I purchased an aftermarket dual exhaust system for my 1977 F150 w/ a 302 V8 and according to the catalog it was supposed to fit 77-79 F-Series trucks w/ a 302 engine. The first thing I noticed when I pulled the down pipes out of the box, was that they had a different style of mounting flange on them compared to my original exhaust. The new pipes have what I would call a ball type flange, where the flared end of the down pipe was designed to mate with an exhaust manifold with a ball shaped mounting connection. My 77 manifolds were designed to seal with "doughnut" style exhaust gasket. When I reviewed the installation instruction sheet, it stated that this dual exhaust system was designed to fit 1977-1/2 to 1991 F-Series pickups w/ 302 engines, so I am guessing Ford had an exhaust manifold change in mid 1977.

This leads me why I'm asking this question in this forum. In order to make my new exhaust system work on my truck, I ordered a set of 1980-95 exhaust manifolds for my truck that have the correct mounting design. My 77 exhaust system used a flat flange, two mounting studs, nuts, and exhaust gasket to mount the exhaust down pipes to the exhaust manifold. My question is how are the down pipes connected to an 80's style exhaust manifold? Are there any gaskets used? What shape is the sliding mounting flange? Do you attach the flange with similar stud style system as the 77's or do they use some kind of spring bolt system to keep the joint under pressure? Sorry about the long posting, but I thought some background may help you to better understand and answer my question. I would appreciate any pictures of this connection if anyone has them as well. Thanks.

 

I could be wrong, but I think the reason for the ball type end on the pipe is so you wont need a donut gasket to connect it. I have a 79 Capri with a 74 302, and it had a 70's era manifold on one side and an 80's manifold on the other side(since replaced with headers). They both had the same connection with a donut type gasket.