Ryan Thompson

I will save this in my 928 files. Thanks so much! :

docmirror

Oh, I apologize. I got this from post 51: " Tried prying on the flywheel and it didn't apear to move at all." The 'it' was assumed to be the crank.

So, new news leads to new procedure. Leave the 2/6 rod journal alone as at least to me, I don't see any issues there. If the crank spins, then you can remove the plugs, rotate the engine by hand, and pry the crank as far back as possible, then do the dial indicator check of the thrust play. I'm quite sure it will be well out of spec.

I don't know where you want to go from here. The engine is out, there's clear damage to the thrust face, the crank has suffered heat damage to the main journal cheek. While this engine can be cleaned up, put back in and run for many miles as is, it's degraded and eventually it will fail catastrophically. While you have it to this point, at a very minimum I would replace the thrust bearing. More likely, you would replace all the main journal bearings due to the metal scooting around in the engine. Further, inspect the 2/6/ bearings and based on condition, replace all the rod journal bearings. Remove and replace the crankshaft. How far do you want to go?

Imo000

Sounded like rod knock noise?!?! Well that certainly points to a direction of a spun connecting rod bearing. Main bearings usually don't make a knocking noise. Before pulling the main bearings, I would start pulling the rod caps (make sure you label them where they came from and what way were they oriented on the connecting rod). Better yet, if the look good, put the caps back, don't need to tighten them to spec just enough not to be loose. OR at least get a small ply bar or HD flathead screwdriver and start gently moving the con rod bearings ends around, The worn one will be a lot looser than the other.

Mrmerlin

I would take the 2 6 rod caps off first
Then or before taking the rod caps off do a crank
K end play check and report what you find
since your talking about splitting the girdle their is a good chance your engine needs to be replaced

Ryan Thompson

Finally got the girdle pulled to find a spun bearing and damaged journal. Time for a new/used motor

jcorenman

Ryan,

That might be less bad than it looks. The bearing is toast for sure (first pic). Are you sure the bearing spun? There are circular marks under the cheek of the bearing-half, are they smooth, or scored? And on either side? Is that the position where you found the bearing?

In the second pic, those big circular marks are not from the crank-- that is factory machining. The radius doesn't match. The little marks where the bearing was do look like the bearing spun, hard to tell.

The side-walls of the center bearing look to be mostly there. The crank is messed up, but remember that the hardened steel crank is a lot harder/ stronger than the bearing material (lead, copper, finally steel). The crank may polish up, if not then good used cranks are readily available.

The real question is how badly the block/girdle are damaged if the bearing did spin, and whether the middle web of the block is cracked. The next step is to unbolt the eight rod caps, slip tubing over the threaded rod studs (to protect the crank-- those rod studs are super-hard), and then pull the crank to get a look at what is under. The question is what the block half of that center thrust bearing looks like, and whether there are any cracks in the web. The lock is an aluminum-silicon alloy, great for cylinder bores, but brittle.

FredR

Like Jim, I am somewhat puzzled as to how you concluded that the thrust bearing has spun. For sure it is toast. Did you reseat the thrust bearing into the "normal position" or is that where it was when you pulled the girdle?

The copper on the crank has been deposited from the thrust bearing and that should polish out. Whether there is any crank damage remains to be determined. From the photos there is no obvious thinning of the thrust bearing rear facing side wall so that is a relatively good sign in a not so good situation.

The original motor in my GTS when I acquired it had about 1.3mm of end float and the rear thrust bearing side wall was obviously thinned. The rear crank thrust face was also machined [gouged] out to the tune of about 0.4mm. We were able to polish that face and the main bearing crank journal was not damaged but the damage was done and that crank is now a paperweight given the heat treatment [nitriding] has doubtless gone.

Now you need to gut the engine completely. Once the crank is out you should be able to tell if the thrust bearing has spun and whether this has cracked the casing [in my case it had].

The other thing that puzzles me is the noise you reported. Whereas my motor felt obviously rough, there were no knocking noises.

In this instance you may just have caught the problem in time to save the engine- only further inspection will determine that one but you are in for a complete teardown if this to be the case. If you have not done so already read John's current thread about his TBF'd motor and his plans for recovery with a "new to him" block- you will find it helpful. Given your prowess to date I suspect you are "up for this" and you will get a lot of help from the chaps.

Good luck

Fred

Imo000

Close up pictures of that bearing please. If that bearing spun, it's the nicest looking spun bearing I've ever seen.

Ryan Thompson

The bearing was spinning. I attached another pic of the outside of the bearing. I took the crank out and all my rods looked fine. Unfortunately, I forgot to get a pic of the block side. The girdle is messed up on one side and so is the block. Is there an acceptable amount of wear? I have a digital caliper.

Maybe it was a lifter that has metal jammed in the oiler making the noise.

I am starting to think overall it would be less risk dollar wise to get the motor from Kevin.

The only bad thing about that motor is I have to change the injectors. Kevin said the PO was running E85 and switched to larger injectors.

It looks like fun to change everything over. Not that I can't do it, but my memory is getting full of where each nut and bolt goes. I have bee pretty meticulous about labeling.

Ryan Thompson

Kevin's motor came from a known Renlister "BC". It sold through 928intl. Does anyone know what they do to ensure the motors are good?

docmirror

Yeah, that looks like it spun. I was wrong, you couldn't get any mileage out of that one. Might be able to salvage the block but if the girdle is messed up, it's a do over with used engine. Sorry. Stuff happens.

First time I've seen a spun thrust bearing. Maybe way too much tension supplied from the bowed TC plate. Whatever it was, it's done now. Swapping the injectors on the other donor engine isn't much of a job, just check carefully after you swap for fuel leaks.

Mrmerlin

I will guess the knocking you heard was from the spun thrust bearing ,
once it turned enough the oil feed was cut off,
with no oil things get hot fast.
Goodluck with your new engine

Imo000

Yup, that's not worth fixing yet. Since the last owner is from here, has BC chqnged the head gasket on the envine you are thinking of buying?

Ryan Thompson

I am in the process of stripping the motor down to sell parts off of it. Won’t sell anything until new/used motor arrives. Just in case need any spares from my old motor.

How do you remove the heads?

I saw on the forum that you may need special tools? I want to keep the cams in the heads and sell them as one unit. It looks as if you must remove the cams to get to the head bolts.

PLEASE HELP!

Imo000

Yup, the cams have to come out to get to the head nuts. You don't really need the cam hold down tool if you loosen the cam caps slowly in stages. I've done it that way many times without any issues. But it's up to you if you want to do it this way or using the factory tool.