is that correct? Any other problems/thing to considering in doing this? thanks

ronterry

You would be much better off with flat tops (I think TRW 2256-*).
The higher compression isn't going to give you a huge gain, and the price & aviability of racing fuel sucks.

I run 64cc RPM heads myself, with TRW forged flat tops. Compression is around 9.8...

I think around 11:1 is about the safe limit on pump gas, and you have to factor in tempature which could rise or lower that number a little along with fuel quality & altitude.

Ron

SweetS10v8

I ran 11:1 in my S-10 w/350 and Aluminum heads and I got occasional knock on 93 octane. It liked 94 octane(SUNOCO)

My 86 Z28 has 12.5:1 and it must have race gas mixed if you want to take out the knock. You can putsy around town on 94, but cant get on it too hard.

But your cam also determines your octane, how much overlap do you have? If you dont know, post your cam specs @ .050

RB83L69

Those high-dome pistons are not a good idea in a 350 in any overbore. Compared to some other way of attaining a given compression ratio, you'll end up with a less efficient motor that is more prone to detonation and various other problems.

Additionally, those heads have a non-stock combustion chamber shape, and off-the-shelf domes run a very high risk of not fitting in them (slamming into the casting ..... ouch). That means custom piston work just to make them fit, which is a poor use of money.

All in all, not the right way to design a motor; no matter what you may have "heard" as to the max CR you can get away with using.

If you really want higher compression than flat-top pistons and those heads, which will be around 10.2 to 10.4:1 with a zero-deck block and a .039" head gasket, have the heads milled a little bit.

Here's a way to estimate whether your combo and CR are matched to each other, that's somewhat real-world based. http://webpages.charter.net/darrell1/dynamiccr.htm

1989GTATransAm

iTrader: (3)

The above posts are correct. I'am having Dyno Don rebuild my 350. He has put in Keith Black flat top pistons with 2 cutouts for the valves. I'am also running 64cc Trick Flow 23 degree heads. My compression will be 10.5:1. I figure that is about maximum for the pump gas in my neighborhood. Allen

ljnowell

too much compression, you can never have to much compression!!!!!!!

Randel '86

thanks guys

SweetS10v8

ljnowell

do you not understand a joke?

GreyFox

i heard airplaane fuel works for really high compression............................or was that explosions?

SweetS10v8

I was hoping you were joking

AV fuel may have higher octane but is designed to be used at 3000+ ft and at about 3000 rpm. I mixed it a lot of times just for the smell.

ronterry

This was like 110 or something, but your not going to find this on every corner


Ron

SweetS10v8

Sunoco offers 94 at most pumps, and 100 unleaded at a select few. 110 is leaded and it $5+ a gallon

ronterry

Yea, but how many are located 50 feet from a 2.5 mile super speedway

Ron