Ok, the diagnosis is complete. Just drove back from the shop. The ding bat on the phone Friday was simply no help, how ever it was well diagnosed.

1. The engine sucked in light duty metal, mechanics best guess BUTTERFLY VALVE related! Strange since butterfly valve stuff should be out.
2. Metal was found in cat, so it went through the exhaust side.
3. No Metal in Pan.
4. Cylinder 1 is scored, but shops opinon is it is not a problem.

So yanking the heads and replacing damaged valves is the likely fix. Maybe even prepping some heads from the AZ crew stock in advance, and adding these to the back up pile to save time? Also going to get a quote from the local shop.

Here's the machine shop i was talking about, Kelly Mulhern


sales@kmperformance.com


I think this will be a better alternative to Clearwater heads, This guy knows Mitsu's and is well known for good work. Probably going to get a stage 1 set of heads for Dave's SWB.

I also just noticed he doens't have a listing for DOHC heads, so we'll just have to ask if he is willing to rebuild them. I do know that the 3000GT guys switch to SOHC, I've read that the 24v SOHC heads are better for building big horsepower. So maybe a Stage 2 SOHC head could be better than a stock DOHC?????

I've got 3 different heads in my garage from my fiasco. I'm sure we could probably get 2 decent heads out of them with some refurb if needed.

I was just reading another thread when i realized something, on more than one occasion rockers have slid out of place on these 6G motors for a couple different reasons. It makes a ton of noise and since we now know there is no metal in your oil and cylinders have been scoped to show minimal damage (possibly normal wear and tear of an old motor) It could be very possible that some of your rockers have become wedged sideways holding the valve partially open when it should be closed fully. since there is no valve marks on your piston You should pull your intake and valve covers before we get too far ahead of ourselves. If this is in fact the case with your motor we can just ship you the replacement parts or possibly make a weekend trip to New Mexico (if some of the guys want to carpool) for what i'd call a minor repair. your weather is better than ours at the moment.

That is an interesting theory. Low compression on two cylinders..what are the chances there is not valve damage?

We also put those update lifters on...could they be the problem?

IF this is the case and you've confirmed there is no damage on the pistons the valve should be ok. I lost 2 on my diesel it's interference as well, it didn't hold them open enough to make contact. Mine just wouldn't open or close all the way, ran like garbage and made a tone of "death noises". fixed the issue and got right back on the road. Pull your valve covers and take a few pictures for us.

A couple of questions. First, I have never taken the valve covers off, I assume it is not hard? Second, what the hell would keep this from happening again?

Being as the issue occurred under high RPM's, that would be a point a bad lifter my let go....

if a lifter collapsed it will let the rocker loose, OEM lifters are expensive but if this is the case it's an inexpensive (comparatively) lesson to learn.