How to seal up a ex manifold to pipe flange?

[71 SE3834V]

I've got a leak in the above connection. A new gasket was installed last fall during the engine rebuild process. Manifold and pipe flange was cleaned. Don't remember if I put a straight edge on the flanges. I could hear a slight leak but just getting around to investigating it.
I dropped the pipe down. Gasket looks real good. Obviously it's not sealing. Slight warp somewhere or the manifold has rusted away some. I put a straight edge on it last night but can't really see up there.

My question is: Is there a quick fix? I first thought of doubling up the gasket but don't know if there is enough flexibility in this type of gasket to fill the gap. Or can I use Permatex Ultra Copper on the gasket or some other product? Will that just blow out? If that will work I'm guessing I will need to let it fully cure 24 hrs before firing up the engine?

Just my luck. I wanted to drive the car somewhere tomorrow morning.

[68 RT]

Try these, I used them on my 68 hp manifolds. They seal great!  http://www.ebay.com/itm/Remflex-6005-Exhaust-Collector-Gasket-for-Mopar-Set-of-2-/371326447053?hash=item5674c7edcd&vxp=mtr

[71 SE3834V]

How thick are those? I would think I would need something thick enough to fill the gap.

Forgot to say this is a stock HP manifold pass. side. I'd like to find something I could pick up locally and get the car back on the ground for a weekend show. Might just try the ultra copper and if it doesn't work I'll have to deal w/it later.

[firefighter3931]

Try the Ultra Copper. Let it set-up overnight and just snug the bolts down so as to not push all of the RTV out. The next morning you can torque them down. 

Fwiw, I've used Ultra Copper in place of a header gasket and it worked great....no problems sealing. Did this while we were testing multiple header combinations on the old 446. We had 4 different sets of headers on the motor over the two day dyno thrash. Just let it set up for 30 minutes and all was good. Obviously not the best method by not allowing several hours of cure time. 

With a warped flange a MLS style gasket would be the best choice. I use the Percy's header gaskets and have had the same set for several years...been on and off the car a dozen times. I wonder if they make a flange gasket....might be worth looking into. I also use the Percy's collector gaskets with the same excellent results. 


Ron

[68 RT]

They are thick and will compress, If your pipe flange is warped a regular gasket will not fix. I tried 2 gaskets and cooper rtv on mine it will last for a little while depending on how bad it is warped.

See this info:•See Part Number 6006 for 2-1/4" Pipe Flange; Mopar Exhaust Collector Gasket 2-1/2" Pipe, 2 Bolt Holes (One slotted) 3-29/32" Bolt Hole Spacing, 2/set
•Heating and cooling of the exhaust system causes header and manifold flanges to warp resulting in gaps between the head and header which Remflex exhaust gaskets seal completely due to the thickness and compressibility of the 100 percent flexible graphite
•Remflex exhaust gaskets come in a standard 1/8 inch thickness and are designed to crush 50 percent allowing them to fill any pits or gaps in the flange surface up to 1/16 inch
•The aluminum cylinder head and steel header or manifold combination are configurations that readily cause gap issues in the mating flanges due to contraction and expansion of the dissimilar materials; Remflex exhaust gaskets fill those gaps permanently
•There are no rubber binders or composite materials in Remflex exhaust gaskets so they will not shrink or harden due to time or temperature eliminating the need to go back and continually retighten your flange bolts

[John_Kunkel]

How thick are those? I would think I would need something thick enough to fill the gap.

Description says "Remflex exhaust gaskets come in a standard 1/8 inch thickness and are designed to crush 50 percent allowing them to fill any pits or gaps in the flange surface up to 1/16 inch".

[71 SE3834V]

Thanks for that info. It sure looks like they'll do the job unfortunately their arrival time would be while I'm on vacation and I need to put the car away before then.

I got a mirror up there and it appears the pipe flange might be the culprit. Some rusting. I picked up a new standard gasket and installed it w/ultra copper per the "Ron" method. That'll have to do for now. I'll keep the above info on hand to deal with it in the future. A new exhaust system might in the plans anyway as I'm getting tired of the drone of the glasspacks.