Replacing the gasket between the upper and lower intake manifold

[Turbosix]

I think my gasket has a leak. Is this repair relatively straightforward? Is there anything special to look out for in doing this repair? Any suggestions are appreciated.

 

[salvageV6]

I would suggest a Jay Jackson modified upper plenum and throttle body along with a Race Jace power plate while you are in there.

Don't strip the bolts and make sure the gasket is pre stuck to the upper plenum with a skim coat of gasket sealer or gasket RTV, let it dry before putting it back on. All the holes will line up much easier in MHO.

 

[Turbosix]

One thing I was worried about is messing up the TPS setting when taking off the upper manifold, since I don't have a scantool. (Yeah, I know I should have one). Can the repair be done without messing this up?

 

[WarpSpeed]

Probably no, it won't change it,, BUT, I'd check it anyway. You don't need a scan tool, just a digital, or, any, voltmeter. Simply probe the middle wire on the connector(a small nail in the connector works for me.) Look for .43 - .45v volts, idle, car running, or , .41- .43v key on engine off.

 

[strikeeagle]

Why do you think the gasket is leaking? The reason I ask is because if it isn't, it would be best not to disturb it.

Most guys spray O2 sensor compatible throttle body cleaner around the gasket and observe whether the idle changes up or down. For that matter, check all the gaskets and vacuum lines in the neighborhood. DO NOT USE STARTING FLUID for this purpose - highly flammable.

The biggest concern I can think of is the potential for stripping things. Be very careful to use a little engine oil on the fasteners, then to start them back in slowly and correctly. Finally, do not overtighten them or the aluminum they thread into will give it up.

You have to remove the HARNESS, PCV Boost Gauge Vac (the 2, black painted, metal hard lines) from the stud on the passenger side rear of the upper intake to do the work. This harness is nutted to the stud on the top. DO NOT TWIST and tear up the harness. This is best accomplished by using a very thin 13 MM open end wrench on the stud below the tab on the harness, and applying a little heat to the nut above via a well placed bernz-o-matic torch, then removing the nut with a socket or box/open end wrench. When you put it back on use a little anti-seize, and don't tighten it much - after all, it's only securing the harness.

You should have a new GASKET, Harness Vac handy to replace the one you'll be disturbing on top of the upper intake. Do not overtighten the 2 screws that secure this or you'll crack the HARNESS, Egr/Purge/Fuel/Vac (aka the little, black, plastic vacuum manifold atop the upper intake).

So you see, you have more to think about than IAC and TPS...

 

[RCchuck]

Does any one know the GM part# for the plenum gaskets?

 

[strikeeagle]

P/N 18:

http://www.gnttype.org/numbers/partsdiagram.html

 

[RCchuck]

Thanks strikeeagle