Cant seem to stop annoying leak at rear of manifold.

[Lil Ape]

So I keep getting a leak at the rear on my intake manifold, roughly at the rear middle of manifold, where the oil pressure switch is at. This is the third time this has happened since installing a new rpm air gap manifold. I've used new felpro gaskets and high temp gasket sealer every time I've had to remove the manifold. Also use proper tightening sequence and torque to specs. And it still happens. Its a constant stream When the rpms pick up. I've put a small bead of gasket material along the front and rear of the block like is recommended and just throw away the included black rubber gaskets. leak runs out the rear, then down the driver side of the bell housing and hits the header.

I'm thinking maybe I'm just not adding enough gasket material at the rear of the manifold. Or maybe I should use the included rubber gaskets and add some gasket material on top of that. Anybody have any recommendations before I attempt this again? I Don't think its leaking out of the threaded hole for the oil pressure switch.

[mongoose]

dont use anything on the front and back just a big bead rtv... i like to use the right stuff.. always seals.

also amke sure its not leaking out of the dist. hole too.

[weider1717]

your manifold is warped. Take it off and to the machine shop to be milled to true it up. DONE.

[trixter99]

Originally Posted by mongoose

dont use anything on the front and back just a big bead rtv... i like to use the right stuff.. always seals.

also amke sure its not leaking out of the dist. hole too.

What he said and make sure your PCV is working.
Posted via Mobile Device

[Lil Ape]

Yeah my dad seems to think it might be warped a little. Which I'm really hoping it isn't.

[weider1717]

it's not biggie whenever they're removed it's common practice to have them trued up before chancing it.

[gramps]

BIG bead of rtv. seen it so many times where people dont use enough of it, and results in a gap between the mani and the block and a leak.

[BigBlocksRule]

Originally Posted by gramps

BIG bead of rtv. seen it so many times where people dont use enough of it, and results in a gap between the mani and the block and a leak.

I've torn down at least 2 big blocks and a smallblock that had a big chunk of silicone that broke off from one of these monster beads and jammed in the oil pickup. Killed all 3 engines.

Your bead should be about the size of a pencil. Throw away the junk GM rubber china rail gaskets, they're junk. Before you start, get some brake parts cleaner. Clean the bottom of the intake and the top of the china rail as much as you can, then spray both down with the parts cleaner. This stuff will absorb any remaining oil and evaporate it, so you'll start with a very clean surface. NO silicone or other caulk will stick to dirt or oil. Either get help or get yourself in a position where you can lower the intake STRAIGHT DOWN onto the engine. Take a practice run or two with no silicone so you don't have to do it again.

Warping doesn't matter - silicone fills in, doesn't care.

[Rufton]

Originally Posted by BigBlocksRule

I've torn down at least 2 big blocks and a smallblock that had a big chunk of silicone that broke off from one of these monster beads and jammed in the oil pickup. Killed all 3 engines.

Your bead should be about the size of a pencil. Throw away the junk GM rubber china rail gaskets, they're junk. Before you start, get some brake parts cleaner. Clean the bottom of the intake and the top of the china rail as much as you can, then spray both down with the parts cleaner. This stuff will absorb any remaining oil and evaporate it, so you'll start with a very clean surface. NO silicone or other caulk will stick to dirt or oil. Either get help or get yourself in a position where you can lower the intake STRAIGHT DOWN onto the engine. Take a practice run or two with no silicone so you don't have to do it again.

Warping doesn't matter - silicone fills in, doesn't care.

I bet the the jammed monster beads weren't from the intake rails. Maybe from pan flanges?

I cut heads off bolts to assist the "STRAIGHT DOWN".

[BigBlocksRule]

Originally Posted by Rufton

I bet the the jammed monster beads weren't from the intake rails. Maybe from pan flanges?

I cut heads off bolts to assist the "STRAIGHT DOWN".

I can promise you that's where they came from, that was the only RTV on either engine. It's also the ONLY one that people tend to build TOO BIG.

[INSIDIOUS '86]

Clean with some iso alcohol so the rtv will stick.
Posted via Mobile Device

[Rufton]

weider1717 has a good point; good to check warp next time it's off.

I'd use a mirror, etc. to verify leak source and avoid tail chase.
When not using gasket I like a scuffed flange for sealant bite.
I apply a thin bead of RTV on both flanges and quickly wipe to a thin film.
Quickly apply a fat bead of RTV on manifold end flanges and quickly position manifold.
Verify w/ mirror etc that bead is thick enough.
Torque bolts after a few minutes.

[Lil Ape]

what gasket material do y'all recommend? I've been using the red high temp rtv stuff but a friend recommended the black rtv. said it seals better.

[BigBlocksRule]

Right Stuff.

[Rufton]

Many like "The Right Stuff" but I'm still using RTV. My favorite RTV is Permatex Ultra but I like calk gun VersaChem RTV too. The Right stuff is designed for quick assembly and cost $20 last time I checked.

[bilfman]

Ditto on permatex ultra, great stuff. Comes in several colors.
Posted via Mobile Device

[Lil Ape]

I'll use the ultra black rtv. I still have some left, plus the right stuff is a little much. But how long should I wait before putting the manifold back on after laying down the rtv? I usually just put it back on after a few minutes buy read this stuff needs to sit for a little while.

[LynnJr]

LilApe
When you pull the manifold use some Acetone or Laquer Thinner to clean all the surfaces and dry them with paper towels.
While the manifold is off clean the area were the distributor will sit and dry it with a paper towel as well.
Glue your distributor gasket down and install the distributor and clamp it lightly.Set the manifold aside so it can fully dry.
Take a clean paper towel and put some acetone or laquer thinner on it and do the 4 corners were the heads meet the block and the manifold front and rear.When dry apply some sealant to those 4 corners and let it fully dry.

Put some more sealant in the four corners and install your two side gaskets dry.You can slightly bend the corners so the side gaskets stay in place.

Add a healthy amount of sealant to the front and back and while its setting up you can remove the distributor from the manifold and re-wipe the bottom of manifold with cleaner on a clean paper towel.

After it dries set the manifold in place and make sure everything is in alignment.

Install the bolts but don't snug them down.Eat a sandwich drink a soda wash your hands and then snug the bolts up.
Let it sit two days to fully cure.

Now pull one bolt out at a time and cover the threads with sealant and re-install.This will prevent oil from climbing up your bolts.

The next day you can clean the distributor with acetone and clean paper towel.Add sealant to the ring that will sit on the gasket and install the distributor and fire the engine long enough to set your timing.Let the sealant cure.

Most people don't let the sealant cure and they drive the vehicle way to soon.

The PCV valve only works decent at idle and if you romp on the motor before the sealant cures the crankcase pressure will blow the sealant out giving you an instant leak.

It use to be common to take a center punch and dimple the front and rear of the block to keep the end gaskets in place.

Today with the better sealants and clean oil free parts that isn't necessary.

[Rufton]

Originally Posted by Lil Ape

I'll use the ultra black rtv. I still have some left, plus the right stuff is a little much. But how long should I wait before putting the manifold back on after laying down the rtv? I usually just put it back on after a few minutes buy read this stuff needs to sit for a little while.

When RTV is too old it won't cure.
Good idea to squeeze a dab out and verify it cures.