View Full Version : Installing the intake manifold

12-17-2015, 05:21 PM
I experienced an oil leak from the intake manifold front seal so I took the time to pull it back off and re-do it right.

For those who are unaware, most engine builders will recommend that you do not use the cork gaskets for the front and rear seals. Instead, "glue" new gaskets for the sides (between the manifold and the heads) using grey RTV on the coolant passages. Then put a 1/4" bead of RTV grey on the front and rear seals. Let it harden slightly (one hour) then "stack" a second smaller bead on top of it. Place the manifold on and torque down immediately.

The last time I did this I had a strong helper and although we were careful as we could be, the heavy manifold still dug into the front bead of fresh RTV, and therefore it started to leak oil soon afterwards.

This time I rigged up a bracket out of wood and threaded rods to make the installation nearly fool proof. The long member is a 2x4 pine ripped in half. The short pieces are 1/2" x 1-1/4 oak. All are scrap from other projects. I bevel-cut the long member to accept the short ones so they are more-or less at the same angle as the carb plate. The oak gets pre-drilled holes and fastened to the pine with deck screws.

This rig isn't strong enough to break the old gasket seal- I use an axe handle in the front thermostat housing to do that. Then I used my bracket to raise the manifold off the engine, about 1/2" off the front seal and 2" or so off the rear seal by simply turning the four nuts in sequence.

Along with a helper this allowed me to use the "handles" to pick up the manifold, move it back 3/4" to clear the small bypass hose, then lift it out and onto my workbench.

I measured the heights of the nuts on the threaded rods to set the bracket in the same position for the placement, then removed it to allow cleaning the underside. Then I remounted the bracket and used it as a handle to carefully maneuver the bypass onto the short hose, with little chance to smear the fresh RTV. Once I got the manifold hung above it's final position I used the nuts on the threaded rods to gently lower the heavy casting exactly where it needed to be. I dry-fit the distributor during this process to get everything lined up perfectly. Once the four nuts lost tension I removed the bracket, threaded the ten manifold bolts in and torqued them all down, four stages to 35 #-ft, in the Ford recommended sequence.

Ian M Greer
12-17-2015, 10:06 PM
Steve , I like your creativity , Ill try and keep that in my old memory banks , Ian ( Remember Not All Birds Fly South )

12-20-2015, 05:24 AM
Very nice job of field fabrication of tool you needed my hair is off to you sir

12-20-2015, 09:49 AM
This is the only engine I know of that the pushrods go through the intake manifold, so remove them FIRST and install them LAST.

I don't like the design of FE intake manifold hold-down bolts. They go directly into the heads. The problem is, they also inhibit the intake manifold from descending

Anything that inhibits the intake from descending must be relieved, that's why we leave the front and rear block gaskets off.

Here is my procedure:
Get all oil and grease off the front and rear block where the gasket usually goes. Use lacquer thinner and clean rags. No sealer will stick to oil or water. When you're done cleaning the casting, do it again. Now clean the mating surface of your intake manifold using the exact same procedure.

I use Permatex Black on the whole engine build. For intake gaskets, I put a thin coat around both sides of the water ports and let them skin-over, then place them on the heads. There is no rush here. Now work-in a thin but jagged coat of Permatex on the front and rear 'rails' of the block and the intake's mating surface. Again, there is no rush. Let it skin over.

Place the intake manifold into position. Install the distributor without the hold-down bolt and make sure it rotates freely. I usually use aluminum manifolds so weight is not an issue for me. Screw-in bolts WITH FLAT WASHERS (smooth-side down) hand tight, making sure the manifold seats nicely. Torque the bolts 1/4- tight (which is loose). Hook the bolt heads from the back and tap them 'up' so the manifold can slide down under the washers.

Let me stop right here because the bolts are the very problem. When tight, nothing under them moves, or if it does move the tension makes the gasket 'squirm' and distort. I have heard builders say to wait overnight to give the manifold time to 'settle-in'. Ford didn't and I don't either. By tapping the bolt heads 'up', vibration slides the bolt and washer up as the manifold slides down. You can see it happen as the bolts are progressively torqued and 'tapped' to spec. Each bank of the "V" affects the opposite side so alternate sides as you tap the bolt heads.

The last thing I do is fill the 'gasket gaps' in front and rear with Permatex Black. Since there is already a thin coat on the castings, it sticks to itself very well and it is too thick to run. Just make sure you aren't pumping gobs of sealer into your block; more is not better. Use your finger to 'finish' the gap then let it cure. I've never had an intake manifold leak oil, vacuum or coolant.

The intake is all the way down, evenly distributed and sealed properly for another 250,000 miles. Time for those pushrods. - Dave