burnt pistons....what happened? picture included.

General engine tech -- Drag Racing to Circle Track

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neracer
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Post by jfholm »

Steve,
I was wondering if you were able to make any determination on what may have killed your front pistons. I talked to my cousin who wrenchs on a top fueler here and asked him if he knew anything that would apply to your problem. He did say that in every case where the front was made richer was in an injected situation. He said in their top fueler and an alcohol car he helps on once in awhile the front nozzles are bigger to make it richer. He is in the process of building a blown big block Chev for a guy with 2X4 barrels on top. He has talked to the company who made the system and also a couple of other guys locally here that are running blown gas engines with carbs and as far as he can determine they are all square jetted. He did say one common factor on all of them here was they had MSD boost retard systems. The more boost the more they retard. He said these gas guys say that is essential. One other thing how much over drive if any do you have? He and I were talking and some of the street guys here are running at the most 3% over drive and some as high as 10:1 compression. On the race versions they are running much lower compression but really over driving the blower. That way they claim they can pack more air fuel in for more horsepower, but that is also more top end. The street guys are running higher compression and less over drive more in the interest of low speed torque. That is their claim. I was wondering what you have found.
John
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Post by Rommel Racing »

jfholm wrote:Steve,
I was wondering if you were able to make any determination on what may have killed your front pistons. I talked to my cousin who wrenchs on a top fueler here and asked him if he knew anything that would apply to your problem. He did say that in every case where the front was made richer was in an injected situation. He said in their top fueler and an alcohol car he helps on once in awhile the front nozzles are bigger to make it richer. He is in the process of building a blown big block Chev for a guy with 2X4 barrels on top. He has talked to the company who made the system and also a couple of other guys locally here that are running blown gas engines with carbs and as far as he can determine they are all square jetted. He did say one common factor on all of them here was they had MSD boost retard systems. The more boost the more they retard. He said these gas guys say that is essential. One other thing how much over drive if any do you have? He and I were talking and some of the street guys here are running at the most 3% over drive and some as high as 10:1 compression. On the race versions they are running much lower compression but really over driving the blower. That way they claim they can pack more air fuel in for more horsepower, but that is also more top end. The street guys are running higher compression and less over drive more in the interest of low speed torque. That is their claim. I was wondering what you have found.
John
Hey John, no I have not looked the engine over yet, actually the motor is still at Jack's place,as I told him, I do not have the room here untill I finish one of the other four motors on the go here.

He did say he has 8:1 compression and is overdriving the blower,I'm not sure but I think around 6%, he said it is making around 12lbs boost. I believe he was running 94 octane pump gas with a octane booster when it expired.

I will let you know what I find when it gets torn down .

If it was detonation that killed it,do you think the bearings will show some signs?

Thanks for your help,
Steve
-3400lb stock suspension 67 Camaro
-10.5-1 compression pump gas 540bbc.
-th-400, 4200 stall 9" convertor
-12 bolt 4.10's
-29.5x10.5 Hoosier radial slicks
- Best on motor only 9.59/142.24mph
pistoncrazy

Post by pistoncrazy »

What are the ring gaps set to..... Had the same on a 351 cleveland 9 lbs ring gaps to small closed up due the extra heat and broke out at the weekest part ( valve relief to top ring ) ....
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