To Gasket or Not To Gasket?

[Bill Musarra]

I am wondering whether to use exhaust gasket material between the headers(stainless) and the aluminum heads? Bolting up the headers is a job and a half. I had to alter a 3/8" box end wrench just to get them on with the tight clearances. Would the gasket makeup for slight irregularies in alignment(read leaks)????

Bill

 

[Cliff Beer]

Bill, you're going to end up with leaks at the header flange if you don't use appropriate gasket material - you'll be back in there fiddling with that box end before you know it. So, yes, gasket material will help with a small amount of misalignment, but not much.

 

[Mike Drew]

You definitely need SOMETHING in between the header flange and the cylinder head; even the most precise header will leak something fierce without something to seal it to the head.

Historically this has meant some sort of gasket; they are available in a variety of different styles and materials, with some performing much better than others, some being more 'maintainable' than others (i.e. you can remove and reinstall the exhaust system without trashing the gasket).

In the past few years, chemicals have been invented which substitute for the traditional fiber/cork/copper/whatever gasket. I'm talking about goop in a tube, form-a-gasket impregnated with copper or something similar. Many OEM applications no longer call for a conventional exhaust gasket as a result; goop is carefully applied to the exhaust manifold and then it's bolted to the engine.

Although I tend to prefer high-quality, conventional gaskets (I've had failures with high-zoot copper gaskets), my Cobra ran for years with nothing but blue Permatex RTV sealing the headers to the heads (not my first choice).

If I were to forgo gaskets today, I'd use Permatex copper gasket maker instead (available at any auto parts store). Carefully apply a 1/4 inch bead around each opening on the header flange, then lay the exhaust in place and tighten the bolts just finger tight--just enough to ensure full contact on both sides. I'd then let it set for 24 hours, then apply final torque to the header bolts.

The stuff works. I've got a VW Scirocco that had a broken exhaust stud; fixing it would require taking the whole motor apart, so I decided to just use the copper stuff on that cylinder (the motor uses individual gaskets for each exhaust port). It sealed up great and has been holding up perfectly for more than 15 years.

That should do ya. :thumbsup:

 

[Jack]

I've used the Permatex Copper gasket maker without problems on many installations.
Pretty good stuff. Carefully follow the instructions though.

 

[Randy V]

Done the same myself many times over just using the Copper RTV.. Hard to find header gaskets that match both the ports anyway..

I typically put a bead of it on the header flange and let it just skin up (20 min to an hour depending on temp) and then install. No leakers that I'm aware of..

 

[Bill Musarra]

I was out looking for supplies for our spring cleanup and yard work. It was near a NAPA store, so I stopped in to see what they had for my 351. Told them what I needed and that it was for the square ports. They came up with a FelPro set of exhaust gaskets. They are the aluminized variety for the 98-69 engines. Took them since they didn't cost that much. As you can see they fit pretty well.

Trimmed them and had to do a little modification of the tubes so the new 3/8ths wrench would fit. Had to do a little grinding on the wrench, but it worked. Added thread locker to the studs and waited til this morning to attach the pipes.The gasket moved the pipes a little. The same sided pipes were moved out, and the crossovers moved closer in. So the pipes had to stay loose to get the merge collectors in place with a rubber hammer, then tightened the flanges down. The first heat cycle will probably fix their shape.

Bill

 

[Randy V]

I was out looking for supplies for our spring cleanup and yard work. It was near a NAPA store, so I stopped in to see what they had for my 351. Told them what I needed and that it was for the square ports. They came up with a FelPro set of exhaust gaskets. They are the aluminized variety for the 98-69 engines. Took them since they didn't cost that much. As you can see they fit pretty well.

Trimmed them and had to do a little modification of the tubes so the new 3/8ths wrench would fit. Had to do a little grinding on the wrench, but it worked. Added thread locker to the studs and waited til this morning to attach the pipes.The gasket moved the pipes a little. The same sided pipes were moved out, and the crossovers moved closer in. So the pipes had to stay loose to get the merge collectors in place with a rubber hammer, then tightened the flanges down. The first heat cycle will probably fix their shape.

Bill

Good tip on the gaskets from NAPA... If your heads and headers will accommodate gaskets properly I see nothing wrong with using them. Just that some heads (particularly stock ones) don't seem to have the same amount of gasket area around the ports as the aftermarket ones - which forces you to trim the gaskets a lot, thereby leaving little gasket margin between the inside of the port and the outside world. When this happens, the gasket burns through quite readily.

I like studs, but the only issue I see is that in order to change out the gasket, you're forced to remove the header system rather than letting it hang on the front and rear bolts to slide the new gasket into position.

Your headers install much in the same manner as mine although I've not had to resort to using the rubber mallet yet..
I think if one were to lubricate the tubes as they slide into the merge collectors, it might go just a bit easier. Lubrication could come in the form of high temp RTV if concerned about leaks, to Anti-Seize for those systems that are exceptionally tight.

 

[John P]

Check your header flange with a precision straight edge to insure it's true. If the header uses a one piece flange and a little warped, a machine shop can true it for you. I like the Felpro #1416 exhaust gaskets for Ford small blocks, It has slots at the end bolt hole position, this will allow you to loosely install the header using the enf bolt holes, then sip the gasket in between the header flange and the head, then install the rest of the bolts. I use ARP 12 point header bolts, because of the reduced wrench size, usually there is no need to modify a box end to tighten the bolts. Header bolts should be retorqued after the first couple of heat cycles to insure they are tight.

 

[Jim Rosenthal]

ARP sells exhaust manifold/header bolts which have a small head but 3/8" thread. They are a lot easier to drive since the bolt head is 5/16". I used these on my Kirkham Cobra because there was so little space for the header bolts. The 12 point bolts are also a good idea, they will work in some installations. I think they also make 12 point bolts WITH reduced diameter bolt heads as well. And, as usual, everything I have ever gotten from ARP worked great the first time. (providing it was the right size; we won't mention the metric flywheel bolts that a well-known equipment company sold me for my non-metric flywheel...that wasn't ARP's fault...)

 

[Pat Buckley]

Please remember that if you leave the headers loose so you can get the collector on easily you will never be able to tighten the header pipes to the head. There is such little leverage at the head tht you will probably round off your fastener before any serious "drawing in" takes place!

Always tighten the headers first - if that means you have to wrestle with getting the header pipes into the collector, oh well. They bend way easier out there.......


Edit: Oh, I use high buck copper gaskets (trimmed) as well as the copper RTV...

 

[Johan]

I don't use gaskets because they can blow out and they are not the right shape for my ports without being modified. My headers have individual machined flanges for each pipe and sealing them with a smear of goop is a breeze.

 

[Leon]

Hi Bill.......lots of good advice on this thread so thought I'd offer some Kiwi advice as well, if you use gaskets you have to make shore you keep tweeking the header botls the fisrt few times you use the car as the gasket will give alittle to begin with and you will find the bolts will come loose and your blown a gasket before you Know it. My engine guy who races Saloon cars over here never uses gaskets, a smear of Hi Temp Silicone on the header flange and tighten them down, I did this on my Race Truck, never had another problem. Cheers Leon.