Gasoline Additives

[Oaklyss]

I run my stock 12:1 ZL-1 motor on 91 octane with no detonation problems. The stock ZL-1 cam closes the intake valve at 94 degrees ABDC (@ .015), duration @.050" is 262/273! I did install hardended seats only because the originals needed replacement

[69Z28freak]

Very interesting. Does that apply to all? Does it make a difference with a 12 to comp motor? I have been told constantly that a motor can't run more than 10 to 1 with Pump gas. We can get 94 octane in Canada. I am thinking of building a motor and want to know what would be the correct comp ratio to use. Obviously higher comp will make more power.

Depends on the engine and the tune - there are LOTS of 11:1 60's small-block Corvettes and Z/28's out there with factory "30-30" cams that run just fine on pump premium; the "30-30" has a late-closing intake valve that bleeds off some cylinder pressure at low to medium rpm that makes it much less sensitive to detonation. Aftermarket cams all close the intake valve much earlier in the quest for more power, and most of them won't work without detonation at 11:1 as a result.

Thanks John. My engine builder guy that I just found who is going to rebuild my old 350 is recommending 10 to 1 compression. I will post the engine specs, but it will be an old school LT1.