Hi Gary,
OK, now you are into a project!
When you clean the head area (that the intake manifold bolts to), you need to protect the engine from the debris. Lay towel(s) or other protection that is carefully shaped so the towel(s) sit under the heads and under the front are rear as much as possible. Clean carefully but thoroughly. Ensure you don't get crap into the lifter valley. Obviously, all the surfaces that contact the intake manifold need to be nice and clean and oil free. Carb cleaner will help get it clean and nice.
Once your intake and engine are cleaned appropriately, try dry fitting the intake a couple of times. Especially with a cast iron intake manifold, it is not easy to carefully set one into fresh beads of oil resistant silicone without smearing and screwing it up.
So do this (once everything is clean):
a) Put the intake gaskets loosely on the heads (dry and without any silicone). These are the long gaskets with the 4 rectangular shaped holes for the intake runners. Your gasket set will also come with two shorter cork gaskets for the front and rear of the engine. Leave these small gaskets out for now.
b) Set the intake manifold on the engine. There are three things to learn by doing this:
1) How you need to place the manifold back on the engine smoothly and, when doing it for real, so you don't screw up your gaskets and silicone.
2) The front and/or rear of your engine will have little pins that help locate the small front and rear gaskets. If they stick up too high, they impede the ability of the manifold to seal. Are the pins hitting the manifold at all? One thing you can try is to rock the manifold side to side a little bit and try to feel if it is rocking on the pins. If the pins are too high, they must be filed down or removed. (You can also look on your intake manifold for witness marks these pins have left. If there are witness marks, you likely have an issue. If I'm not mistaken, some stock manifolds have a recess in them I think - then you are OK.)
3) Once the pins in the step above are OK, how much space is there between the engine and intake manifold at the front and back of the manifold? Look at this gap vs. the thickness of the cork gaskets that came with your gasket set. Is it bigger or smaller than the thickness of these gaskets? If the gap is significantly smaller than the height of the gaskets, you should use silicone only to seal the front and rear of the engine. If it is only slightly smaller, or bigger than the gasket thickness, I suggest you use those gaskets.
c) Repeat step (b) several times until you are comfortable with the fit and clearances of everything. When you are ready, go for the final "drop".
d) To seal the intake manifold, use
oil resistant silicone. Don't just buy any silicone off the rack. I have attached a picture below of a good silicone I use.
View attachment 1318339
e) Now
lightly smear silicone on the intake gaskets between the heads and intake manifolds (a super thin amount should be on the gaskets - thick does not help you here). Stick them to the heads where they belong.
f) For the front and rear of the engine: If using the cork gaskets smear both sides with silicone and stick them into place. You must make sure that the height of the silicone and gaskets is greater then the gap you measured in step b3, at most about 1/8" higher. Too much and you squeeze silicone into the engine. Too little and you have an oil leak.
If you are not using the gaskets, simply put a nice bead of silicone on the engine side that is at most about 1/8" bigger than the gap, but again, not less.
g) Put an extra bead of silicone at all four corners where the heads meet the engine block. These corners are problematic and you want to be sure the manifold does not leak here.
h) Place the manifold on the engine. This is where the practice from step b pays off. Once in place, check the placement of the gaskets by looking through the bolt holes in the manifold. Stick a small screwdriver in the bolt holes to slightly move the intake gaskets around if they moved a little.
i) Insert bolts and lightly snug them up. Then torque them down to 35 lb ft. Since you may not have a torque wrench and probably can't use one on some bolts even if you had one, that means tight but don't go ape $hit on the wrench. Always torque and tighten the middle bolts first, working your way out to the edges.
Good luck!
(If I missed any key suggestions or steps here, I'm sure the brain trust here will add on! - Please do so Gary will have a successful project!)
Hawk
