[03_StangGuy]

Originally Posted by ReverendDexter I'm surprised no one's mentioned fuel. There's a difference in what compression ratio you're gonna be able to run if you can only get/afford pump gas vs if you can run e85 or 100+ octane race gas.

Unless someone mentions E85 or race fuel I assume they are thinkin pump gas. Most people that are serious enough to use e85 or race gas know to mention it and/or arent asknig these kinds of questions.

[VM0824]

I didn't have any detonation before with the stock 9:1.

[BassMaster5000]

Originally Posted by VM0824 ive been trying to calculate it myself, but i called the shop and told them to aim for 9:1 and to calculate piston volume from that. very cool thoery. i kind of figured that CR was some arbitrary calculation that correlated to some real math. with that in mind, the stock cam on my 89 is fairly "small" no? so the DCR would be fairly close ?

Since you have the stock cam, the seperation isn't as significant such as on a custom ground cam for boost. This just means that your intake valve closes, causing combustion earlier in your cyclinder, than if you had a different cam for instance.

Originally Posted by VM0824 I didn't have any detonation before with the stock 9:1.

I think everyone is just trying to throw out preventive measures to insure that if you up the boost in the future, that you don't have any problems. You can always consider changing cams/pistons/heads/headgaskets, or going to e85/c16/meth injection, but I personally feel you will be fine. This isn't like your adding 15#s to a motor with a 11.5:1 CR.