My stock manifold leaks air

[rmorrell]

This post didn't get much attention in the general forum so I thought I'd try here. Here's the original post:

Hey guys, I've been troubleshooting a vacuum leak for quite some time now and finally decided to make a custom pressure block off for the intake tract. I pressurized the system to about 15 psi, sprayed soapy water around the engine and found leaks at the vacuum block, at a vacuum line, and at the intake manifold (the worst being the rear of the intake manifold on the drivers side). I just replaced the intake manifold gasket but it must be garbage. I used the felpro metal valley gasket.
Has anyone else had issues with a stock manifold? I'm wondering if the manifold needs some milling because of poor stock alignment...

Any opinions? I need to get this fixed! Tired of dealing with vacuum leak issues...

 

[earlbrown]

The only way to know if you're intake is out of line is to measure you're exact intake on your exact long block.


See if you can find a thicker blue fel-pro gasket and try again. If you're not running an EGR the early style without that hole is a few bucks cheaper.

 

[turboclam]

I wouldn't use the rubber seals either. Use RTV on the rails and around water ports.

 

[Nick Micale]

This is from a recent thread:

"Heads almost always need to have the intake port alignment and block clearance checked closely.

You also need to determine the proper intake gasket thickness for your build. I have used gaskets from 0.030" to 0.200" thick to obtain a proper intake fit.

The clearance at both ends of the block to intake must be measured to determine how you are going to seal those areas as well.

Sometimes the stock rubber end seals are too thick and will not allow the intake to mate tightly to the heads."

The stock rubber seals work well in many cases. I just used them recently on an intake that had RTV at both ends of the intake, but blew out in the rear as there was more clearance that at the front.

I have has issues with stock intake gaskets, aftermarket gaskets, rubber end seals, and combinations of all, BUT I also have been very successful with all of the above!

Different situations and conditions will require checking and measuring for fit and clearance to determine what and how to use.

A stock intake on stock heads should fit and work fine using a stock or Felpro gasket if they are properly installed.

If you have question that are not answered here, just give me a call.

 

[jemook]

Not just regular rtv, use The Right Stuff, it works great. Seals better and faster the plain rtv.
John

 

[SHADOWII]

TAperformance carries various thicknesses in their intake manifold gaskets, however, they are not the valley pan style.

 

[TurboBuRick]

Just throwing this out there. I had a situation where aftermarket bolts were being used and they were too long.
Should not be a problem with stock bolts but might as well cover all angles.

Rick

 

[rmorrell]

Thanks for all the replies! This is my 2nd or 3rd time replacing this gasket (not for this reason exactly)... Last time I used the rubber seals and had bad luck with them. The rear seal ended up leaking oil out a corner. This time I just put a thick line of GM engine sealant (gray in color, best stuff I have used so far, expensive but worth it imo) on front and back of the block and thick in the corners. My intention was to fix the oil leak, which it did. After it was together I tested for vacuum leak and here I am.

Some other notes:
I did just recently make an EGR delete plate I put underneath the unit.
I am using the stock intake bolts and have torqued them to spec.

I will keep you updated on the process, hopefully I can get most of it figured out in the next couple weeks after I take some spacing measurements.

 

[NorCalTurbos]

Right now I have leaks all around my intake I'm just curious to see how yours worked out and what gaskets and sealant did you use?