Did i destroy my pistons?

[talon187]

I've got weisco 8.5.1 pistons with eagle rods. I got my car running again a few days ago. seemed to be running really well for only 15psi when i was running 22ish before. I got my a/fs in check then i noticed i was seeing knock. So i checked my maf pro and for some reason it was running -10 across the board. I put it back to 0 where it should be according to jeff at dsmchips.com took the car for a ride and it bucks/hesitates at like 3-4kish. I and it doesn't knock in second gear but knocks it 3ard. I'm wondering if maybe i did some engine damage. sound like it? what should my next step be?

 

[->PrOjEcTGS<-]

Compression and leak down tests to determine the integrity of the bottom end.

 

[Detective Coating]

^ Exactly. If you just rebuilt that motor you shouldn't be upping the boost to 15psi already, it needs some time to break in.

 

[HIGHPSI4]

Sounds like a timing/fuel issue. Check your settings, base timing, etc and make sure you do not have a bad sensor such as a knock sensor.

 

[PieEyedPiper]

^ Exactly. If you just rebuilt that motor you shouldn't be upping the boost to 15psi already, it needs some time to break in.

Some would disagree.
This thread isn't a debate over break-in methods, but many have good experiences using the motoman method.

 

[Detective Coating]

Some would disagree.
This thread isn't a debate over break-in methods, but many have good experiences using the motoman method.

I won't disagree with that but its better to be safe than sorry. I know whenever I build my new motor I'll be doing the traditional method of changing the oil within 500 miles, retorquing head bolts, double check ignition and ground timing, and keeping it under 3000rpm's. But thats just me, I know this thread isn't about that but I figured since he just got it done I'd warn him to take it the safer way so that he doesn't destroy the pistons like he originally thought he had done.

 

[talon187]

well i did a compression test its 120 across the board. the motors ben borken in for quiet sometime im debating on changing my piston and rods.....im just not sure what to go with if i do it. if i do change them i want 9.1 compression

 

[Sam@RRE]

120 across?? and thats cranking till it wont come up anymore? Do a wet test. Its highly unlikely that you can have that low of a compression number and it being equal across the board. how many miles on it and big question, what kind of oil have you been using? Sounds like the rings aren't fully seated yet.

 

[TOONAH]

Severe detonation can punch holes through the piston dome. Pinging, as we Brits call it is usually an air fuel timing issue. On the old MG's we had to retard the ignition timing and use a colder plug. There is a lot involved in the recipe, but check your base timing and fuel pressure first. Check connections to the injectors and make sure you have good gas in the tank. My thought on breaking in a turbo motor would be to keep the boost down to say 7 psi until the rings are seated. Did you gap the second ring slightly more than the top one? Some say this allows blowby to escape preventing ring flutter which can trash a new ring if they are not yet seated.

 

[BoredDSM]

Did you perform basic methods of a break-in? Re-torque after 3 heat cycles, use a mineral based motor, make sure you set the base timing, and how did you set it? Generally the rule of thumb to breaking in an engine is drive it like you normally plan to drive it.