Looking for input on collector extensions in a door car application. In my situation I have a 414 c.i. SBC with Dynatech tube chassis headers that are 2 to 21/8 to a 31/2" collector. Is there any use in playing around with different length extensions on the collectors? Or no extension at all? Thanks for your help LC

i read somewhere that you need to put a slightly long collector on and mark it with chalk of sorts (lengthwise)then make passes the heat will burn the chalk.where it stops burning is the length you need.i did try it once a long time ago.cant say there was any magic there

This message has been edited. Last edited by: rusty,

I've tried it years ago and found no improvement on the time slip.

Have to agree that there is little improvement to be had, but maximizing each little opportunity is a worthwhile goal. Along with the chalk concept above, paint the collector with cheap white paint and see where the "heat ring" appears.

Cheap paint like Canted Valve said, or a stripe of Grease Pencil is what I used years ago. Changed the sound of the car some, but no measurable difference in time slip performance vs no extension, or long extension.

In our karting days. It was normal to alter and change pipe lengths. Little KT100's, we would buzz them 14K rpm. 1-2 HP was crucial.

yeah I have messed with them over the years, saw nothing on the timeslips that were not also a function of track conditions and/or weather. I have to build another set of headers this off season for mine and have some ideas. One of them is sure to make some people mad but I don't care.

If you had a 2 stroke engine, yeah the pipe length, chamber design/shape, everything is real important. 4 stroke is much MUCH less sensitive.

I saw 0 in ET but there may be advantages depending on what you’re trying to accomplish. Torque below stall speed seemed noticeably improved.

I modified my headers to equal length at the same time the extensions were added so not sure if that helped the bottom end, but regardless, unmeasurable on track ET improvement.

Always wanted to try merge collectors but haven’t yet. I have a pair of tri y collectors too but never tried them. They are smaller outlets 3” vs 3.5”.