340 Header Gasket (copper or aluminum) recomendation

Hey folks,

Looking for copper or aluminum header gaskets for 340 standard port X head. Thanks!

Neither one by themselves will seal that well. You'll need to put some copper high temp rtv sealer on them. Metal to metal is either touching or it's not if you think about it. They don't have any give to them.

Other will say Remflex.

I used Remflex on my J-heads with excellent results. The failed to leak when the passenger side header caught the trailer and was bent significantly. Tube to flange weld/seal broke, but the flange didn't leak. I can't imagine a standard style gasket surviving that. They are worth the cost and all I'll use in the future.

Remflex are the best I have used--they sealed on cheap headers that I could not get to seal with other gaskets.

Remflex, nothing else.

If you buy remflex you wont use another gasket. Just follow the instructions!

I gotta agree the Remflex will seal for sure. My question for other Remflex users. Have you reused the gasket? My Remflex gasket stuck to the headers when I removed them and they tore apart.

We have used the Fel pro graphite type gaskets with Excellent results on a multitude of applications. The same type of gasket is made by different companies. They are somewhat soft and crush when tightened. Every set of copper or aluminum ones we have seen, leak Could be the for a number of reasons but the graphite have always sealed in those same applications without changing anything but the gaskets

BTW I have plenty more pictures like the one below

I have had copper header and collector gaskets on my 340 w/ J heads since I put the car back on the road in 2002. No leaks, still working fine. I did not coat them with anything. (I have TTI headers.)

Regardless of who's gaskets you use, you have to look at the flange-to-head and mate up the gasket... to see IF it'll make physical contact and seal. Some headers, example Hooker 5115 Super comp (SB Mopar), have poor flanges with the factory welded beads not allowing contact with the gasket ports completely around their ports... NOTHING will then seal!... and you'll have to apply extra surface area of welding and or hi-temp JB Weld epoxy around the port so the gasket will have some contact.

My buddy does reuse them. He builds demo derby cars and reuses headers on all the small block chrysler engines he's swapped from car to car. One set of headers has been on 6 cars in 11 derby's so far, I just bought some used TTi's headers and will be running Remflex on those.

The part of your statement I bolded is critical and often overlooked. But I'm not sure the hi temp JB will take that kind of heat on a prolonged basis. I know fel pro does sell the graphite / composite material in sheet form if you have to make your own as we have had to on occasion

Whatever happened to the idea of cutting the header flanges to make 3 individual pieces? A lot of time that thick flange doesn't give and if something is slightly off, make sealing the headers a pain in the rear. If you cut the extra metal between the cylinders, except the two in the middle (for non hemis), you now have "floating" flanges and have some flexibility to them. Not to mention it may give you some more room for your spark plugs. You can even cut the gaskets down or leave them as one piece for easier installation.

We still do it when needed but as MM said, step #1 is to check the port to flange sealing area.

I don't know why there is some resistance to cutting the flanges as you say, RoadrinninMark??

I have posted that solution maybe 10 times over the years, it works just as you say.

Never a leak here.....

Joe

I have been real happy with the TTI Gaskets. They seal great and due to some transmission issues I have re used my passenger side one about 5 times now from pulling that header and have had zero issues.

Agree, Joe

same here. i always cut the flanges. plus, drill one bolt hole per flange oversize. this allows the flange to "float" a bit during heating and contracting.
no leaks on even the thin, flimsy flanges.
i stole this idea from a member here years and years ago, and it just flat out works !

That's a new one for me, thanks X!

I'm a former aftermarket gasket applications engineer from Fel-Pro... 22+ years from the 70s-90s... with my interest in Mopars, they allowed me to work on many of the Dodge/Ply/Chrysler applications.... it was a great fun time and a great company back then!