Flex pipe replacement

  • 79,125 MILES

So I have replaced my flex pipe (from catalytic converter to back pipe) the ends of the old pipe were wedged in could not cut farther back so I cut it at weld point on old flex pipe. Then bought next size down ( calls for 2 and 1/4x10 I used 2x8) centered the pipe then used exhaust putty to fill gaps once dried applied heat shrink tape and then clamps over that. My question: will the smaller pipe create any back pressure? And do you think how I installed it is good enough? Sorry for the long winded explanation any insight would be helpful. Thanks!

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Thursday, March 30th, 2017 AT 4:35 PM

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I am trying to visualize the repair, but there is no place for putty. If you ever find that in an exhaust shop, find a different shop. I worked for seven years in a shop that specialized in exhaust repair, and everything we installed was with clamps. Some mechanics prefer to weld on new pipes, but that eliminates your ability to re-position parts if necessary. Clamps seal perfectly when the mating pipes are the correct sizes and slide together tightly. If one pipe is able to fall out of the other one, and/or the clamp is over-tightened, it will creates dimples in the outer pipe that will never seal up. Huge indentations in the pipes are not needed. The clamp will do its thing with just a few turns on the nuts with a hand ratchet.

I have never heard of using any type of tape either. That sounds like a fire waiting to happen.

If I understand your question, I think you are asking about back-pressure due to using a smaller-diameter pipe. You did not list an engine size. There are often two or three different systems used on a specific car model, depending on engine size. In the 1980's, a two inch system was standard for cars with smaller V-8 engines. Those with the larger V-8s often came with 2 1/4" systems. Your original system was sized to handle the volume of exhaust gas at wide-open-throttle. How often do you drive that hard? Even at that, the pipe section is not going to offer very much resistance, and I doubt you'll even notice a difference.

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Thursday, March 30th, 2017 AT 5:41 PM

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