Couple of problems....

[Black Box]

I finally finished all the stuff I wanted to do for my winter buildup! Took the car out for a ride yesterday, did some part-throttle blasts and then got on it hard and was greeted with about 2 LOUD (as in gunshot-loud) backfires. Turns out the boost was at 20 psi Got a THDP and RJC PP, I think that's why it was so high (never checked the WG rod length after installing tht THDP ) Got about 4* of KR. So I turned it down to 17psi. Started playing with the FP, as I think it's way too rich for my combo right now (set at 44psi, line off), as it's still stumbling and sometimes popping at WOT. Boost seems to hold steady. It seems worst if I just floor the throttle. If I 'roll' into it it's not anywhere near as bad, almost nonexistent.

I noticed that there is a rattling noise now coming from the engine. Take a couple 3/8" nuts and tumble them around in an empty coffee can, that's the sound. The waterpump is not leaking and the pulley does not wobble. I did the 'screwdriver stethoscope' test and it sounds almost like the noise is coming from the turbo. I never removed any part of it except to put the THDP on, removed the stock elbow. I took the MAF pipe off, the compressor wheel spins, but doesn't 'freewheel', it stops as soon as I take my finger off of it. Is that normal, or should it keep spinning for a few revolutions?

Could I have wrecked the timing chain or cam sensor with the hellacious backfires?

Lastly, the trans shifts seem to have gotten a little soft. The fluid level is OK (changed it late last season). I did remove the throttle cable bracket from the doghouse when I did the 009's and JJ TB and Plenum, but did not remove the TV cable from the bracket. Should I try re-adjusting it anyway?

Thanks for the help.

 

[Berman]

Put a screwdriver up to the turbo and stick your ear up to the end of it. If you hear "tink tink tink" it's definately coming from the turbo and it is bad. The turbo should definately freewheel, btw.

 

[Black Box]

Thanks for the reply. So what usually causes that tink tink tink? Bearing in the turbo or the compressor/turbine wheel?

Anybody else got any further insight?

Steve

 

[blackbuick87]

I dont know about the tink tink tink but I would definitely check the valvesprings too. How old are they? That would cause a WOT backfire if they were bad.
The compressor has to be able to freewheel in the turbo so it can spin at 10's of thousands of rpms. Probably the bearings are shot. If you fix it now you may be able to have it rebuilt before permanent damage is done

 

[Black Box]

The valvesprings are original, car has 29.7K miles. Guess I should go for the LT1 valve springs and a new timing chain?

Steve

 

[blackbuick87]

LT1's are a little high on pressure I believe. With a stock cam a set of Comp Cams 980's should keep your valvetrain plenty stable at higher rpms. Get that turbo looked at!

 

[Black Box]

Gonna call Jack Cotton tomorrow. Thanks for the advice.

Steve

 

[Black Box]

Found at least one problem....

Took the turbo off and it has about 1mm of up & down movement when I grab the exhaust wheel nut. I had a better grip to do the 'spin test' with 2 fingers on the exhaust wheel nut and it does move freely and doesn't immediately stop, makes about 1 - 1 1/2 revolutions before stopping. But either way I'm guessing that it's NFG with the shaft play. Bummer.

Anyone know where I can get new bearings installed in it? I don't exactly have $500 for a complete rebuild and certainly can't afford an upgrade for a coupla months (think July)

Steve

 

[RealFastV6]

Re: Found at least one problem....

Originally posted by Black Box
Took the turbo off and it has about 1mm of up & down movement when I grab the exhaust wheel nut. I had a better grip to do the 'spin test' with 2 fingers on the exhaust wheel nut and it does move freely and doesn't immediately stop, makes about 1 - 1 1/2 revolutions before stopping. But either way I'm guessing that it's NFG with the shaft play. Bummer.

Anyone know where I can get new bearings installed in it? I don't exactly have $500 for a complete rebuild and certainly can't afford an upgrade for a coupla months (think July)
Steve

You may be alright if it only moves a little bit up and down and doesn't touch the housing. You're looking for IN and OUT play, thats what a beaten/wiped thrust bearing will feel like.

I can't for the life of me think of what would cause a "tink tink" noise near the turbo area, other then something (nut, etc) trying to escape out the header through the turbine housing. (Not trying to scare you, thats just all i can think of).

What kind of turbo is it? Stocker?

 

[Black Box]

RealFastV6,
Yeah, it's the stock turbo, 29K miles on it. 1mm movement is about all it moves (eyeballed it) up & down. There is no in & out movement whatsoever. There is no visible damage to either the compressor or turbine wheel, and neither wheel appears to touch the housing, but when I turn the shaft I can hear a *very slight* squeeking noise. I'm guessing (I'm full of guesses these days ) that when it's spinning under engine power, the squeaking becomes the tink tink I'm hearing? Maybe it's just squeaking 'cause there's no oil in it now since it's sitting on the workbench? I'm gonna pull the spark plugs and make sure all the ground electrodes are still there....maybe one of 'em went south from the backfire? I don't know.

I called Jack Cotton and I'm taking it up there tomorrow night to have him look at it.

How fast does the turbo spin at idle anyway? The noise doesn't get louderat all, and doesn't get significantly faster with increases in engine speed (just a little bit).

Thanks for the help,
Steve