The Hayne's repair manual for my 1990 F150 makes no mention of using any gasket sealer on the intake manifold gaskets, except at the corners. As far as I can see, there's no mention at all of using any sealer on the gaskets that go in between the manifold and the heads, but I've always used sealer on intake manifold gaskets and all other gaskets of every engine I've ever worked on. I feel better using sealer than not, but I don't want to screw up anything. These gaskets are Fel-Pro and they look a little different from other gaskets, though, so maybe they don't need any sealant. They are kind of a gray color and are soft and sort of plastic or rubbery, not hard like exhaust manifold gaskets, but not cork either.

What do you guys say? Sealant or no? And if so, then what kind?


Thanks,


Matt

 

You could use sealer around the coolant ports, but it's not neccessary. I've never put any on (except for the front and rear intake oils seals) and I haven't had a problems thus far.

 

Are those Fel Pro "print-to-seal" gaskets? If they are they already have a sealant applied. If not use the gaskets dry with a small amount of sealant in the corners. Remember gaskets are actually "gaskets" that seal the irregularities not sealant.

Excess sealant squeezes out and clogs up oil passages and the oil pump. I use spray adhesive on some parts to hold the gasket on then put grease or silicone dielectric grease on the other side of the gasket to make it come off easy for rebuilds. More of a release agent than a sealer. The gasket seals the joint.

I pulled a 302 apart a few years ago that had an oil pump shaft fail. The cause of failure was a tiny piece of Permatex form a gasket about the size of a pinhead that had squeezed out from the pump pickup tube gasket surface and jammed the pump. That part had a gasket but someone thought it needed sealer also...

I have seen many oil pump pickups clogged with silicone and many oil drain passages clogged also. Use the gaskets dry or with some "release agent" like grease, Vaseline, or dielectric grease.

 

Eric,

How do I know if the gasket is a "print-to-seal" type? Does it say on the box? Maybe I should go look at it. I don't have it in front of me at the moment, though - I'll have to wait till I get off from work.

Perhaps instead of using adhesive or grease, as you mentioned, maybe I could use a thin layer of copper coat. That would hold the gasket in place and surely it wouldn't hurt anything?

As for using excess sealant, I undestand what you are talking about. I did not use any sealant on the pickup tube gasket or the gasket that goes between the pump and the block. I figured, "what's the use?" since I'm not really trying to keep oil from seeping out of the pickup tube and not trying to keep dirt from getting into into it, and plus, like you said, I was concerned that a piece of it would come off and do some damage somewhere. I used to apply gasket sealer liberally all over engine gaskets, but over the years I've thought about it some more and also heard horror stories like the one you mentioned, so I now use sealant very sparingly. I use it on most or all gaskets, but just a very thin layer of it.

 

I would not use copper coat. It will extrude out.

The Print-to-seal gaskets have a small line around the ports that is a different color than the base gasket material. usually some wild color like green, yellow, red, orange, etc.

I only use gasket sealer for those corners like the instructions talk about. I usually use Permatex aviation form a gasket for those applications.

On the pickup tube you are only concerned with it leaking air into the pump intake which causes cavitation and will destroy the pump.

Here is an engine building tip- Do not use a gasket between the oil pump and engine on a V8 or V6 type application. I make sure both surfaces are flat and smooth with no nicks or burrs then bolt the parts together with socket head cap screws torqued to 75% max specs for the bolt. This avoids any tendency for the bolts to loosen due to vibration working at the gasket material. Very little oil will escape the gap between two machined surfaces like that.

 

Thanks for the tips, Eric. The intake manifold gaskets do not have any different-colored lines or regions around the ports, so I doubt they are the type you are talking about.

 

If the factory didn't use it then you don't have too.

 

I don't know what the factory used. My old gaskets and the manifold and head surfaces were so messed up, covered with crud, that I had a hard time separating the gaskets from the those parts. I couldn't tell by looking at them whether or not they had any sealant.

And besides, I don't firmly believe that the factory does everything the best way in some cases.

 

Well, I torqued down the intake gaskets and found that I had to go around the entire pattern about a dozen times (no exaggeration) to get the bolts to the point where they were all finally torqued to the specified value.

In other words, after the first pass, I made a second pass to check the torques (my usual procedure for most gaskets), and when I made that second pass, the bolts were all below torque. I was able to turn them some amount before I reached the target torque. So I torqued them all again, in the correct order, and made a third check. During this third check, the bolts were all below torque again. I had to do this over and over again, each time wondering if I was doing the right thing. Finally, the bolts got to the point where they were fully torqued and needed no further turning to get them up to spec.

But I still wondered if there was something wrong....so I found a Fel-Pro Tech hotline and spoke with a company tech rep. He said I should not have done what I did, but rather I should have just left it at the first pass or maybe even a second pass. He said that when you keep torquing up these manifold bolts, it pushes the center section of the manifold harder and harder against the block (via the end gaskets) and it effectively lifts up on the heads, and he says this results in head gasket failures sometimes. He said this is more of a problem with aluminum heads than cast iron ones. Nonetheless, it sounds like something to avoid, if it's true.

Has anyone else heard of this phenomenon? Do you guys torque up your intake manifold bolts repeatedly until they maintain torque, or just one or two passes?

Basically, the info above is straight from the horse's mouth or so it would seem, and yet it almost seems unbelievable. After all, there's a compressible gasket between the intake and the block, and those intake bolts are a whole lot smaller than the bolts that hold the heads onto the block.

What do you guys know about this?

 

Basically I make 2 to 3 passes and then do the break in run. Then I re-torque them again.

I feel the same way you do. I would not think that the intake bolts could "pull up the heads". There is a very small amount of movement in the difference between the head bolt holes and the head bolts, but I would not expect the head gaskets to fail even if somehow the heads were torqued down with all of the bolts at the extreem far side and the entire difference was pulled up with the manifold bolts. (If that made any sense).

 

I do the first pass at 75% torque then follow up with two passes at full torque. The factory probably just runs them all down at the same time once with some sort of multiple drive fixture.

I can't imagine that the manifold would pull the heads much. You did not say if this was part of a rebuild or just a manifold replacement. It does not matter much since the unit is already sealed up. If the heads have been milled and other machine operations done sometimes the end seals are too thick. If this is the case people usually use a bead of silicone RTV instead. Test fit with a single gasket to simulate crushed gasket thickness. You can measure the gap and compare it to the end seals with about 10-20% crush. If extensive machine work has been done the manifold must be milled. A machinist can figure the machining required. The gasket makers may have better figures. This has worked for me in the past.

 

I wasn't satisfied with what I had done (re-torquing over and over again), so I pulled off the manifold last night and bought a new gasket set - this time it's a Print-to-Seal set like you recommended. It's more expensive, but I want this done right.

Anyway, I think the instructions that came with the gasket set said to expect the crush to be anywhere from 20 - 60 % for the cork gaskets (if I remember right). That's a pretty big range, but I guess it depends on how much the heads were milled, whether or not the manifold was machined, etc. I did have my manifold machined, by the way, in order to smooth up the surfaces and get rid of several thousandths of warpage that existed. The machinist took material off the sides, as well as the bottom.

In answer to your question, I am installing a remanufactured engine in my truck. I purchased a long block from S & S engines in WA state, and I'm attaching all of the external parts.

Along the lines of what you mentioned, a friend of mine always uses beads of sealant at the ends instead of the end gaskets, even if there is enough gap for the gaskets. I think I will do that too. He lays down the beads last thing before putting the manifold on, so that they are still wet and sticky.

Also, I bought some Super Tack from my auto parts store. It's not a spray-on adhesive, but it is an adhesive, nonetheless (comes in a tube like sealant). I guess I'll use that to hold the gaskets in place. The gasket kit provides very specific instructions on how to do this, but doesn't mention how much and where to apply the adhesive. I guess I'll figure it out. Feel free to provide any more input, though.

Thanks

 

Your initial setup should have been OK. How did the old gasket look? Did it look like you had any sealing or alignment problems?

I use spray adhesive on the removable component if possible, in this case the manifold. That is probably not possible tho with your manifold setup. There should be some sort of locating tabs/holes to position the gasket tho. Just use a minimum amount of adhesive, a small dot, maybe at the ends. I use 3M photomat adhesive available at craft stores. I have been using the same can since about 1980.

I don't like to crush those end gaskets much or they tend to extrude. Certainly not 60%... I can't tell you how many times that they have extruded on me or others that I have observed, both cork and rubber, back in the old days before fire, er I mean RTV They always seemed to extrude inward along the back of the engine where you could not see. They made for a fine oil leak.

Use only the minimum size bead of RTV on the ends to ensure contact with the manifold. You don't want it to extrude either.

 

When you say, "initial setup," I assume you mean the gasket that I originally put on a few nights ago? If so, then it looked ok. As far as I can tell, it had good contact all the way around. Of course, that's sort of hard to tell, but it seemed like there was evidence of contact all the way around each port, so that is good. I expect that it should contact fine, since I had the manifold machined. One the other hand, if you mean the old gasket from the old, worn out engine, then that is a different story. There was evidence of leakage in many places, and the manifold was heavily corroded around the water ports and was definitely warped. I checked with a straight edge. I didn't even use that manifold, but rather purchased another used one that looked to be in much better shape, but even it had a little corrosion and a slight amount of warpage, so I had it machined. Like I said in my previous post, I like to do things right and don't like to have problems down the road. This vehicle is my primary transportation and I want it to last another couple of hundred thousand miles with as little trouble as possible. I haven't given in and purchased a new vehicle in my life so far, and I don't intend to if I can keep from it, so the work I do has got to be right.

As for the positioning tabs, yes, you are correct. This engine does have these tabs, which seem to hold the gaskets nicely, so I wondered why the instructions would say to use any kind of adhesive. I guess it's to prevent the small amount of motion that can occur as you set the manifold in place. Your statement to use a small dot confirms that. Other than that, no sealant at all. So I'll follow that line of thinking, too.

As for the end gasket crush, I checked last night, and confirmed that the Print-to-Seal gasket instructions indicate that the end gaskets (which are cork) will crush anywhere from 15 - 60%. The ones in the first set that I installed the other day seemed to crush about 30 or 40% (just eyeballing it). When I did a dry run with that first set of gaskets, I set the side gaskets in place, then set the manifold in place, but without the end gaskets. This gave me a good idea of what clearance existed at the ends, and I was able to just barely slide the end gaskets under the manifold, which seemed about right. Nonetheless, I may go with just a thick bead of sealant in place of the end gaskets, as that is what was recommended by my friend (actually a friend of a friend), and since you mentioned it as well. Although, I will keep this bead to minimum, as you mentioned, in order to keep the bead from extruding.

Thanks again for all your help. Some of my questions may seem basic, but I really am not quite that green. I have completely rebuilt one engine in my life (flathead 6 from a 1949 Dodge Power Wagon), and have done fairly major work on a few other engines and other components (removing heads, manifolds, clutch job, suspension rebuild, etc) and lots of minor work on many other engines/vehicles, but believe it or not, I had never changed a manifold gasket on a v-8 engine before. All of the major work I had done previously was on inline engines, which I seem to remember having a different gasket, more like an exhaust manifold gasket, on which I used copper coat. I am accustomed to using gasket sealer on just about every gasket on an engine (just a very thin coating), and have never had any trouble doing that, but these 302 intake gaskets looked so different, almost as if gasket sealer wouldn't even stick to them, I wasn't sure what to do. Thanks again for you help.

If you have any more comments, please let me know.

Thanks & sorry for the long posts.


Matt

 

That is the one I meant.


Good, avoid anything that creates unequal pressure.

Like I said before. Using a single gasket rather than both gaskets gives a fairly accurate indication of the end seal gap.



I measure the end gap and if I see more than 20% crush I use the RTV seal. When the end gaskets crush much more than that they seem to have a strong tendency to extrude or split. They can be secured to the block with adhesive but they still want to slide...

Try the cast iron intake for an FE engine if you like excitement.

I don't use sealer on any gaskets if I can avoid it. It makes replacing the part gasket scraping hell the next time.

Have fun and no problem. For any specifics on your engine you might check with the 302 forum.