New/Modified Header Design?

[Daryl Smith]

Will,
Yes I have the program. Although it is NOT a 'dyno' program, it is an exhaust system design program. It does give some very interesting information.
PM me your flow info, and include the information in the top boxes of the first screenshot of the PipeMax website above. I'll post some Basic info.

[Daryl Smith]

Ok...For Will's car with a peak HP at 7000 rpm of ~200 crank hp (Will's geusstimate) the program shows:

4-1 header at 1 3/8" primaries and a 2 1/2" collector

4-2-1 header at 1 1/2" primaries and 1 5/8" secondaries with a 2 1/2" collector

I guess I need to do some more research myself because I don't understand why there is a difference in the size of the primaries between the 2 styles of header.. ....but it is a thorough program done by someone with a lot more research time and experience than I.

Want to experiment Will? Go to S & S Headers ( http://www.headermania.com/mm5/merchant.mvc" onclick="window.open(this.href);return false;? ), get a couple of 1 1/2" and one 1 5/8" parallel merge collectors and modify your 1 1/2" header to a 4-2-1 style and see how that works.

[SLOroadster]

You know, thats almost tempting, however thats not a cheap experiment when the dust settles. All my stuff is Jet Hot coated, and to weld the entire way around the tubes, I'd have to fully cut the headers apart and almost start over. That and the next time the engine comes out of the car its getting a full once over, I'm not planning on doing that any time soon.

Thanks for running that, I have to say, when I installed the bigger pipe I found some large gains in hp, and then when I put the 1 5/8 headers on I could tell I made some more power. I'd really like to do a merge collector on a set but again, I don't really want to cut up some nice headers.

I'll have to ponder this idea for a while.

Will

[Daryl Smith]

Anyone have worn but useable 1 1/2" header for Will to experiment with?

I'm not sure if the 'slip on' style collectors need to be welded all around....
Probably not at the experimenting stage anyway.

Comparing parts I have here for my header, it shouldn't end up more than about 1" longer (at the collector) than the standard vendor header when modified to 1 1/2" - 1 5/8" - ?

Running the numbers, this sizing of header is about right for the 2L stroker as well, if anyone wants to try it there............

[SLOroadster]

One thought about being longer at the collector, what about running a flex pipe? I seriously need one on my car, but installing one is darn near impossible with the engine in the car. There just isn't room and I cant rotate the pipe to get a good weld on top because the pipe is ovalized. Now here is a thought, what about running a flex pipe that opens up into a glasspack immediately after the front frame rail. It would be like an expansion chamber, then into the rest of the exhaust system after that? Alfa did this on their stock exhausts, and the school of thought from those guys is that its good for some hp and torque, but I don't see it done that often so it makes me wonder. The exit velocity would slow, but the volume would go up shortly after the collector, would this be of any benefit?

Will

[Daryl Smith]

".....what about running a flex pipe that opens up into a glasspack immediately after the front frame rail. It would be like an expansion chamber,....."

This is pretty much what I'm doing and is covered in the "Go Fast News" exhaust thread I posted previously. Theory is that the 'chamber' should be a minimum of 8 times the volume of one cylinder. For your engine, at least 247 cubic inches (4050cc).

Here is a rough drawing of what I am attempting:


1) Flex Pipe - I currently have a 6" long flex pipe which fits (lengthwise) with the vendor supplied header.
2) Termination Box - Sometimes called a resonator or expansion chamber. I am trying to figure out how to get a decent 'bell' (trumpet shape) on the pipes which will be inside on each end of the box. I am designing for 250 CI.
3) Muffler - Straight thru design. I'm using a Magnaflow which fits in the stock position quite well.
4) Megaphone - I'm trying to figure out how to get a slight trumpet shape here also with a rounded end, much like the velocity stacks. I don't know if it will help, but I'm sure that it will and am curious enough to give it a try. How much might it help? Won't know unless I put it or somethng similar on a flow bench.

I'm using 2" pipe.

[Daryl Smith]

Finally have all the pieces to build my header......




Ross at Sports Imports is helping me out by allowing me to take a rolling frame in to the header shop so they can build it easier without having a body in the way.
Thanks Ross!

And also a very BIG thanks to Mike Hudson (23yrRebuild) for doing the CAD drawing of the flange!

[dbrick]

Let me know how it works, and if the header builder can make more. I need to buy a header in the near future, so a 4-2-1 would be ideal.

[23yrRebuild]

How in the world do those pieces go together to make a header? ........The only pieces I can figure out are the collectors, and of course that great looking flange.

[SLOroadster]

How in the world do those pieces go together to make a header? ........The only pieces I can figure out are the collectors, and of course that great looking flange.

You cut the curves to fit, and the straights go where they need to be. This is the art of header building. I'd love to try but I don't have a car taken apart that far, and I don't have a welder.

Will

[23yrRebuild]

Duh!

[Daryl Smith]

It apparently takes some skill to get a clean weld for flow and reliability. I have a stainless steel header, here done by someone else (too big), which had a problem with cracking at the joints.
Was wondering if 'peening' the weld joints might prevent this from happening again?

I am leaning toward having a 'captive' nut mounted, similar to the stock manifold, to help prevent this, as well as the flex pipe, which should take a lot of the stress off the header.

It will also be ceramic coated, and the shop building it gaurantees it for life against cracking at the welds.

[dbrick]

I was thinking, while your at it, may as well put in an O2 sensor bung. Good for tuning or FI inthe future.

[23yrRebuild]

Roger that, ...I'll bet Daryl's already all over it! I put one in my collector with a narrow band O2 sensor and A/R gauge from Summit. It's a fun little gadget, I'll probably Ebay the gauge and sensor this summer and install a wide-band sensor and digital gauge.

[Daryl Smith]

Yes, I currently have the Innovate LC-1 wideband on the exhaust side of the flange which connects the header to the rest of the exhaust.
Will probably require a change when I change headers, so likely it will swap over to the header just aft of the last 2-1 collector and before the flex pipe.

The header builder can build more, they use headers as a fill in for down time between regular exhaust repair/replacement. I'm told to expect about a 2 wk completion period, and 'maybe' 8 to 10 hrs work. Had a good talk with the fellow, and sounds like he's done a fair amount of experimentation, figures I'm on the right track with the resonator and megaphone, but also figures equal length and dyno time is the best way to 'dial' it in. Which I know already, but haven't got the $$$ for that kind of developement. I won't be going equal length, but more following the lines of the stock manifold, so the outer runs will be longer than the inner.

What's the header for Dave? R16/Stroker or U20? There is a good exchange rate on the Canadian $, but what will it cost to get it across the border and shipped? Do you still have that header you were offerring for experimentation earlier in this thread? Might be worthwhile modifying it for an experiment?? Could save you some coin........

I take the parts and chassis in on the 25th, should have the header by the middle of March.