Ported Intake Gasket Woes

[Polo-1]

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..

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

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

[scottfab]

Originally Posted by chriskinzel

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]

Originally Posted by 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

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:

[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]

Originally Posted by 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.

....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....