Comp ratio and HP #'s?

[Anonymous]

Has my machine shop gone conservative on me? My machine shop came back after many discussions and much referal to the performance book, with the following build. Flat top pistons .030 over bore, -.015 head mill, -015 deck height, w/ final CC volume 51. He provided me with the following #'s.

Deck volume before .41ci after 23ci
gasket volume .40ci
sweep ? 33.80
head volume 3.29 b4 3.27 after
TDC volume 4.12 ci b4 3.92 after
est. static comp ratio 9.65 to 1

These numbers do not take into account 260 cmp cam, over sized valves, headers or port & polish. I'm concerned we are not going far enough. He claims the flat top add compression where he left it off on the decking & milling. He unable to give me any HP est Falcon6 projects 10.3:1 at 139 HP. Any feed back would be great. Thanks Craig

 

[Anonymous]

If you are going to drive it on the street, around 9.5 to 1 is about as high as you want to go to avoid detonation using the standard premium pump gas. This is of course dependant on several factors, and depends on how easily a given engine tends to detonate. If you had aluminum heads, which disapate heat faster than iron, you can run a full point or two higher, in fact, need to run it high to get the same power advantages. If it had hemi chambers, you can usualy run a full point higher, because they dont detonate as easy. Our ford's chambers, OTOH, do detonate, and preignite. If you simply must have more, you will have to shell out alot of cash for high octane fuel and additives.