Upon further inspection, oil was leaking from the rear main seal, not just the pan gasket. Do I have to take off all the main caps, or can I just take off the 1 one rear cap, slide out and replace the old seal and retorque to spec? I just wasn't sure if it was bad to just undo 1 cap and not all the rest since it might be uneven or something?

Also, is there a preferred method to installing valve seals? I have the positive lock viton type, with the spring around the top. They are very tight going on....half of them leaked from the original build and now that I'm replacing them I wasn't sure if I possibly did it incorrectly the first time. I had to use a rubber mallet to get them on the first time....I'm guessing I roughed them up too much the first time.

 

Well, you don't have to remove the crank. The top half of the seal should slide right out of the block and then slide a new one in. Remember to slightly stager the seals parting surfaces so they don't line up with the main cap and block and put some RTV sealer on the cap and seal ends. When you replace valve guide seals you have use the clear plastic tube that should come with the seal kit. This tube is used to cover the valve stem o-ring and lock groves on the valve stem so they won't gouge the seal as you are sliding it over the stem. An effort should be made to try to center the seal on the guide if you don't have a seal instalation tool. If your seal kit didn't come with the plastic tube you might try a large plastic straw.

Auggie

 

If it's the original engine in the car in your sig, you don't have to pull off the rear cap at all.

Since 1986 all SBCs have a 1 pc rear main seal. It's easier to change than a 2 pc, but more work to get to.

With a 2 pc. rms, all you have to do is drop the pan, pull off the oil pump, pull off the rear cap, R&R the seal, and put it back together.

With a 1 pc. rms you have to remove the tranny, remove the flexplate/flywheel (and everything else that's associated with the transmission), remove 4 bolts and pull the rms seal housing off, R&R the seal, and put it back together.

Much easier once you get to it, but a PITA to get to.

 

Didn't notice the "87". Thanks for correcting that AJ.

Auggie

 

My bad for not clarifying.

This is a 70s truck block (350). 2 piece rear main.

The engine was swapped in place of the 305 last summer. Only 2000 miles on it, leaked oil everywhere.

I didn't know if it was okay to take off ONLY the main cap holding the rear main seal. Replace the seal, then retorque the main cap. Leaving the rest of the caps undisturbed.

I wasn't sure if having the one cap off the would stress the crank or something to that extent.

 

It's alot easier to get the seal out if the crank is free to move a bit. If it's not, it's real hard to get the new seal in without deforming it or tearing the back of it on the edge of the block. That would involve loosening all the main caps in addition to removing the rear one, although you wouldn't have to remove the crank.

 

So just loosen all the caps , replace the seal and retorque to spec? Probably the only thing that was done correctly was the bottom end assembly so it kinda sucks I have to disturb the main caps. I'm not replacing the bearings (though I might as well check them for wear).

Anything I'm missing or just loosen, replace, retorque and done. Last thing I want to do put it back together after I replace the seal and throw a bearing on startup.

 

Yup, that's about it.