Ported Intake Gasket Woes

[gbmidyear66]

I have a recurring problem with gasket sealing after porting my plenum (so thinner gasket and less meat for them to hold onto) . I'm on my second set of gaskets after porting, and just ordered my third set tonight from Jerry.

My first (std thickness) failed after a month - the vacuum literally pulled the material towards the intake hole. My second set (50% thicker) have lasted about 4K miles. Tonight I notice my idle is up to 1,000 RPM, whistle coming from under the hood. Sprayed some water and found the leak at #1 cylinder.

I normally just use contact cement to attach the gasket - can someone recommend a better solution?

Thanks

Glenn

Glad I did the coolant bypass - at least the plenum removal is easier now....

[LGAFF]

Glenn is this the plenum to IH or the IH to head? I assume its the plenum to IH......I would just use the bare gasket, I never use a contact cement, etc

Did the gasket fail in the same spot both times? Were the bolts tight?

[scottfab]

You might try cutting your own set out or rubber. I did it.
It was amazingly easy.

You can cut them slightly larger at the outside edge.
As the rubber squishes down in thickness it does two things.
It gets smaller at the metal to metal contact area but retains
it's resilience and wants to expand back to it's original size.
This action keeps it tight.
AND it stays original size at the outside edge (where you left it
larger) such that it resists being pulled into the plenum whereby
a leak might happen.
Another advantage is that they can be used over and over and over.
The rubber resists sticking to the metal.

Here is a sight that sells flat rubber but I see Amazon now sells it too.

http://www.grainger.com/Grainger/rub...071&sst=subset

[Paul Workman]

I agree w/ Lee. Dom and I both had issues with thicker gaskets; Dom experienced it a couple times, similar to what you're experiencing now, I believe.

Jerry recommends his gaskets, which are thin(er) than those that failed. I do use a thin coating of sealant around the coolant port (IH/head gasket), but nowhere else, on either the plenum or the IH gaskets. Excellent results: no leaks in 3 years.

Forgot to mention de-greasing the metal surfaces first.

[A26B]

Originally Posted by gbmidyear66

I have a recurring problem with gasket sealing after porting my plenum (so thinner gasket and less meat for them to hold onto) . I'm on my second set of gaskets after porting, and just ordered my third set tonight from Jerry.

My first (std thickness) failed after a month - the vacuum literally pulled the material towards the intake hole. My second set (50% thicker) have lasted about 4K miles. Tonight I notice my idle is up to 1,000 RPM, whistle coming from under the hood. Sprayed some water and found the leak at #1 cylinder.

I normally just use contact cement to attach the gasket - can someone recommend a better solution?

Thanks


Glenn

Glad I did the coolant bypass - at least the plenum removal is easier now....

Glenn,
I would suggest you inspect both surfaces to insure they are completely flat AND that there is no damage to the surfaces.

I do recommend installing gaskets dry, but the mating surfaces must be degreased with brake cleaner or carb/choke cleaner to remove all residue.

The gaskets have a nitrile rubber bonding agent and grip very well, as long as the mating surfaces are clean & dry.

[gbmidyear66]

Thanks for the advice guys (my issue is the Plenum to I/H). I am going to...

1) Re-torque all the bolts. Assuming that does not solve....

2) Install new set of gaskets bare after checking fit of Plenum and I/H and degreasing. If that does not solve...

3 Make up a set of Rubber gaskets - thanks for the info Scott

[gbmidyear66]

Glad I ordered a set of gaskets....

As I suspected, the Plenum gasket has been sucked into the runner, leaving a gap between the IH and Plenum. You can see in the photo...

I re-torqued all the bolts tonight and found they had loosened up since I installed the plenum. I am guessing that the gasket compresses with time and heat cycling, and that if I had re-torqued a month or so later - it would be fine. Since I didn't, I guess it became loose and managed to suck itself inwards over time.

If this happens a third time - I think I will give up on gaskets and go with Scotts rubber gaskets.

[scottfab]

Originally Posted by gbmidyear66

Glad I ordered a set of gaskets....

As I suspected, the Plenum gasket has been sucked into the runner, leaving a gap between the IH and Plenum. You can see in the photo...

What a horrible thought to have a piece of solid brittle gasket be sucked in and break loose. What would a valve do with such a piece?

Originally Posted by gbmidyear66

I re-torqued all the bolts tonight and found they had loosened up since I installed the plenum. I am guessing that the gasket compresses with time and heat cycling, and that if I had re-torqued a month or so later - it would be fine. Since I didn't, I guess it became loose and managed to suck itself inwards over time.

If this happens a third time - I think I will give up on gaskets and go with Scotts rubber gaskets.

A solid rubber gasket on the plenum stays flexible and puts pressure
on both surfaces, hot or cold. I just checked my bolts, nice and tight.
A rubber gasket on the plenum works well because the temp there does not get so frigging hot.
Other locations would not fare so well.

[Schrade]

Go to your local roofing contractor's (Acme Roofers [?] ) for leftover EPDM.

(although no one said what guage is best???)

[chriskinzel]

Scott, What is the thickness of the rubber you use for those gaskets?