guys ive ran into some serious trouble. about a month ago i had a my bottom end rebuilt. cp pistons and eagle rods. so with the turbo and everything bolted up i called the tuner to come start the car so i can get the tuning spot on from start up. at the 1000miles i had the tuner do the final tune. 1500miles later the car started heating up, so my mechanic pulled the head and found that all four pistons had cracked. can someone please let me know where i possibly went wrong?? i own a wideband and at no time was it reading lean or rich.


Modified by ah789454 at 5:03 PM 11/18/2005

 

your tuner sucks?... cracked the pistons where?

 

the tuner is very good. he has one of the fasted hondas in alabama so he know what he is doing. is there anything else

 

without pics or specifics, there is really nothing we can help with you

 

post some pics so we can help you...

 

Should have done the final tune right away, and not have waited 1000 miles.

 

was road tuned from 0 miles. not boosted at all during breakin (1k miles). dynotuned for boost after that. 10.9-11.0 all the way to redline. timing conservitive, 18' max. had always heated up on the hiway. all pistons had broken around the intake valve releifs. like a triangle pattern was left. they broke aorund the thinnest parts, as u would expect formt he CP piston design. 1 wedge missing from each side of the piston. every piston was the same. plugs were fine the entire time. no detonation. always used good fuel. im pretty sure the damage was done on the hiway, no boost at all. 3hr drive. cooling system was totally brand new, and i couldnt work out why it was heating up.

 

Hmmm, I'll be watchign this thread.

 

I've begun assembling a customer's engine with the same parts you're using, and I noticed the thin wall on the intake valve reliefs that you're talking about, got me a little nervous....I'm hoping I don't run into any problems like yours. I don't see how no detonation, pinging, leaning out, etc. would cause the piston to break, though. Try and post pics...

 

damn i just rebuilt my block too so i hope you find out the cuase of this good luck bro.

 

It's running lean. It explaines the overheating. The lean causes excessive egt then the cold fuel hits it on hard acceleration and it snaps off from the side of the int valve relief to the piston ring land. Happens alot on chev circle track engines. Probably a mid range lean. Have a whole shelf of them in all brands and types to show a customer who insists it was the pistons. CP has a great product.

 

I had the same problem with my JE pistons I was running high comp and boost. as everyone knows it is not a good combination (it is until it blows up) My motor detonated even though I did not hear it. I melted all 4 pistons and actually broke the valve releif outer wall off of 2 of the pistons. I ran my **** too lean. (It sure was screaming before it came to a sudden deceleration.) My car didn't run long enough after that for it to overheat.

 

what kind of injectors are you using? My cousin did the same with 2 JE's and my other buddy did the same with a CP. Let me know what type of injectors and if i'm guessing right then i know your problem

 

How did the plugs look. were they all white with shiny dots stuck to em, did the ends melt off ? what.. Would like to see pics to see exactly what Im looking at.

 

Plugs looked fine. i pulled them every 200miles. the 2nd last time they were perfect. a little tan, a little sooty. Then the last time, 3 of the plugs were covered in oil. no. 4 still was fine though, even though the pistons were cracked in every cylinder the same way.

There was NO midrange lean. As i said, i had the wideband on it the entire time. Soon as boost hit, a/f hit 11.0. My cruise A/f was around 13.8 on the hiway, when the overheating was occouring - so it wasnt a lean overheat.

Sorry im still in the process of getting pictures.

 

injectors were RC750cc's. They were flowed before i put them in and came up ~754cc each. Pump was a brand new walbro. Like i said, less then 2k miles on everything by the time it blew up.

 

i was thinking your injectors might have locked up, but RC's usually dont do that, I know DSM's have a bad reputation of that tho... but i really dont know, i hope onthing like that happens to me b/c im about to build my motor.

 

Yeah Im stumped.. I dont know what the hell could cause that much energy to crack all 4..?
When you find the answer post back cuz this is strange.. Still like to see pics of the tops and sides of the pistons and the rings.

 

What compression/how much boost were you running, and what fuel were you using?

 

he was using 98RON and the piston were at 9:1

 

Are they cracked at the corners of the intake valve pockets?

 

post some pics of pistons and plugs

 

Rocket: yes, that would be a fair description. The thinnest part of the valve pocket to piston wall. Andits not just cracked, a small pizza slice shaped chunk is missing.

As for pics, i'll get some this weekend. I am going to pull the engine. I live in another state during the week. soz.

Boost was 16psi. i prolly hit boost about 20 times over the total life of the engine. Revved to 7k.

my hunch atm was oil leaking into the combustion chamber (either piston->wall or valve guides) and causing hot spots on the pistons. I was always getting a little smoke on high-rpm de-accleration. No idea why, the head was freshly rebuilt along with the bottom end. All i can guess is someone fucked up, somewhere.

 

just to further my first line: EVERY valve pocket (2 per cyl) is missing the exact same kinda chunck. Its crazy.

 

That's usually from going detonation from a bad batch of gas or going too lean. Happened to us a bunch of times.