I recently replaced my old exhaust manifold with a very nice repo part.
But now I have this fairly good looking original and hate to throw things away. There had been no evidence of leakage at the block (3 in 1 type gaskets), so I figured the manifold might be in pretty good shape other than corroded threads at the tailpipe joint. Before offering it to anybody else or taking it to a swap meet, I decided to check for warps by placing a straight edge along one side of the four ports.
YIKES !! The aft port of the manifold was half an inch out of line. Can that be ?
Has anyone actually straightened a manifold that was so warped ? I assumed people were talking about straightening manifolds that were 1/8" or so out of line.
Best way to check is to place your straight edge at the bottoms of #'s 1 & 4 - then see where #'s 2 & 3 fall into place.
They can be straightened by heating and forcing on a jig to the proper position then letting it cool. This is difficult to do without cracking the manifold and the cost of a new one is low. The main reason for the warping of the manifold is because the 4 glands are left out when the manifold is installed. The use of the 3 in one gaskets has led some to leave out the glands, thinking they are not needed. If the manifold becomes overheated, and they do if the mixture is too lean or if the spark is too far retarded. I have seen exhaust manifolds glow red hot! Without the glands, the weight of the rear portion of the manifold and also the heat, because the exhaust from all ports goes through the rear outlet it will sag and over time you experience the warpage which you have noticed.
I have straightened them and have a jig set up for that but frankly it is not worth the effort or the expense when you figure how much acetylene and oxygen you have to use. The repro manifolds are great and cheap enough
Agree with Val. My repro from Langs is beautiful. Fits very well and the copper rings with steel glands installed easily. Go repro. Cheers, Bill