Engine: rear oil seal

[swvalcon]

Is there anything I should look out for or any special tricks to be sure the rear seal on a 289 doesn't leak oil?

[Jeffry Cassel]

Does it leak now? R&R is a fairly big job. It requires oil pan removal, removal of rear main cap, and loosening all main caps. then -maybe - if you are super lucky you can slide upper half of seal out. If you get that far, the rest is not too difficult; you just half to be very careful not to damage seal when sliding it back into place. Best way is find a good mechanic with a lift. Once again: if it ain't broke don't fix it!

[JoeHall]

Many threads here on how to glue the oil pan in place. It's also important to clean the seal journal, then scuff it with 320 belt paper. Loop the belt over the journal, pull back and forth, rotate the crank 1/3rd turn, then repeat. Careful to only scuff. Last 10 to 12 strokes are in direction against engine rotation.

[JoeHall]

After stuffing, clean with mineral spirits, dry, wipe with dry cloth. Light coat of oil on journal, seal lip and backside. For top half, push seal firmly against journal, then rotate into place.

[swvalcon]

Thanks Joe. Yes I plan the polish the crank with some fine emery cloth. and clean everything as good as possible. The block is ready to assemble as soon as the rods get back from the machine shop. Got them checking the size and roundness of the big end after I installed ARP rod bolts. I was just wondering if there was anywhere that needs a small drop of ATV sealer. On a small block chev it helps if you put a small drop right at the rear of the main cap in the corners. Plus there's several companies that make a offset rear main seal for them. Know of anyone that builds one for a Stude? It moves the seal just enough so it has a new spot on the crank to run.

[altair]

If you have the engine out, the front and rear should both be done at the same time. The rear seal has some small tabs that must be fit in to their respective positions as well as the two small cork tabs. When the cork seals are installed they are extra long and should sit on top of the cork gaskets. The oil pan should be then be tightened evenly front and rear. You will need some extra long bolts to start the pan as you bring it down then insert the regular bolts and continue tightening until snug do not over tighten. Be sure the pan is flat before assembly, if somebody has over tightened the pan the areas around the bolts may be convexed and will require to be flattened. Additional sealants shouldn't be required however that is optional. If all surfaces are flat, clean and torqued evenly it will not leak. I would suggest after a short time of running that the pan bolts be checked and re tightened slightly as needed. I would suggest with the front aluminum spacer that longer bolts be used in lieu of the supplied short ones. They only enter the aluminum spacer a short distance and tend to strip the threads out causing a loose fit and a sure leak at the front. There is considerable thread depth available for longer bolts. This is an inherent problem with front seals.

[swvalcon]

This is a complete rebuild. Bored .030 new pistons, bearings, rings, heads rebuilt, hot tanked all new frost plugs, cam bearings etc. Thinking of up grading to a r-1 cam as I got a 4 barrel intake from Jeff Rice at the national meet. I just want it to leak as little oil as possible.

[JoeHall]

Thanks Joe. Yes I plan the polish the crank with some fine emery cloth. and clean everything as good as possible. The block is ready to assemble as soon as the rods get back from the machine shop. Got them checking the size and roundness of the big end after I installed ARP rod bolts. I was just wondering if there was anywhere that needs a small drop of ATV sealer. On a small block chev it helps if you put a small drop right at the rear of the main cap in the corners. Plus there's several companies that make a offset rear main seal for them. Know of anyone that builds one for a Stude? It moves the seal just enough so it has a new spot on the crank to run.

I looked into an offset lip rear main seal for 259/289, including other seals that may fit and, by coincidence offset the lip. No such luck. The reason the GM folks came up with the offset lip is the same reason we need one: the seal lip tends to wear a groove in the crank journal. Recently, I had to replace the seal twice in the 62GT to get it to stop leaking. What I did the second time is exactly as I advised you.

As for other sealing concerns, insure the little square seal legs (for lack of better term) lay correctly in the grooves in the main cap. You can add a dab of your favorite sealant on them, and also on the seal ends. But be very careful not to get any sealant on the crank journal.