Author Topic: Headers (another one for the rocket scientists)  (Read 2697 times)

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Blueoval77

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Headers (another one for the rocket scientists)
« on: February 16, 2022, 10:38:48 AM »
OK , so I am about to start on this set of 2" stainless headers for this 70 and I wanted to get some opinions on cross overs. Dougs has the rear tubes crossing over and it actually is quite handy for a couple of reasons . It helps with installation and starter access and using up tubing to get length  .
Does anyone have any real data either way on if this helps or hurts power numbers significantly ? What if two were crossed over ? I dont know that I would have a need to do that but its a nagging question .
I want to pick these up about an inch higher than the Dougs and have them allow for a T Pan as well . If I cross that last cylinder over or the second to last then I am only left with one problematic tube for length and there is plenty of room for it at that point... If you dont cross over you are left with that curly q deal going on that REF employs...

If Crossing over lets say hurt the engine a couple of HP I feel its still worth it in most cases just for the ease of packaging and maintenance.. Not the class guys that need everything they can get out of what they have of course.

Thanks
It just ocured to me that I should have put this in the all thigns FE headers thread.
« Last Edit: February 16, 2022, 10:50:51 AM by Blueoval77 »

jayb

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Re: Headers (another one for the rocket scientists)
« Reply #1 on: February 16, 2022, 01:10:09 PM »
What I've learned over the years is that sharp turns are never a good thing, and primary tube length is not as important as a lot of people make it out to be.  A nice, smooth, high radius tube that is a bit shorter or longer than optimal is better than a sharp turn to make a specific length.  Also, I've found that merge collectors will pick up a little power, but not all that much over a standard collector.  I don't have any experience with the crossover headers though...
Jay Brown
- 1969 Mach 1, Drag Week 2005 Winner NA/BB, 511" FE (10.60s @ 129); Drag Week 2007 Runner-Up PA/BB, 490" Supercharged FE (9.35 @ 151)
- 1964 Ford Galaxie, Drag Week 2009 Winner Modified NA (9.50s @ 143), 585" SOHC
- 1969 Shelby Clone, Drag Week 2015 Winner Modified NA (Average 8.98 @ 149), 585" SOHC

   

FrozenMerc

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Re: Headers (another one for the rocket scientists)
« Reply #2 on: February 16, 2022, 01:44:38 PM »
When it comes to this topic, I cut my teeth in the 2-stroke world were pipe length, expansion chambers, power valves, etc can all have very significant effects on not only peak power, but power and torque over the entire operating range.  I have found that 4 strokes, (especially the large displacement, slow reving v8's that we love on this board) have a much higher tolerance for bad exhaust system design.  This is primarily due to more power being lost due to exhaust system back pressure than gained from scavenging, so reducing back pressure is typically the better way to free up more power.  The turbo guys are particularly aware of this as they can generate back pressures of 50+ psi at the piston.  But as far as tuning your pipe length to generate a scavenging effect alla 2 strokes, it is very difficult to make it happen over more than a couple hundred RPM range.  This is due to the nature of pressure pulse frequency and how the pulses merge and act together within the pipes.  This effort is probably worth your time on a race car that operates in a very narrow RPM band, but on street cars that operate from 800 to 5500+ rpms, the juice just isn't worth the squeeze.  As Jay pointed out, the best thing to do is keep your back pressure minimized, via smooth bends and correctly sized pipe for the flow requirements.


cjshaker

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Re: Headers (another one for the rocket scientists)
« Reply #3 on: February 16, 2022, 03:17:04 PM »
I don't believe you'll find many SuperStock racers running crossovers, if any at all. That pretty much says it all. Length, size and collectors are where the power is found.

2 strokes will have a HUGE difference, but not so much with big 4 cycle V8's.
Doug Smith


'69 R-code Mach 1, 427 MR, 2x4, Jerico, 4.30 Locker
'70 F-350 390
'55 Ford Customline 2dr
'37 Ford Coupe

gt350hr

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Re: Headers (another one for the rocket scientists)
« Reply #4 on: February 16, 2022, 04:02:00 PM »
    The typical "crossover" tubes were 4 and 8. This helped the firing rotation to where only two cylinders fired out of sequence in the collector instead of the usual four. Doug did it in an attempt to make the primary length more equal. A "true" 180 firing order set would have 4 tubes crossing over and are NOT worth the aggravation or expense. The tubing diameter and collector sizing make them VERY RPM sensitive. I ran them for about three years before I wised up and put on regular four tubes and picked up.

machoneman

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Re: Headers (another one for the rocket scientists)
« Reply #5 on: February 16, 2022, 04:08:54 PM »
And after adding a killer set of headers and mandrel bent pipes we go and....put mufflers on our street cars! Oh well!
Bob Maag

Blueoval77

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Re: Headers (another one for the rocket scientists)
« Reply #6 on: February 16, 2022, 07:33:20 PM »
So there is the rub . To get a 2 or 2 1/8 into collector on either side you then have to do some pretty stupid things with the tubes to keep them at about 40"  . In the mustang chassis this means tight bends around in circles

For instance , cyl 1 and 2 is right about 40" total length . Number three you can get the 40 without too much gymnastics , but some  , well now that youve done that number 4 is simply a nightmare. Doing number 4 without what youve done with number three wouldnt be bad but you had to do it so now here we are... If we cross that 4th tube over then it removes it from the equation and keeps its length and you do your 3rd tube and go have a drink or a smoke or something...

If you want to pack them all into their individual collectors you end up with this https://i.postimg.cc/C5hnJBGR/REF-FE-Headers-Mustang-Cougar-390-with-automatic-006-rs.jpg . Mind you , you still need to steer the car and that mess is all kinds of hindering that endeavor !!!! I would love to see those things on that cougar in detail to see just how its woven around the steering components.

Bob , this one isnt getting much for mufflers......

Thanks for the input guys
« Last Edit: February 16, 2022, 07:46:51 PM by Blueoval77 »

Rory428

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Re: Headers (another one for the rocket scientists)
« Reply #7 on: February 17, 2022, 12:51:26 PM »
On my Fairmont, the first set of headers that we made, had number 3 and 7s primary tubes crossover under the oil pan, and dump into the opposite collector, purely for packaging . The front 2 tubes on each side hung down, similar to the Hooker "race" FE headers, and the 4 & 8 tubes were considerably shorter than the rest. After those headers basically fell apart after 14 years, TomP built me a new set of 2" primary custom headers, with no cross over, that were much closer to "equal length", and tucked up tighter to the engine, so no more crunching the headers coming down from a wheelstand. And the car ran exactly the same with both sets of headers. Equal length may be a good thing, but if the tube is a different length, but a smoother, less restrictive bend, I think that is more important.
1978 Fairmont,FE 427 with 428 crank, 4 speed Jerico best of 9.972@132.54MPH 1.29 60 foot
1985 Mustang HB 331 SB Ford, 4 speed Jerico, best of 10.29@128 MPH 1.40 60 foot.
1974 F350 race car hauler 390 NP435 4 speed
1959 Ford Meteor 2 dr sedan. 428 Cobra Jet, 4 speed Toploader. 12.54@ 108 MPH

preaction

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Re: Headers (another one for the rocket scientists)
« Reply #8 on: February 17, 2022, 03:09:41 PM »
When it comes to this topic, I cut my teeth in the 2-stroke world were pipe length, expansion chambers, power valves, etc can all have very significant effects on not only peak power, but power and torque over the entire operating range.  I have found that 4 strokes, (especially the large displacement, slow reving v8's that we love on this board) have a much higher tolerance for bad exhaust system design.  This is primarily due to more power being lost due to exhaust system back pressure than gained from scavenging, so reducing back pressure is typically the better way to free up more power.  The turbo guys are particularly aware of this as they can generate back pressures of 50+ psi at the piston.  But as far as tuning your pipe length to generate a scavenging effect alla 2 strokes, it is very difficult to make it happen over more than a couple hundred RPM range.  This is due to the nature of pressure pulse frequency and how the pulses merge and act together within the pipes.  This effort is probably worth your time on a race car that operates in a very narrow RPM band, but on street cars that operate from 800 to 5500+ rpms, the juice just isn't worth the squeeze.  As Jay pointed out, the best thing to do is keep your back pressure minimized, via smooth bends and correctly sized pipe for the flow requirements.


This post remindes me of when I read the Two-stroke tuners handbook by Gorden Jennings circa 1973.

cammerfe

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Re: Headers (another one for the rocket scientists)
« Reply #9 on: February 17, 2022, 10:22:43 PM »
For a set of well-tuned, equal length headers, look at a big block Ford GT. But to use them, you'd have to have a rear engine, or run them through the firewall and along the trans/diveshaft tunnel to get them out the back. And drive from the back seat. ;)

KS

pbf777

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Re: Headers (another one for the rocket scientists)
« Reply #10 on: February 18, 2022, 10:30:40 AM »
.................... you'd have to have a rear engine, or run them through the firewall ................


      We have repeatedly revisited the 'true' 180° exhaust header for fitment in front engined chassis (retaining the firewall! :o ) but with no luck, as the primary tubes just get too long (for truly 'racy' applications ::) )  in the effort. In the end, and in discussions with Dave Crower, we concluded that if the exhaust timing effect was going to be so important to the project, we should just incorporate a 180° "flat-crank".   ;)

       Scott.

gt350hr

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Re: Headers (another one for the rocket scientists)
« Reply #11 on: February 18, 2022, 10:46:52 AM »
For a set of well-tuned, equal length headers, look at a big block Ford GT. But to use them, you'd have to have a rear engine, or run them through the firewall and along the trans/diveshaft tunnel to get them out the back. And drive from the back seat. ;)

KS

     For that matter "all" Ford GT's had 180* headers.

Blueoval77

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Re: Headers (another one for the rocket scientists)
« Reply #12 on: February 18, 2022, 10:55:28 AM »
Thanks Rory  , thats pretty much exactly what I was looking for. I value the packaging much more than a few horses  , hell , even up to 20 Horses if they look cleaner and can easily be taken on and off for service of items. I think I can get 4 and 8 to the right length without too much trouble and just cross them over .

My biggest issue with Dougs header design is that the tire rods fall down onto the tubes of 3 and 7 with the front suspension at full extension which can be a bit un nerving for the first 100 feet or so... . Not that the Dougs would work with this starter or steering box anyway.

wayne

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Re: Headers (another one for the rocket scientists)
« Reply #13 on: February 19, 2022, 05:02:32 AM »
This is why  pickup headers work good straight out and smooth bends .

Blueoval77

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Re: Headers (another one for the rocket scientists)
« Reply #14 on: February 19, 2022, 11:13:51 AM »
Yep , and the polar opposite of that would be the mustang . Personally I feel that the damage is done not 3 inches from the heads and all the other work you are putting in really doesnt help you to overcome that. Im sure that somewhere along the line Jay has Run a mustang header and a truck header on the same engine on the dyno and could tell is that is indeed the case.