thrust bearing: easiest way to change?

[vagrant_mugen]

i just finished putting new sprockets, chain, rails, tensioner, gaskets and all seals in the m42 i just picked up(175k miles).  go to put the flywheel on and hear a "thunk" when i push the FW down.  take off the FW, andgrab the crank pully and push/pull off the timing case and my crank is thrusting in-out a good 1/32" or more. :mad:

so, as  need a car to drive ASAP and just got everything done and almost back in the car, im gonna run it gently for a few weeks till i get my other car back in order, with some Lucas oil additive.  then either find a low milage block or try to change the thrust bearing or all the crank bearings.

questions are:
 
Has anyone changed the thrust bearing without dissasembling the motor?
   like leaving the rods bolted on the crank, take off the chain, remove the main caps and drop the whole crank an few inches, pulling the pistons to the bottom of the cyls?  and maybe swapping in a new thrust(360*)bearing?

Or must i take it all apart and rebuild a block while im there??
  if so id probly do some Eagle rods and maybe stock pistons w/ a low C/R MLS gasket and ARPs.

Any thoughts or advice?


TIA

[JP 91iS]

You're hardcore.  I've yet to get that deep under my M42, but it sounds like you could do what you said and replace the bearings w/o taking the whole thing apart.  Probably depends on how bad your problems are.  If you go that route, be sure and post up some pictures.

here is a quote from a post on R3V, you may want to ask him:

Here is my experience with rebuilding 2 M42's. One took 3 engines to make one good one.

We will start with the factory flaws and how they should be corrected.

1) Stamped steel chain guide. These fracture and break apart. Replace with upgraded dealer part, its a all nylon/plastic construction. You will need one new 45mm long bolt in conjunction with the new guide.

2) Steel oil pressure relief valve, aluminum front cover. The steel valve can seize causing a immediate loss of all oil pressure, good by engine. Replace with updated dealer part, made of nylon/plastic. Make sure you get the spring and spacer as well. The spring is slightly longer so it all a matched assembly. You will most likely want to replace the oil pump rotors, front pump cover and bolts. All of this is about $45.

3) Front chain cover. These are known for leaking profile gasksets. The rail that holds this gasket gets corroded and leaks. Every one notices when it leaks outside the block, but no one notices when it seeps behind the block. This creates a rust cavity potentially damaging the front face of the block. Expect to at a minimum to replace the front cover. If the block is damaged, you can surface the front face to clean up any rust damage. .015" MAX.

4) Main thrust bearing. The factory in all their wisdom decided to only use half a thrust bearing shell. This is not capable of handling the high rpm loads created by the M42. You will find the bearing to be rounded and burnt black. The crankshaft thrust surface must be inspected carefully. On the 2 engines I built one crank was scrap and the other barely within spec. To correct this problem you will want to replace with a full 360* thrust bearing. I do not know if the standard replacement bearings come with 2 halfs. I use the early eta M20 main bearing set and have the lower main caps custom machined so they fit. This not only gives me a full 360* thrust surface, it also gives me a full 360* oil groove for improved oiling to the rod bearings. As a note, I pulled the oil pan on a M42 with 80K miles, it already had thrust bearing material in the pan, along with 4 oil pan bolts.

5) Crank pulley. While the stock crank chain gear does not wear very much a new upgraded part is available from the dealer. It has 2 rubber rings molded into it. This helps keep harmonic vibrations in check. This may help prevent the oil pan bolts from backing out

6) Rod bearings, I use custom Clevite 77 NASCAR performance bearings. This is a upgrade, the stock peices should work just fine as well.

7) lock-tite all your upper oil pan bolts to prevent them from backing out. This is a big problem on the front 6 bolts that surround the gasket for the oil pump pick area of the pan gasket. When these back out and fall into the pan the gasket can push out and you lose oil pressure. See number 5.

Regarding valve guides, they should be fine as they have very little side laoding due to the valve train arrangement. I did not need a cam removal tool either. When loosening and tightening the cam tower bolts, take your time, do it slow and evenly. Remember the camshafts are hollow and can break easily.

If anyone tells you the stock M42 is a great engine, they are pulling your leg or don't know the M42 very well. The stock M42 is very self destructive.

I have pictures to back up every flaw I just described above. Everything I said above comes from direct experience with the M42 engine.

Expect to pay about $2,500+ in parts and machine work to properly rebuild the M42. If you need help/advice along the way just give me shout.

[vagrant_mugen]

i know i can get one done cheaper than that.  and i think that the stock replacement bearings are 360, but not 100% sure.  

very helpful info.  i was hoping peerless would chime in on this.  but the motors going back into the car tonite.  i need a car, and im picking up an audi 4000quattro in the next few weeks, so ill get the block square away then.

thanks, more input is welcome