How to measure header collector length?

[jet1]

According to pipemax I should be looking for a collector length of 16.3" . At which point does the collector start? Right at where the primary tube stops or right where the 4 into one begins being round? I am 18" from wheer it is round and 26" from where the primaries end.

[pamotorman]

According to pipemax I should be looking for a collector length of 16.3" . At which point does the collector start? Right at where the primary tube stops or right where the 4 into one begins being round? I am 18" from wheer it is round and 26" from where the primaries end.

i remember some thing about paint a white paint strip on the collector and where the point burns you cut

[RevTheory]

I've always measured from where the primaries dump into the collector so basically measure from the welds back. Of course, I've been known to be wrong on occasion.

[ZIGGY]

i remember some thing about paint a white paint strip on the collector and where the point burns you cut

Paint a new strip after the cut and see what happens...

[cgarb]

That's classic...I kept painting and cutting, all I have left is a 2" stub at the flanges...Just a joke fellas no hurt feelings intended.

[cgarb]

On thing to add, I was helping a friend get new headers on his 390 FE in a Torino. He ordered the wrong collector adapters, it was a 3.5" flanged collector with 3.5" turnouts. He ordered adapters for 3.5" collector to 3" exhaust. In the name of time savings and experimentation I talked him into leaving the adapters intact and sliding the 3.5" turnout over it and welding it to the flange. It was more like an anti reversion type baffle than anything I guess. It would always burn the paint off the turnout right where that adapter ended inside. Thinking about the stripe painting made me remember it.

[pamotorman]

http://bangshift.com/general-news/tech- ... ng-part-1/

[jet1]

Ya I watched that. It mostly just an idea of what you might see. They talk about 18" collector extensions mostly and the effects of shorting it. My motor is mostly steady state at close to peak tq so it may not make any difference.
with pipemax I am trying to figure out if it is from the primary pipe end or from where the collector starts to be round in a 4:1 header.

[engineguyBill]

I've always measured from where the primaries dump into the collector so basically measure from the welds back. Of course, I've been known to be wrong on occasion.

This is the way that I measure collectors and it is the correct way, as far as I know . . . . . . . .

[jacksoni]

The effective end of the pipe is where the area expands the greatest (essentially) from the end of the primary into the collector. With typical straight primary into either a crimped together into cloverleaf pattern whether that tapers some or not to the main collector, the junction is at the end of the primary. Merge collectors may behave differently. See my comment under the recent "merge collector thread" posted by Bigjoe.

[pamotorman]

a lot of race headers use a venture built into the start of the collector.

[jet1]

Looks like I should be cutting off 6" or so off my header then according to this. This engine runs at 6000 rpm for long periond of WOT.

collector.jpg

[jet1]

Ok so have been doing alot of reading on the subject and it really looks like I could gain some power here by shortening the collectors to 16.3 and even choking them from 4" to 3 3/4" or 3 1/2". Anyone have any thoughts on that?

454 ci
roughly 750 hp@6500
run it at 6000 rpm mostly endurance jet boat

[Alan Roehrich]

I believe Larry Meaux (PipeMax software) probably has the best explanations and diagrams regarding how to measure headers. A quick search will yield all sorts of stuff from Larry, including his website and bulletin board, where you can find a lot of information you're looking for.

[Walter R. Malik]

According to pipemax I should be looking for a collector length of 16.3" . At which point does the collector start? Right at where the primary tube stops or right where the 4 into one begins being round? I am 18" from wheer it is round and 26" from where the primaries end.

I have always used the ending of the primary tubes separation ... which can vary some if a "spear" is used in the collector.

I think "pipemax" uses the primary tubeing ends as the beginning of the collector.