: LT1 Intake Replacement

02-07-07, 12:39 PM
Anyone on here replaced the intake on their LT1 before? I did my TBI 350 before twice and that was peanuts, (I think this might be easier since the LT1 does not have coolant flowing through the intake. :) ) but just want to check to see if there is anything I might miss the first time. Do I need new intake bolts? I am not getting a performance one by any means, but my Intake is leaking oil in the back and it is getting worse by the day. I am going to buy some gaskets and have my intake planed and do it right the first time, just asking on some pointers on what others have done... Thanks!

02-08-07, 01:56 PM
The intake manifold is quite easy, especially if your an experienced wrencher on other cars.

Removing throttle cable is a pain. Press in really hard with a small screwdriver on the little metal cylinder. All the plugs for sensors are pretty much sized so they can only go in one spot, so it isn't necessary to label them. It helps to have extra hands hold the main parts of the wiring harness apart when removing and installing manifold as it tends to fall into the valley. WHen the heads are exposed, I like to stuff rags in the ports to keep debris out of there.

There are a few studs in the middle, not just bolts. I use a small box and poke holes in the top and number them to keep them all in order for reinstallation. The studs usually have a sensor bracket or something that is held down with a nut over that, so remember to do that upon reinstallation.


There are two "hard" gaskets for the intake manifold, one on either side that lays across the head. The front and rear seals are actually made by gasket goop high-temp RTV in a tube (black stuff). Use a fair bead (1/4 to 3/8") all along the cleaned surfaces at the front and rear of the block where the intake will touch. Continue the bead about 1/2 to 3/4" up either side of each head so that when you lay the "hard" gaskets across the head the tabs of the gaskets will sit in the goop and be held into place (this is actually per factory service manual, from my memory). Allow the gasket goop to sit for ten or so minutes to harden slightly before setting intake back onto the block. The gasket goop should ooze a bit over the edge. Wait quite a few hours to set up before starting engine if possible. Watch out for the oil pressure switch on the back of the block.

There is a torque sequence and measurement for the manifold, as seen below. Make two passes, first is 71 in. lb. Final pass should be to 35 ft. lb. The TB can be in the way, but with a good swivel socket extension you should be able to get around it and a bracket.

02-12-07, 02:54 PM
Thanks for the info! It ended up being fairly easy. I wish I had that fuel line disconnect tool to move the injectors out of the way thoguh. The intake came right off, with my friend holding the wiring harness and me pulling the intake out. I found the pictures you posted in the FSM that I have. One question though, do you get your intake planed? I am going to have mine done so there is no question on straightness. $60 to plane the intake is cheap insurance to me. Also, I had a fairly LARGE amount of condensation under the intake in the lifter valley. I KNOW this is not normal. Is there a TSB out for this? I had a bunch of yellow goop on the bottom of the intake manifold (oil mixed with water, i think?). It was really nasty. I cleaned it all out with rags and a shop vac, but I don't want this to happen again if I just reinstall the intake manifold. Waht do you think??? This is really odd to me as I have never seen this before... I have no idea what the cause is or what to do to stop it from happening?!?! :confused: I remember oen TSB I read stated the AIR pump produces condensation and puts it in the intake and produces hesitation in the car, but not into the ENGINE ITSELF!!!! Please help!


02-13-07, 02:00 PM
If the AIR pump is left on the vehicle for long enough it is entirely possible for it to take in the condensation all the way through the TB and coat the intake like you see.

The LT1 is also prone to leaks at the rear of the intake where it meets the block (where gasket goop is at). I suppose it could pull in outside unfiltered air and maybe some condensation if the leake was severe.

I wouldn't spend money on planing an intake, but that is me. I don't see much of a benefit unless you think it leaks so bad that it needs it in order to seal up again.

02-13-07, 06:26 PM
I did plane my intake. It was so bad, it was the worst one that he has seen before, not that he does a lot of LT1 intakes. It was not warped, but twisted, the entire intake. The front right was .050 out of straightness and the back left was .085 out of straightness. Pretty bad if you ask me, so the planing was needed. That explains why there was oil coming out the back right and leaking a little oil in the front right. I think you are right in the condensation part. It was coming in the back and laying in the lifter valley. I am 100% positive that is where it came from, but just to make sure, I am going to disable the AIR pump too. The EGR Tube gasket is a son-of-a-gun to find. Had to order from the dealership in town for $5. Thought that was a little expensive, but needed, so I paid for it anyway. Thanks for the info and feedback BCs71! Painting it tonight and putting on tomorrow. Replacing all the vacuum lines too. :)

02-15-07, 10:58 AM
Didn't paint it. Just put it on. IT'S ALIVE!!! My car is up and running and running great! No more leaks and the engine is running as smooth as glass. I need to get rid of the Bosch plugs though and get the AC Delco plugs in there. Otherwise it is great! I think there was a pretty large leak at the rear of the intake and it is now sealed. More power too!! Just thought I would give an update. Easier to put back on than taking off. Pretty simple!