670 heads and race fuel

[bigrog2001]

Good day everyone! I'm new to the site and I was hoppeing to get some help. Hears my concern, I have a fresh pontiac 400 bored 030 over with TRW flat top pistons and a 510 lift cam and some 670 heads. I was told that I have to run straight race fuel but some say I can run a mixure of race fuel and 93oct. During the break in period I ran straight 110 race fuel. Before I put it on the road I would like to get and idea on what I can run. Any information would be greatly appreciated.


Thanks.

[MrPbody]

If this is a street car, your engine builder needs to be "slapped". A small "dish" in the piston would reduce static compression to 9.5:1, the "practical limit" for 93 otane. I know, the horse is already out of the barn... Sorry.

Mixing 3 parts 110 to 7 parts 93 is usually enough to "make" 100 octane. The 10.5 or so:1 you have will be okay with that. Timing can be set to the "stock" 12 BTDC and a max of 36 "total". 670s are "closed chamber" (unique to large-valve Pontiacs). Therefore they "like" a bit more total timing than the later large-valve heads. Good cylinder heads if properly prepared.

Do you have any idea what camshaft was used? It CAN make a difference in resistance to detonation.

Jim

[bigrog2001]

Thanks for the info, My cam is ISKY.

[MrPbody]

Sorry, I should have been more specific. I meant the cam specs.

Jim

[bigrog2001]

Shop lost my cam card, I went threw a lot with this shop all I no is that it has a 510 lift.

[MrPbody]

Sorry, dude. Not familiar with Isky Pontiac grinds. If you can possibly find the card and tell me what duratin "@.050" is, I might be able to help a little more. The guy obviously wasn't a "Pontiac shop", eh? We (most Pontiac builders) don't use many Isky cams in relatively stock engines, at least in the last 20 years or so.

Jim