96shee84z28 Posted February 9, 2004 Report Share Posted February 9, 2004 i just rebuilt my top and bottom end with 60mm wiseco pistons and a hot rod crankshaft. i went to glamis and just puted around to brake it in. i ran about 4 tanks of 91 octane gas mixed at 36:1 and on the 5th tank it all the sudden started bogging out and died so when i got it home it had a hole in the middle of the right piston. why the hell did this happen and how do i prevent it. does this have anyting to do with the 20cc domes??? my mods t5s, coolhead 20cc domes, vforce reeds, uni filter, other small things. Quote Link to comment Share on other sites More sharing options...
cb67rs1 Posted February 9, 2004 Report Share Posted February 9, 2004 what was your jetting , sound too lean Quote Link to comment Share on other sites More sharing options...
got1banshee Posted February 9, 2004 Report Share Posted February 9, 2004 I don't have a clue on why your engine did. I just wanted to say SORRY man, that really suck and I hope you get it worked out. Quote Link to comment Share on other sites More sharing options...
lucky13 Posted February 9, 2004 Report Share Posted February 9, 2004 WHAT IS YOUR JETTING HOW ABOUT COMPRESSION BEFORD IT LET GO Quote Link to comment Share on other sites More sharing options...
96shee84z28 Posted February 9, 2004 Author Report Share Posted February 9, 2004 my jetting is whatever the t-5 jetting kit said to run i haven't changed it after that Quote Link to comment Share on other sites More sharing options...
frocashmoney24 Posted February 9, 2004 Report Share Posted February 9, 2004 can you take a picture of it, i wanna see it, maybe pre ignition? or to lean Quote Link to comment Share on other sites More sharing options...
SICK BOY Posted February 9, 2004 Report Share Posted February 9, 2004 Sounds lean,what are your mods? Quote Link to comment Share on other sites More sharing options...
Hiram Posted February 9, 2004 Report Share Posted February 9, 2004 With 20cc domes I wouldn't run anything less than 93 octane, also is your timing advanced? Quote Link to comment Share on other sites More sharing options...
boonman Posted February 9, 2004 Report Share Posted February 9, 2004 A hole in the center of the piston is not jetting. Jetting can attribute and provoke an already screwed up situation. You had a problem with detonation. Detonation blows holes in the piston, not jetting. Jetting will melt the piston at the exhaust port side. Lean jetting can help out by creating added heat. You need to run higher octane or lose some compression..... Quote Link to comment Share on other sites More sharing options...
Ducman Posted February 9, 2004 Report Share Posted February 9, 2004 A hole in the center of the piston is not jetting. Jetting can attribute and provoke an already screwed up situation. You had a problem with detonation. Detonation blows holes in the piston, not jetting. Jetting will melt the piston at the exhaust port side. Lean jetting can help out by creating added heat. You need to run higher octane or lose some compression..... Exactly like boonamn said. You may have been jetted too lean but the detonation is what killed your piston. After breaking in the motor you should perform a plug chop test to check the jetting because the pipes manufactures jettting recommendations are usually only good for their pipes on a completely stock motor with only the air box snorkel removed. I have head of people running 20cc domes even with a small ignition advance (+2 or +3 deg) without a detonation problem on pump gas but that could have been with 93 oct. With 20cc domes it is so close to needing a higher octane than you can get with pump gas that if you are jetted too lean it will create higher cylendar temps and bring detonation into the picture. If you aren't pretty familiar with how to check your jetting (plug chop proceedure) and jet a little rich to be on the safe side then you should run 1/2 race fuel and 1/2 91 octance pump fuel mix. I personally would either run the higher octance fuel or go to 21cc domes. Quote Link to comment Share on other sites More sharing options...
96shee84z28 Posted February 9, 2004 Author Report Share Posted February 9, 2004 so if i run av gas there shouldn't be a problem? Quote Link to comment Share on other sites More sharing options...
Ducman Posted February 9, 2004 Report Share Posted February 9, 2004 so if i run av gas there shouldn't be a problem? If the AV gas is around 98 octane or higher and you are jetted correctly then you should be OK. The key thing is that you are jetted correctly because lean conditions which cause high exhaust gas temps heat up your piston and head which can lead to detonation even if you have a fuel with a suficient octane in some cases. Quote Link to comment Share on other sites More sharing options...
Banchetta Posted February 10, 2004 Report Share Posted February 10, 2004 I agree w/ boony and ducky..... Your problem is detonation....91 octane is border line w/ 20cc domes. I'd run larger domes to start w/ and check the jetting....Toomey is way off on the jetting charts and I'd start there and run it rich to start and work down after break in w/ plug chops....Depending on the air box and filter setups, we can get you very close to the jetting and determine your compression from there.... Quote Link to comment Share on other sites More sharing options...
96shee84z28 Posted February 11, 2004 Author Report Share Posted February 11, 2004 so what should my jetting be with these mods?? my mods t5s, coolhead 20cc domes, 60mm pistons, vforce reeds,toomey 2 into 1 uni filter, and a few other small things Quote Link to comment Share on other sites More sharing options...
96shee84z28 Posted February 11, 2004 Author Report Share Posted February 11, 2004 heres what the piston looks like.... Quote Link to comment Share on other sites More sharing options...
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