Thread: pump gas

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Originally Posted by skids72

Very funny.... I was thinking of the exact same question last night but with the variation of 91 octane at high altitude (which should be roughly the same as 93 at low altitude). I think techinspector1 has some crazy mind-control that makes us think of these things

BTW: I've heard you should run DCR no higher than 8.5:1 on "pump gas" but I was wondering the same if you can run higher with "premium" and maybe alum heads....

Yes, a higher DCR can be used with higher quality fuels such as race gas or alcohol. I'm not sure about the figures, but I think somewhere between 9.0 and 9.5. Again, not sure but I think it was Erik who said he has run motors with cranking pressure in the area of 220 psi on pump fuel with all things being optimized, no PCV or EGR to pollute the incoming mixture in other words, everything polished, squish optimized, exact intake closing point for the SCR, etc., etc.

If you read the tech tips on Crane's site, they suggest limiting cranking pressure to about 160 on pump gas. Now, of course, they are gonna be conservative because the rodder in East Treestump probably isn't going to go to the trouble or even have the facilities to set the squish properly and do the other things that will produce a valid motor with 220 cranking pressure.