I plan on installing the 7777 series intake manifold gaskets this weekend to cure my oil leak before winter. I have never pulled the manifold on the LT4, and was looking for as many tips as possible from you guys so feel free to share. One question I do have, what product should I use to clean the surface between the manifold and bock? TIA

 

Lacquer thinner will work.

 

a few tips:

Take a scuff pad, scotchbrite is best, and scuff the mating surfaces at both ends, not on the heads, but on the block. then, if you are careful, use a drill and pop a few shallow dimples into the block and intake at the front and rear ends.

this will give the RTV seal something to really stick into.

Torque it down, according to the manual and let it sit for 24 hours!!! Otherwise, the crankcase pressures will blow the new seal out.

 

Pulling the intake is relatively simple... remove the ground cable from the battery...you'll need to pull the altenator and it's rear bracket, remove the throttle cable from the linkage by simply pulling the cable forward lining it up with the open notch on the TB linkage bracket.... now to gain access to the retaining bolts you must first remove the fuel rails and injectors... remember to relieve the fuel system pressure: passenger side rail should have a little knurled cap (slightly larger than a valve stem cap) remove it, place a rag under/over the exposed fitting and use a flat head to push the relief pin/valve up fuel will come out into the rag and system pressure is now relieved. Now you loosen the four bolts holding the fuel rails down to the intake and then lift both rails at the same time gently prying the injectors free from the intake... you can fully remove the injectors from the rails by removing the retaining clips from the tops of the injectors but it is not neccessary.
Next remove the A.I.R. pipe from the back of the manifold..should be connected with two 10mm bolts... then you will probably need to remove the entire pipe to make it easier to set the intake back down so you;ll need a Crows foot socket (opened wrench might work but it's a tight space and the best way I found is to use the crows foot with a tall extension) to remove the pipe from the passenger side exhaust manifold...use plenty of pentrating oil as it will be stuck in the manifold fairly well. the A.I.R. pipe fits to a black rubber hose on the drivers side so simply removing it from the hose there will be sufficent.. word of caution that hose has a T-fitting just down from the pipe connection..it looks like it would make things easier to remove it from the bottom hose ..DON'T!! that hose on my car was a huge pain to get back on the T-fitting. Finally pay close attention to your vacuum lines..the one on the drivers side goiong to trhe ASR controller needs to be removed/unattached from the intake; remember to pull on the boot connector at the manifold and not the PVC line as it will snap! finally remove your bolts and lift up the intake, may take some prying under the front with a large flat head to break it free. .... .... oh dam I almost forgot..if you haven't installed the coolant bypass then you have two options... remove the TB mounting bolts and pry the TB from the front of the intake or..drain the coolant system down some and remove the coolant lines from the TB before you lift off the intakemanifold.... sorry I did away with that on mine car a while ago so it slipped my memory for a minute...


As far as cleaning up the gasket surfaces... wouldn't go with out my little scotchgaurd scrub pads for the air grinder or drill... you can get these at NAPA, Autozone, Advance... for like $15-20 a kit... comes with assorment of pads and sand paper discs as well as the pad mount bit or what ever you'd call it... basically it's a drill bit with a mount for a little 2" dia scotch pad or sand paper you put in a drill and man do they clean things up quick and easy...a must for any gasket replacement job.

Good luck and happy wrenching...
Jason

 

Plus you can pop the fuel rails and injectors all together and I always put them in a plastic bag and tape off the bottom so no dirt gets on them.

The LTX manifolds aren't to bad to do at all since the distributor is not a concern! I guess thats one positive thing about the optispark!

 

A drill?!

I'd use a hammer and a punch. You just want to create some very shallow "dimples".

Personally, if your oil leak isn't excessive right now, I'd skip the dimpling alltogether. Just a bead of fresh RTV should do it.

Also, you might want to try re-torqueing the bolts around the manifold. I had a bad oil leak on my LT1 Caprice, and I found that the bolts on the back were only finger tight. Torqued 'em down to spec and no more oil leaks.

 

If the intake base bolts go through the heads into the valley, chase the threads and apply some Permatex #2 to the threads before installing.

I would use a little coarse sandpaper on the front & rear engine lands and on the mating surface under the intake base. Use enough RTV that a little comes out when you torque down the bolts.

Drop the intake base straight down onto the RTV, do NOT move it fore/aft as this can destroy the seal.

As said, torque the base bolts to spec in order, let stand at least 23hrs and retorque before completing assembly.

 

Don't forget to carefully clean the top of the engine BEFORE you start. Particularly where the manifold meets the heads. Any grunge or dirt here will likely fall into the lifter valley when you pull the manifold.

Cheers

 

I used a paint preparation product to clean the mating surfaces. I found it at AutoZone and I think it might be called Prep-Sol or something similar. It cleans nicely and does not leave a residue. Make sure that you get it very clean! Prior to pulling the intake, clean up the area to ensure that debris does not fall into the lifter valley and after the intake is removed, cover the lifter valley with shop rags to prevent debris from falling in.

There is a bunch of stuff to unplug so you may want to take notes as you disconnect things. You do not have to disconnect the fuel line from the fuel rail/injector assembly, simply pull the assembly and let it rest against the windshield on a towel or something similar. There is a hidden 14mm bolt that holds the AIR bracket to the rear of the passenger cylinder head that has to be loosened. Other than that it is pretty straight forward. Chase the intake manifold bolt threads to get them clean.

I did not dimple the mating surfaces and I do not think it is necessary if you use a quality RTV and let it properly cure. On the manifold ends I would recommend using "The Right Stuff" RTV. Have a helper assist you in placing the manifold back on, you want to get it on straight and if you don't you will need to clean it up and try again. Put a pencil or equivalent in a couple of the bolt holes to serve as a guide in lining it up. Follow the recommended torque sequence and procedure found in the shop manual. I would check the torque after 12 hours or so and by all means do not start the car for at least 48 hours to give the RTV plenty of time to cure. Take your time and all will go well - good luck!

 

Am I the only one wondering why you would remove the fuel rails just to R&R the intake? I've had my manifold off several times to do various work and only removed them this last time to install onto a new intake.

 

I installed mine around 25k miles ago and still have no leaks. Although there are many good suggestions here, the most important is to simple wipe the mating surfaces really well with acetone. Acetone cleans better and leaves less residue than anything else. I used the green scotch brite pad that comes in a little sheet.

You don't have to slather the sealer on but do get a nice round bead applied. I did not start my car for 2 days to allow the sealer to dry. If oil hits it while wet, it will never cure properly.

Also, there are two small holes in the back of the engine block at the top where the bell housing bolts up. I had to replace my rear main seal because it was slinging oil up through those small holes and allowing it to drip back down over the back of the engine. It looked like a leak from the top of the heads/manifold but was the rear main.

 

I also use GM brake cleaner to clean/rinse everything off after hitting everything with a scoth brite pad on a die grinder (a drill may work just as well). Take your time. I do sometimes 3 or even 6 intakes a week and use the GM gray rtv.

 

Wow guys!!! Great replies. I feel like a pro and I haven't even done it yet. Seems like everything has been covered, but if not keep em coming. THANKS!