Don Terrill’s Speed-Talk

panic wrote: ↑Sun Nov 08, 2020 9:19 am 6-3 not only joins pairs with uneven firing order, but different order depending on which pair.
1 & 2 are 240-480-240, 3 & 4 are 360-360, 5 & 6 are 480-240-480

Inline 6 inlet manifolds on engines with three siamesed inlet ports are connected as you describe, with results understandably ranging from woeful to simply horrid. But the headers in the pics when on the intended engine (and likely every other inline 6) are connected in pairs to cyls exactly 360 deg apart, all three pairs.

Edit -> Yeah, sorry panic, I took another look at those pics and it does look a bit sus. The last ones I saw in the flesh many years ago were as I described, but these ones maybe not. I’ll have to look a bit further into this!

Edit 2 -> They are plumbed correctly. They are grouped 1 and 6, 2 and 5, 3 and 4. They way they are layered is different in the two pics. I got confused about it too.

Edit: wow a 2009 thread dig. Not my fault :p

So are you talking 6-2-1 vs 6-3-1
Or 6-2-1 vs 6-1?

I haven't seen a 6-1 that looks simple yet, not with the needed collector and pipe curves to get even-ish lengths.

Also I'm in favor of the 6-2-1. It doesn't need to have two cylinders with 90 degree bends straight off the head if you're going for short primaries. Also I've just put an aftermarket exhaust on a flat 6, and a perfectly symmetrical 6-2-1 sounds fantastic...

(Also I know which of the following I'd rather have to build)

How about a vertical exhaust? This was me and my dads former pulling tractor. This was a Burns Stainless 6x1 1-5/8" dia primary tubes, the primary configuration followed the firing order in a circular pattern.

This may be application specific, but the best header commercially sold for my Jeep 4.0 is the arh 6:1. Here’s a pic of mine. It also uses the rotational firing mentioned by others.



The next best header is a 6:2:1 design and doesn’t make near the power the arh does.

bthomas wrote: ↑Wed Nov 11, 2020 11:11 am This may be application specific, but the best header commercially sold for my Jeep 4.0 is the arh 6:1. Here’s a pic of mine. It also uses the rotational firing mentioned by others.



The next best header is a 6:2:1 design and doesn’t make near the power the arh does.

How was the torque on the 6:2:1? Back in 2004 or 05 Burns told me that they did not recommend the 6:1. I told them I was ok with killing off some mid range, my thought was to carry more past peak hp for tractor pulling. Seemed to have worked.

inline6 wrote: ↑Thu Nov 12, 2020 9:37 am

bthomas wrote: ↑Wed Nov 11, 2020 11:11 am This may be application specific, but the best header commercially sold for my Jeep 4.0 is the arh 6:1. Here’s a pic of mine. It also uses the rotational firing mentioned by others.



The next best header is a 6:2:1 design and doesn’t make near the power the arh does.

How was the torque on the 6:2:1? Back in 2004 or 05 Burns told me that they did not recommend the 6:1. I told them I was ok with killing off some mid range, my thought was to carry more past peak hp for tractor pulling. Seemed to have worked.

Yeah a 6:1 could make a higher peak number but area under the curve no way. 6:1 would almost be like zoomies where the very large collector acts kinda like ambient

Here is the set I use, nothing too flash but good enough to make 1.72hp per cube..

lc-gtr-1969 wrote: ↑Thu Nov 12, 2020 8:55 pm Here is the set I use, nothing too flash but good enough to make 1.72hp per cube..
IMG_4645.jpg

That's a serious head you got there!

Yeah, it's all in the head- this combo with a 9 port head, even a really good historic race spec head flowing say 215cfm- would be lucky to make 280hp. The cam is fairly mild really, well mild compared to what others run with similar setups.

This head flowed 284cfm at .700 lift! The port cross sectional area to flow ratio is very good which has kept the engine having pretty decent signal- even though I am not using all the potential of the head with this setup.

A .700 lift solid roller would really get this engine moving but this is a pure street engine and reliability/longevity concerned me with that deal, rightly or wrongly.