Running a high compression engine on pump gas

[elonblock]

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Hemicolt</div><div class="ubbcode-body">Have the valve seats been changed to hardened versions? </div></div>

The seats have not been replaced yet.

[Hemicolt]

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: elonblock</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Hemicolt</div><div class="ubbcode-body">Have the valve seats been changed to hardened versions? </div></div>

The seats have not been replaced yet. </div></div>


The reason I asked about the seats is because based on your first post, I wasn't sure if it was a used engine or not.
If I missed that point, sorry for my oversight.

If it is used, and you do know for a fact that the seats havn't been replaced with hardened pieces, then there is an unknown, (concerning valve seat condition), that may need to be figured into your decision.
If that is the case, I probably wouldn't take a chance on not running some type of lead additive. This way you will not give any possible problem a chance to become bigger.

If it's a stock type rebuild that you are doing or have done with no miles, then this is a moot point. But I believe it's well worth mentioning.

Kudos for the point being made again about camshaft specs affecting cyl. pressure bleed off. Another point that was worth mentioning again, it's not always about the dist. mechanics.

[VintageMusclecar]

No, no need to.

[Hemicolt]

I was asking the author of the thread.

[miket1]

I agree with Eric, I have ran 11.1 engines for many years on 93 octane Shell gas setup same as his,
use mechanical advance , make sure the carb. is not running lean,

[ss427copo]

In 'ol Yeller, it's 12.7 to 1 and I've run AV gas since 1984. For every 5 gals., she gets 3 1/2 ounces of each lead additive and Lucas Octane Booster. Runs great and all looks good with a recent removal of the heads for a long overdue sets of valve springs....

[VintageMusclecar]

Sam, you're right...I think I was having a &quot;Sheldon Cooper&quot; moment there.

A *truly* pure stock L72 won't measure an honest 11-1 compression, it will probably be closer to 10-1 (see Rob Clary's comments on the 2nd page of this thread). As such, you should be able to run pump premium (possibly with a splash of race gas) as long as the temp and timing are kept in check, and the carb is set up correctly.

Sorry for the data dump.

[TDW]

I run my bone stock 69, L78 car with 93. No problems at all.

[m22mike]

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: TDW</div><div class="ubbcode-body">I run my bone stock 69, L78 car with 93. No problems at all. </div></div>

Me too, and I suspect the compression is not close to 11:1 like Eric suggested.

Mike

[69 Post Sedan]

My motor is around 10.4:1. We have one gas station in Janesville that has 93 octane with no ethanol. It runs great on the street but at the strip I add NOS octane boost and have had great results. According to studies it bumps the octane up to 98.

Kurt