Replacing Intake Manifold Gaskets

[brianhiggi]

I suspect there is an air leak from the base of the intake manifold on my '78 SC. To replace the gaskets on all 6 manifolds can I just undo the nuts on them and lift the entire CIS high enough to slip the new gaskets in without having to remove anything else? The engine is still in the car. Is that a common place to have a vacuum leak?

[Bob Kontak]

Common. But don't jump the gun as the gaskets are pretty stout. Not metal like exhaust gaskets but not wimpy. Most issues I have run into are where the nuts are loose.

If the engine is running, spray starting fluid on the base of the gaskets. You will know right away if they are sucking air. You can use carb cleaner or propane to increase safety. I read where someone used water in a spray bottle and it will impact idle speed. Never tried it but it sounds good.

I do not know if you can do the lifting trick without removing fuel line connections, etc. It will be a nasty swear-a-lot job and you will have to get some fancy 1/4 socket swivels. You would be better off taking one runner off at a time, clean the mating surfaces and re-install with new rubber sleeves on the air box. It may help to loosen all of the base nuts first for a little wiggle room.

Replace both injector o-rings when you have the intake runner out. This can be done in the car but access is much easier when out.

[tdskip]

Anyone know the torque setting for the intake bolts off hand?

[brianhiggi]

Thanks Bob for the smart advise. I didn't think to change them individually at the base of the airbox. I'll start by tightening the any loose bolts on the manifold, and YES if somebody has the torque requirements on those, that would be great.

[kidrock]

18 ft lbs / 25 Nm

[mthomas58]

Originally Posted by brianhiggi

I suspect there is an air leak from the base of the intake manifold on my '78 SC. To replace the gaskets on all 6 manifolds can I just undo the nuts on them and lift the entire CIS high enough to slip the new gaskets in without having to remove anything else? The engine is still in the car. Is that a common place to have a vacuum leak?

Gasket replacement project:

Intake Gasket Replacement Project with pics

[Nine9six]

Be mindfull that intake gaskets many times break apart and stick to the parent material of the heads. As I understand it, this is a tedius, backbreaking job of cleaning and scraping old gasket material from around the intakes. If you dont remove ALL the gasket material, you'll be sucking air again...

[1990C4S]

I am quite sure that SC's can be done in the car. I did it once, it is not easy or fun.

But the car sure ran a lot better when we were done.

[mca]

I still can't believe that some of you have done this with the engine in the car. Seems like an impossible task!

Personally, I wouldn't do it unless the engine was out for two reasons:

1) Room: It is hard enough to get #6 free with the engine out. Then there is the fact that #2 has the WUR attached, #2 and #3 may or may not have a bracket that spans both, and #5 has the AAR attached ... so trying to lift any of these manifolds off of the intake studs is going to be a tall order. And possibly result in broken wires and/or vacuum lines.

2) Dirt / Debris / Hardware: Think about the crud around the engine. When you lift off the manifold, crud is going to break free from around the manifold base, boots and other parts of the CIS. That crud will then be able to fall into the heads. With the engine out you can use a shop vacuum to prevent chunks of dirt from entering the heads - if dirt does enter, you can vacuum out the heads. You also have to be VERY sure that you collect every single washer and nut that comes off of the manifold. And who knows if there is a rogue washer laying around the engine just waiting to find a way into the heads?

Not trying to bust your balls. Just wanted to share my thoughts. But I've been know to be a tad OCD.

Cheers,
Craig

[1990C4S]

The car I did was quite clean. And had some big air leaks, which were 'compensated' for via the mixture screw. It was amazing what a difference a days work made.

[GothingNC]

It can be done with a partial engine drop

Remove my CIS while in car

[enzo1]

be particularly careful when u pull the intake not to drop the washer under the nut into the intake.... per John Walker instructions to me when I did this...."can be done. easier on a 79 and earlier due to the absence of all the frequency valve bs. i'd rather pull the engine on the later ones. account for every nut and washer, check the ports for before reinstall and turn the engine by hand a couple of revolutions to be sure nothing fell into a cylinder."

[Bob Kontak]

Originally Posted by kidrock

18 ft lbs / 25 Nm

+1 Confirmed in spec book.

[mca]

Originally Posted by enzo1

be particularly careful when u pull the intake not to drop the washer under the nut into the intake.... per John Walker instructions to me when I did this...."can be done. easier on a 79 and earlier due to the absence of all the frequency valve bs. i'd rather pull the engine on the later ones. account for every nut and washer, check the ports for before reinstall and turn the engine by hand a couple of revolutions to be sure nothing fell into a cylinder."

The frequency valve stuff really doesn't make it more difficult. The O2 sensor simply unplugs. With backdated heat and no a/c, the later SCs clean up real nice.

My fathers "California" 79SC was a royal rats nest of emissions junk. EGR, smog pump, etc. YUCK. Even with a partial drop I wouldn't have attempted to pull the CIS off of his car. It was a leaking mess back in the triangle of death. Dirt, oil, debris, sunflower seed shells, pine straw, etc. No way would I want that to fall into the heads.

[mca]

This is what I'm currently dealing with on my father's 79. Look at all of that nastiness! Not to mention the dirt .