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So I'm replacing the rear main seal on the stock 5.0 HO engine in my 1987 Mustang GT. It has over 150k miles on it, and the gaskets and seals are going. Having a really hard time removing the rear main seal, I took off the rear main bearing, and found that copper is showing through about half of the shell. Here's a picture:
I thought I always took pretty good care of the engine, with religious oil changes every 5000 miles, never abused, hardly ever raced. So I'm a little surprised that I got so much wear on the bearing.
I prefer not to pull the engine for a full overhaul at this time, so I'm thinking of just dropping the crank and sending it to a shop for re-finishing and get some new main bearings. Good idea? Bad idea?
I haven't looked at the rod bearings yet, but I'm guessing they're in the same condition. Has anyone successfully done replacements like this from underneath, with the engine in the car? Am I postponing the inevitable?
The babbitt plating on the bearing shells is very thin, so that bearing might not actually be worn out. The way to check is to put a jack on the crankshaft on either side of the bearing to push it upwards, then check the clearance with plastigauge.
If there is excessive wear, then you probably can just replace the bearings with new standard ones, providing the crankshaft is not worn too much. If you did take good care of the engine, then the crankshaft probably will be okay.
There are some visible lines, but I can't really feel them. But that little nick on the journal has me concerned. It looks almost as if the journal was hit with a hard sharp object, like the corner of the main bearing block. Other than that, can you tell how the journal looks?
Chris, I had to drop the oil pan to replace its gaskets; the original cork gasket is leaking as well. It seems to have shrunk enough to actually leave gaps. I had to drop the K member to do this, as it's a custom piece that has reinforcement tubes that prevent the pan from just being slipped around. Here's a picture of it when I was installing it some years ago:
Other than the divot in it, that journal looks excellent. With nicks, dents etc. on journals the important thing is that their edges don't stick up. Obviously this isn't the case with your crankshaft or the old bearings would be gouged.
When a journal gets a nick from a rod bolt, tool etc. one carefully dresses it down with a file or stone. Having a small bit missing from the journal as in yours causes no harm. Just call it a "high performance oil retention pocket".
You can purchase plastiguage at any auto parts store.
Consider using the late model one piece reinforced rubber oil pan gasket.
That divot appears to have no edges sticking out, so I'm guessing it was inflicted during assembly, and maybe dressed down then.
I got lucky and just found a real local auto parts store open on a Saturday that carries plastigauge. Will be going to get some real soon.
I got the Fel-Pro (National) teflon rear main seal and their one-piece oil pan gasket set. Both have instructions that say to install dry.
The rear seal may be a bit of a challenge, as the lip doesn't expand like a rubber seal, so they say to use the protector/installer device that came with it. It has a large end, which I assume goes over the end of the crank flange like a sleeve, and I guess you have to force the seal over that and let it snap onto the crank. Then you remove the installer sleeve and let the seal sit for 4 hours to take its shape around the crank flange. The net wisdom says you can make an installation tool using a 4" PVC pipe cap to apply even pressure on the seal to force it on, so I'll be getting one of those as well.
I'd use a little sealer in those sharp corners. Doing it upside down on an engine stand is one thing, but underneath the truck is a different story. I love the one piece, but I've had more leaks with it than regular pan gasket.
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66 Bronco Half Cab, 203ci I6, CI aluminum head and intake, Isky 256/256 cam, Keith Black pistons, Clifford header, Holley 390cfm 4v, 9.7:1 comp, DSII ignition
Thanks GFW, I was thinking of the same thing. Plus where the front cover joins the block is not a perfect match, and it leaves a slight bump there, so I'll be gooping that seam as well.
The plastigage said the main bearing clearance is just under the high end of the Ford specifications; about .0015". So I re-assembled it last night and started to put the rest of the car back together. (It took me a few hours to re-install the K member and get the engine attached to it again.) I won't be able to test it until I can get at least the bell housing and exhaust system attached. No time today, so it will have to wait...
I noticed that one of the rear corner flanges of the oil pan appeared to be bent down ever so slightly, leaving visible gaps between the pan, gasket, and block. So I took it off again to try to straighten that part out. It went back to looking bent after I installed it, but this time, I dabbed sealant in that area. I watched it squish out a little as I tightened the bolts, so now at least I'm sure it's sealing.
A number of things caused delays, making this task take 2.5 weekends spread over 2 weeks.
The custom K-member made it impossible to drop the pan without dropping the K-member. That required some rigging to hold the engine up first.
Then I discovered one of the bolts holding the driveshaft U-joint to the differential flange had damaged threads. Since this is the first time I know that these were disassembled, I have to assume that this was done at the factory when the car was being built by our very skilled UAW workers. This damaged the hole in the flange, so even when I got replacement bolts from one of the remaining Ford dealerships in my area, the bolt would not thread into the hole. Fortunately, the flange had a second set of holes 45 degrees from the original, I was able to use those.
Everything ends up being more difficult than you expected it to be. I just hope it really is sealed up. I took it for a short drive tonight, and will check tomorrow for leaks.
It's possible the gap at the oil pan gasket would have disappeared when the bolts were tightened up, but a small amount of sealant is probably a good idea.
I always wondered why they put two sets of threaded holes in late model differential pinion flanges. Now I know.
Well, the first time I noticed the gaps was after I had torqued the bolts. I was about to install the rear main seal, and found I could see day light looking from behind the block through that corner. I just didn't feel confident the way it looked, so I dropped it again and applied the sealant. The second time, I saw sealant getting squished out, filling the gaps, so that made me feel more certain that it was getting a good seal now.
As much as I enjoy working on my cars, this is not something I want to do again any time soon...unless it is to replace the engine with a new crate motor or something like that.
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