I'm replacing the old 5.0 in my 90' RS for a HO 350 or 383. The problem I'm having is with a streetable compression. I see a lot of 9.5:1 and up for anything with good power. Is that too high for pump gas? Whats a good ratio for pump gas around the 90 octane mark? I've heard that you can go as high as 10.1:1 with aluminum heads.

 

My 94 LT1 runs 10.5:1 and I run 92 octane with no problem.....you can run 10:1 with iron heads, if you burn 92 octain

 

Depends on the details of your motor.

Good combustion chamber heads are more tolerant.
Like vortecs and LT-1's
Lt-1's are reverse cooled design and computer controled
efi with knock retard .. thats why they can run 10.5:1

I run a true 10:1 on my 350 with vortec heads and a mild hyd cam. On 92 octane.. Never detonates.

If you're using old design heads use 9.5:1 or less
for 92 octane.
Not worth trying to squeeze the last bit of compression out of it.
Once you reach the detonation tolerance point power goes
way down.

Improve the total head/manifold air flow not the last bit of compression ratio for good street performance.
Way more power in that.

 

i run 10.5:1 with iron heads on my 350 on 93 octane.. did have some detonation problems at first but after upgrading to a becool radiatior and heat rapping all hoses and using steel braided fuel lines with a fuel cooler i run 93 octane with no problem on the street every day.

 

riley i was reading ur sig.. the bin laden thing is a matto the usmc is using. pretty damn funny.

 

Thanks for the help guys. That answers a lot of questions. Let me run one more by you. Pretty much what I wanted was a 383 short-block with a holley systemax top end with the 66cc heads. Its supposed to be around the 10:1 range and about 440Hp. Another option was the edelbrock performer RPM with the 76cc heads(keeping the systemax cam etc.), but I'm not sure what the power rating would be. Any ideas?