I'm considering changing out my rear main seal, due to suspicions of leakage. I have the engine out right now with tranny and everything off of it, so it's a good time. Is there anything in particular I should know, watch out for, etc.? I have never done this job. It's on a 383 stroker.
Thanks, Patricia

If it's a late model block it's a one piece seal, goes in around the crank from the back side. Use a little loctite on the outer surface and drive it on straight with a suitable sized seal driver. If it's an early block it's a 2 piece seal, the rear bearing cap must be removed and the seal worked around the upper bearing. The bearing cap must be installed with a little RTV sealant, but you must be very careful not to get any RTV on the seal itself. Usually the seal kits have detailed instructions on how to install and where to place the RTV. There are also some little strip things included in the kit that aid in working the seal around so it's not damaged. The smallest little nick will probably come back and haunt you. The hardest part will be removing the old upper seal half, you might need to get a little puller that is sort of like a cork screw. It threads into the edge of the seal so you can pull it around and out. Be sure to re-torque the bearing cap using the proper procedure. ARP bolts are torque to yield and it's a 3 step process to get them properly tightened. Factory bolts are not torque to yield. Normally an engine builder would include the ARP bolts in an engine like this.

It's a 2-piece rear main. I'm actually not sure if it's leaking; my pan and valve covers were definitely leaking, but I don't know if the rear main seal may also have been leaking. I do know that the 4-speed I had in the car had an out-of-round input shaft, which we did not realize until it had been with that engine for 5000 miles, plus it was speedshifted some. So, out of prevention I'm thinking of swapping it now while it's easy. However, if I were to leave it in the hopes it's okay, what kind of job would it be to swap it out later? One source I read mentioned needing to remove the bellhousing's dust cover, while the other source said nothing of it. I will be installing a Lakewood scattershield which is, of course, 1-piece with no dust cover to remove, so it would mean tranny and clutch removal IF it's true you have to normally remove the dust cover. Is that the case, or can the job be done merely removing pan and pump?
Thanks, Patricia/'75 w/aftermarket crate 383

It's certainly a LOT easier to do with the engine out of the car, especially if it's on a stand. Sounds like the car was run pretty hard, might not be a bad idea to have an engine builder mike out the bearings and crank to make sure everything is allright. How many miles and what was the oil pressure like? Any grit or metal laying around the inside of the oil pan? How about crank end-play? any noticeable end play could be problems.

It's a new engine; it only has 5k miles on it. All those miles were with the 4-speed in it which we later found out (after continuous issues with popping out of gear) to have an out-of-round input shaft. I bought the tranny as a rebuilt unit to replace the sad original; he figures the tranny must have come out of a car that had a bang-up. The case showed no damage but that input was messed up.
Yes, there would be a little bit of metallic sludge on the magnetic drain plug on oil changes, but then perhaps some of that is from breaking in? Engine ran like a champ. I did play with it a bit, such as revving to 5k rpm and popping the clutch for some fun take-offs, plust some speed-shifting, but I didn't do it very much. Mostly it was around-town driving. It leaked like a sieve, but I found the oil pan bolts to be way too loose and the cork gasket was soaked. I changed it to a silicone 1 piece and I swapped out the valve cover gaskets, too. I just really want the thing to be dry so it doens't leak all over my new susp.

I would at least check for any crankshaft end play and see how the rear main looks while you have it apart. Might not hurt to look at the front main as well as it is farthest from the oil pump. You wouldn't think there could be very much wrong with a 5,000 mile engine, but a whole lot of things can happen.

Is it possible to describe in a few words how to check crankshaft endplay? And what do I look for with regard to bearing condition? I'm not familiar with the guts of a motor just yet. My main concern is that this engine lasts about 5 years for me, after which time I ought to have $ for something more interesting. So I'm not overly worried about really high mileage on this one.

Any play that you can actually see and feel while forcing the crank end for end is reject. Look for any unusual wear marks on the bearing and crank bearing surfaces whil you have the bearing caps off. Any wear marks would at least be an indication you will need to go farther and get an engine builder to measure things out. Those bearings should be barely broke in with only 5,000 miles.

|UPDATED|1/21/2004 4:37:25 AM (AZT)|/UPDATED|

Big Fish:

A little clarification here. What does ARP stand for and please define "yield" and the three step process for torqing the bolts...Thanks.

Mike

First, if you loosen all of the crank main bearing caps, just a few turns of the bolts, then pull on the crank away from the block, the top of the rear main pulls out very easily. A bit of motor oil on the new one and it slips back in easily. Of course you need to retorque all of the main bolts.

Three step. First run all of the bolts down, and make sure the caps are seated. Then tighten the bolts down to about 1/2 of the torque spec. Then step to about 3/4 of the torque spec. Now tighten to full torque spec. Retorque and double check. I know that's more than three, but it will assure everything is correct. I always do any torque in this manner.

Remember do each part in a pattern. Don't torque one cap or one bolt all the way then go on to the next. Do every bolt one step before doing any of the next ones. Then do all the next step on every bolt, etc. If you don't keep it even, you could create a failure even when the final torque is reached. Don't overtorque. Even if you loosen the bolts and retorque the bearing , or in some case gaskets, can be overcrushed and will never be correct.

Ken Styer