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/rubber-sheets-and-strips/rubber/raw-materials/ecatalog/N-c1z#http://www.grainger.com/Grainger/rubber-sheets-and-strips/rubber/raw-materials/ecatalog/N-c1zZ1z132gp?Ndr=basedimid10071&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]

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]

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?

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 [?] :mrgreen: ) 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?

[Polo-1]

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..

Sounds like you need to use Flatout Gaskets copper set. I needed them for siamesed plenum.

https://www.flatoutgroup.com/factstips.aspx

[scottfab]

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

1/8 in

[gbmidyear66]

I've been looking at the Grainger site Scott, Thanks. Planning for the likelihood that I'm not successful with my third set of paper gaskets....
The specs on the product below (maybe not the color...) looks like a good choice to me (temp, hardness, etc) - any opinion on that?

Thanks

Glenn

Rubber, Silicone, 1/8 In Thick, 2 x 36 In




Rubber Strip, Extreme Temperature, Commercial Grade, Silicone Rubber, Thickness 1/8 In, Width 2 In, Length 36 In, Red, Smooth Finish, Plain Backing Type, Min Temp Rating -60 Deg F, Max Temp 400 F, Durometer 60A, Elongation 200%, Tensile Strength 500 PSI, Standards ASTM D2000 GE


Grainger Item #1MWT6 Price (ea.)$10.45

[scottfab]

I've been looking at the Grainger site Scott, Thanks. Planning for the likelihood that I'm not successful with my third set of paper gaskets....
The specs on the product below (maybe not the color...) looks like a good choice to me (temp, hardness, etc) - any opinion on that?

Thanks

Glenn

Rubber, Silicone, 1/8 In Thick, 2 x 36 In




Rubber Strip, Extreme Temperature, Commercial Grade, Silicone Rubber, Thickness 1/8 In, Width 2 In, Length 36 In, Red, Smooth Finish, Plain Backing Type, Min Temp Rating -60 Deg F, Max Temp 400 F, Durometer 60A, Elongation 200%, Tensile Strength 500 PSI, Standards ASTM D2000 GE



Grainger Item #1MWT6 Price (ea.)$10.45



The specs are certainly impressive. Better specs in all categories
than what I used. You could almost use one 2x36in sheet
and cut it in two. (36/2)
But I think you need 17in ea. And I'm not entirely sure 2in is wide
enough. I do have a spare set I could go measure later on. The
plenum looks to be 2in wide. I just don't remember if I cut mine a bit
wider.

The temp specs on the rubber I used were not as high as what you're
looking at so you should be good to go. The temp at the plenum is
not as high as the engine.
That is probably why mine are holding up. When using rubber there
is no nasty glue or adhesive from the gasket to clean off either if
you need to get under the plenum later on for something. Just don't
over tighten them. No need to tighten until you get metal on metal.
I used 2lb less than OEM spec for torque.

You could use the new gaskets to lay over the rubber and trace out
the pattern to save time later on. I had to use the plenum itself to
make a pattern that I then put over the rubber to cut. The first one
I cut I used an exacto blade. The second I used a small pair of
curved scissors. The results were the same both ways.
Here is a pic of the template I cut:
http://zr1.net/forum/picture.php?albumid=199&pictureid=2340

[XfireZ51]

I did the same when I would make gasket for my Xfire manifold. In fact I still have a "rubberized" gasket material from NAPA. Used hole punch for the bolt holes.
However, you may want to use Jerry's gaskets on plenum w Pliobond as the fixative. Haven't had an issue w gasket being sucked in.

[chriskinzel]

Thanks for the info Scott.

[gbmidyear66]

My intake seriously sucks, you can see what it did to the gasket. Just the one spot where I developed a leak. When I used std thickness gaskets in the past - had a much worse problem - with leaks on both sides.

I have been using contact cement to attach the gaskets to the plenum. I've cleaned and lightly sanded both mating surfaces and will attach dry this time, and will re-torque after a few temp cycles.

If this doesn't work - I'll experiment with the rubber gaskets.

The mating surfaces seem to have good planarity - don't think that is the problem

[A26B]

Couple of questions please.

1. Is the photo of the gasket as it is attached to the plenum, or did it come loose & was just laid back over, roughly where it is shown?

2. What brand and product did you use to attach the gasket?

3. You mentioned the mating surfaces "seem" to have good planarity.
A. Were you able to actually use a precision straight edge that would cover the entire surface, end to end?
B. Was the plenum AND injector housing checked for flatness, end to end, across the entire surface? Results? usually checked w/feeler gauge and locations mapped.)

Difficult to tell for certain from the photo resolution, but it looks like the gasket has good compression from L to R in the photo, and on the R end bolt hole. However, I do not see the same indications of gasket compression on the #1 cylinder ports. This is usually an indicator of mating surface irregularity.

The gasket also appears to have been affected chemically, by the buckling and distortion around the #1 cylinder ports.

If the gasket is laying in the same position as before the plenum was removed, then the outboard being "sucked in" by vacuum doesn't correlate to the position of the gasket on the inboard side.

Going to a thicker material with greater compressibility is treating the symptom, not the cause. Looking at the port work done to your plenum & injector housings, there is sufficient gasket surface present to retain the gasket, if the surfaces are flat and the gasket is properly installed.

If all you have to check flatness is a long steel ruler, check the flatness using both edges of the ruler to find out if the ruler is straight.

I would really like to resolve your problem. It's not the gasket and it's not your porting being too large, as I can tell from the photo. Something else is in play.

[scottfab]

My intake seriously sucks, you can see what it did to the gasket. Just the one spot where I developed a leak. When I used std thickness gaskets in the past - had a much worse problem - with leaks on both sides.

....snip...

The mating surfaces seem to have good planarity - don't think that is the problem


Something is wrong (obviously). Have you heard any backfires?
or does your fluid level go down at all?
Like Jerry says, using a feeler gauge or some such method to
be sure it's getting down flat would be in order.
What if you use no gasket as a test? Tighten to spec and see
if you can run a 0.001 flat gauge anywhere through the intakes
at #1.
The only other thing I can think of is uneven metal expansion
but can't think of any way this is possible unless a water passage is
partially blocked. This is truly a new one on me.

[LGAFF]

He did mention the Plenum was loose, I am wondering if after putting the contact cement on, during the shifting as you adjusted the plenum, the gasket could have grabbed stretched or torn...then as the bolts loosened it lead to a failure.

I agree a check with a feeler gauge is a good idea, however the engine ran for 4K miles with no issues.....dump the contact cement and torque it and then recheck it....

[gbmidyear66]

Thanks for the questions and suggestion Jerry, Lee.

OK - The last 2 times I attached the gaskets to the Plenum using contact cement - maybe that was not such a good idea.

The plenum seems to have good planarity (see pic), I can't get a sheet of paper under the level. The IH are not quite as planar, I can get a sheet of paper under - but just (see pic).

Something I did notice is that my plenum overhangs my IH on BOTH sides by about 1/32 - so I loose a little bit of gasket mating surface. I guess the IH has some play when it is attached - I didn't pay attention to this when I re-installed them after porting.

Ran the car up to temp (it now idles nicely again at about 700) - let it cool and re-torqued. I'll re-check torque after I put some miles on.

Hope this is the end of my aggravation with this....

Glenn

[gbmidyear66]

Jerry, read your questions more carefully. Your observation that the inboard gasket material is pushed out is interesting. I was focused on the vacuum leak - the outboard area pulled in - which I assumed was caused by vacuum. But that would not explain why the inboard is pushed out.

The gasket was bound in place as you see it - took an hour to scrape it off the plenum last night - but obviously I never mounted it like that.

Somehow it seems to have become distorted - I tightened the plenum down from the center working out towards the ends. I can only think that the gasket may have been slightly misaligned relative to the bolt holes and under stress - and what we see is the result?

By NOT attaching the gasket this time - it pretty much had to go on without any stress in the X-Y plane - hope this does it.

[XfireZ51]

Did u follow the torquing sequence outlined in the FSM?

[gbmidyear66]

Yup, per FSM - sequence and Torque. I believe Marc H uses a different sequence - but I used FSM sequence. #4 and #6 Torque may be a bit off because my socket wont fit between the runners - so I use an Allen key and do those by feel.