MERGE COLLECTOR ??? BUILDING HEADERS

[garym]

So for my winter project (along with my other projects) I plan to build another set of headers for my top sportsman car.I read on a few forums that in order for merge collectors to work the primary tubes have to be placed in the merge collector so that each adjoining cylinder exhausts/fires in a circular pattern.On my big block chevy there does not seem to be a problem on 1357 but on the right bank cylinders 2468 will take a lot of work/figuring.The header kit that I bought is the Dynatech kit and like the other set of headers that I built I used this same header kit, but with conventional collectors.Any input/advice on merge collectors would be helpful. This is a GREAT FORUM and I enjoy reading the different threads,etc. THANKS garym

[ptuomov]

I’m interested in this question as well.

My thinking is that the circular firing pattern only matters because it allows the merge angle between consecutively firing cylinders to be shallow. The merge angle across the collector is necessarily a little wider. For the absolutely ideal collector, maybe it matters. For anything that isn’t optimal to start with, probably makes a really small difference if any at all.

This thinking (by me) only applies to long tube headers. I think that for short tube headers where pulse interference isn’t solved the collector pairing and geometry seems to be a whole different animal.

[bigjoe1]

I have seen very little or NO difference with those collectors



JOE SHERMAN RACING

[garym]

Thank you for your reply.I think as remember on my last header build the primary tube length was about 28-29 inches long.I was able to get all primary tubes within 1/2 to 3/4 inch which I thought was real good.The merge collectors that I have are the Edelbrock collectors and I think that the primary tube length will be around 28" .I looked over the first set of headers that I built with the same header kit and it looks like I will have to move the 4&6 tubes to get the circular firing/exhaust pattern that is supposed to be the way these merge collectors work.Any further advice/input would be great. THANKS garym

[andyf]

Sounds like a good myth buster story. My guess is that there is zero benefit to having a circular firing pattern in the header collector. I just can't see how it would matter at all. Do people think that the exhaust pulses add energy to the collector if they are circular? Some sort of tornado effect or something??

The pulses are uneven on a V8 for one thing so that disrupts the flow. I'll say the myth is busted but I'm always open for dyno results if someone has built two sets of headers and tested them back to back. Show me the data and I'll become a believer.

[Ed Wright]

I agree with Joe. I have seen two different guys A-B-A test merge collectors, seeing no gain.

[exhausted]

It matters if your trying to get the choke as small as possible. Not too many folks get there.

[cjperformance]

It matters if your trying to get the choke as small as possible. Not too many folks get there.

Exactly, basically running one firing pipe after another into the choke/collector reduces turbulence when compared to firing a pulse opposite the last pulse. Less turbulence here means more direct flow thru the choke so a smaller choke can be used and an more efficient collector can be constructed.
We're not talking gigantic gains here, its just one of the small 'attention to detail' gains that adds up with all the other small gains.

[exhausted]

I have always worked to make all the 4 into 1 headers I have built have a "rotating" firing order. There is no proof I have ever heard to verify any benefit but I believe it is better. Just watch your darn toilet, Ha!

[swampbuggy]

Exhausted, I am going to try to employ an exhaust system as close to what NASCAR is doing as possible for my 8500 RPM project. Do you know what they are doing BETWEEN the 2 collectors and where the exhaust exits out the pass. side? Thanks Mark H.

[hoffman900]

Look under Calvin's profile, and start going through all his old posts. Some of the best information that's ever been shared here, and exhausts in general, anywhere on the web.

[swampbuggy]

THANKS Hoffman

[digger]

It matters if your trying to get the choke as small as possible. Not too many folks get there.

have you found and guides on how small you can go? for example on a 3 into 1 (240* separation) couldn't you make the choke the same size as the throat of the port e.g. 0.9 x Valve Diameter?

[Alan Roehrich]

The problem with blanket statements on components such as merge collectors, is that they're the type of component that requires, or creates the opportunity for, other changes or adjustments, in order to take advantage of what they offer.

Adding a merge collector by itself, with no other changes, will usually only offer a return in increased power if the exhaust is not already optimized.

[exhausted]

Exhausted, I am going to try to employ an exhaust system as close to what NASCAR is doing as possible for my 8500 RPM project. Do you know what they are doing BETWEEN the 2 collectors and where the exhaust exits out the pass. side? Thanks Mark H.

Big. 3.4 or 4" oval tubing and some type of connection between the two.