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Author Topic:   Compression running with methanol.
rnoswal53
Dirt Maniac

Total posts: 120
posted April 23, 2005 09:17 AM  
With my old gas car I had to worry about which fuel I was using with my high compression engine. I guess there is no problem with the methanol engines in the need to search for the right "octane" level. I hear people running anything from 9 to 1 up to 14 to one running methanol.

I have a high compression engine in my modified. I am running the hypertectic pistons with the high dome. I am wondering if there is a limit to what a piston like that will take as far as compression, timing and methanol goes. The reason I am asking is that I had a piston break above the ring land the other night. I know there are all sorts of forged pistons out there in as many different engine combinations. I was running the engine at 35 degrees of advance, water temp was around 190 during the race and the distributor is a good one that did not move during the race. There had been no transfer of metal to the spark plugs to indicate any detonation and there doesn't seem to be too lean, just a piston failure.

So I guess I was just wondering if there was a limit to compression using methanol and if there was a limit with these pistons. The other seven look great and I was thinking of just replacing the one, but not if they are on the edge all the time as far as reliablility goes.

Thanks
Russ

CCGRT9s
Dirt Full Roller

Total posts: 31
posted April 23, 2005 01:46 PM  
Though some might disagree with me, you need to run really good pistons like JE, Diamond, Mahle, or equivelant. Though KB and others are fine for certain applications (and are good pistons), running alky + high comp. + high RPM's + on & off throttle abuse in our mods, spend some money on high quality.

mavrik82
Dirt Forum Racer

Total posts: 93
posted April 23, 2005 06:56 PM  
High compression is high compression, gas or alky.Most of us need to try to save a few bucks where we can,but the pistons are not where I like to do it. Hypereutectic pistons were meant to be an upgrade from cast for street cars and the hi domes were meant to get decent street compression with open chamber heads. I would sooner buy a used set of forged pistons off the internet than use hyper's on a race motor with real horsepower. I bet I've seen a dozen hyper piston failures around our track in the last couple years, and these were definite piston failures, not caused by something else. If your talking SBC, I'd sooner run a cast crank, 2 bolt main and recon'd stock rods and put money in pistons. I sure there are a bunch of guys here that have had great luck with them, but if they are pushing big horsepower, luck is the key word.I have a big block methanol motor that is literally ver 16-1 compression and the pistons have been in 3 motors, one of which split a main cap in half. Buy a good set of pistons and never worry about them.Forged pistons also live longer thru overheatings and detonation and if you beat them up a little from detonation, sand them up and run.
Good luck,
Brett

rnoswal53
Dirt Maniac

Total posts: 120
posted April 23, 2005 11:16 PM  
Thanks guys. I had great luck with the Wiseco's in my mini stock, they were tough pistons. I guess I will bite the bullet and invest in some good quality pistons. I appreciate the input very much.

Russ

uforacing51
Dirt Forum Champ
Total posts: 570
posted April 28, 2005 11:28 PM  
alcohol likes lots of compression. keep that in mind

Dman
Dirt Freak

Total posts: 270
posted April 29, 2005 07:21 AM  
We have successfully run hypereutectic pistons with quite a bit of compression. They were not KB's.We had 3 KB's come apart before we went to the Speed Pro Hypers. The SP's were actually lighter and we didn't have to run the big ring end gaps (blow by city)like we did with the KB's. The kb piston has it's upper ring land moved up which causes the ring gaps to tighten up with heat and take the top of the piston off.We haven't had this problem with the Speed Pros in our claimer motors. We run SRP's (forged) in our good open show motors with no problems. I know,Iknow, There are alot of KB motors out there with no problems but we didn't have good luck with them unless we ran the jetting real rich.

spde
Dirt Freak

Total posts: 243
posted April 30, 2005 01:34 AM  
13.1/1 compression or better. We run 14/1 Also with hyperutectic pistons, most ot them swell arot more so you have to have a bigger ring gap. When the pistons get hot, the rings will litteraly cut the piston in two. ltr gl.

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