FE Power Forums
FE Power Forums => FE Technical Forum => Topic started by: C8OZ on August 07, 2020, 01:26:13 PM
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I have a set of 6376 Hooker adjustable headers, the 2" version of the 6375 (2.125).
Any idea how much power I'm leaving on the table with the 2" primaries?
I'd like for the build to live quite a while, so I'm okay bringing the peak RPM down some.
These are for a 4.375 x 4.375 Tunnel Port, single Holley 4500, 13.5:1-ish and E85.
Shooting for 3400 pound max, 4-speed, 29" tire, weekend 1/8 mile car, not a max effort racer.
The rest of the specs are tbd, as it's still early. I just hate to take hammer to car and pipes in mockup if these need to stay on the shelf for a smaller CI build.
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What kind of power do you anticipate making, I've seen tests between 2" and 2 1/8" on a 700hp BBC and the bigger headers were 5hp better.
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I'd like it to go mid-sixes 1/8-mile and live. I haven't done that with an FE, so I'm making some guesses. But 700 ballpark is my goal depending on how much weight I can drop.
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Not a hairy difference. Not enough to loose sleep over.
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Might not show at all. 2" used to be THE size to use.
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Does anyone make a stepped, 2 - 2 1/8 header. That might be interesting.
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REF Unlimited will make step headers, custom sized.
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Thanks guys.
A slow project gives me plenty of time to start questioning parts choices. I'll plan on putting the 6376 to use.
I've read that a third version of the Hooker adjustable was stepped 1 7/8, 2, 2 1/8, but I've never seen a set.
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I think my 390 would prefer the 6376 headers given it's smaller size but these haven't been made in years. All I ever had/have are 6375's and they seem to not hurt performance no matter the cubic inch. I doubt you'll see any difference with your combo. I'm fairly certain the Hooker Race 1 7/8" which I've never seen either were not a step header. Seems the jury is still out on any real benefit on step tubes anyway. Now Hooker doesn't make any of them for some reason.
REF makes some good headers but apparently nothing out of the ordinary. A guy at the track today said he (or no one else for that matter) would build Headers for a 66/67 FE Fairlane with a rear sump pan. He ended up making his own.
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Here’s my REF 1 7/8 headers, had jet hot coat them. They’re for a 67 Fairlane, he was a pretty cool guy to talk with. His opinion was I could shove quite a bit of power through 1 7/8. We shall see.
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Try again with photo
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Ugh
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Everything I've seen from REF looks top notch. I like that those collectors angle inboard where the Hooker is straight back.
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I'm making 575 in a 393C with 1 7/8" tubes so IMHO go with what fits. You'd not know the difference.
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I made 561/595 with 1 5/8"-1 3/4" stepped FPA on my 375 CI Y Block. Fits '55 Thunderbird. Same headers made over 600 hp on a different engine. There are a lot of dyno tests that prove the stepped headers work if you actually do back to back testing. REF is a race header, but he designs them for specific chassis, so they fit SE and SS cars classes as well as street. Joe-JDC
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If you ever go to a NHRA National event, take a look at the size of the header primary tubes on a 950 HP SS/AH Hemi Mopar, or Competition Eliminator V8, I think many would be suprised at how small the header tubes are. And believe , those guys don`t leave any crumbs on the plate!
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Jack Davis (rip) formerly of Hooker headers claimed he was the "inventor" of stepped headers. He built hundreds of sets for NHRA drag racers in all different classes from stock to Pro Stock and went to North Carolina several times to build Nascar headers. Jack tried two step and three step designs that really made a difference on the dragster I was crew chief for. He made me a set for my Shelby that ran the same as the former non stepped set. That was ahead scratcher.
Looks like Calvin Ellston makes most of them now.
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Yes, Elston makes the 289 headers for Vintage racing classes with stepped tubes. They are listed on Cobra web site. They start at $3500.00 and go up from there. When I called him to ask about making a set for my Thunderbird, he would not talk to me at first, then quoted me $3500.00 and bring my car to him in NC and leave it. That trip alone would have cost $3000.00 with hotels and food. Joe-JDC
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That sounds excessive - but the stainless 2"~ 2 1/8"you see on most of the BBC dragsters start at $1200~1400 or so. A good friend did the once on my car, thankfully as best quote I had was $1300. I have about $650 in them for parts and the coating - some for the custom water jet flanges that mate to the AFD exhaust ports and a dragster header pipe kit for a BBC that we repurposed. Plus some cool megaphone collectors he engineered from scratch on the bench.
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Here's the instruction sheet for anyone as easily entertained as I am.
You just don't see bumper jacks mentioned enough nowadays.
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People with only bumper jacks tended not to have welders to put those tabs on.
I think they listed the three step #6374 headers for a couple years, 1 7/8", 2" and 2 1/8" tube steps. But i wonder if they ever made any? I've never seen a set and when i tried to get some they were not available.
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Here is a Formula
Area of the Primary Tube (PPA) = (peak torque rpm ÷ 88,200) x (c.i.d. ÷ number of cylinders)
For example, let's look at a 350 c.i.d. small block with a peak torque goal of 5,000 rpm.
PPA = (5,000 rpm ÷ 88,200) x (350 c.i. ÷ 8)
PPA = 0.057 x 43.75 c.i.
PPA = 2.49 square in.
PPA Primary Tube Diameter
1.78 square in. 1 1/2 in.
2.07 square in. 1 5/8 in.
2.41 square in. 1 3/4 in.
2.76 square in. 1 7/8 in.
3.14 square in. 2 in.
There is several links if you search exhaust header size. Mike
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People with only bumper jacks tended not to have welders to put those tabs on.
I think they listed the three step #6374 headers for a couple years, 1 7/8", 2" and 2 1/8" tube steps. But i wonder if they ever made any? I've never seen a set and when i tried to get some they were not available.
I saw a set on a C/SA car at Seattle several years ago but I don't remember who's.
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I checked a few ~600hp engines in the Gonkulator - as a rule, 2-1/8 headers are worth 5-10hp more vs 2" headers (not very much out of 600 total), and about the same on torque - sometimes the bigger 2-1/8 even lose a few ftlb. Not worth going for the extra 1/8 unless of course you have em already.
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Can you do stepped primary's on your Gonkulator or add a merged collector with different size and length collectors?
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Can you do stepped primary's on your Gonkulator or add a merged collector with different size and length collectors?
I haven't put a lot of effort into that because:
a] the Gonkulator routine I normally use here is a fast one so makes more approximations for headers.
b] I'm not sure I understand the gains yet. Seems like a lot of work to do all the steps, and the gains might only show up if you have open headers. And, those gains are going to be convoluted with the fact that the smaller pipe sections can now be less bend-constrained and therefore flow better.
So you'd have to do some pretty deliberate design & testing to separate out the effects of JUST the steps vs less kinks & bends.
Maybe they're worth it, I just don't know. Would be nice to see more data before I put more effort into it.
Great question!
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Werby whats the difference from 1 7/8 to 2 inch, just curious.
HP and torque
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Werby whats the difference from 1 7/8 to 2 inch, just curious.
HP and torque
OK here is a bored 428 t-wedge, Gonkulates to 632hp, with just exhaust changes:
2.125 632hp
2.000 621hp -11
1.875 604hp -28
1.750 579hp -53
CJ-iron 534hp -98hp
All the headers are of course way better than the 428CJ iron manifolds.
Also, the smaller tubes might lose a little less in reality, because you have more room to be more generous with the bends.
I did NOT gonkulate that because it's too subjective - only a dyno would tell that.
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Werby, here are a couple of data points for you that may help you make a more accurate simulation. This is from a 504" dyno mule that I used for testing the 351C intakes. HP loss with the smaller 1-3/4" tubes is about 35 on this 700 HP engine, vs the 2-1/8" tubes. Torque GAIN with the smaller tubes in the lower speed ranges was about 35 foot pounds. If you want details from the engine look at the Dyno Mule to Test 351C Intakes thread on page 2 of the Member Projects forum.
Also I would point out that step headers are far easier to build than headers of a uniform tube size. This is because at the step, you can slip one tube inside the other to hold it in place. I'm currently building headers for the dyno mule to run my new cylinder heads and with most of the tubes I can mock them up completely before tacking them, simply by tacking the first tube to the flange, and then slipping the next tube over the first one by 1/2" or so. That tube can then be rotated to the right position or pulled off and modified or recut if necessary to make the tube as a whole work. This works all the way into the collector, in my case 3 of the 4 tubes on each side were completely assembled this way before being tacked in place, stepping from 2" to 2-1/8" to 2-1/4".
Finally, I think it would be a great idea for you to try to figure a way to include tube bend radius into your simulator. My testing has shown that a larger tube bend radius makes more power; you don't want to bend the exhaust any more than you have to. This is way more important than equal primary tube length, which seems to be the thing that everyone focuses on.
Hope that helps - Jay
(http://fepower.net/Photos/Posts/supercompvadjrace.JPG)
(http://fepower.net/Photos/Posts/supercompvadjrace2.JPG)
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I have come to believe that cubic inches is a driving factor in tube sizing up to a certain horsepower level. IE 600 hp with <400 cubic inches works better with the 1 5/8"-1 3/4" steps to a 3" collector with a 2 1/4" merge cone. Above 400 cubic inches and over 600 hp, the tubing will need to be increased depending on both factors. Average torque and average horsepower makes dyno testing very interesting if you have the time and parts to verify what works and what is just theory. Joe-JDC
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I've been over 700 on the 2" Hookers
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Jay,
Thanks for the encouragement.
I've built some complicated header routines, but use a simpler one usually for the typical Gonkulator to save computing speed. The Bend Radius criteria is a good one (but hard to get such data - usually all you get is a picture of the headers if you're lucky). Usually the header makers don't even give tube lengths or ranges, let along bend radii.
So I do "guess" a little - I penalize the flow of headers that have tight bends, and reward those that don't, eg fenderwell headers or some dyno headers. I think Hooker really did a good job on those 6114 headers - they make basically a right angle turn out of the ports to fit the Unibody FoMoCos, as they must, and yet still perform well, so well that they really don't want much "penalty" in the Gonkulator. I'd guess differently looking at them.
It seems folks don't "Flow Bench" headers very much - kinda like head or intake flows. Exhaust has to flow a LOT of air - all the air the intake took in, plus a few more net combustion molecules, and then mainly that air is about 3x hotter than the intake air so takes up 3x the volume. It's at pressure which helps a little, but still, a lot of air to flow.
BTW in your dyno runs, do you recall where you set those Hooker 2-1/8 adjustables? They say you can adjust the primary tubes from 30" to 38", which, if all the tubes are the same length (are they?) can make a big difference in the peaks.
Really enjoy your testing, pictures, and graphs. 500hp used to be a lot for a pump gas FE. Now it's more like 700hp.
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I didn't use any of the primary extensions, so they should be 30" - Jay
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Did any one see the tv show were they tested headers someone called in and wanted to know how much it hurt to dent them to make them fit. They had some tubes 2/3 shut and lost no hp the engine was a small block rod knocker.