Leaking Lower Intake

[ptstew]

I am trying to solve a Qt per 500 mile oil consumption problem caused by leaking lower intake manifold gaskets. The FelPro steel reinforced PrintOSeal gaskets I have tried twice are not sealing. With the upper intake removed I can see wet oil at the gasket on both PS and DS when I look down the intake ports.

I am considering either trying the thicker FelPro composite gaskets (1262R 4 or 5) or simply using RTV instead of a gasket. RTV works well on the china walls and water ports so why not use it everywhere?

I have E7TE heads and a 1993 Cobra intake.

Thanks for any input.

[mburger]

Hey Phil!
I’m assuming with E7 truck heads they haven’t been milled? Just wondering if the intake to head angle is off?

[ptstew]

Thanks, Mark. The heads were not machined. The lower intake was belt sanded by the guy from whom I bought it. I agree that angle and or flatness may be an issue. I eyeballed but did not measure.

[CraigS]

There was a thread here 5-6 yrs ago where a guy had similar problem. Turned out that the combination of aftermarket heads and aftermarket intake caused his intake to bottom out on the front and rear walls of the block. That held the head up just a tiny bit which caused the leak at the intake/head joint. So, before you install the intake, set it on the engine w/o any gaskets and see how it fits. It should bottom out on the heads and have a bit of clearance to the block walls. Also look at what gaskets you use on top of those walls. The 1/4 inch thick cork ones that come in a lot of intake gaskets sets often don't work. Many people skip the wall gaskets entirely and use a bead of their favorite gasket maker instead. Especially for this I like Permatex UltraGrey because it is slightly thicker than the more common black or blue. Think peanut butter vs mayonaise.

[rich grsc]

The 93 intake with exposed tubes? They are know to use oil because the baffle under the pcv valve is too short, and sucks oil through the valve.

[Railroad]

The intakes of that era I have dealt with have a disc of mesh steel wire under the pcv grommet. If this was removed, it is more likely to draw raw oil into the pcv valve and hose.

[Jeff Kleiner]

The 93 intake with exposed tubes? They are know to use oil because the baffle under the pcv valve is too short, and sucks oil through the valve.

Rich is correct. Some of the “Cobra” intakes were produced with a two element baffle (installed on the intake shown) which proved to be insufficient. These were replaced with the larger one piece baffle which is shown unattached.

https://i94.photobucket.com/albums/l88/McFly_08/cobrakit213.jpg

Used to be that the one piece baffle was available through Ford Racing or could be harvested from an Explorer intake.

If yours has the two piece baffle system this might be a potential cause.

Jeff

[rich grsc]

Thanks Jeff, I didn't have a picture.

[ptstew]

Thanks so much for all the comments. Jeff, Rich, Railroad, my intake does have the small baffles and I was alerted to this issue by you from other threads. I tried to eliminate that problem by installing a new OEM PCV and screen and an oil separator between the PCV and intake. I get only about an ounce of oil separated every few hundred miles. I also tried driving the car with the PCV line blocked and the crankcase vented to the atmosphere. Oil consumption was not reduced. I see no oil in the upper intake nor the first part of the lower. Attached is picture looking down through the lower intake to the gasket area. The shiny area at the gasket is wet oil.

Craig, good point on the china walls. I have seen other comments by you on this issue and I did use Permatex Ultra Grey RTV instead of cork or rubber there. When I removed the intake the first time I observed what I thought was a reasonable thickness of old RTV from those areas during cleanup. Definitely worth checking again, though.

The other attached picture is of the lower intake after the old gasket was removed. Note from the “head side” marking transfer that the old gasket was installed upside down. This old gasket was a FelPro MS 63334 sized for the stock heads. I thought a properly installed, larger port MS 95952 gasket, sized for the ‘93 intake, was the answer, but oil consumption did not improve. Also note the finish lines on the intake. The guy I bought it from belt sanded that surface and said that others he had done like that worked fine. Are those grooves preventing seal? All spark plugs are wet and have feathery carbon buildup on the shoulder indicating that the leakage is not localized.

So, back to my original question, would a thicker composite gasket or more extensive use of RTV around the intake ports, with or without a gasket, be a reasonable fix? I realize that I would have to be extra careful about china wall interference without a gasket.

Thanks again for comments.
158335158336

[ptstew]

Input from Permatex is that a 1/8” bead of Ultra Grey RTV around the intake ports, instead of a gasket, will work well in this application. They also recommend torquing to Ford spec. Anyone tried that?

[CraigS]

I have never tried skipping the intake gasket. I do skip header gaskets. I use intake gaskets from Felpro. This is some info I have saved but I don't know if it is the newest info. The 'S-3' indicates they are steel reinforced.
1250 S-3 (port size 1.20" x 2.00")
1262 S-3 (port size 1.28" x 2.10")
1253 S-2 & 1253 S-3 (SVO/Yates head w/port size 1.35" x1.95)
I do a thin smear of UG around the water ports. I also use studs and nuts instead of bolts and I do many retorques. It usually takes 5-6 tries until the nuts stop moving. This a lot of work though w/ the upper intake in the way so hopefully someone w/ more experience w/ 2 piece manifolds will chime in here.

[rich grsc]

Seeing as someone took a belt sander to the intake, :confused::mad: I'm thinking the mating surfaces are not flat and sealing with the heads. They needs to be checked with a quality straight edge

[ptstew]

Thanks, Craig. Good info. I am leaning toward the 1262s3 maybe with some supplemental RTV.
Rich, you are probably right that the intake is either not flat and/or not well angle mated to my heads because if the sanding. Thanks.

[bobl]

The intake gaskets are crucial in keeping the ports lined up(especially the water ports). You need to verify the port alignment carefully. Decking the block, or milling the heads quite often requires machining the intake surfaces to get them back aligned properly. They make a couple of different thickness intake gaskets to correct it.

"Or it's possible that your intake was machined but the heads have not been."
Oops! said this backwards. Should read "heads machined but intake not".


Then, not running a gasket might work if the intake didn't bottom out on the china wall, but not the recommended approach. Using a thin layer of Ultra black or grey RTV on both sides of the gasket will help it seal, but may allow the gasket to slip. I like to do the head side and then lightly bolt the intake on, checking alignment carefully. Let it sit overnight, remove the intake making sure everything is still aligned properly and apply rtv to the other side and china walls and reinstall. That way you're sure it didn't slip.

[CraigS]

Bob's comment about the gasket slipping reminds me of another benefit of using studs and nuts vs bolts.

[ptstew]

I really like this approach detailed by Bobl of using both the gasket and RTV. In my case, the heads from Blueprint look original but the intake was belt sanded. I have been assembling with bolts but I did make four slotted head studs, one for each of the intake corners, to position everything when lowering it to the head. My next step is to take everything apart again this winter, do some measuring and proceed from there.
I’ll post an update when I get there.
Thanks to all for sharing your knowledge.

[CraigS]

I am sorry that I somehow missed the part about the intake being belt sanded. That fact would put me very, very close to just trashing the intake. Do you have any way to know exactly how that was done? How much metal was removed? Was it a hand held belt sander? I have used my hand held sander on header flanges but they are steel. I wouldn't even consider using it on an aluminum intake. I also have a stationary belt sander. It isn't quite long enough to do and intake but I have done many many projects on it. I can say that I need to be really careful using it because it is easy to sand an object at a slight angle if I don't hold it perfectly. Even if it were large enough to do an intake I still wouldn't use it. I will be cheering for you when you get it apart and try to measure it.

[rich grsc]

You may not want to hear this, but those intakes looked way better than they performed. I had one on my old build, loved the look, but I couldn't say it ran better. I think you need to take it to a GOOD engine/machine shop and have the surfaces reground to be sure they are flat and the correct angle. OR just get something new and better. I know it'll cost more, but you'll be able to drive it.

[first time builder]

In one of your photos i would be suspect that the sanding has been done to create a mismatch. where the gasket goes near the bolt holes looks like not much gasket sealing is being done.
There are a few manifolds on Ebay for less than 100. I would go in that direction. I would prefer to get one that has not been "cleaned up" so I can do the cleaning and not use a sander.
Even using a scotchloc in a die grinder can remove some material (aluminum) .
Kenny

[ptstew]

Yeah, I agree. Trashing it may be the best answer. Thanks.

[ptstew]

You may not want to hear this, but those intakes looked way better than they performed. I had one on my old build, loved the look, but I couldn't say it ran better. I think you need to take it to a GOOD engine/machine shop and have the surfaces reground to be sure they are flat and the correct angle. OR just get something new and better. I know it'll cost more, but you'll be able to drive it.

You’re right, Rich. I was going for the looks. How often does that work out?

[mburger]

You’re right, Rich. I was going for the looks. How often does that work out?

That one bites me all the time!

[rich grsc]

You’re right, Rich. I was going for the looks. How often does that work out?
In my case it works, I look great. :rolleyes::eek: