Thread: Upper Intake Manifold and Lower Intake Manifold Replacement/Overhaul, due to leaks

I am looking to swap my defective (leaking/warped) L36 upper IM for a better one. Is there a benefit in going to an L26 upper, and/or is it more costly, than just doing the $130 Dorman? Less costly? Does it require more work/parts?

Please help if you can. I've been trying to figure out the best route to take, and the car is down, and need it back up ASAP.

I'm also thinking of doing the Lower IM Gaskets at the same time, and possible the HV3 (High Velocity Intake Inserts, supposedly 20-30hp for $200, ZZPerformance).

Thank you in advance. (FYI, if you didn't figure it out, I have a '99 3.8 GT)

Edit: I can get an L26 upper IM for $50 at the junk yard. Base on that, please.

Next, I read about the Lower IM Gaskets:

Originally Posted by BillBoost37

I'm going to rebutt the quackers and agree with you. The UIM doesn't magically go bad on the L36, but what happens is when you remove the TB, there's a tube coming up in a hole in the manifold. Taht's the EGR tube. It heats that area in the UIM and over many heat cycles it'll crack the UIM. Well there's a coolant jacket on the other side of that plastic and it'll leak into the LIM and fill it. In the meantime, you'll burn some coolant. Well...when that crack lets go and coolant pours into the motor, you'll hydrolock.

It's a good idea to change the UIM when you do the LIM. It's also a good idea to block the coolant passages going into the UIM for the future. That way this can never happen again. See the How to on modding a LIM.

Where is this "How to on modding a LIM?" I'd like to block the coolant passages going into the Upper IM.

Lastly, I noticed all the .php videos are gone, what happened to them, can they be restored? I need these:
http://www.grandprixforums.net/intake_gasket.php
http://www.grandprixforums.net/lim_lifter_video.php

I did some searching and came up with the following:

Originally Posted by UR LOSN

Originally Posted by oldsman105

Hi.. I am researching a turbo kit for my car and have read about people using the L26/l36 Intake manifold compared to the blocked off M90 case. What are the benefits to this setup compared to the M90 casing?

Mot of the GTers use the stock L36 UIM....but..the L26 UIM wont shatter under HIGH boost.......

the L26 is a better option....and with a little modification will fit onto the LIM of a L36.

the blocked off SC housing is what most SC cars do...as it is little to no modification.

if you were to add the LIM from a L36/L26....onto your L67/L32....you would have extra injector ports...as the L67 fuel injectors spray through the heads.....

you would either have to block these ports off....or it would be a good time to add a direct port nitrous kit ontop of it..lol depending on how big you want to go.

Now, I'm just wondering what the "little modification" is. A stronger Manifold is better than an updated Dorman manifold incase I ever decide to go with a turbo kit down the road (likely not). I can get the L26 upper for $50 at a junk yard, and the updated Dorman upper L36 is about $75 more than the just the Upper IM gaskets. Looks like the L26 Upper would be cheaper AND better, just takes more time for me to get it.

Thank you for your reply, and for the video. you wouldn't happen to know what the "little modification" is to get the L26 upper work with the L36 lower would you? Are the throttle bodies, between the two manifolds, interchangeable?