My motor has less than 1500 miles on it. forged pistons and rods, stock crank, MS3 cam, and ported LS6 heads. It was bored to 3.905 and all the other machine work done that you would normally do. When I went to the track last week the car was slower than last year when it should of been faster. and more passes i did the slower it got so i decided to leave. on the way home I noticed a sound from the engine. I pulled over and it sounded like a spun rod bearing to me. checked all the rockers and springs and everything to me looked good. so now were getting ready to pull the motor out. I was wandering what could cause the motor to go bad so fast. Could the tune be the problem if it was too advanced, or the balance of the rotating assembly or what could it be?

 

What was the a/f reading ? Bad tune running too lean and detonating the crap out of it will kill it in a hurry. Were you getting detonation? Are your knock sensors working? Was the block honed properly ? Compression check? Oil pressure?
How was everyone else running? You the only one with complaints? Were the conditions good for making power?

 

a/f should of been good because the car was dyno tuned with a wideband. I don't know about the detonation part. yes my knock sensors should be working, they are new. I am guessing the block was honed properly, they guy that did all the work has a good rep. One time I did do a compression check on it and all cylinders were very close in pressure. I did a compression check because during WOT the dip stick was blowing out and shooting oil under the hood. I think the a/f was too rich and the rings weren't seating. after the dynotune the dipstick didn't blow out anymore and the car made about 20 more whp. the oil pressure is always above 40lbs and I have the "revised" pick up tube o ring.

 

You need to find a new machine shop. Sounds like they do **** work. Did you check your clearances with Plastigage when you put the motor together? doesn't sound like a tune problem to me...

 

Before everyone gets hung out to dry, get the motor apart and see what damage you have. This will point you in the proper direction. You also need to invest in some guages to monitor your expensive investment.

 

Troof!

 

im going to go ahead and say it was your tune possibly running too much timing. Chipped a piece of the ring landing and ring. This happened to me. I though it was a spun bearing or rod knock. Too much timing weakened the piston and broke it apart slowly. It gradually got slower.

 

woldn't that cause excess crankcase pressure?

 

wouldnt what cause too much crank case pressure? too much timing? broken piston?

 

i'm not blaming anyone even after we find the cause of the problem. but what do you mean i need some gauges?

 

Yes it can be damage due to detonation

 

I know that, i was asking him what he meant by his question.

 

what is detonation?

 

Geez man.


Two options.

Pre detonation or detonation.

Pre is where the WHOLE mixture lights way before or without the plug sparks. Pre detonation is lighting the fire without the plug basically. Bad deal because usually the piston hasn't gotten that close to TDC etc...... This isn't the type your worried about. My moms 85 riviera could just about drive around on the dieseling after you turned it off LOL

Detonation is where there are one or more "pockets" of mixture that ignite on their own AND the flame pocket started by the plug. If timing isn't just right it makes too much heat/pressure and allows the mixture to do that. The explosion caused by the plug and the explosion that started from too much heat/pressure slam into each other and make mondo cylinder pressures via a shockwave.

And then you get busted stuff.

 

thanks. that's pretty much what I thought it was but never had it explained.

 

check the trust bearing, crank walk can take out the trust. ive done it in two passes

 

i hope to have the motor out soon, aka i hope to know soon...