340 Chrysler Street Header Questions

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340 Chrysler Street Header Questions

Postby Mattax » Thu Feb 26, 2015 3:47 pm

After reading reading all those great posts by Calvin, 900HP, Proheader and others who have been so generous in sharing their insights, I have some questions regarding building a street header for my car. Maybe a case of the more I learn, the more I learn I don't know. Anyway, I'm calling this a street header because
that and autocross are the primary uses, plus an occassional track day.

The headers need to cover two possible engine configurations, but the lower Hp one is the target. Pipemax gives very similar recommendations recommendations for both. Essentially looking at peak hp around 320-350 at 5400-5500 rpm in the planned configuration, and peak hp a bit over 350 at 5600 - 5700 rpm in the current configuration. The goal for power after peak is that it can hang in there to 6200 or so.

First question: How important is it to step up diameter after the blowdown length? Both Calvin's guidelines and pipemax agree that 1.5" primary tube would be a good start (assuming we can stretch it to the port). Keeping 1.5"dia the whole length buys more space, ground clearence and possibly gentler radiuses. On the other hand, 1 5/8 tubing is without question doable. In fact we can use some existing headers as models, at least in part, and they are all 1.625 primaries or larger.

Second question: Should we look at the decision between tri-y and 4 into 1 mostly as a matter of fitment, or are there performance advantages that would make one preferable in this application? My impression has been that 4 to 1 can be more forgiving in terms of design and less likely to be peaky (due to longer length tubes). I should mention that the guy building the headers is experienced, but not with this chassis and engine. A 4-2-1 does not intimidate him in the least. However I still think it could be more time consuming, and it is my money.

Third query: Is there really an advantage to steel over st st flanges? Is this true even if the flanges are cut into individual flanges for each port or pair. Calvin mentioned he likes to do this (seperate flanges, I don't recall anything about plain steel but someone else mentioned it) and my old Headers by Ed have individual flanges for each tube or pair.

Speaking of Headers by Ed, one of 900 hp's or Proheader's posts mentioned Ed's recommendation to form the primary tubes into a cross at the collector. I'll
post a picture. The idea of smoothing the merge always seemed to be a good one to me. Does anyone else think this method has value as a low cost improvement over the diamond in the middle?

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Re: 340 Chrysler Street Header Questions

Postby Mattax » Thu Feb 26, 2015 10:18 pm

Apparently too late to edit the original post. Somehow I previously missed
A 421 header is lighter, easier to build, offers more ground clearance and broadens your power band. There are few reasons to consider any other layout if your engine runs under 8500 rpm. One of those is simply not knowing this. So Madbill is forgiven.... :)
Calvin Elston
in First time header build
I assume that applies here as well.

and it was 900hp who mentioned the Ed's method of making a cross in the primary in his first build. My apologies. There's so much packed into those threads, I'll be reading them more than twice.

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Re: 340 Chrysler Street Header Questions

Postby 900HP » Fri Feb 27, 2015 10:04 am

Mattax wrote:Apparently too late to edit the original post. Somehow I previously missed
A 421 header is lighter, easier to build, offers more ground clearance and broadens your power band. There are few reasons to consider any other layout if your engine runs under 8500 rpm. One of those is simply not knowing this. So Madbill is forgiven.... :)
Calvin Elston
in First time header build
I assume that applies here as well.

and it was 900hp who mentioned the Ed's method of making a cross in the primary in his first build. My apologies. There's so much packed into those threads, I'll be reading them more than twice.


I listed that as a "budget" way of joining a 4-1 header if a person didn't want to spend the money/time on real merge collectors. It's an old trick from Ed Henneman "Headers by Ed" and it helps to cut down on turbulence. The only reason I built the 4-1 headers for the '55 Chevy with the 409 (pictured in the first few pages) is that the customer insisted on 4-1 headers otherwise I would have built 4-2-1's in a heartbeat.

Don't let your header guy build the primaries too long and the secondaries too short, a common issue with 4-2-1 header design, Pipemax has it wrong.

IF and I say IF you can match a 1.5" tube to the port, I would do that. 1.5" for 8-10", 1.625" for 8-10" for the primary, 1.88" for 12-16" for the secondary with a 2.125" choke and 2.75" collectors will suit you very very well. :wink:

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Re: 340 Chrysler Street Header Questions

Postby Mattax » Sun Mar 01, 2015 2:05 pm

900HP wrote:Don't let your header guy build the primaries too long and the secondaries too short, a common issue with 4-2-1 header design, Pipemax has it wrong.

IF and I say IF you can match a 1.5" tube to the port, I would do that. 1.5" for 8-10", 1.625" for 8-10" for the primary, 1.88" for 12-16" for the secondary with a 2.125" choke and 2.75" collectors will suit you very very well. :wink:


This is one of the reasons that would seem to favor 4 -1. 4-2-1 seems to be require 'just right' lengths and if we blow it , we've really blown it. :shock: Yes??? :?:

Using the counting squares, port area at the mating face varies from 1.47 to 1.59 sq in. Hopefully that's not too much of a stretch. But if it is, then the whole primary length should be 1 5/8???

I appreciate the insight on Pipemax's length recomendations being long, and maybe too small on the secondary pipe? My presumption has been that Larry's focus has been harmonics and not incorporated the "blowdown" theory Elston has been sharing here and on his blog. Elston has me convinced. Hopefully my builder will be too - I've sent him links to those discussions.

FWIW, below is Pipemax calculation for 3400-5900 rpm, 325 hp
--- 2-Step Equal Segment Length TRI-Y --- ( Low to MidRange RPM TQ and HP )
1st Y-Segment Dia. inches= 1.406 Length= 17.1 to 18.6 inches long
2nd Y-Segment Dia. inches= 1.531 Length= 17.1 to 18.6 inches long
Combined Total of all Segment Lengths= 34.1 to 37.2 inches long

--- 3-Step TRI-Y Specs --- ( Low to Mid-Range Torque and Hi RPM HP )
1st Y-Segment 1st Step Dia. inches= 1.406 Length= 17.1 to 18.6
1st Y-Segment 2nd Step Dia. inches= 1.531 Length= 8.5 to 9.3
2nd Y-Segment 3rd Step Dia. inches= 1.656 Length= 8.5 to 9.3
Combined Total of all Segment Lengths= 34.1 to 37.2 inches long

--- 3-Step TRI-Y Pipe Specs --- ( Higher RPM Horsepower, possible TQ loss )
1st Y-Segment 1st Step Dia. inches= 1.531 Length= 17.1 to 18.6
1st Y-Segment 2nd Step Dia. inches= 1.656 Length= 8.5 to 9.3
2nd Y-Segment 3rd Step Dia. inches= 1.781 Length= 8.5 to 9.3
Combined Total of all Segment Lengths= 34.1 to 37.2 inches long

--- Megaphone Collector Specs ---( Diffuser or Diverging Cone Shape )---
( TQ ) Diameter= 1.749 taper to 2.749 Best Length= 20.4 or 40.8 inches
( HP ) Diameter= 1.999 taper to 2.999 Best Length= 20.4 or 40.8 inches

H-Pipe= 20.4 X-Pipe= 81.6 distance behind end of Primary Tube ends


and here's the 4-1 Street header - same combo
344.506 CID Exhaust System operating RPM Range from 3400 to 5900 RPM

--- Single Primary Pipe Specs --- ( Low to Mid-Range RPM Torque and HP )
Diameter= 1.406 to 1.531 Total Length= 34.1 to 37.2 inches long

--- Single Primary Pipe Specs --- ( Mid-Range TQ to Higher RPM Horsepower )
Diameter= 1.469 to 1.594 Total Length= 34.1 to 37.2 inches long

--- Conventional Straight Tube Collector Specs ---
( TQ ) Diameter= 2.499 to 2.749 Best Length= 20.4 and also 40.8 inches
( HP ) Diameter= 2.749 to 3.249 Best Length= 20.4 and also 10.2 inches

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Re: 340 Chrysler Street Header Questions

Postby Mattax » Wed Jul 01, 2015 9:59 pm

IF and I say IF you can match a 1.5" tube to the port, I would do that. 1.5" for 8-10", 1.625" for 8-10" for the primary, 1.88" for 12-16" for the secondary with a 2.125" choke and 2.75" collectors will suit you very very well. :wink:


Stretching the 1.5" tube to the port is a problem! Could do it by expanding the end of a 1.5 to 1.625". But wouldn't that create a drop at the top of the port as it transitions into the tubing? Also not sure we can expand and go into a curve as quickly as we need to in some locations.

So if we can't do 1.5" off for the first 8"-10", should we just do the whole primary in 1.625 for 16-20" or something else?

- Matt

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Re: 340 Chrysler Street Header Questions

Postby 900HP » Thu Jul 02, 2015 8:50 am

Mattax wrote:
IF and I say IF you can match a 1.5" tube to the port, I would do that. 1.5" for 8-10", 1.625" for 8-10" for the primary, 1.88" for 12-16" for the secondary with a 2.125" choke and 2.75" collectors will suit you very very well. :wink:


Stretching the 1.5" tube to the port is a problem! Could do it by expanding the end of a 1.5 to 1.625". But wouldn't that create a drop at the top of the port as it transitions into the tubing? Also not sure we can expand and go into a curve as quickly as we need to in some locations.

So if we can't do 1.5" off for the first 8"-10", should we just do the whole primary in 1.625 for 16-20" or something else?

- Matt


At that point I would move up a size. 1 5/8" step to 1 3/4" (20-22" oal), 2" for 12" or more, 2 1/4" choke and 2 1/2" or 2 3/4" collectors. These are actually the dimensions I'm using (as per Calvin's advice) for my own street 383. The exhaust port dictates the size you have to start out with more or less.

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Re: 340 Chrysler Street Header Questions

Postby Mattax » Thu Jul 02, 2015 10:06 pm

Be curious to see how that turns out even though you have the room of truck's engine bay to work in
But 40 more cu in. ? (and I took a look at your 383 posts - that's heck of an engine.)

We're still looking at a way to make the 1.5" work. One possibility would be to stretch it as much as possible top to bottom and accept the bottom of the ports being somewhat blocked. Brian (the builder) doesn't like that and I think its a risk of doing weird things to the flow. Another is to get a flange made with a taper in it - that's what he's done for some of the engines he normally works on.

The Barracuda's engine bay is relatively tight. We looked at some possible routing with mostly 2.5" radius bends. Getting #7 past the steering column and the odd side pairings somewhat equal looks like the big challenge.
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Re: 340 Chrysler Street Header Questions

Postby 900HP » Fri Jul 03, 2015 10:45 am

Mattax wrote:Be curious to see how that turns out even though you have the room of truck's engine bay to work in
But 40 more cu in. ? (and I took a look at your 383 posts - that's heck of an engine.)

We're still looking at a way to make the 1.5" work. One possibility would be to stretch it as much as possible top to bottom and accept the bottom of the ports being somewhat blocked. Brian (the builder) doesn't like that and I think its a risk of doing weird things to the flow. Another is to get a flange made with a taper in it - that's what he's done for some of the engines he normally works on.

The Barracuda's engine bay is relatively tight. We looked at some possible routing with mostly 2.5" radius bends. Getting #7 past the steering column and the odd side pairings somewhat equal looks like the big challenge.


You don't want the area of the tube more than 10-12% smaller than the area of the port.

If you are going to stretch it, have the tube align with the roof of the port and tack weld it, then stretch the tube to the floor. The match at the roof is the most important as that's where velocity is highest.

If you are stuck with tight bends you are better off with larger tubs as the bends offer more restriction so you need a larger tube to compensate.
it's a series of compromises and you have to decide which compromises will hurt you the least. Given your apparent port size and the tight bends I would go to the larger tubes.

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Re: 340 Chrysler Street Header Questions

Postby Mattax » Wed Jul 15, 2015 12:07 pm

We're just on the line with 12% reduction on the 340 casting. But the bulk of the port isn't that big, just last 1/4" or so - someone may have touched it a little to match the exhaust manifold?

360 castings port area = 1.47 to 1.59 sq in.
340 castings port area at exit = about 1.75 sq in
.050 wall 1.5 " tubing inside area = 1.54 sq in
1.75-1.54=.21 => .21 sq in divided by 1.75 = 12%

I suspect you or Calvin could blacksmith the 1.5" tube to these ports. I say that because a 1 5/8 tube fits real nice. But we're not as confident in smithing it and don't want to risk the step up at the bottom. Also we know we've got a turn almost right off the head and reshaping on a curve is that much harder and we're putting a high priority on smooth and gentle. So, we're going to take the time and get custom flanges made. The flanges will transition from exhaust port shape to tube. It would be similar to the ones Brian has had made for the 2.2 and 2.4 liter engines.
22flange-head.jpg
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Re: 340 Chrysler Street Header Questions

Postby 900HP » Wed Jul 15, 2015 12:15 pm

Mattax wrote:
I suspect you or Calvin could blacksmith the 1.5" tube to these ports.


I'm not sure how Calvin does it but all I do is squish the tube in a vice to get the basic shape I want. Then I put the tube in the flange. If the roof lines up perfect, I tack weld the roof. If the roof doesn't line up, I'll heat the tube with a torch until it's red and then I take a solid bar (round or square depending on what I'm working on) and I lay the bar inside the tube and hit it with a hammer until the roof is a perfect match. Once the roof is welded then I heat the tube with a torch and match it to the rest of the port working from the top down. It's not too hard, really.

Smooth and gentle is the name of the game here, you'll get it :wink:

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Re: 340 Chrysler Street Header Questions

Postby Mattax » Fri Oct 23, 2015 11:17 am

Here's the flange we had made.
Custom-SS-LA-Flange-portside.jpg

Custom-SS-LA-Flange-tubeside-.jpg


Brian has started to lay out the driver side routing. Right now, it looks like the best path for #1 & 5 primaries may be between the steering box and the block. First photo was the begining where #5 would cross #1. Second photo is starting #5 such that it should be possible to go side be side. Number 3 will angle up and cross over the top of #5. We don't love how tight these run to the steering box, but it would result in primaries closer to equal and a bit more room to join the secondaries. General plan is to step up to 1.625 tubing after getting below the steering box.

- Matt
ImageDS-10 on Flickr
ImageDS-11 on Flickr
ImageDS-12 on Flickr
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Re: 340 Chrysler Street Header Q..now Build

Postby Mattax » Mon Nov 09, 2015 4:53 pm

Progress on the driver side routing and construction.

DS-15-web.jpg

Difficult to see in the photos is the step ups to 1 5/8 tubing after the first major turn, about 10" off the flange. Brian also managed to work it out so only one tube is really close to the steering box (instead of the two mentioned in my previous post).
At the moment, the plan is #5 will remain a slip joint to make installation and removal easier. The mating tube will probably be a slip joint were it goes into the first merge (next to the starter).

Just some reduced photos for now. Maybe later I'll load to flcker and edit this so it links.
DS-16-web.jpg
DS-21-web.jpg
DS-23-web.jpg
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Re: 340 Chrysler Street Header Questions

Postby Solid LT1 » Tue Nov 10, 2015 2:18 pm

I remember my old 340 Duster had either Cyclone or Headman headers on it and all the divers side tubes slip fit into the collector to allow installation.....exhaust leak city but, I was in high school and thought it was cool. Looks like a talented guy doing the header fabrication....NICE WORK!

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Re: 340 Chrysler Street Header Questions

Postby 77cruiser » Wed Nov 11, 2015 8:40 am

Looks like a nightmare getting those in there. Nice job though!
Jim

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Re: 340 Chrysler Street Header Questions

Postby Mattax » Sun Nov 15, 2015 7:54 am

Thanks gents. Yes its tight in there, but maybe not quite as impossible as the photos make it look. :)

I'm not sure which mass produuced brand had a mopar a-body header with a slip fit collector. The earliest I recall were from around 1989. I believe Blackjack headers were same as Cyclone at that time and fully welded (tried a set with the rough ceramic coating - tighten the bolds and the headers hit the chassis LOL-not). Hedman had some offerings - even through MP but looked promising. Eventually I went with the Headers By Ed which were multi-piece, using 2-bolt flanges on the primaries. Another possible candidate for mass produced slip collector header a decade or more ago was something made by Hooker.

At one time Doug Thorley offered a THY-153 4into1 that had a slip fit for #7 primary in the driver's side collector. In that respect design is similar to the current TTI offering. The current company called Doug's (not the same as the current company called Doug Thorleys) has fully welded 4 into 1 for the 67+ a-bodies, and also is making a header with slip fits for the pre-'67 a-bodies. I believe it is similar but not the same as the older pre-'67 header which had multiple slip fits and is very tight fit. I've seen photos on the 'net of surviving headers from the 1960s-early 70s racing efforts - not sure if they were produced in any numbers.


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