3.0L engine swap

[Farrar]

Well, the Dodge Monaco O-rings are a perfect fit (of course) but I still have a vacuum leak at cylinder #4.

Although the package says "Not for use with gasoline," I decided to use some leftover RTV to bolster the O-rings and bolted everything back down tonight. It didn't look like much when I squeezed it in, but when I tightened the manifold down it squished out and looks rather horrible. I'll leave it to cure overnight and see what the morning brings.

I just can't imagine why the O-rings that were installed were problem-free for hundreds of miles, and then when the car sat for three weeks they had somehow shrank. I don't get it.

[Drive Stainless]

Well, the Dodge Monaco O-rings are a perfect fit (of course) but I still have a vacuum leak at cylinder #4.

Although the package says "Not for use with gasoline," I decided to use some leftover RTV to bolster the O-rings and bolted everything back down tonight. It didn't look like much when I squeezed it in, but when I tightened the manifold down it squished out and looks rather horrible. I'll leave it to cure overnight and see what the morning brings.

I just can't imagine why the O-rings that were installed were problem-free for hundreds of miles, and then when the car sat for three weeks they had somehow shrank. I don't get it.

I would pull the intake off and remove the RTV ASAP. You don't need it, and it could make removal very difficult next time.

[Farrar]

I would pull the intake off and remove the RTV ASAP. You don't need it, and it could make removal very difficult next time.

What would you use instead?

[dn010]

When I had my original PRV I used a thin coat of Indian head shellac on the orings.

[Farrar]

When I had my original PRV I used a thin coat of Indian head shellac on the orings.

Oh, man! That stuff is even harder to remove than RTV! LOL Good thinking, though. I had forgotten about that stuff. Thanks!

[Drive Stainless]

What would you use instead?

I assume you want to use the RTV because you're unsure where the vacuum leak is located. I would determine if the new o-rings resolve it first on their own.

EDIT: You don't know whether the leak is at the o-ring or the adapter plate on #4, correct?

[Farrar]

I would determine if the new o-rings resolve it first on their own.

They do not.

Hence "they fit but I still have a vacuum leak" in the earlier post.

[Drive Stainless]

They do not.

Hence "they fit but I still have a vacuum leak" in the earlier post.

Is the leak definitely at the o-ring or is it at the adapter plate gasket?

[Farrar]

Is the leak definitely at the o-ring or is it at the adapter plate gasket?

I don't know. The adapter plates are glued on with anaerobic sealant. When I removed the old O-rings, the cylinder #4 O-ring had about 1/4" right at the top of the mating surface which was dirty, so obviously air had been sucking in there. (And so had brake cleaner, since I used that to troubleshoot with the engine running.)

So I have been working on the assumption that the O-rings are the problem, but there could be a problem elsewhere, too.

During troubleshooting I blocked off the vacuum ports except for spark advance and none made a difference in engine performance, so at least I know vaguely the location of the leak.

[Drive Stainless]

I don't know. The adapter plates are glued on with anaerobic sealant. When I removed the old O-rings, the cylinder #4 O-ring had about 1/4" right at the top of the mating surface which was dirty, so obviously air had been sucking in there. (And so had brake cleaner, since I used that to troubleshoot with the engine running.)

So I have been working on the assumption that the O-rings are the problem, but there could be a problem elsewhere, too.

During troubleshooting I blocked off the vacuum ports except for spark advance and none made a difference in engine performance, so at least I know vaguely the location of the leak.

Bill has another type of o-ring that he uses that may help seal the leak without resorting to RTV, etc.