Introduction

When I did the 350 engine swap, I encountered a pretty big problem. The passenger (right hand side) exhaust manifold did not fit on to the cylinder head on the 350. Specifically, the heads were drilled to accept 6-bolt style manifolds, but the manifolds that came with the car required a seventh hole that is farther back from the exhaust port at cylinder number 8.

I tried to get away with leaving it mounted incorrectly, but it leaked exhaust like crazy once the engine warmed up. I couldn't come up with a combination of stock exhaust manifolds that would fit both the motor and the car, so it was time for an all-new exhaust system.

New Exhaust System

I chose a set of full length headers from Hedman, part number 68290. They have 1 5/8" diameter primary tubes, and 3" collectors. I also got a 3" x-pipe kit from Summit Racing. The mufflers were Cherry Bomb Turbos with 2.5" piping.

Header Fitment

Fitting the headers was not easy. The engine had to be unbolted and lifted up on the driver's side, and the header brought up from underneath. Not only that, but the tubes intersect directly with a small metal safety brace on the frame. I ended up cutting off the brace with an angle grinder. It will be replaced with a stiff brace which clears the tubes. The passenger side header did fit reasonably easily.

Transmission Crossmember

As with most old school GM cars, I had to modify the transmission crossmember to get the driver's side exhaust to pass through. Many people just chop out a section of the crossmember, which weakens it significantly. I wanted to do something more elegant, so I took it out and brought it to a fabrication shop. Below is a picture of what it looked like when I got it back.

Unfortunately, I did not get the dimensioning correct, so I had to modify it further. It is still much stronger this way at least.

Side Pipes

The original idea was to have the exhaust exit at the sides of the car, to save money on having over-axle pipes fitted, and because side exhaust is so cool. It was a very bad idea.

First, the mufflers could not be mounted in the cavity where they belong, so they hung down very low. I had no ground clearance at all.

Second, the short tubes after the mufflers gave the exhaust a very loud, deep drone when at low engine RPM, such as idling when stopped. I drove it for about 200 miles like that, and I ended up getting stuck in a slow-moving traffic jam for a while. I had to listen to it the whole time, and I now have permanent hearing damage from it. No joke. Luckily, it is only mild tinnitus; I can still hear very well.

Third, and most important, was the fumes. I'm not sure how some cars get away with it, but I had a huge problem with fumes pumping directly into the passenger compartment, as seen below.

I ended up giving up on the side pipes. I took it to a muffler shop, and had them fit on over axle pipes. The labour was very expensive. At the same time, I had them fit Dynomax Super Turbo mufflers, just in case the drone sound was from the cheaper Cherry Bomb mufflers. I'm not actually sure whether it was the fault of the mufflers or the short tailpipes, but with the Dynomax mufflers and the long pipes, there is no longer any drone.

Power Steering Pump

Another problem with the infamous driver's side header was that it could no longer support the bracket for the power steering pump. I managed to drive without the bracket for a week or two, but I decided that fixing it was the proper course of action to take.

Modifying the bracket turned out to be reasonably simple. All I had to do was cut off the back exhaust bolt hole, and stiffen it up at the front with a large bolt, as seen below.

If I could do this all again, I would have gone with shorty headers, a smaller diameter x-pipe, and fitted over-axle pipes myself with an over-axle kit. I learned a lot from this project, but also wasted a ton of money and time. I know for next time.

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Page last modified on December 29, 2009 22:53:03. (ID=74)