How much dimple is too much?

[derekf]

1 5/8" primary headers on an LS1.

It looks like if I dimple both front pipes for frame clearance about 1/4" it'll cure all my (header routing) woes and I won't have to make nearly as many other changes to the headers.

Will this completely ruin performance? It looks like cutting and rewelding the flanges will just create other issues - I'm awful close to the starter as it sits, and I'd end up closer, etc.

[jlcustomz]

I always here the term dent or dimple header for clearance which would mean concaving the pipe in , which would create some restriction. However if you more skillfully oval or d-shape the pipe, then you retain the same exact internal volume. Make sense? If you hold a block of wood, flat metal plate, etc over pipe & hammer it, you can more oval the pipe rather than dent it. Grab a cheap 1 5/8"pipe extension from auto store to practice on if needed.
In general, dents don't always really lower performance, mostly because many engine have larger than really needed headers. In your case, yours are not bigger than needed,so should be more carefully handled.

[derekf]

That makes sense, thank you. The practice piece is a great idea.

[dhutton]

https://www.dailymotion.com/video/x3vupq0

Don

[derekf]

Thank you very much, Don, I feel a LOT better now.

Hell, I'm only dimpling two tubes, I may gain horsepower!

[djorgensen3]

Check this out.

https://www.motortrendondemand.com/detail/exhaust-header-bash-testing-power-loss-from-dents/0_ujj8a8mw/

[derekf]

I think that's the same video Don posted (just on a different site). I don't have a subscription so I can't watch to verify.

[djorgensen3]

I think you're right. Sign up for the 14 day trial. There are a ton of good shows on there.