Intake Leak

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bobscuda67

bobscuda67

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Hey everyone. I have been fighting a vacuum leak on the bottom of my intake. It sucks oil from the lifter valley between the head and gasket on port #3. I've replaced the intake gaskets 4 times this summer to no avail.
I had the blocked decked last winter .015 so I could use an MLS gasket. After changing the gaskets twice I had the intake milled .015. It still had a vacuum leak. So I switched from the Edelbrock fiber gaskets to a Fel Pro gasket with the steel core. No improvement.
I'm stuck on what my next step should be. All the gaskets have been .060 thick and I was thinking if I used a .030 gaskets if that would lower the intake enough to get it to seal. Any kind of a hardening sealer?

Anyone have any ideas short of starting over with new parts. Thanks.
 
What if you removed the locator pins on the block for the intake (if it has any) and pull the driver head. Bolt up the intake to the head with a gasket and look at the under side sealing. maybe you can see the void, and fill it with RTV or epoxy. If it doesnt look like its going to leak, mount the head/intake as a unit and then bolt down the other side (carefull, if it looks like its not going to tighten straight, dont torque and crack your intake) . I know it goes against the star pattern torque procedure but....dont know, worth a try?
 
I was kinda thinking along those same lines. It's like the intake flange isn't wide enough at the bottom to put enough clamping pressure on the gasket. What if I had a weld bead built up and then milled it flush with the rest of the intake?
The thing is I shouldn't have to do that in my mind.
 
lay the intake on the engine with a set of gaskets on it and see how the bolt holes line up.

If they look like they are low the intake won't compress them.

You want them to be a little high so the gasket will get compressed

On a recent engine I built I had to use double felpro gaskets to get the right configuration.
 
Go to a craft store and buy some poster board that's around .060 thick. A light color works best. Take a new gasket and trace it, mark the manifold bolt holes and use a gasket punch, don't cut any water or intake ports.

Install manifold with the poster board and torque to 40 ft lbs in the FSM pattern. Do not use locator pins or the cork rail gaskets.

Remove manifold and look at the poster board crush. You can measure with dial calipers.
If the crush looks good you may have a bad valve guide or seal, and possibly a crack in the intake port.

I always use a 1/4" bead of permatex ultra black on the block rails and let it setup overnight. Toss the cork in the garbage.
 
You didn't say what your combo is. Aluminum intake on iron heads? I had same problem. Oil getting sucked in and engine smoking. Edelbrock 9300 Gasgacinch Gasket Sealer fixed my issue. Aluminum intake and iron heads.
 
I'm working on a Magnum iron head with a Mopar M1 aluminum intake.
When I took it apart last weekend there was oil in the intake ports of the head. You can trace the leak back between the gasket and the head.
I could see the crush on the old gaskets and the intake is only about an 1/8th. of an inch below the intake port.
the head has a dip down flat spot right below the intake ports, but the manifold is straight across. That is why I was thinking to have the intake tig welded and then milled to match the heads profile, by doing this it will create about 1/4 of an inch of manifold surface to clamp the gasket. If that makes any sense to anybody.
I would take pictures but my camera is broken.
 
Maybe these will help to see what I'm doing.
 

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Could be the pic but it looks like you ported into the pushrod opening.

Edit: Another thought is that you can't use the cork end seals if your heads/intake have been milled.
 
Actually, that is the as cast around the pushrod pinch. Just a quickie gasket match, but looking at the pics I can see what you're talking about.
I used RTV instead of the cork seals.
 
Ok, here's a test I just did when installing my intake last week. My heads are cut way down to like 64cc & ported out so I feel your pain on this. I clean everything up and then bolt the intake to one head without a gasket. Now look at the gap on the other side. Use feeler gauges to measure top & bottom of the front and back if possible. This will give you an accurate idea of how thick the gaskets need to be & whether your faces line up. Then take and set the intake down dry with intake gaskets as mentioned above. Check fit, where the bolts line up, ect.

One note: we all have the same approx sealing area below the ports on our old ported iron head motors so it should seal up without any welding if the intake faces do align with the head faces.
 
Update: I made two new wider gaskets and coated them with Edelbrock gasgacinch. It went from 13 inches of vacuum to 15 inches at idle. But when the oil got hot and thin it started to smoke out the exhaust. So back to the drawing board. I'm going to take it apart again, 6th. time, this winter and remove the head too so I can see how the ports line up.
 
Any time you you do more than a clean up cut (4 or 5 thousandths) on a block deck or head surface you also need to cut the intake surface of the head. This is not a straight 1 to 1 cut but is a ratio. I think the magic multiplier is 1.6. I could be wrong on that so check with a competent machinist before cutting your heads. For example, using my multiplier, if you cut the deck surface .015" you would need to cut the intake surface .024". Oh, by the way, cutting the intake manifold only makes the mismatch worse...
 
For every .0100 off the head surface you should cut .0095 off the intake surface of the head is the right number. Not that I am a head porter, but I was told not to port the bottom of the intake or exhaust ports unless you really know what you are doing. Where the heads milled?
 
Yes, the heads were cut from a 62 cc chamber to a 58 cc chamber years ago, but the intake head surface was cut at the same time to compensate.
I just don't get why I'm having problems with just 1 cylinder. If the angle was wrong wouldn't all the ports be sucking oil on that side?
Seem's like I have problems that defy the laws of physics.
 
I use Fel-Pro gaskets with the Printoseal beads. If the beads do not hit where you need them to, I've used RTV on both sides of the gasket in the old days. That seemed to work pretty good. It is not optimum, since RTV dissolves in gasoline, but never seemed to be a problem with my engines.
 
Just reread #1. You cut heads .015 and the deck .015, is that correct? If so thats incorrect, you have an angle issue. Get an angle indicator and measure your head angle, both sides when installed. Now level your intake on a bench across the carb pad amd measure your port angles. They should be equal. If the angle is off even by 1 degree, your gasket wont seal as they are not that compressable. I ran a Cleveland with no bathtub gasket (its a steel shim style seal just had the cut out lower part) and used ultra copper rtv as an intake gasket. I let a 1/8 bead skin for 30 minutes and drpped it on and torqued it down. Damn thing lasted over 3 years like that. They give you little tissue paper like gaskets to reuse and old bathtub intake gasket on these motors. You can run a bead of model clay over an oiled intake but clean the head side with alcohol. Torque with no gasket then untorque and lift carefully. Cut clay with razor blade The thickness of the bead should be uniform, or your surfaces are not parallel. Same procedure as finding piston to valve clearance.
 
When the heads were cut, the intake surface on the heads was cut too.
The block was decked .015 last winter and that's when the problem started.
Had the intake cut .015 after changing gaskets 4 times. Now changed them twice since the intake was milled.
It's weird because it always leaks between the head and the gasket on the same cylinder, #3.
 
Another update:
When I was taking apart my intake for the 6th. time I took out the all the right side bolts. When the last one came out the manifold shifted up, and all the left side bolts were loose.
The intake was a different angle than the heads and it's teeter tottering between the heads.
I removed the .060 thick gaskets and made new .031 thick gaskets. The intake set down snug and doesn't move. I got all back together and started it up yesterday and it was idling
and a little puff of blue smoke can out and then a huge oil cloud. I was pissed and just kept the engine on high idle. Then the cloud was starting to diminish so I took it for a 10 mile drive and there was no oil burning at all. I got home and checked the vacuum and it was steady at 17 inches. Checked #3 plug and it was nice and clean, no oil.
I think I got it fixed, only took all summer.
 
Congrats bro. Hopefully it doesn't give you any more problems and may the only smoke be from the tires.
 
I really hate to post in this thread again but my car started burning oil again after driving it for 100 miles. I took it apart again and it had oil in 4 intake ports, with #3 being the worse. The same problem as the last time. I put a bevel square on the head surface and china wall and it's the same as the intake angle.
I really don't know what the next step is to fix it. Maybe make a gasket out of a softer material to let it compress more? About the only sealer I haven't tried is the Right Stuff on it.
I glued the last gasket on the head with 3M emblem adhesive and what a pain is to remove it. But the hot oil got through it in a few hours.
I am totally stumped on what the problem is or how to fix it.
I am going to buy some poster board and use some dye to see where the intake is sitting, that might tell me something.
 
I think your going to trace it back to bad machine work ,possible wrong angel cut some were another note are your intake bolts too long bottoming out giving the appearance of being tight with all that cutting on everything or the shoulder bottoming out on the bolts, just another thought. also check to see how tight the bolts are going through the intake manifold you may need to open them up some to let the intake move smoothly when torqued down and not bind .
 
bobscuda67 said:
I really hate to post in this thread again but my car started burning oil again after driving it for 100 miles. I took it apart again and it had oil in 4 intake ports, with #3 being the worse. The same problem as the last time. I put a bevel square on the head surface and china wall and it's the same as the intake angle.
I really don't know what the next step is to fix it. Maybe make a gasket out of a softer material to let it compress more? About the only sealer I haven't tried is the Right Stuff on it.
I glued the last gasket on the head with 3M emblem adhesive and what a pain is to remove it. But the hot oil got through it in a few hours.
I am totally stumped on what the problem is or how to fix it.
I am going to buy some poster board and use some dye to see where the intake is sitting, that might tell me something.
Click to expand...

If you feel like you need a custom thickness gasket, try the cometic aramid fiber gaskets. They have about any thickness you would need. Here is a link to the page.

http://cometic.com/custom-gaskets.aspx
 
I did open up the manifold bolt holes a little because they were rubbing a bit the first time I bolted the intake on. And I did check the shoulders on the bolts, all ok.
I can make any gasket thickness that I would need. The .030 lasted longer than the .060 gaskets. I don't think it's a thickness problem, more a angle problem. I just don't know how to start to get it corrected. Thanks guys.
 
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