BOP 455 Rear seal Install- Step by Step by Jim Weise

By diyauto
( 2 )

6 minute read

BOP 455 Rear seal Install- Step by Step 

Compliments of Jim Weise @


I have had a few folks ask for this, and don't mind sharing.

Once again, as I mention in every "how to" I post.. this is how I do it.. and it's been proven by dozens of installs. Someone else may have other ideas, and that's fine, I don't mind..

Step by Step:

1. Insure you have purchased the BOP RMS 02 rear seal.

2. Open the package, and discard the instructions, unless your building a Pontiac.

3. Fit the seal.. I have found the best way to do this is to use an old rear main cap from another engine, or if your careful, you can fit both halves, using the cap that goes to the engine your working on. Our parting line is right in the center of the mains on this engine, so you just use the cap to fit both.- Line one side up so it's flush with your cap, and then grind the other side so it's out about .005 to .010.. or just above the surface. I will confess that I have done this so many times, I just do it by eyeball now.. One side flush, and one side sticking up "just a little bit" is what we are after here. Do this to both halves, grind only one side of each seal.

I use a small right angle variable speed die grinder with a 2" rolock "green corps" 40 grit disc to grind the seal very carefully. Keep the ends square and straight. you can use a bench grinder, disc grinder, file board.. whatever.. Main thing is to keep it straight and square.

Now let's check our fit..

Install the rear seal so the parting line does not line up with flush with the cap.. like this:

Offset the seal half in the block so it will work with the seal as you have it installed in the cap. Now install the cap, and tighten the bolts.

Here is what we see..

What we want to observe is the seal halves coming together, with no bulging.. like this

On this seal, I actually left it a little big, to illustrate what you don't want to see.. look at the bulge here, where the halves come together..

Once you have verified that you have a good dry fit, it's time to install the sealer.

4. Use Permatex "the right stuff" in either the cheese-wiz can, or the calking tube. You want a small tip for this, so don't go hogging to much off the end of the tip. put a very small bead of sealer in the block and cap seal groove. Do not put any sealer in the area where the seal ends will come together.

Now, you can see that someone was here before me, and dimpled the block with a punch.. don't do that! I am fairly sure that the dimple hurts more than it helps.. the seal is not going to spin with the sealer on it.. in fact, you will need a pliers to pull it out someday.

But if it's been dimpled like this one.. no biggy, the sealer will save the day for us.

5. Now take a Q-tip and take most of the sealer you put in, back out.. we are looking for a thin coating, about the thickness of a sheet of paper here. It should look like this:


Note my finger at the point where I stopped with the sealer.. this is where my seal halves will come together.

6. Now install the seal, lip pointing toward the inside of the engine. I have built many wet sump vacuum pump race motors, and never turn the seals around, and never had leaks. I limit my vacuum pumps to 11-12". Dry sump motors may be different, consult your pump manufacturer for their recommendation.

7. Now refit the main cap on the engine, and tighten the bolts.. inspect the seal to insure that no sealer is around the lip of the seal, remove any that may have squished up there, but if you followed these directions, there should be nothing.

In final assembly, lube the seal generously, and put a see thru film of the right stuff on the main cap, in the area around the seal.


I have used this method on rear seals on 455 Buicks since the 90's, when we used to cut the Caddy seals down. Then TA found the Ford seal that works (no trim) and I bet I installed at least 50 of those No trim TA seals.. never had one leak that I am aware of. I only ever had one rear main leak, that car also leaked with the BOP seal, it had a rare issue with the crank.

Good luck, and happy sealing..