About Us

Bungee · 09-10-2002, 05:02 PM

I remember reading somewhere that the OEM Pontiac rear main seals (also called the "rope" seal?) is problematic . . . I think the article said they were prone to leaks.

I just bought a Fel-Pro OEM gasket set for my 455. Should I be looking for a better rear main seal?

Thanks

Bungee · 09-11-2002, 04:39 PM

Aren't there 2 rope seals though? (front and rear?) And should I replace BOTH rope seals?

Thanks

[ September 11, 2002, 04:45 PM: Message edited by: Bungee ]

60man · 09-12-2002, 08:21 AM

Thanks OMT. I have heard pros & cons on this BOP seal. I guess I'll try one in this motor under construction.

Jim Zeek · 09-12-2002, 09:15 PM

You can also use a rear main seal from a early 70's 500 cu.in. Cadillac Eldorado. You can get them at any parts house. May need to be ordered and take a day to get it. Last one I got at NAPA cost only $13.99. Works great. You only need to put a small dab of sealer where the two ends come together.

Tim Corcoran · 09-13-2002, 02:44 PM

Jim Zeek,

I used the cadilac seal in my 455. It worked for a while but now leaks like a spagitti strainer. Next time I freshen it up I will be using the BOP seal. My 428 has the rope, and it leaks a bit also. From now on the BOP seal will be used in all my engines.

Tim C

Bungee · 09-10-2002, 05:02 PM

I remember reading somewhere that the OEM Pontiac rear main seals (also called the "rope" seal?) is problematic . . . I think the article said they were prone to leaks.

I just bought a Fel-Pro OEM gasket set for my 455. Should I be looking for a better rear main seal?

Thanks

Old Man Taylor · 09-11-2002, 04:45 PM

The BOP in BOP Engineering stands for Buick-Olds-Pontiac. The rope seal is only in the rear, not the front. One half of it is in the block and one half of it is in the rear main cap.

Wade Congdon · 09-12-2002, 09:24 AM

We have yet to see a seal failure caused by serrations with close to 3000 seals in service. I can count the number of failures on one hand and they have all been traced back to a few key items.

First you must fill the anti-rotation holes on the 3.25 inch seal in both the block and the cap. It is recommended but not mandatory to fill the holes on a 3 inch seal. This is because the 3.25 inch seal is narrower than the 3.00 inch seal and the AR holes are the same size.

Second do not use silicone on the backside of the seal. This can cause excessive lip engagement. The tolerances for lip engagement are designed in and adding silicone changes those tolerances. It’s like making the OD of the seal larger which forces the seal against the crank beyond the optimal sealing point causing friction and premature wear.

If your block has been align bored multiple times or if you are using aftermarket caps. Pay close attention when fitting the seal to make sure that the deflection of the lip from the crank is relatively even. We had one customer’s mains that were bored so far to one side that the lip was smashed on one side and not touching on the other.

It never hurts to check everything!

And finally, 3 inch seals are now in stock again

1965 Pontiac Parisienne · 02-04-2009, 04:46 PM

Hi, i have just bought the BOB Viton rear main seal. I have my engine on a engine hoist.. so i can move the engine . I have removed the rear main cap and loose all other 4 main caps so i can pull the crank a little bit, cleaned, inspect and fresh oiled. Easy to install the new BOB:
My question:
After removing the first old orginal seal (it was very difficult to do (see pic) i have a very little scratch from a tool in the half moon in the area where the BOB seal will be placed in the engine block.
Can i apply a little , a very thin!!, film of threebond sealer (BMW offers) around the outer of the BOB Viton seal? You wrote on your installation script not to seal the outer of the BOB seal, but if i do it a little little thin film bit can it be do something wrong??
Thanks, Bjoern

uforacing · 02-04-2009, 10:30 PM

I have a new BOP seal that I will see how it looks but I still have 3 of the old seals just in case. Never had one leak if it was put in correctly. I am glad that I bought some of those old gasket sets a few years ago at the swap meet.

1965 Pontiac Parisienne · 02-05-2009, 03:51 PM

Hi friends,
have done it today..here`s an actually pic of installation the rear main seal ..have done it like in the script from BOB`s ..have useed BMW Dreibond "threebond" sealer.. a little bit at the edges..i havn`t need to cut any material.. some pics...hope it will works
Cheers, Bjoern

Old Man Taylor · 09-13-2002, 01:32 AM

Rick Lightfoot - There is no question you can feel the reduction in drag with a new seal of each type and no pistons or rods attached to the crank. However, if you check the drag on an engine with a used rope seal you will find them to be about the same. My point was that it will not yield a measurable performance improvement.

Wade Congdon · 09-13-2002, 03:23 PM

There are 2 problems with the CAD seal.

The first is that the shape of the OD does not fit the Pontiac groove. Those who have used this seal "successfully" have reformed the seal groove with silicone or a hardening sealer of some sort by positioning the seal and allowing the retaining medium to harden being careful to line each half up. If this is not done properly the seal will leak.

The second is that the sealing surface is a single knife edged lip that is relatively hard. This means that lip engagement must be accurate and is dictated by the setup described in the first problem. Also this edge has only one line of defense, if oil gets past the lip it's going to seep out of the motor. The BOP seal uses a more pliable lip with multiple circumferential sub-lips (much like a door sweep) to stop oil from escaping.

Rick Lightfoot · 09-10-2002, 05:20 PM

You might say that the Pontiac rope seal is a leaker. I have never had a problem with the rope seals. The newer batch of rope seals provided with the engine gasket kits are of lower quality due to the absence of asbestos and are even more prone to leak.

BOP Engineering recently came out with a Viton Rear Main Seal for both main journal sizes. 3" Main Seal..........$34.99
3 1/4" Main Seal....$34.99... [img]smile.gif[/img]

Other alternatives before the BOP seals did not always work well. Some people used to take a neoprene 460 Ferd rear seal and use it on the 3" main engines, and the Caddy 472/500 rear seal for the 3.25" mains.

Bungee · 09-11-2002, 04:51 PM

Got it! I'm placing an order with them right now.

Thanks

73ta · 09-12-2002, 11:46 AM

Thank you Wade for the seals. I replaced a leaking rope seal with the motor in the car. Had difficulty filling the anti-rotation holes, used a syringe, but the seal works like a charm.

Rick Lightfoot · 09-13-2002, 06:11 AM

Quote:

Originally posted by Jim Zeek:
You can also use a rear main seal from a early 70's 500 cu.in. Cadillac Eldorado. You can get them at any parts house. May need to be ordered and take a day to get it. Last one I got at NAPA cost only $13.99. Works great. You only need to put a small dab of sealer where the two ends come together.

<font size="2" face="Verdana, Helvetica, sans-serif">Jim, I personally know of a few guys that have used the Caddy seal, and had nothing but problems with it because it is not an exact fit. With the new BOP seals out there that are relatively cheap for the BS that a leaky seal causes, why bother?

Taff · 09-13-2002, 05:42 PM

It sounds like a good seal,I'll use one next time I rebuild a Pontiac,just in case.

Will · 09-11-2002, 02:11 AM

Forget about using the seal that came with your Fel Pro kit and get one of the BOP seals. Installed correctly they don't leak.

Taff · 09-11-2002, 05:44 PM

I've never had a problem with the rope seals on any of the Pontiac engines I've built, or any of the Pontiac cars I've owned. Must have been lucky.

Menu

About Us