455 and 94cc heads

Hi  I am planing on putting a pair of 94 cc 6X heads on my 455 that has a 30 over boar using Felprow head gaskets. what do you think the compression ratio will be. I am hoping for 9.5 or lower so I can still run on reg. gas. Paul  

The C.R. should be 9.6:1 with flat top pistons.  
professional hi-performance engine builder

Horsepower sells engines and torque wins races

http://www.projectpontiac.com/ppsite/content/view/16/30/


Find out for yourself. All you need to do is add in the information that you have in your build. Remember that SCR static compression is only when you turn the key. Dynamic is the running power of an engine.

http://www.kennedysdynotune.com/Dynamic%20Compression%20Tech.htm

That will explain Dynamic CR.

Going by half of the information you offered I have come up with a 9.2:1 SCR, but without all info Paul, I can't help you.  

Try to run 87 with 9.5:1 compression and your motor will ping to death. The only way you can run 87 is with 7.6- 8:1. Anyone who says they've done otherwise hasn't looked at their bearings after they've run gas that's too low in octane for their compression.

Geno  

I agree on the issue of compression ratio vs octane. A good rule of thumb for a street engine is to consider what octane fuel you can get and how much it costs, then put a decimal point in the middle of the octane rating and use that as your maximum CR. 87 octane = 8.7:1 CR, 92 octane = 9.2:1. With 92 octane as the highest easily available fuel in most of North America, it doesn't make sense to build engines over 9.5:1 CR for street cruisers, especially with many such cars getting way less than 20mpg. My Firebird runs mid 14's on a 7.6:1CR 350, yet I constantly hear of 10/11:1 street motors 400+ CID that don't run much quicker and my gas is cheap compared to their mix of 92 pump gas and racing or aviation fuel. And yes, I've seen what bearings and pistons look like after running 11:1 CR on 92 octane. The rings had to be pried out of their grooves and the top rod bearing shells and bottom main shells were pounded thru 2-3 colors of material after about three months of Saturday night dirt track racing (28 laps or 7 miles, one night a week, you do the math!).
Steve  
Trying to help... 'cause we don't all have to learn the hard way!

Yep, I decided to run the stock 4c's on my 350 instead of the no.48's just to have a simple 87 octane cruiser again (still building my 455 w/ 6x-4's though). The 350 will still be happy w/ a 750 holley and headers so I know the car will still be fun to drive.

I'm going to lower the CR on that 455 also since I live in Socal and crappy 91 is all we get- I think 9.2:1 w/ some dyno tabs for protection should keep the bearings intact with the 455.

Geno