[Mike S]

My comp. is 12-1 and have been running VP c-12. Car has been 6.04 in the 1/8 at 3100lbs. I shift at 6400 and go thru the traps at 6600 (1/4 Mile). It is a 455 60 over with older E-heads, Cranking compression is 190lbs hot with carb wide open. Being the cranking compression is so low, do you think this would run on 91 octane? I would like to use it on the street for local shows and cruises.
I was thinking of making a pass with race fuel and then with 91. If it is detonating it will slow up correct? Could I hurt anything making 1 pass on 91?

Anyone familiar with water/meth injection? Would this help running pump gas?

[Stan Weiss]

Mike,
Isn't 93 octane available at the pump where you live?

Stan

[Mike S]

All gas stations around me have 91. I have to look around to see who has 93.

[Steve C.]

93 Octane Gas Finder

https://www.zeemaps.com/mobile?group=1385950


There are other sources as well


.

[Jay S]

A pass on 91 only sounds like a bad idea to me. Blend in some 91 with your c12 first, it might go quicker. Work your way down.

I tried something like that once, went to straight 91, thought the pumping compression was low enough it would work. We ended up draining the gas, cause it was pinging all the time even in park.

[mgarblik]

I honestly think you are on the ragged edge at that compression ratio even with aluminum heads. I would proceed carefully. If your engine has headers and a loud exhaust, you will likely not hear mild detonation and it can be damaging. The other wild card, is once you go to pump gas, you need that safety factor because you never really know for absolute certain what you are buying. Mistakes are made all the time at the gas stations and the wrong gas ends up in the tanks. With C12 or other race fuel, you know what you are putting in the tank. I recently put a new street engine together and it has 10:1 static compression. It will run on anything, 87 and up octane. Runs best on 91 no alcohol fuel. Fairly sure I am giving up 25-30 HP. with compression that low. If I was starting over, I would probably bump it up 1/2 point. Obviously, camshaft choice has a big effect on octane tolerance as well.

[t money]

Have you looked into Snow Performance Boost Cooler Forced Induction Water Methanol Injection Kit. My understand it cooling the chamber in higher compression

[Half-Inch Stud]

Water injection, without methanol is supposed to be better. Water Atomization is key. Adjust mixture! Vizard has a Youtube video on it.
https://www.youtube.com/watch?v=jextyKc2UN4

A decent lesson in doing water injection correctly.

[opeliac]

It all depends on how much you are planning to drive it, and how comfortable you want to be...My old 455 was 11.8:1, and I drove it on 89 octane almost daily...It was jetted fat, and over the 5 years that I had it together, never had an issue...I even drove it to the track once and made several passes on the cheap fuel...I had a 1050 on it, and like I said, it was pig fat...I tried a holley 930 on it once, and that didnt work...

We've also ran numerous big block chevies the same way...Had a 14.5:1 496 in a DONK...He ran premium unleaded in it, and as far as I know, its been together over 10 years now(limited driving)...A 13:1 477, pump gas for years...

Lots of cam, and lots of fuel...Its not perfect, but its worked for years.

[chiefbigb]

I run aviation fuel in my street cars. 100 octane low lead. If there is a small local airport around there they will probably sell you some. I get 50 gallons at a time in a drum. 6 to 7 dollars a gallon and lasts forever. No ethenol.

[grandville455]

Why not just switch over to E85 and be done with it..

[Skip Fix]

My Mopar buddy with a wide band on his carbed then Hilborn EFI would see wide ranges of the AFR between batches of pump gas. EFI can compensate some when the carb could not.

[PAUL K]

These high compression pump gas fallacies need to stop.... Someone might think you guys are serious!

[PAUL K]

Originally Posted by chiefbigb

I run aviation fuel in my street cars. 100 octane low lead. If there is a small local airport around there they will probably sell you some. I get 50 gallons at a time in a drum. 6 to 7 dollars a gallon and lasts forever. No ethenol.

What you need to do is raise your compression ratio a few points and use 93 octane.... Then you'll make big pow'a!!!

[R 70 Judge]

Originally Posted by grandville455

Why not just switch over to E85 and be done with it..

I second this

[Mike S]

the closest station with e-85 is 27 miles from me.

[chiefbigb]

There may be something to this compression makes more power thing. May try that theory one day. I'm impressed with Mike's car.

[Tim Corcoran]

With 12:1 you don't need 112 octane C10 would be more than adequate.

[grandville455]

Originally Posted by PAUL K

What you need to do is raise your compression ratio a few points and use 93 octane.... Then you'll make big pow'a!!!

U be the first!! lol

[PAUL K]

Originally Posted by grandville455

U be the first!! lol

Already did.... Bent two rods and popped a head gasket instantly. That was 10.5 with 93. Now after reading this thread I believe my mistake was the 93 octane. Most likely should have used 87 to keep it safe.