12.50:1 compression ratio

[mancu5.0]

Im building a 347 .040 over wanted to know if 12.50:1 compression ratio is too much for a street motor no power adders any input appreciated.
thanks

 

[Shaolin Crane]

WAY too much. You need to stay in the 10.5-10.8:1

 

[NIKwoaC]

Well, it depends. If you want to run pump gas, then yea, you can't get away with much more than 10.5-11. If you plan on running $10 a gallon race gas, then you can get away with more, haha.

 

[srtthis]

as they said... its a bit much for 93 oct pump gas... youd be better off around 11 with some timing in it then 12.5 with timing pulled

 

[85_SS_302_Coupe]

My buddy ran about 11.3:1 on pump gas without pinging. I've always heard you can get away with a bit more compression with aluminum heads because they draw heat out of the cylinders faster than iron. I wouldn't feel safe with anything much over 11:1 myself.

 

[Rick 91GT]

With a custom cam you could bleed some of the cylinder pressure off to make it work if you had to, although that defeats the purpose of having the compression

 

[mancu5.0]

Thanks for all your help