Removing Rear Main Cap

Stinch

Stinch

Senior Member
I'm helping a friend address a large oil leak out the flywheel housing hole when he shuts off the engine. I've read Pat's excellent article about oil leaks (http://www.antiqueenginerebuilding.com/REARMAINLEAK.html). More than likely the rear main cap will have to come off to inspect for a clogged drain tube and/or repair a missing tube. This work will be done with the engine in the car. With the rear main cap off, there is no support at the rear of the crankshaft with the flywheel hanging off the back. Is the any risk of damaging the crankshaft with the rear main cap off? Would a jack under the crank be good enough support for a weekends worth of work?

Rich
 
No need to worry, the only reason to jack it up would to use "plastigauge" for checking clearance ---but for what you are doing aluminum foil works better.
 
Chances are, the rear main cap is cracked and needs to be replaced. It's not a hard job if you can find another cap that's the right size. Some parts suppliers carry main caps in various sizes.
 
In order to remove the rear main with it in the car, I need to shove the bolts all the way up. Trouble is, they won't go all the way up. Is there something I'm missing?
 
Trust me, in this install, they do. There is a harmonic balancer on the front face of the flywheel that is preventing it from dropping all the way down.

Question is: where are the tops of the bolts located and how can I get them pushed up further -- about 1/2 to 3/4" more would do it.

Thanks.
 
There are some missconseptions about what I am reading. How can you get the rear main or any main rebabbited with the crank in place. The repored main will need to be bolted to the block, both sides line bored and that requires the engine to be out, upside down and the boreing bar be clamped in the main bosses. We are talking about thousands of a inch for clearance. This can not be done while in the car, unless I have missed some thing in the last few years. When a good amount of oil leaks from the rear main after shut down, that oil is coming from the valve chamber and leaking past a poor fitting rear main. Chances are good the babbit is cracked or missing some material, and this is NOT an easy under the car repair. Get ready for a major repair if its to be properly FIXED. Iceman
 
Several of us in the Orange County club just went through an identical drill. A 30 Tudor was pouring oil out the rear main, even though the engine performed very well. When we pulled the rear main cap off we found it was badly molested. Sections of babbit were missing and had been replaced with JB weld. Part of the cap had also been machined away. The engine was still in the car, we only dropped the oil pan to access the cap.

I contacted Bill Barlow in Bend Oregon and asked if he could re-pour just the cap. We sent him the removed cap along with another cap that was not molested. We measured the thrust movement of the crank before we removed the old cap, it was .015. We measured best we could the diameter of the crank journal. With all this information, plus the old cap, Bill was able to determine needed dimensions and re-pour the good cap we sent him. He was able to add to the thrust washer to compensate for the excessive thrust.

When we installed the new cap we only had to remove one shim. When all back together we road tested the car and it was no longer pouring oil.

Tom Endy
 
Bill has done several for guys in our club with the same results that Tom outlined above.

But first, I have to get the old cap off.
 
CarlG said:
Trust me, in this install, they do. There is a harmonic balancer on the front face of the flywheel that is preventing it from dropping all the way down.

Question is: where are the tops of the bolts located and how can I get them pushed up further -- about 1/2 to 3/4" more would do it.

Thanks.
Click to expand...

To really do it's job, doesn't the harmonic balancer need to be on the front of the crank?
 
The harmonic balancer came with the lightened flywheel / pressure plate assy I got from Ron Kelley. I really don't know that much about them, but I do know that the one I got would never fit up front of the crank. It's way too big.

But I still need to get the bolts retracted far enough to get the main cap out.
 
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The only way I can think of, off hand and not being there would be to use a I/8 th inch welding rod to push the bolts up. But just enough to get the cap out. Don't want to push them alll the way out of there holes.
 
I can push them up only so far, then they hit something, just don't know what that something is. I still need them to go up another inch or so in order to get it out.
 
I'm thinking you would be hitting the flywheel housing. Where it bolts to the block. Maybe turning the bolts so the flat on the head would line up and perhaps clear the housing.
 
I fear you might be experiencing the same issue as one runs into when trying to remove the rear main with a counterbalanced crank. There is no longer enough clearance to do it because of the additional "bulk" of the counterweight on the crank throw whereas it was no problem with a stock engine. This results in having to pull the engine, separate the clutch and flywheel housing from the assembly, so that you have access to the rear main. This is true on at least SOME of the engines I have seen. Needless to say, you want to absolutely make sure you have the clearances correct before putting it all together. Unless of course you enjoy yanking engines and putting them back in.
 
The rear main bolts will only move up maybe 1/8" before hitting the F/W hsg.With the harm-bal in the front of the F/W,you will not be able to remove the rear main without pulling the engine.You would have the same problem with an "A"F/W hsg with a "B" engine.At least with a "B" engine you can drive many thousands of miles before having to adjust the mains,especially if it has the C/B crank.
 
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