I have exhaust leaks, both sides, getting progressively worse on 68 442, original 400 engine & manifolds. I suspect rotting or loosened flare fitment at the pipe-to-manifold, as the exhaust system is 30+ years old (aluminized steel). Mufflers & tail pipes/trumpets seem fine. Looking for recommendation on head pipe replacements - custom bent & fit, or anyone have good results with pre-bent pipes from a supplier?

Thanks.
Mike

 

You may already know that Olds didn't use donuts on these manifolds. The seal is metal-to-metal on the flare. Be sure the tapered surface on the manifold outlet is clean of any rust and scale. I've found that Walker Acousti/Seal works wonders for getting pitted flanges to seal.

 

For my 69 Cutlass with a 70 455 4 speed (Thornton's W & Z manifolds) I bought Down Pipes from PYPES. These are like 3' to 4' long each. (I have 2.5" exhaust)

The Passenger side fit perfect and the Drivers side needed cutting and welding at about 12" down so that the pipe flare fit the manifold outlet squarely and the pipe would be centered between the frame & starter +-, Pypes said it was my issue but I complained and they sent a free replacement that also did not fit / same as the 1st one ...

I have no idea why my car was different from others that said they were a good fit right from Pypes.

I used Remflex Gaskets and Permatex High Heat at the Pypes to the 2.5" Exhaust Flange adapters, I didn't have that part welded so I could dis-assemble the band clamps if necessary.

 

You must have a Cutlass Supreme.

Kidding!