im getting a 350 that is 9.5:1 compression. im replacing the cylinder heads with the vortec style heads. my problem is that the way the vortec combustion chambers are designe, they raise compression. does anyone know ho much they raise the compression. and what is the highest compression i can run on pump gas 91 octane, this is goin to be my daily driver. thanks

 

Although they may raise the compression, these are fast burn heads and can tolerate higher compression than standard heads. With proper tuning you should be able to handle 10.5:1 on premium fuel.

 

thanks, when i have the engine running and in the car, where should i take to get it tuned, a performance shop, or will anyplace be able to do it for me

 

My advice would be to take it to a performance shop that does alot of work with 350's. Can there be a " diamond in the ruff " engine tuner anyplace? Sure... there could be. But the best path to take would be find a shop that has alot of experience with 350's and go from there.

 

I think you could probibly run it on 89 or possibly 87. I had a 396/350hp and it ran fine on 87 octane with 10:25:1 compression. Now i'm building a 350 with 10:25:1 or 10:50:1 compression and it to will be a daily driver.

 

i have 12.8.1 in a 327 and i run on 93...but i'm also detuned...but run it everyday...

 

What heads are on it now, if they are the stock 76cc heads and you have 9:5:1 you will run abit above 10.5:1 with the 64cc vortecs. As Pete said they are less prone to detonation due to the design(spark plug location) the bad thing is they need a different intake. As far as compression/detonation goes I think the biggest influence really dependsless onstatic compression and more on dynamic compression ratio which is controlled by camshaft selection, which might be a reason some can get away with higher static compression than others. Aluminum heads would also help that.