L6 header's - opinions please

[luvemfast]

Hi guys,

I got these off eBay. Never seen ones like this before.

And thought I'd get some opinions on what to expect when fitted.

They are tuned length, but a 6-3-1 design.

The primaries are coupled sequentially, in firing order (1&5, 3&6, 2&4). Then they run the 3 secondaries into 1 collecter, that exits via a 2.5" flange.

 

Should have it running next week, then take it to an exahust shop to mate it to my 2.5 system.

(L30, domed Forged ø89mm pistons, ported P90 head, FJ20 rods, 76° cam, 590thou lift, triple 44PHH Mikuni's)

 

So...... experts, Opinions?

[EmptyZ]

They look nice! Ebay is kind of hit and miss from what I have experienced. I have heard the quality has gotten alot better than the old days though. I dont know if those are from china but if they are I always heard gusseting around the flange is a good idea. I use to have a dsm and any of the guys that bought the manifolds off of ebay always strengthened them.

[johnc]

You'll want a 3" exhaust with the engine specs you list.

[t-tom]

what was the seller ID on those? I wouldn't mind trying a set. You can pm me if you dont want to put it on here

 

Thanks, Tom

[luvemfast]

They look nice! Ebay is kind of hit and miss from what I have experienced. I have heard the quality has gotten alot better than the old days though. I dont know if those are from china but if they are I always heard gusseting around the flange is a good idea. I use to have a dsm and any of the guys that bought the manifolds off of ebay always strengthened them.

Sorry, should have mentioned they were made locally in Adelaide, Australia. Designed by a Tarmac rally guy down here. They were too large for an L26, so should be sweet on my L30

 

You'll want a 3" exhaust with the engine specs you list.

I was going that way, when funds allowed. Already have 2.5" on, just need to connect.

 

what was the seller ID on those? I wouldn't mind trying a set. You can pm me if you dont want to put it on hereThanks, Tom

Sorry mate. Custom job.

But looking into it.

 

Any expert opinions on how these will go?

Edited March 25, 2012 by luvemfast

[RebekahsZ]

Why the O2 ports on each 2:1 collector? At first I though it would allow you to tune each carb that shares a butterfly shaft, but I was wrong...I traced the tubes-you couldn't tune an individual carb from those, each pipe on the shared O2 sensor goes to a different carb... In this case, would you gain anything with this O2 sensor set up over just a single O2 sensor in the common collector?

[Leon]

I'd prefer the more typical setup of a 6-2 header with 1-2-3 and 4-5-6 sharing collectors. That way, you're equally alternating between each collector, dictated by firing order, and each cylinder is scavenged essentially equally. A 6-1 works in this regard as well.

 

Your header, with 1-5, 3-6, and 2-4 being shared in three collectors, will have more unequal cylinder scavenging. Starting from the top, cylinder 1 fires and the subsequent exhaust gasses should scavenge (drop pressure in) the cylinder 5 tube since they are joined together. Then 3 fires and scavenges 6. Same with 2 scavenging 4. As you can see, only 3 out of 6 cylinders get the scavenging benefit, since cylinders 1, 2, and 3 don't get a pulse in their collector shortly before firing.

 

However, this is theoretical stuff. I don't have any data as to suggest by how much performance will differ using your header versus a good 6-2 (or 6-1) design. Care to run a comparison dyno test for us?