[namba209]

V-6/T-5 Engine/Tranny Swap Phase V

Building the exhaust manifolds

With the engine/tranny package in the car it was time to see about fabricating custom headers to be able to use the twin oxygen sensors and the 3-stage EGR valve. I have a set of manifolds off a Fiero and a set of headers from an early S-10 V-6. The Fiero manifolds are cracked and need to be welded and opened up inside before they can be used, if that’s the way I go. The S-10 headers have the mounting flanges 90 degrees off for the 3.4 engine. They will have to be removed, rotated vertically, and be rewelded before they can be used. Again if that’s the way to go.

Also, additional trimming is needed to the foot well for exhaust clearance. I slid the Fiero headers in the along the engine on the passenger side and they bolted right to the engine. The driver’s side was more of a hassle, I had to cut the footwell back further and trim the front edge closer to the steering shaft. These cuts were made with the engine in the hole and will be redone and made neater after the engine is back out. Both Fiero headers bolted up to the engine after the holes were made bigger/longer. This type of header is what will have to be used as there is not enough clearance to run the exhaust down and back from the center of the block. The engine mounting plate and starter are in the way on the right side. The clearance is not enough on the left side, although a header pipe will fit behind the oil filter, the clearance for the brake lines and fuel lines is too close for my comfort.

After consulting with the custom header shop, it was decided that a log type manifold is the way to go in this application. Because of the clearance issues a decision was made to use 1 ½” square tubing, with the port flanges welded on one of the flat sides and bring the exhaust to the front of the engine, then down, back, with a 2 ½” headpipe that will go over the subframe. This will give more clearance and the manifold will be closer to the head because of the absence of stub ducts to the log manifold and also be useable to mount the EGR valve on the right side of the engine and the oxygen sensors will be mounted on the down tubes just after the down bend. The square tubing was decided upon because using that versus round tube of the same size gives a volume increase of about 25% more exhaust flow than the round tubing. At least that’s what it looks like on a paper drawing of the cross sections of each type tube.

It has been almost a year since I contracted the construction of the square tube manifold and I got the passenger side finally done. The only problem was the configuration cannot be used with the EGR valve. The valve either sits too close to the flange bolts or too close to the spark plugs so neither can be removed or installed. This is a recording “Back to the drawing boards”.

After seeing the really neat work done by Bob Legerre (sp) AKA Rally Bob on his “Quest for Carlisle” thread, I contacted him and got his source and part numbers for really good looking steel fittings that could be adapted to exhaust system use. They are from McMaster-Carr and as luck would have it, they have an outlet here in sunny SoCal. A phone call and I had the fittings in 1-2 days. Also, there was a person who makes flame cut exhaust flanges selling his wares on E-Bay. A quick check of his ads and I find he is less than 20 miles from me. Life is getting good. I contacted him and he made up a pair of ½” thick flanges for the V-6. Normally they would be 3/8” thick, but I wanted the extra thickness to try and eliminate warpage during the welding process. So I ordered the elbows, “Ts”, some 12” long seamless steel tube in 1 ½” diameter, and two 1 ¼” – 3” reducers, foregoing Bob’s recommendations of 1 ¼” fittings. Big mistake, again! The larger fittings do not allow any room for the ARP exhaust bolts to fit in the holes in the flanges. So I ordered the whole mess again only this time in 1 ¼”. but I kept the reducers. Both sizes were priced about the same so I spent about $100 twice for the fittings and $40 for the extra thick flanges. To insure the flanges were perfectly flat, I had both sides machined at my local motor machine shop. They couldn’t believe how hard the steel was, it took almost 6 hours to get them done at a cost of $90 because of the extra time it took.

So now I have perfectly flat flanges, all the elbows, Ts and tubing I need for the manifolds to be built. I laid the pieces out on the flanges and stuck a piece of 1” PVC tubing down the fittings to hold everything in place, kinda sorta. I called my favorite welder over and he torched them all together for me. While he was here, he also welded up some temporary header pipes with 2 hole flanges to mate with the flanges on the manifolds. Another minor mod I would do is to change the fairly large 2 ½” flanges with the 3- hole variant, they appear to be a little smaller in overall diameter. So far initially, they look really nice and will look even better after I clean up the welds. The only minor problem is the bolt holes in the flanges have to be cleaned up, because I had the welder weld the fittings to the flanges on the outside of the fittings. A better plan would be to have the welding done inside the flanges to allow better access for the bolts and minimize the welding clean up.

The right manifold bolted right up to the right head with no problem, but some more clean up will have to be done on the bolt holes after the engine comes back out. I need better access to the holes to do that and it’s hard to do with the engine installed. The left side had the same problem, more clean up on the bolt holes is needed, but I could attach the manifold to the head to see what was needed to close up the holes I cut to make room for the engine on the driver’s side of the engine compartment. After looking real close at the engine from the inside of the car, I decided to use some 3 ½” exhaust tubing cut in half lengthwise to kinda wrap around the manifold and give me a decent heat shield. Flat stock will be welded to that to close up the hole. In order to be able to remove the manifold at a later date, I’m going to build an access panel that will bolt or screw into the existing sheetmetal to secure the panel and maintain structual integrity.

After laying the piece of 3 ½” tubing in place along side the manifold, another problem raised its’ ugly head. The steering shaft is going to be in the way of the heat shield. I’m getting tired of going back to the drawing board. There are two options I can take. One is move the steering column. A major undertaking, the firewall will have to be cut and the instrument panel will have to be modified for the different location of the column. Second option, make the exhaust manifold closer to the engine. After remembering that there were two sizes of elbows in the McMaster-Carr website, I went back to it and found that I could get an elbow that was shorter than the one I used initially, but there were no Ts of that length on the vertical legs, so I have to cut them to equal the length of the new elbows, and to gain a little bit more room I ordered another flange but in 3/8” thickness rather than the ½” I got initially. I got all the pieces, cut the Ts and laid everything up on the flange and put the PVC tube is to help line everything up. I didn’t make real exact cuts on the Ts but after discussing it with the welder, he told me it would be no problem, and that the way it looked, he could weld the inside of the flange and fittings with no problem. So now I won’t have to clean up the welds on the outside of the flanges for the bolts to sit flat on the flanges. The welder cut the reducer and the attached elbow off the old manifold and proceeded to weld up the new manifold. Everything is going smoothly, as soon as I cut the bridges from between the flanges I can bolt on the manifold and see how much clearance I gained for the steering shaft. Just looking at the manifolds side by side it appears I have between ½” and ¾” shorter on the new manifold. After bolting in the manifold and checking the clearance between it and the steering shaft, I’ve gained almost an inch clearance. All that’s left to do to the new manifold is weld the reducer and elbow assembly to it. Then I can see about getting the flanges surface ground again just to be sure it’s all nice and flat and there will be no leaks.

I finally got the bridges between the exhaust port flanges cut and the welder attached the elbow with the reducer to the manifold. This was a little tricky because I had to hold the elbows in place and shield my eyes from the arc. I used the temporary headers bolted to the reducers to assist in this part of the assembly. There is very little room between the steering shaft and the timing gear/water pump covers for the 2 ½” head pipe to go down between, but it is enough, barely. With manifolds finally assembled, I treated each one with RestoMotive’s POR-20, their high temp exhaust paint, to make them look pretty. Then both manifolds went back to the machine shop for final surfacing to be sure they are perfectly flat.

Now, all that’s left is to pull the engine, set it on the dolley and insure the manifold welds are cleaned sufficiently to allow the ARP bolts seat down flat on the flanges. And when the engine goes back in the car, a trip to the local front-end and muffler shop for a check of the alignment and new custom mandrel bent 2 ½” tubes all the way back to the rear of the car to exit through nice neat chrome tips.

Well, kind of, I still have to finish up on Phases II, III, IV, and V. That will be Phase VI, integrating all the phases into a finished product. Then, after it’s all together, reupholstered and painted, a trip to the local drag strip to see if it was all worth the hassle, time and money expended, Phase VII. Stay tuned, it’s gonna be fun, I hope.