I can’t get my vortec 350 intake to seal (water leak)

[eric_ss]

I’m gettin super frustrated. 1998 Tahoe 2 door with 195k miles. I had a small leak from the front of the lower manifold so I took it all apart, bought the fel-Pro 98000 gasket set, and went about tearing everything apart. When I put it back together I had a pretty significant leak from the rear of the passenger side head. Frustrated I tore it apart again, bought another Fel-Pro 98000 gasket set and a new set of Fel-Pro bolts, cleaned it up real well again, and put it back together.

Prior to putting it back together the second time I noticed that the wire bracket bolted to the back of the passenger head kept the Fel-Pro gasket from sitting completely flat prior to being torqued down so I figured maybe that was it. I ground it down a little so that the gasket wouldn’t touch it and I put it back together. Started it up and I have same leak!

I did notice some minor pitting on the head and lower intake but I didn’t think it would be enough to cause a leak. I’ve attached a few photos. One shows how the gasket extends slightly beyond the head prior to being torqued down and comes in contact with the bracket. The other shows how it looks after I ground a little slit in the bracket at head level and reassembled the engine. There is some space now between the gasket and bracket.

Any ideas???

 

[eric_ss]

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[east302]

Do you have the RTV on the head side of the gasket lower tab before putting it on?

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And does the China wall RTV extend onto the tabs of the gaskets?

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Torqued to spec?

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In your photo, is the gasket tab really hanging off past the China wall? It’s hard to tell by the photo angle, but the gasket locator pins should line everything up.

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[eric_ss]

Do you have the RTV on the head side of the gasket lower tab before putting it on?

You must be registered for see images attach

And does the China wall RTV extend onto the tabs of the gaskets?

You must be registered for see images attach

Torqued to spec?

You must be registered for see images attach

In your photo, is the gasket tab really hanging off past the China wall? It’s hard to tell by the photo angle, but the gasket locator pins should line everything up.

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Hello. All good questions.

1) I did RTV the corners prior to putting the gaskets on and did run a bead across the top of the valley like in your photos. Permatex Black is my go to.

2) I did torque to spec using my 1/4 drive torque wrench in the correct sequence.

3) the photo is exaggerated when it comes to where the bottom of the gasket is located. It is lined up with the China wall when flat. It is not flat against the head in the photo to show how the back of the gasket hangs past the head a little and hits the bracket. You can see in the other photo how the back of the gasket hangs slightly over the end of the head where I had to cut a slot in that bracket.

 

[east302]

Did the RTV cure before starting the engine?




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[eric_ss]

Did the RTV cure before starting the engine?




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I started it a few hours after installing everything for a few minutes to time it (to adjust the cmp timing to +/- 2°) Then I waited probably 18 hours before allowing it to heat up quite a bit. I’ve never had a problem in the past with starting small blocks not too long after sealing an intake, but this is my first Vortec that i’ve worked on. Does the RTV need to cure for a while on these Vortec engines due to the 4 bolts vs 6 on older small blocks?

 

[east302]

I don’t know if it *has* to sit for so many hours per the RTV label or not. I don’t remember how long I waited the first time I did one, but think it was probably a day or two after when I did the one on my Tahoe.








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[eric_ss]

East302: now that I look closer at your diagrams I definetly didn’t extend the China wall RTV 13mm up the gasket. Probably 5mm or so. I wonder if that’s the issue.

EDIT: i’m Going to try it one more time and extend the RTV up higher and i’m Also going to put a very thin layer around the head water jackets with my finger. Hopefully that will seaL them better

 

[east302]

Can you tell where it is leaking - through the top and running down by the valve cover to the back or is it leaking at the intake/block seam?

If it’s at the seam, then maybe the length of RTV has some validity. If you’re opening it up for a third time (wow, I’d be so pissed) then I’d definitely make sure it is to that length.

While it’s out, you might as well take a straightedge to the manifold and heads to see how it looks. A new GM/Delco manifold is around $400, but it sure makes installation easy when working with a clean part.




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[eric_ss]

Can you tell where it is leaking - through the top and running down by the valve cover to the back or is it leaking at the intake/block seam?

If it’s at the seam, then maybe the length of RTV has some validity. If you’re opening it up for a third time (wow, I’d be so pissed) then I’d definitely make sure it is to that length.

While it’s out, you might as well take a straightedge to the manifold and heads to see how it looks. A new GM/Delco manifold is around $400, but it sure makes installation easy when working with a clean part.




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My plan later tonight is to put my phone back there and take a short video to see where it is leaking from exactly. I’ll let you know what I find. I wish fel-proJUST sold the intake gaskets instead of the whole set. I have a bunch of extra gaskets now And they aren’t cheap. Thanks