Lotus Elan

Intermediate pipe measurements

PostPost by: Famous Frank » Tue Jan 08, 2019 3:54 pm

Please forgive me if this is not in the correct section. I'll be happy to move it if I knew where to.

Most all of us know the early Elans came equipped with an oval intermediate exhaust pipe for more ground clearance. I would like to manufacture one for an early Elan I am restoring. It has no exhaust but it still has its original cast iron exhaust manifold. I am currently attempting to reproduce the original down pipe with the integral resonator. The information I'm looking for is the dimensions of the oval intermediate exhaust pipe. If someone still has one they would like to sell, please contact me. Or can someone provide measurements.

Measurements needed:

1) Total length of the intermediate pipe?

2) Length of the front portion to the kink?

3) Pipe diameter ID or OD?

4) From the front and from the rear of pipe, how many inches to where the pipe becomes oval?

5) Thickness or height of pipe where it is oval? So I know how much to crush the pipe. I'm assuming (that always gets me in trouble) the pipe is round at both ends ad is only oval within the center. Correct?

Many thanks,
Famous Frank

66 Elan S2 SE
65 Elan S2
66 Elan 26R
69 S2 Europa
06 Elise
67 Barracuda
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PostPost by: prezoom » Tue Jan 08, 2019 4:56 pm

I gave some thought about the same issue when I was constructing the exhaust system for the Plus2 Zetec installation. Including factoring in the area of the oval section of the pipe to equal the area of the round section. It was further complicated in that my system expands in diameter the pipe from the "Y" pipe to the silencer. I made some increasingly sized mandrels that could be drawn through the pipes, using a ratcheting come-along, to pull the mandrels through. But, the anticipation of getting the car finished has meant the project was never completed. Round pipes were quickly fabricated to speed things up. My stumbling point was the two curved sections where the pipe curves up from beneath the chassis to the entrance to the silencer. Unfortunately, the only NASCAR style flat oval pipes readily available are much larger than that needed for our sized engines. One of these days, when other more pressing projects are completed, I may resurrect the project.

One place substantial road clearance was increased was in the header section of the system, including the "Y" pipe. I converted the hydraulic clutch release system from and external slave to a concentric slave within the clutch housing. This permitted the removal of the cast ring that formally held the external slave cylinder to the clutch housing. This allowed the even larger diameter pipes, including the "Y" pipe to be raised above the cross brace and the bottom of the chassis. The exhaust system only now drops below the bottom of the chassis where it passes beneath the chassis just aft of the gearbox.
Rob Walker
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1964 Elva Mk4T Coupe (awaiting restoration)
1965 Ford Falcon Ranchero, 302,AOD,9",rack and pinion,disc,etc,etc,etc
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