[1971455HO]

I built my engine this last time using the highly acclaimed, by many, BOP neoprene seal. Many years earlier I used the factory type standard rope seal, The old rope seal showed up leaking a little a few months later but nothing ever really too bad. This neoprene seal is not what I had hoped for. I followed BOP's directions to the letter.. No leaks for the first few months. But not now. It's not profuse but it's way worse than I can stand.

Anybody else?

Hopefully the Comp Cam oil additive isn't the cause.

[tom s]

2 pc or the new 1 pc?Im 50-50 with the 2pc and 100 % with the new 1 pc.Tom

[Bill Meyer]

I have installed over 50 BOP 2 piece Viton seals with 0 leakers. Make sure it's not the pan seal around the rear main. If you use the rubber finned one it may find it's way out. I only use the cork one, and glue it in place a day before I seal the pan. This seems to work the best. Just my opinion- Bill

[Goatracer1]

My rebuilt 421 started blowing huge amounts of oil from the rear main seal. I pulled the pan and found 3/4 of an inch of the new rope seal missing. I replaced it with the Viton seal and it has been leak free for 5 years.

[lust4speed]

Make sure that the oil isn't coming from the valley pan or valve covers. They have a nasty habit of leaking and running down the back of the engine. The BOP Viton seal should either leak at the start from a bad install, or should be good for many thousands of miles.

[grivera]

Large or small journal block?

[1971455HO]

My car has 3.25" mains. i installed the two piece Viton back in 2007. It sat for 4 years while i waited for my car to get done. No leaks for a while. Well guys, you've woke me up. I just may have been an ass by being too quick to blame BOP's rear seal. I had a friend who runs a transmission shop install new bearings & races in my differential. It had a high pitched whine that was killing me. They were the 45 year old originals. While he had it he mentioned to me that I had a pretty good oil leak going on at the rear of the engine. Honestly I have not really double checked to verify if it was the seal. I'm going out now and put it on the lift to be sure. I would smile if it's just a pan leak. Thanks for the responses.

Eddie

[leeklm]

Just another thought... Does your crank have the raised "etching" on the rear sealing surface? If that etching is too pronounced, it may not be very friendly with a lip style seal. My new eagle crank had more of a raised etching pattern than what i liked, so brought it to the crank shop. The sealing surface diameter already had a measurement considered minimal by BOP, so they ground it, built the surface back up with a weld, then ground/polished it back to a perfectly smooth and round surface. Cost about $125, but worth it if I prevent a leak!

[intense]

Mine leaked too and I followed the directions ..Got pissed and took it out .I ordered the rope style from best, and it hasn't leaked a drop.. here is what I bought ..

http://www.ebay.com/itm/Pontiac-400-...6c7c64&vxp=mtr

[1971455HO]

Originally Posted by leeklm

Just another thought... Does your crank have the raised "etching" on the rear sealing surface? If that etching is too pronounced, it may not be very friendly with a lip style seal. My new eagle crank had more of a raised etching pattern than what i liked, so brought it to the crank shop. The sealing surface diameter already had a measurement considered minimal by BOP, so they ground it, built the surface back up with a weld, then ground/polished it back to a perfectly smooth and round surface. Cost about $125, but worth it if I prevent a leak!

Yes, my crank also has the angled sweeps centered on the main seal area. What you described, were my thoughts exactly. I had reservations about using the very narrow viton seal because of that, thinking, how can this work with this sealing surface. I just figured that BOP knew what they were talking about, I'm the amateur, they're the pro's, so I installed it. It's not a bad leak, but any leak is bad now that my car is restored. Don't want the bottom of the car messed up with oil spray.

In BOP's defense, I still have not had time to fully investigate if it truly is the rear main seal or....the rear pan gasket. I hope it's the pan. Thanks to all for your input.

[mrennie]

Another possibility that isn't really the seals fault is that it could be the seal groove not being concentric to the bearing bore. 455's are known to have problems in this regard, and a rope seal works OK where a 2 piece neoprene may not. I tried the 2 piece neoprene and it leaked badly, and then switched to the graphite rope and it was OK. My seal groove was NOT concentric to the bore, so the issue in my case was the factory machining, not the seal.

[Vengeance Race Engines]

When I first started using them years ago, I wondered whether the little grooves would matter with this type of seal. So we usually polish this area as to eliminate high spots to prevent "cutting" into the seal. To this date I haven't had any leak. Unfortunately, no matter how perfect you think you installed it, you don't know how long it will seal for.

With that said, I DO have a customer who claims it is pouring from the seal since he started it in the car. The weird part is this engine was on the dyno with a good amount of pulls on it and didn't leak a drop. Customer was there and witnessed it come off the dyno, and actually ran his fingers on the back to see if it was leaking because the last builder used a BOP and it leaked so he was "double checking it" this time around. Not one trail of oil. Yet it leaks in the car from day one and doesn't tell me until many months later? I don't see it being the seal but I won't know until it is in front of me. I am leaning towards the pan gasket..

On a side note, I have been using the TIP rear seal as of late, mainly just because I wanted to try it. No issues either. I have not tried the BOP 1 pc yet. Moral is, while taking all the precautions you can when installing it, you just don't know what can happen. I am certainly not bashing or saying anything negative about BOP's stuff..we still use them.

[1971455HO]

Thanks for info guys. I'll be looking deeper into it next weekend.