To my other GT6 pages

January 24, 2020

Exhaust Manifold

GT6 exhaust manifolds were pretty conventional cast iron affairs.  Weighing in at almost 13 pounds, they are fairly robust, and don't seem to often cause problems.   They are basically a 6-2-1 arrangement, but without equal length runs as a true header would normally have.

My manifold was rusty, as they usually are after 50 years on the car.


 

First job was to separate the manifold from what was left of the downpipe.  It took way more effort than it should have.  All three studs survived the experience, but they were in pretty rough shape.  In the wrestling matches to remove them, the results were: studs, 2; me, 1.  For all three, I had to resort to penetrants, heat, and a welded-on cheater bar.




Cleaning up the rust makes the piece much more pleasant to work on.  My 5 gallon de-rust bucket was only big enough to do half of the manifold at a time.  I use a solution of phosphoric acid. 




The acid bath leaves a black residue on the surface, but it brushes off pretty easily, leaving bright metal.




I ended up drilling out the remnants of the two broken studs.  It is a really good thing that the head-side and exhaust-side flanges are at right angles to each other.  It made the drilling setup pretty straight-forward, though not exactly easy.




While it was set up, it seemed to make sense to face off the flange face.  It was pretty pitted.




I ended up facing off the head-side flanges, too.  They were in better shape, but weren't exactly co-planar.  It took three passes, totaling about 0.020" to get them all flat.




A couple of coats of silver manifold paint, and new stainless studs and brass nuts.




So this puppy goes on the shelf with the growing number of refurbed  parts.




This was a pretty simple one, even with the stubborn studs.  I also want to add a couple of bungs for oxygen sensors for an AFR meter, but I'll wait until the engine is installed to determine the best places to put them. 

Cost for this little exercise was under $10 for the studs and nuts.

Comments to Ed at mailto:elhollin1@yahoo.com

To my other GT6 pages