Just installed SS

Pypes 2.5” manifold back exhaust on 68 442. I checked it for leaks using vacuum and noted both down pipes where slightly leaking at exhaust manifold connection. Am I missing some kind of donut here or is the fix just installing high temp sealant around the mating surfaces??

Thanks!
Chad

 

This is how they fit ,but seem to have it aligned perfectly before tightening and even then they can be finicky. Ive had to have the downpipes bent just slightly for proper fit.i have them on my 76 as wells as 80 and both were a pain to get just right .You shouldn't need sealer. yours actually looks like a better fit than mine.

 

Loosen snd tighten the bolts several times, it may be the flange isn’t mating to the manifold perfectly. If that doesn’t get it to seal, some high temperature RTV will for sure. Drop the head pipe, put a bead around the manifold flange, reinstall and torque. Wipe off the excess, let it set up a little and start it up.

Hoe did you use vacuum to test for an exhaust leak?

 

Walker Acousti-Seal. P/N 35959. Available at NAPA and other usual sources. This stuff is magic. My truck has never been quieter.

 

That's good to know.

 

I also installed Pypes 2.5” down pipes on the manifolds of my 72 Supreme 350. After fussing with them for several hours and still having leaks, I finally cut the stainless flanges off and welded “alumanized” steel flanges in their place. Bolted them on, I now have a perfect seal.

 

Looks to me like the bolts/flanges are not even. Even them up. (the gap between the pipe & mani flange).

Next loosen the connection enough so the pipe taper moves on the manifold conical. Assuming you don't have the mufflers and tails connected yet, wiggle it around giving the bolts a few degrees toward tightness as you wiggle until tight, repeat as needed.
What this does is it gets the softer pipe profile to witness (seat) to the exhaust manifold conical. Then retighten. May have to do this a few times?

Once you are happy then apply a thin film of the sealant if needed and then perform the final torque/alignment.

TIP: coat all threaded fastener hardware and any slip fits with copper or nickel anti-seize. All of it... the clamps, manifold to head bolts, head pipe bolts etc.... You will thank me the next time you need to remove anything.
Remember to back off 10% on the torque value when using the anti-seize. Heat cycle the system for a few 100 miles recheck torque.

 

I covered one exhaust with a rubber glove/tape and placed Ridgid vacuum on "blower" and stuck it in the other exhaust pipe with some tape to seal it up. Seems to work pretty well.

 

Awesome...thank you! Should I put anti-seize on the ARP exhaust manifold bolts as well??

 

A small dab on the manifold to head bolts yes. The threads and a small amount under the bolt head. A little goes a long way. Use too much and it can ooze out and stain. Only a concern if you have a show car.
Important to verify torque on the manifold fasteners after a few 100 miles.