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Technical => Matt Shaff's Engine Shop => Topic started by: Roger on February 11, 2017, 08:23:09 AM

Title: Zoomies vs collector headers
Post by: Roger on February 11, 2017, 08:23:09 AM
In a current thread there’s been a conversation about collector headers and zoomies on FEDs. I agree with most, zoomies belong on FEDs and I think they also belong on altereds. With that said, has anyone out there done an actual comparison between the two? I’ve been studying, or trying to, the difference in performance between the two. The only actual dyno test information I’ve been able to find is one conducted by Joe Sherman in which he stated “have seen as much as 55 or 56 HP (less) on a 1000 HP engine“ compared with collector headers. Now zoomies won’t have the inertial scavenging of a correct length and diameter pipe (roughly 28” to 34” long) because they are to short and it won’t have the wave scavenging of the collector because there’s no collector to share the wave with other cylinders. But what a set of zoomies have working for them while hanging out in the breeze at 180mph is the Bernoulli principle effect on drawing exhaust out of the cylinder. That’s the same effect that draws fuel out of a carburetor bowl and draws a crankcase vacuum with a pan-evac system. Any comparative tests out there of zoomies vs headers or any thoughts?
Title: Re: Zoomies vs collector headers
Post by: dreracecar on February 11, 2017, 09:45:23 AM
7 seconds is not enough time to worry about scavanging
On a blown car the collector outlet area is restrictive vs open pipes
For what I have seen, the dyno shop has headers set up to use in their room with all the hook-ups, and there might be a difference between those and the headers that fit the vehical, also consider that open zoomies in the dyno room without someway of collecting the exhaust, contaminate the air in the room, which hurts performance.
NASCAR teams spend $100,000's on header designs and dyno testing because the runs are longer and take advantage of every  single 1 hp gain, If they change cams, it might also need a header swap. We on the other hand are happy if they just fit right off the shelf
Title: Re: Zoomies vs collector headers
Post by: coupemerc on February 11, 2017, 04:07:42 PM
I know that Bill (masracingtd1167) has run his FED with both header types. His engine is a normally aspirated SBC on methanol. It used to be quicker with the 4 into 1 collector headers but recently he made some changes to the car and ran his best et ever. I think he had the zoomies on it. Maybe Bill will chime in on this thread.
I agree with what Sherman said. Recently I went to the dyno with my injected, methanol SBC. I run zoomies on the car and I did not want the scavenging effect of collector headers to give me bogus (higher) dyno numbers. I ended up using custom dyno headers that are basically 12" long zoomies that dump into an 8 inch "log". They were more representative to what I run on the car. The idea came from Scott Parks.
Title: Re: Zoomies vs collector headers
Post by: masracingtd1167 on February 12, 2017, 07:44:35 AM
I can't honestly say witch one is quicker ! I have been using a collector header on my cars for a long time and we always ran quicker with them ! When I built the zoomie headers for my current car my plan was to slow the car down for 7.50 racing and I did not notice much difference in performance at all ! Back when we started running the collector headers we were also running on gasoline and the headers were worth a solid tenth !I think the only way to really tell the difference is with an a to b to a test . Also about 10 lbs lighter with the zoomie header . This picture is from the early seventies   
Title: Re: Zoomies vs collector headers
Post by: JrFuel Hayden on February 12, 2017, 10:41:25 PM
My experience with dragster pipes has been it depends on the fuel, head flow, and RPM. When we were running a non-raised runner 23° Iron SBC, we used 1 5/8 pipe zoomies, on alky, then as we started running raised runner heads, we increased the pipe size 1 3/4, then 1 7/8, then 2" and now with the bigger cam, and 10,000 RPM, we have 2 1/8" zoomies.
On my 1'st 1962 dragster, C/D on gas we tried different pipes based on formulas , we didn't learn enough, since it broke allot and only race it a year. Next dragster I ran for 5 years [63-68] it was a real nitro JrFueler, again we tried long pipes, short pipes, different pipe sizes, For us none of the formula pipes seemed to make a difference burning nitro. I ended up with just about 8" zoomies, because they were just lighter, and out of the way to work on the valves, etc.  The other thing is we always aimed the traditional zoomies back toward the slicks. Remember the big deal on the funny cars zoomie angles last year, action/ reaction, helps moves the car forward. I had a B/ND motor in a car and I put my angled zoomies on it and took the mostly upright zoomies off. The car picked up MPH.
I don't know any team that has found any improvement while burning injected alky. I know of one team that runs collectors on his injected alky, and he said he just picked 4-1 because he just wanted to look different and he runs the 7.60 class, and not looking for max performance. 
Good Luck
Jon
Title: Re: Zoomies vs collector headers
Post by: dreracecar on February 13, 2017, 08:06:39 AM
Plus it keeps the rocks out of his engine without have to use covers
Title: Re: Zoomies vs collector headers
Post by: Roger on February 13, 2017, 12:38:58 PM
I agree with Bruce that a blown car with a lot of exhaust volume probably doesn’t need or work well with headers. For now I don’t have a blower and was looking at this more through the lens of a naturally aspirated engine. It’s interesting that Bill’s cars were a tenth or less slower with zoomies. Having been told they don’t work well in the past with n/a engines I was curious as to how much the engine performance was actually affected and at least in his instance it wasn’t much, if any. Of course the car would weigh less with the zoomies. The ones I have weigh 10# for the pair and the headers I have for the street rod engine weight 34#. Now Jon brings up an interesting point about how far to lay the pipes back from vertical. With the case of big show cars they have a huge amount of exhaust that’s angled rearward to propel them forward compared to a smaller volume and force from a junior fuel car. So while there is some exhaust volume to propel the J/F forward, is there an optimal angle to lay the pipes back to get maximum benefit from the Bernoulli effect? Ya, this is splitting hairs but I’ve always told the kids in my classes that in order to do something right the first time you must have some knowledge of it before you start. Thought Scott’s idea of the test zoomie thingy on Chuck’s car was I good idea. Kind of reminds me of some of those old lakester style headers on steroids!

The pictures show the Bernoulli effect. First photo is a glass of dyed water with a straw in it. Second is the same glass and straw with 60psi blown across the opening. In this case it drew 3-1/2” of water.
Title: Re: Zoomies vs collector headers
Post by: George on February 13, 2017, 12:51:50 PM
Agree. Ya, this is splitting hairs.  :o
Title: Re: Zoomies vs collector headers
Post by: THE FRENCHTOWN FLYER on February 13, 2017, 12:57:39 PM
I wonder what 60 psi equates to in FPS/MPH?
Title: Re: Zoomies vs collector headers
Post by: dreracecar on February 13, 2017, 02:36:04 PM
My question on the "tenth or less" statement,   was the test done on back to back same day runs??? under the same conditions??
Title: Re: Zoomies vs collector headers
Post by: masracingtd1167 on February 13, 2017, 03:00:58 PM
When we first tested with collector headers was a long time ago and yes it was same day same conditions . That being said we were running injected on gasoline in c/d so a tenth was a huge gain ! So I stuck with that theory for years ! Like I said we put the zoomey on recently and noticed no change but it was different days . This season I will try a a to b to a test just to see what happens !

Title: Re: Zoomies vs collector headers
Post by: denverflatheader on February 13, 2017, 03:13:38 PM
My first response would be the glass of water is in what could be termed a low pressure condition.  Within an engine’s exhaust system, there would be again what I’ll term low pressure condition as long as the engine is not expelling exhaust.  Once the exhaust pulses start, the low pressure condition would diminish, and as the engine rpm increases from idle to redline, the low pressure condition may not be measureable.  My guess is the Bernoulli effect shown by Roger’s example may also diminish with higher rpms.  That being the case, design the exhaust exit for optimal forward thrust and traction.

Agree there’s hp increases with properly tuned exhaust, however, even more hp gain with camshaft options.  Back to Roger’s question; if you want every single hp, you must design your exhaust system properly.  If you have headers and collectors with incorrect tube diameter and length for your engine and camshaft application, you might be equal or even outperform that "mistake" with a suitable set of zoomies.

Here’s a well written article on effects of camshaft design on scavenging from Specialty Products Design, Inc., Company started by Jim Hill.  Note possibility on achieving greater than 100 percent volumetric efficiency:

“The exhaust systems role in increasing engine performance centers around improving volumetric efficiency. Volumetric efficiency (VE) refers to the ability of an engine to intake and expel gases (i.e.: air/fuel and exhaust gas), in relation to the actual pumping volume of the engine. Free flowing intake and exhaust systems help an engine to achieve this. Achieving greater than 100% VE is done in part by optimizing exhaust gas scavenging to draw out exhaust and bring in air fuel mixture during valve overlap. As the piston reaches the top of the exhaust stroke, it dwells as the crankshaft sweeps across the top of its stroke. This is where valve overlap occurs. Before the piston reaches Top Dead Center, the intake valve begins to open. The trick is to design the exhaust system so that the exhaust pulse (pressure wave) leaves behind a pressure drop or vacuum to take advantage of the valve overlap. If successful the combustion chamber will exchange residual exhaust gases for a fresh air/fuel mixture before the piston has any real effect on the intake charge.

To design a successful exhaust system or tuned header, the tube size and length are selected based on a list of engine specifications and application characteristics. The tube size controls the speed of the exhaust pulse, too big and the velocity (energy) is lost. The tube length is all about timing the pulse to synchronize with the cam in a specific RPM range. 

At the collector, the timing of the pulses is crucial to scavenging. Imagine a four lane freeway on ramp merging into one lane. If you get the timing and speed right, the pulses draft each other like stock cars at Daytona, increasing their speed.  This is where the Merge Collector comes in. It makes that transition from primary tube to collector as smooth as possible. This reduction in turbulence helps maintain velocity through the collector, thus increasing the scavenging power of the header system.”
Title: Re: Zoomies vs collector headers
Post by: wideopen231 on February 13, 2017, 03:59:13 PM
Ok while we are on exhaust flow and zoomie. Old thing from harleys especailly with drag pipes.They made a cone shaped piece that goes in between pipe and head.Idea it icreases velocity.Band aide for improper pipe being used.Dragpipes suck IMO.They add some needed restriction also.

question has anyone tried this on N/A engine,especailly with zoomies? Have thought about making a set to test at some time.

Probably well know but here is another thing on flow.The adapters made for sbc running bigger pipes that relocate bolt holes can also increase exhaust.Ind cylinder heads was selling plate for Hemi heads at one time 500 per set.Mine cost 100 per 3 sets and two days on mill.You have to match ports in basically make it a longer port.Now this was all done on blower motors and be beifit for N/A motors.
Title: Re: Zoomies vs collector headers
Post by: dusterdave173 on February 13, 2017, 04:16:52 PM
I know that when I ran a door car we ran about an 18 inch torque tube on the end of the collector--we started with about 2 ft --put a yellow tire marker crayon line down the tube--made several good runs and the wax crayon would be burnt to a certain distance we cut he pipe off right there--Car ran faster and the 60 ft was better--the sound of the car changed so much I could not believe it--folks beside the starting line always covered their ears after we 'tuned" that header--it was awful to be inside or beside of it during burnout!! Would knock your ear drums out
Title: Re: Zoomies vs collector headers
Post by: dreracecar on February 13, 2017, 04:20:29 PM
Jim Fueling (rip) came up with those anti-reversion cones/headers back in the late70's, if they worked, they would still be used today you think?
 Again, long runs at a constant rpm could show some improvment (B'ville) but for the short duration of a drag race and that the classes that allow collectors are index/bracket---whats the point??
Title: Re: Zoomies vs collector headers
Post by: noslin on February 13, 2017, 05:57:08 PM
Jim Fueling (rip) came up with those anti-reversion cones/headers back in the late70's, if they worked, they would still be used today you think?
 Again, long runs at a constant rpm could show some improvment (B'ville) but for the short duration of a drag race and that the classes that allow collectors are index/bracket---whats the point??

whats wrong with having a discussion about this (or anything else) even if your bracket/index racing?  The OP did not say anything about bracket/index racing.  its just a discussion between the two.
Title: Re: Zoomies vs collector headers
Post by: Roger on February 13, 2017, 06:22:44 PM
That's OK noslin. Look at all the great discussion this generated. Everyone has different opinions and that's cool. I'm going to go back through all this and see if I can learn something from it.
Title: Re: Zoomies vs collector headers
Post by: Paul New on February 13, 2017, 07:06:38 PM
When we ran our car injected alky with a mild SBC we switched from collector headers and lost a tenth and was never able to get it back with the zoomies..... we switched because zoomies look cool but HP was not the same. Later we ran at an event that required mufflers car went quicker again with the collector headers, even with this we went back to zoomies and sold the collector headers and put a blower on the car!!
Title: Re: Zoomies vs collector headers
Post by: Roger on February 14, 2017, 06:56:39 AM
Here’s some of the little published info I could find on the subject:

ZOOMIES vs HEADERS
Stahl Headers Newsletter, Issue #4, March, 1988
“It appears that most current late model dirt engines are 406’s to 430’s. Zoomie pipes (8 individual exhaust stacks) will run quite well from 3500 to 4500 and from 7000 to 7500. But, they give up from 25 to 35 HP at 5500 to 6500 which ends up being on the chutes where you can use all the power you can make. However, compared to Zoomies the “Shorties”, as we have labeled that collection of pipes that vary in pipe length from 14” to 16”, are the real disaster. Reports from several prominent dirt late model engine builders indicate as much as 45 to 50 HP difference between 5500 and 6500.”

With this input in mind my little 325hp street engine that goes in the roadster first will never see the high side of 5700rpm and might see little if any loss of performance between headers and zoomies. Maybe run quicker with zoomies because the headers added weight! So, I’m going to run both on my car and see for myself. Then when the race engine is done I’ll do the same thing again with zoomies and a set of larger headers that I’ll beg, borrow, or temporarily appropriate. From all the actual experiences that’s been shared here I’ll have a good chance of being a tenth slower with the zoomies. I’ll find out.

The Denverflatheader posted what I thought was a really good article that starts to look at cam timing that could help get back some of the power that was lost without headers. After talking with 4 different cam companies (who all had a little different idea of what was needed) they all pointed to a cam that needed more exhaust duration, an increased lobe separation angle, and minimum overlap as compared to a similar cam used with headers. Jones Cam Designs told me they did some tests years ago using zoomies and were emphatic that the exhaust side of the cam needed 10 degrees more duration than the intake.

And I found this little piece of information:

“I have found a consistent 5-8% power increase if the primary pipes are kept separate (zoomies), with a megaphone fitted to each primary”. This was written by A. Graham Bell, a noted engine tuner and tester in England about the same time David Vizard was also running similar testing in England. Megaphones on the end of your zoomies? Not a chance with me:)

Thanks to everyone for all their input. After all, a little shared knowledge can go a long ways in helping everyone better understand the technical parts of our sport. And that’s the point.
Title: Re: Zoomies vs collector headers
Post by: denverflatheader on February 14, 2017, 04:38:32 PM
Roger – am a strong advocate of empirical testing too, like your “plan to do” for your roadster.  Calculations and what-if scenarios are excellent today with computers, so easy, but the answers are hard to recall with passing of time.  First-hand testing, you remember forever.  Alan

dusterdave173 – good one on determining torque tube/collector length without a pyrometer.  Read that and saw immediately the benefit with your idea, and has a built-in correction factor (e.g. 4.00 versus 5.00 inch diameter).  You have to start somewhere… Alan

Title: Re: Zoomies vs collector headers
Post by: wideopen231 on February 15, 2017, 07:16:36 PM
If anythinhg I hope that 5500 to 6500 is only place you loose.My combo is setup to leave at 6800 and shift at 7600 and cross finishline around 8800 to 9000.I can see zoomies loosing out on bottomend and have no problem with that.
Title: Re: Zoomies vs collector headers
Post by: noslin on February 16, 2017, 09:36:05 PM

  After talking with 4 different cam companies (who all had a little different idea of what was needed) they all pointed to a cam that needed more exhaust duration, an increased lobe separation angle, and minimum overlap as compared to a similar cam used with headers. Jones Cam Designs told me they did some tests years ago using zoomies and were emphatic that the exhaust side of the cam needed 10 degrees more duration than the intake.

 


one thing ive learned from hangin with my buddy who is the gearhead when it comes to engines.  he is a n20 guy, from what i understand the n20 guys move the exhaust lobe depending on how much hp they plan on making.  i think technically, they add the duration for the added exhaust from the n20 but then have to move the lobe to get the overlap back where they want it.   so, maybe in the sense of what the cam gurus are trying to do is help the scavenging of the exhaust by haning it open longer and also as the n20 cam guys do, move the lobe to get the overlap where it needs to be. i dont know if this is correct thinking but its something to discuss.

i wonder if its really fair test if just changing the headers and not changing the cam.  if setup is designed for collector style header setup and put zoomies on or visa versa, is it really an accurate assessment if one makes less/more hp then the other.
Title: Re: Zoomies vs collector headers
Post by: dreracecar on February 17, 2017, 08:08:11 AM
Exactly,  If only we could build our motors from the Jegs or Summit catalog based on advertised HP gains listed with the parts, one could build a single carb 350 Chevy that made 1200 HP for $2500
Title: Re: Zoomies vs collector headers
Post by: noslin on February 17, 2017, 11:02:52 AM
Exactly,  If only we could build our motors from the Jegs or Summit catalog based on advertised HP gains listed with the parts, one could build a single carb 350 Chevy that made 1200 HP for $2500

you sure your on the right thread?
Title: Re: Zoomies vs collector headers
Post by: Roger on February 17, 2017, 05:14:35 PM
My view of how to maximize power output with zoomies falls in line with what wideopen231 & noslin have said. If Stahl’s concept that you lose power between 5500-6500rpm is correct, then have a convertor that flash stalls to at least 6,000rpm to minimize the hole in the power curve might be a wise move just as wideopen231 mentioned.

As far as noslin’s thoughts, they might be right on the money. If you don’t have the effect of a collector headers to help evacuate the cylinder then you have to do something like opening the exhaust valve longer to do a better job of clearing the cylinder of burned gases. And to keep exhaust reversion, that’s exhaust flowing into the intake, to a minimum then add a few degrees of lobe separation in order to reduce the amount of overlap time for the reversion to occur. That’s the way it was explained to me by some very experienced (didn’t want to call them old!) and well known cam designers. Of course, this has little if anything to do with supercharged engines. But they weren’t the focus of my original question, I probably should have made that more clear.

As far as changing a cam and headers, the best I can do is use the same cam designed for zoomies with more exhaust duration and a wider lobe center angle and then put the headers on and see what happens. But it’s a good point.

Picked my updated car up from the chassis shop today so here’s a quick photo. Will post more in the Altered section after I get back from a short leave.
Title: Re: Zoomies vs collector headers
Post by: BK on February 18, 2017, 04:41:12 AM
“I have found a consistent 5-8% power increase if the primary pipes are kept separate (zoomies), with a megaphone fitted to each primary”. This was written by A. Graham Bell, a noted engine tuner and tester in England about the same time David Vizard was also running similar testing in England. Megaphones on the end of your zoomies? Not a chance with me:)

Maybe not  Megaphones. But what about stepped Zoomies?
Title: Re: Zoomies vs collector headers
Post by: coupemerc on February 18, 2017, 06:27:11 AM
Good discussion but don't loose sight of the big picture which is "the car". For example, I'm attempting to race in B/ND. Collector headers are prohibited, car is very light and I'm limited to a 12" wide tire. I don't know that I would want a ton of low end torque.
Title: Re: Zoomies vs collector headers
Post by: noslin on February 18, 2017, 08:28:11 AM


Maybe not  Megaphones. But what about stepped Zoomies?

in reading a bit, it sounds like the larger the exhaust opening (end) the stronger the negative pressure wave will be.  maybe this is why the megaphone is better then single diameter tube. 

maybe with the stepped zoomie there might be some benefit to this if calculated out correctly for each step.   i wondered about a reducing step and what effect that would have on the negative pressure wave if any.   sticking with conventional enlarging stepped headers, depending on where the step is, could tune it for the 5500-6500 range and probably wouldn't look bad either.

on my vw we went with stepped on third order.  total length was bout 36" long.  first two at 13" and then single about 13"   the turbo had divided housing and to effectively keep pulses equal for each side paired up opposing firing cylinders (1432 order) 1/3 2/4.  it would spool 30lbs in about .6 seconds on 70mm wheel for 140 cubes. 


dean

Title: Re: Zoomies vs collector headers
Post by: Roger on September 03, 2017, 01:33:51 PM
Update on collector headers vs. zoomies.
Took my roadster to the local 1/8 mile track yesterday and tested headers & zoomies. In an earlier post on this thread I took a guess that in certain low horse power circumstances, both exhaust systems would create similar if not close to the same results. This will be the first of two or three tests with future engine combinations, God willing:) The engine used in this first test is a Chevy 350 street machine engine that produces about 260hp in the car, idles at 700rpm, and pulls 14” of vacuum at idle. The cam has 1 degree of overlap at 0.050” lift while the compression ratio is 8.3-1 with the stock 86,000 mile dished pistons, cylinder walls, and stock heads.

 The car is foot braked and uses a 2100rpm stall convertor along with 4:10 gears and 31 tall slicks. Since the power band of this engine is relative low compared to an all-out race engine, it’s shifted at 5300rpm and goes through the traps at 4450rpm. While it would probably go quicker if I shifted it at a higher rpm, the Stahl Headers Newsletter comments earlier in the thread that zoomies have little effect at lower rpms compared to collector headers was the reason for this test. My header tubes have a 1 5/8” dia, are roughly 39” long, and have a 3” collector. Just about right for this engine’s rpm operating range. The zoomies are 10” long and have a 1 ¾” dia. The zoomies weigh 10# per pair while the headers weigh 24#.

The first 2 runs were with headers and the air temperature was 80 degrees. The last 3 runs were with zoomies and the temperature was 85-90-85 degrees. Everything else about the car stayed the same.

1st run with headers:   7.008et at 100.45mph
2nd run with headers:   6.975et at 100.22mph
3rd run with zoomies:   6.924et at 101.58mph
4th run with zoomies:   7.014et at 100.22mph
5th run with zoomies:   6.985et at 101.12mph

Average with the headers is a 6.991 at 100.33mph, and with zoomies is a 6.980 at 100.97mph. That’s an average difference of only 0.011 elapsed time between the two and a difference of 0.64 miles per hour, with the zoomies having a tiny advantage. If you apply these numbers to a performance calculator the headers make 254hp at 1620# race weight while the zoomies make 257hp at 1606# race weight My take-away from this test is that it makes little, if any, difference between the two types of exhausts if you operate at less than 5300rpm and your cam has little or no overlap. The lack of overlap will negate some of the wave scavenging effect of the headers. And the zoomies are staying on this engine as long as it’s in the car. When the race engine is done, we’ll do this all again with larger & shorter collector headers along with the same zoomies. Testing ideas start somewhere and this first one is the ground floor. The car may be slow right now but I’m supporting my local race track and enjoying life!
Title: Re: Zoomies vs collector headers
Post by: denverflatheader on September 08, 2017, 12:42:04 PM
Roger - enjoyed seeing initial results, your tests very accurate confirmation of the Stahl Newsletter.  Alan
Title: Re: Zoomies vs collector headers
Post by: hemidakota on September 14, 2017, 12:35:15 PM
I have played the zoomie vs header on a 565bbc in a fed. The biggest difference was the tune up. Headers required quite a bit more fuel and made a ton more power down low. I would say headers make more power but too many changes needed to be made to get good results. Had to leave at a much lower rpm also or would just blow the slicks off at the hit with the headers. Was fun to do.
Title: Re: Zoomies vs collector headers
Post by: JrFuel Hayden on September 14, 2017, 05:15:49 PM
On Gas or Alky, and what RPM did you shift at ?
Jon
Title: Re: Zoomies vs collector headers
Post by: hemidakota on September 15, 2017, 07:07:28 AM
injected alky shift 7500 rpm, thru traps at 7800.
Title: Re: Zoomies vs collector headers
Post by: Roger on September 15, 2017, 09:20:55 AM
Was there much difference in MPH?
Title: Re: Zoomies vs collector headers
Post by: JrFuel Hayden on September 15, 2017, 04:00:41 PM
not a surprize theory goes long pipes and injector stacks is for bottom end power, shorter good for higher RPM power. Matter-a-fact I have suggested to some racers to put their short stacks on when they are at a bad traction track, because it will take some bottom power away.
Title: Re: Zoomies vs collector headers
Post by: hemidakota on September 19, 2017, 06:09:27 PM
MPH was the same that day, but I don't think the tune where it needed to be, was still a little lean. Just got it close on the last pass. 60' was better by .05 and it picked up 3 mph on the last jet change. There was just not enough time to make enough changes to get it happy.
Title: Re: Zoomies vs collector headers
Post by: Roger on September 22, 2017, 11:18:30 AM
The reason I asked about the MPH was because of some other pieces of anecdotal information I’ve seen on some other web sites, including the performance boat sites. They tend to indicate the same things you voiced; bottom end torque takes a bad hit with zoomies but the top-end power doesn’t seem to be affected. Their words:

“1984 UGF back to back runs: 129.31 headers & injectors (staggered tubes), 130.81 Bassett Zoomies 2-1/4. No other changes.”

“Our Unblown Gas Boat has a 555 Chevy… was man-handling our drag boat out of the gate. The boat came out so hard that it was out of control…installed a set of zoomies and a prop…the boat now leaves the gate under control…was almost 4 tenths better than we have ever ran…pulling about 8300rpm in the lights.”

“Had the same deal on one of my hydro engines. Collector made more on the dyno, zoomies faster in the boat. I wasn't racing a dyno so I ran the zoomies.”

The Stahl Headers Newsletter this thread was based on made mention that zoomies ran “quite well from 3500 to 4500 and from 7000 to 7500.” Your experience and the ones I found seem to indicate that once you’re into that 7000-7500rpm range the zoomies may have little effect on top end performance, just as stated in the newsletter. That leaves the 5500-6500rpm range where Stahl says that the performance on a 406” SBC will see “as much as 45 to 50 HP difference between 5500 and 6500.” The 383” SBC engine I’m assembling now will operate in that 5500-7000rpm range to run the 8.5 quarter index and the 5.50 eighth index. Should be interesting, will run the tests again next year with the new engine and will post the results.

Roger
Title: Re: Zoomies vs collector headers
Post by: PSweeney on October 02, 2017, 03:19:16 AM
I've also tested zoomies and headers before.  There is no one single theory as there are so many contributing factors from car to car.  Headers came out marginally better for the engine I was running, but no amount of power increase would make me run them on a digger again, just looks plain wrong.
Title: Re: Zoomies vs collector headers
Post by: Guido on October 13, 2017, 08:13:07 AM
There's allot of great info on this thread! I am running a sbc with a small blower and was wondering about what size of tubing, I have 2" that are approximately 16" from the flange to the tip. Would a 1 5/8 or 1 3/4 work better?
Title: Re: Zoomies vs collector headers
Post by: JrFuel Hayden on October 13, 2017, 05:26:56 PM
If you were not runing a blower the tubing size would make a difference depending on head air flow and RPM, however since a blower doesn't need exhaust tuning, so keep the 2" and spend your money and time on something else to make your combo better. One thing I would look at is your converter, so many racers I know have said the biggest improvement in performance was their converter change.
The goal should to better match your stall to your engine power curve. If your cam/motor comes on at 6,000 rpm, and you have stall of 4,000 rpm, guess what will happen.
I've had great returns on ET using A-1 Converters in WA. 360-574-9966.
BTW I run 2 1/8" zoomies aimed at the top of my slicks [ layed-back] on my all iron 23° raised runner injected alky Heritage JF, good for 9800-10,000 rpm, running low 7.0's, 188-190 mph.

Have Fun
Jon
Title: Re: Zoomies vs collector headers
Post by: Roger on October 13, 2017, 06:01:18 PM
Listen to Jon. A blower engine is a whole different critter than a N/A engine when it comes to exhaust.
Title: Re: Zoomies vs collector headers
Post by: Guido on October 17, 2017, 04:36:35 PM
Thanks for the info,  this is my first experience in a FED I just made my first few passes in it and am hooked! What a blast
Title: Re: Zoomies vs collector headers
Post by: THE FRENCHTOWN FLYER on October 18, 2017, 09:15:54 AM
Pretty car.
Clean.
Simple.
Title: Re: Zoomies vs collector headers
Post by: George on October 19, 2017, 02:11:04 AM
I've also tested zoomies and headers before.  There is no one single theory as there are so many contributing factors from car to car.  Headers came out marginally better for the engine I was running, but no amount of power increase would make me run them on a digger again, just looks plain wrong.


Totally agree on the looks. Collector headers on a front engine car ruin the look for me.