Optimal Header design for 484 FE without shock towers.

[Joe-JDC]

I am just repeating what I was taught in my college courses and what I have experienced working with a factory sponsored race team that did all the porting for a  GTP race series.  When the new for '86 Mustang GT/LXs came out with dual exhausts, Ford made the statement about the pipes not needing to be the same size after the mufflers.  I believed them then, and I still think it works best for street.   I have seen Fox mustangs run in the 10's with 1 5/8" headers, and 8's with 1 3/4" headers, and I have seen them use 2" headers to run 8's NA.  Sometimes we over think the whole process, but some header designs always seem to come out on top when compared to others of the same family.  You can move a header pipe around on the exhaust port as much as 1/8", and pick up 10cfm in some instances.  Getting it to fit the shock tower car is where the problem arises for optimum shape with a FE.  I still think REF in Kingman AZ has as good a handle on what works as anyone for the FE.  Some folks think that it is simpler to multiply the exhaust valve diameter x 1.25% and use that for header sizing.  I ask you how that works out when a 1.600" exhaust on the D-3 Motorsports head flows 300cfm, but we struggle to get 250cfm with a 1.750" exhuast valve on the FE heads?  Cubic inch size has to be taken into account somewhere in the factoring of header tube sizing for optimum efficiency.    Joe-JDC

[jayb]

My thoughts on headers is approaching the ones I have on cams.  The more experience I get the more likely I am to just try stuff & see what happens.  So far I can say that something of at least a short straight run out of the port definitely helps - and is nigh unto impossible in a shock tower car.

My stuff has proven to be MUCH more sensitive to collector length and design than it is to primary features - as long you are in the general rational realm of sizing.  I am also pretty well convinced that some characteristics that show up good on the dyno are not going to be optimal in a car.  The difference is one of running against a load that controls acceleration rate (dyno) compared to running against a variable load while trying to maximize acceleration (car).  Blair has more experience than I do in race car optimization and I would tend to follow his lead there - I've seen some stunningly small choke diameters in use.

Your comments on primary and collector length pretty much repeat what is in David Vizards book; he says on a normal V8 engine (one with a standard crank, not a flat plane crank), the exhaust pulses on the primary are a little fuzzy because of the two cylinders on each bank that fire in succession (4-2 on the right bank, 7-8 on the left).  His claim is that this tends to defeat the purpose of sizing the primary pipe length, and the result is that if all the primaries are in the 30-40 inch range, they will work just as well as if they are all the same length.  On the other hand, he says that normal V8 engines are very sensitive to collector lengths, and that people should spend a fair amount of time and effort playing with those, because there is significant power to be gained there.  Of course, if you attach an exhaust system there is less sensitivity to the collector length.

I'm considering making two new sets of headers for my engine, one where the bends are minimized and the lengths are all in the 30-40 inch range, and one where I keep all the primary lengths at about 33 inches (which will require more and tighter bends), and test them out to see which works better.  I'm also looking forward to trying a "collector comparo" at the track...

[machoneman]

Long ago.....Mickey Thompson swore by and made the Super Scavenger header where, as shown in a linked pic, the unequal length primaries ended up stuffed into a rather large square shaped collector where the pulses allegedly evened out. They were a pretty popular header but I never saw any back-to-back test, track or dyno, that verified his published tests.

 http://forums.hotrod.com/car-craft/70/9646431/car-engine/headers/

What's interesting too is what the Fab Shop makes these days ala' the heavily tapered 4-hole merge collector. Yet, the pics do not show some of the wilder collector extentions (2 into 1) some of the Pro teams run.

http://www.fabshopheaders.com/pro-comp-headers.html

[hrtatk1]

I was actually going have the FAB shop build my headers, but after I sent pictures and he realized I had inner fender panels, he said he wouldn't.
His recommendation was 2-1/8" X 34-36" primary not more than 2" straight off the head with a merge collector with 3-1/2" outlet.
I also called REF and he said 2 to 2-1/8" primary.

[1968galaxie]

Not really comparable...for other reasons
But my most recent EMC engine made middle 600s at 6500 with 433 cubes with a 236@.050 cam....
Back in the day we'd have called that an RV grind as far as duration goes
Same engine with a 242@.050 cam went over 700..

There's always more to it than meets the eye
And some old ideas tend to die hard..

hello Barry,

How on earth can you compare the low duration (0.050" numbers) EMC camshaft with a typical low duration RV grind?
Not really the same are they?
Any extreme camshaft lobe profile (which any low duration EMC build is) coupled with high lift does not make for a long maintenance free lifetime. I am sure you will agree. Hydraulic rollers set up like a solid roller, and solid roller type valve spring pressures.
Not a comparison in my opinion.

I would much rather have a little longer duration with a reasonable lobe design than an EMC type lobe.

[Barry_R]

You can't - - and I said that.

At the same time the point is that you also cannot simply state that something "will not happen" with a set of cam specs unless the rest of the combination is way, way out to lunch.  Five years ago anybody on the internet would have called me out for claiming that I could go to 7000 RPM or approach 700 HP with 236@ .050 - - now its accepted as factual "with a disclaimer".  A good set of heads changes the entire scheme of things.

[900HP]

My thoughts on headers is approaching the ones I have on cams.  The more experience I get the more likely I am to just try stuff & see what happens.  So far I can say that something of at least a short straight run out of the port definitely helps - and is nigh unto impossible in a shock tower car.

My stuff has proven to be MUCH more sensitive to collector length and design than it is to primary features - as long you are in the general rational realm of sizing.  I am also pretty well convinced that some characteristics that show up good on the dyno are not going to be optimal in a car.  The difference is one of running against a load that controls acceleration rate (dyno) compared to running against a variable load while trying to maximize acceleration (car).  Blair has more experience than I do in race car optimization and I would tend to follow his lead there - I've seen some stunningly small choke diameters in use.

Your comments on primary and collector length pretty much repeat what is in David Vizards book; he says on a normal V8 engine (one with a standard crank, not a flat plane crank), the exhaust pulses on the primary are a little fuzzy because of the two cylinders on each bank that fire in succession (4-2 on the right bank, 7-8 on the left).  His claim is that this tends to defeat the purpose of sizing the primary pipe length, and the result is that if all the primaries are in the 30-40 inch range, they will work just as well as if they are all the same length.  On the other hand, he says that normal V8 engines are very sensitive to collector lengths, and that people should spend a fair amount of time and effort playing with those, because there is significant power to be gained there.  Of course, if you attach an exhaust system there is less sensitivity to the collector length.

I'm considering making two new sets of headers for my engine, one where the bends are minimized and the lengths are all in the 30-40 inch range, and one where I keep all the primary lengths at about 33 inches (which will require more and tighter bends), and test them out to see which works better.  I'm also looking forward to trying a "collector comparo" at the track...

Bring that Mustang up here once the engine's done and I'll help you build a REAL set of headers.

[900HP]

On the header thing, please read:  http://www.exhausting101.com/
                                          and:  http://www.speedtalk.com/forum/viewtopic.php?f=1&t=41836
                                          and:  http://www.speedtalk.com/forum/viewtopic.php?f=1&t=36702

A couple of things about header design:

1) most are too big with too restrictive of bends

2) The header tube does not need to be any larger AREA wise (and often smaller) than the exhaust port it's attached to, at least to start out with.  The primary should start with the same AREA as the exhaust port and then step from there depending on power/rpm/etc

3) 4-2-1's will allow a broader powerband with no loss of peak (when designed correctly) and are easier to package and offer more ground clearance.

4) Primary length is about #7 on the list of importance in header design.  As long as it's in the ballpark it's close enough, the reason for this is that unless you have a 500 rpm powerband, one pipe "tuning" at 100 rpm less than another really doesn't matter.

5) the most important part of the header is the port-match and the bend radius off of the cylinder head.

6) When the area increases the exhaust releases energy as it slows down, this can be seen as heat.  This is why collectors and tight bends are always the hot spots, you are giving up exhaust energy.  Once it's gone you can't ever get it back either. This is why header for header stainless steel will make more power.  It 1) keeps it hotter and 2) doesn't rust so the inside stays smoother. 

7) Anti-reversion steps/valves work very well but most put them at the wrong spot.  The cylinder head is the wrong spot, the end of the system is the correct spot


No header is going to get the op the power he wants.  #1, the lobe separation is too wide, especially considering the compression.  #2, th duration is fine, I just built a 464 inch Buick with 230/236 duration and it peaks at 5900-6000 rpm @ 598 hp.  It has heads that are done nicely (hint hint).  #3) if you need to run that wide of LSA because of your efi system, you need a different efi system.  There is power to be had in electronics too, proper injector size (much bigger than you'd think) injector timing, throttle body size, etc, etc, etc.

[900HP]

Are those xfi cam lobes?  If so, I would take a long hard look at your valvetrain setup and to be honest, I've picked up 25 hp by using milder lobes.

Thinking more on this.................................... OP, WHAT LIFTERS ARE YOU USING?  I haven't had an issue with XFI lobes, they aren't as aggressive as some think however, if you aren't using the GOOD lifters you are leaving a LOT on the table.  What's the point of having a hot camshaft if the lifter can't keep up with it?

[hrtatk1]

Survival provided the complete custom Hyd. Roller Cam/Lifters so I would have to defer to Barry on the brand of lifters.

[machoneman]

On "optimal" headers, I'll go out on a limb here. If our poster (or anyone for that matter) runs a full length exhaust with mufflers, I don't believe one set of headers makes a big difference, minimal at best. That assumes a fairy well-designed yet off-the-shelf header with appropriate sized primary, collector, exhaust pipe and free flowing mufflers.

Yet, an open header engine, on any track, does make for testing various designs. I'm reminded of some old pals running Comp/Elim and Pro Stock cars who used to have a ton of various headers that were constantly swapped for real on-track testing in hopes of gaining provable, yet often minimal e.t. reductions. Heck, they had more invested in headers than any complete drag car I ever ran! And yes, Stock (where allowed) and SS cars also benefit by particular designs that do show solid, if not major, e.t. reduction.

But once again streeters that are mufflered-up are in a whole different world. Flame on!   

[900HP]

Survival provided the complete custom Hyd. Roller Cam/Lifters so I would have to defer to Barry on the brand of lifters.

If you got the lifters from Barry they are Morel and they are fine.  I was just thinking out loud...........

[900HP]

On "optimal" headers, I'll go out on a limb here. If our poster (or anyone for that matter) runs a full length exhaust with mufflers, I don't believe one set of headers makes a big difference, minimal at best. That assumes a fairy well-designed yet off-the-shelf header with appropriate sized primary, collector, exhaust pipe and free flowing mufflers.

I don't agree with you on this.  IF the headers are designed correctly they can be made to "ignore" the exhaust system behind them as long as it flows well enough.  It can be as simple as an A/R valve at the collector which is the biggest mistake that I personally made at Engine Master's this year.  Last year we had a nice A/R valve and the engine wasn't affected by the dyno exhaust.  This year there was no A/R valve and the exhaust behind the header drastically affected power. 

Also, a 4-2-1 header properly designed will out-perform a 4-1 header at every rpm you are likely to use.  As rpm band narrows and goes up (think comp eliminator) the advantages of the 4-2-1 become less and less significant.  One more thing about the 4-2-1 header is you will have MUCH better part-throttle drivability and response if it's designed correctly.  Too many people build a 4-2-1 header like a 4-1 header with a different collector and that is not the right way to do it.

Please read the links I previously posted, there is an incredible amount of good exhaust information contained in them.

[hrtatk1]

What does everyone familiar with the FPA-Tri-Y headers think would happen if I was to take my set and modify them with a longer tube straight off of the head flange and then a gradual curve into the existing header, thereby eliminating the tight turn normally there for fitment in cars with shock towers? Would they be adequate for my engine combo?

Barry tried both my FPA's and his Dyno Header on my engine and the results are as follows:

FPA's=540HP@5600,  547TQ@4900

Dyno=553HP@5600,  555TQ@4900

[jayb]

There is no doubt that the near right angle bend at the port of the FPA headers, and other FE headers for shock tower cars, has a significant effect on power.  I think if you re-did the first 6-8 inches of the FPA headers they would work really well.