engine knocking, rebuild?

im sure some of you who rebuild your engines religiously...can answer this pretty easily.

Im not sure if i need to rebuild me engine in my 420a....again...

its been out of tune for some while now, and now its getting to where everytime i shift, the rpms rise above for like 2 seconds, then fall back down, and when this happens, i hear a bad baddd sound...yes...knock.

i shift, rpms go up(instead of down) just a little bit, and it does this for like 2 seconds, and i hear ping ping ping ping ping, like shaking marbles around ina metal cup really fast...lol best way i can decribe it...

now, when its sitting at idle, it runs like a sewing machine, which leads be to believe the engine may still be in good shape, just in serious need of a tune...

so, based on these symptoms, would you say i prob HAVE to rebuild at this point, or is there hope?

fyi* i found a place in fayetville, NC that has a dyno and some techs who do nothing but performance work on dsms...evos and eclipses mostly, and they have quite a tuning record...ill prob take it there for its next tune, so i can watch and learn...

but...engine rebuild? yay? nay? what would you do

Well it doesn't sound good but there is a few things you can check before you tear it apart. Is there oil in the cooland or coolant in the oil? Check compression. Does it knock when free reving? Even on a bad tune you wouldn't get knock at light throttle applications.

no oil in the coolant or vice versa...

free reving?


and, when im driving down the road, under very light boost, it wont knock, lik ei can drive it and make it not knock, but as soon as i boost it just enough...theres knock...

i mean theres no doubt in my mind that it needs adjustments and tuning galore...

but to answer your question...like i say, i can drive around and it wont knock, only under a few lbs does it start doing that business...

ah ok I get what your saying. I wouldn't advise on making it knock anymore. It may be heavy detonation. I would do a compression test, you could have messed up some pistons. You have been driving it around with no WB or tune for a while. I wouldn't be surprised if they did finally give out.

so the compression test would tell me this...

like how do i know for sure that i need a rebuild you know...

it makes the difference on whether or not i gotta pull the motor and do alllll this work...lol

which is fine with me, but if i dont need to then...thats even better haha..

also, I have 8.1:1 je pistons in it now...and for some odd ass reason i cant find them any more....like looking aorund the net...i did, however find some which are 8.8:1...would that make much difference? or would it be ok? this is of coarse, in the event that i need to go piston shopping int he near future...

uh your sig says 8.6:1 pistons? And 8.8:1 is fine as long as you replace all of them. If the compression test comes up low then you have messed up some pistons and will need to pull the motor.

oh damn, must have typoed...ill change it...

so, a compression test it is.

thanks man