Ok guys I'm sure someone has come across this issue. I pulled a 350 out of my 71 Cutlass S coupe. It had factory exhaust. I've installed a 455. When I try to mount the drivers side header it hits the proportioning valve and won't line up. I was told to use a 2x4 and push the header away from the frame. My concern is breaking the flange on the header. Any idea's?

 

You are using 455 headers right? It is also common to have to move brake junction block from side of frame to top for header clearance.

 

Yea, I agree.

My self and others have had good luck with simply unbolting the junction block and carefully bending the lines to the top of the frame...all as a unit. You don't have to break the lines loose from the block.

The trouble I ran into was the back drive linkage and the cable bracket for the console shifter.

I've had two sets of headers in my car, and it seems that no one can make a set exactly alike. One of the collectors will slant off at an angle and not be even with the other side.

 

I move the valve up on top of the frame, had to clearance tubes 1 and 3 for the steering shaft, and clearance the passenger upper A arm a bit as well.

All in all took about 16 hours to install both...

 

There was a header on display at the Nationals this week that supposedly doesnt require you to move the prop valve. Brand new from Mondello.

 

I don't know if you sat through the Mondello infomercial, er, I mean "seminar" or not, but several interesting tidbits. First, Joe introduced Lynn Welfringer as his "business partner" on at least two different occasions, so I guess there's no question as to whether Mondello is still involved or not with the business in Calif that bears his name.

Second, Lynn stood up when showing off this header and proclaimed that it was specifically designed to fit "Cutlasses, Cutlass Supremes. and EVEN convertibles", so the myth lives on.

On the other hand, it did look like a nice part.

 

Moving valve to top of frame sounds reasonable. Thanks for the input from all.

 

FWIW, M&J Proformance makes a header that fits perfectly in 70-72's, and maybe other years as well..
mjproformance.com/