I finished installing a new Magnaflow high flow cat on my 1985 the other day. This was a "direct bolt on" fit according to the documentation. First of all, the old cat had holes that were taped with threads, the new cat just had holes. I was lucky in that I had eight 5/16" bolts and nuts at my shop. The next problem was the old heat shield needed to be modified to handle the new position of the Magnaflow tube. Again no major problem, just a quick ZIP with a cut off wheel and a little bending and we were there. The next was the tube from the cat and engine area. The old cat had a bulge on the tube that fit into the tube coming from the engine area. This was then crimped together with a mickey mouse metal band that was crimped around the two to hold them together. I the past when I wanted to remove the cat to do other work on the car I had to contend with this link. This is how I solved this problem, I used a compression coupler to conect the 1/2" diameter tubes coming from the cat to the tube from the engine area. I only used one coupler in this project. Picture of the coupler:
Picture of coupler on cat tube:
Picture of coupler installed on cat in car:
If I were to do this again, I would cut the tube from the engine area about a foot ahead of the car in an area that the tube is very straight. Then cut off the 3/4" conector on this section of the tube. Install the compression coupler on the cat and with the short section of the tube that was cut from the engine area couple this to the cat. This would give you the flexability to align the compression fitting with the tube on the cat. Now add an additional coupler on this long staright section. This would be very easy to align and couple together and give you and extra 3/4" which I lost when I cut off the conector on the old tube. The cost of the coupler was $1.65. Now if I want to drop the cat to get to other things, just unbolt the fitting on one side and you are ready to drop and remove the cat without contending with the tube.

This is my first try at posting pictures. Hope they come out.

 

I see what you mean, but the pics are real small... like itty-bitty.

I used a piece of high-temp rubber tubing when I repaired the wifes 87. Worked pretty good, really.

 

Let's try this full picture of the the main body of the compression fitting, the compression ring and the threaded conector.

The compression ring on the tube and the threaded fitting that slips over the the other half of the coupler to pull it together.

The complete compression coupler on the cat tube.


Completly installed on the cat in the car: .

 

That'll do it. They need to be aligned pretty well to begin with to use a compression coupling. Also be sure the compression ferrules are snug on the tubes (I assume the tubes are a standard size, maybe 3/8" so this shouldn't be a problem).

 

looks great!

 

Both the car tube and the tube from the engine area are 1/2". I did flare the tube on the cat a very small amount so the compression ring would not slide off. Once I tightened the fitting the compression ring was snug and solid on the tube. This was not a problem on the tube from the engine.

As I mentioned, if I do it again or take it apart I will cut the tube from the engine area about a foot ahead of the cat and install a compression coupler there. This would allow the EASY alignment of the coupler on the cat and the second coupler would be in a nice straight section of the tube and would then be easy to align also.

 

Nice job John. I have a mangnaflow cat also, but I have headers, so I got the one with no tube hole, or the shop welded it shut - I can't remember, I'll have to look when I get home.

 

The 85 direct fit Magnaflow comes stock with the tube. Mine came with a cap on the tube which I had to remove. In California you have to have these things hooked up. I believe my cat was plugged. The new cat was like adding 25 horses!

 

John, thanks for posting this information. I purchased the same cat for my 85 and will install it soon (as soon as the frozen tundra of WI thaws, that is ). If you hadn't posted the info about the cat not being threaded, I would have found myself in a bind. Now I can pick up some bolts/nuts and be set before I begin!

Gary