[4drbronko]

Hey all,
I've got a 427 tunnel port sideoiler in a car I'm getting ready to pick up. 11.5 to 1 compression on a 0 overbore block.
Will I be able to run it safely with 91 octane or will I need to run race gas?
I'm asking here first since I wont be able to talk to the previous owner untill I actually pick the car up this weekend.
Going to be trailering it home, so no worries there, I'm just getting curious.
Thanks
Jeff

 

[dfree383]

I would at least do a mix (50% 110 and 50% 91) and watch your tune. The compression is a little high and unless the valve seats have been replaced they are going to be soft.

 

[My427stang]

If its true 11.5:1 it'll be tough unless it runs a pile of cam, or a real retarded cam for late intake valve closing

However, if its running TRW pistons, and stock iron TPs that werent cut, its probably below 11:1. Those chambers are always way bigger than Ford advertised and the TRW's sit low in the bore.

Odds are though, if you keep total timing below 38 or so and dont let it come in until 3000-3200, it'll run on pump gas.

It will be fussy, but it'll do it, my med riser did it for years, fussy, but it did it. My new 489 is zero decked and built for a low dynamic compression ratio and will run on grape juice if I wanted LOL