105 Headers Comparison/shootout! - Page 6 - Alfa Romeo Bulletin Board & Forums
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post #76 of 126 (permalink) Old 02-22-2019, 03:04 PM
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Originally Posted by davbert View Post
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Originally Posted by Alfa69GTV1750 View Post
What primary tube size would be best for a strong street engine?
its all relative, it all depends on the intent of the motor you are building. first of all what type of header header config? in a nutshell 4-2-1 or tri-Y are better for street vehicles for low end torque but they do hamper high rpm running with the early merging of exhaust pulses. 4-1 are more race oriented for high rpm power and use.

old nords arent dynamos when it comes to revs unless its a purpose built 1300. i would reckon the 4-2-1 configs are better for the majority of builds on this board. pure non alfa race and crotch rockets motorcycles rev happy motors in search of top end power nearly always run 4-1
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Originally Posted by 180OUT View Post
GTA Headers imported from Italy back in the 70's. There is some debate as to whether or not equal length headers are better than truly headers those without.
Tri-Y headers were popular for small block Ford V8s. Not sure how that would apply to 4 cylinders.

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post #77 of 126 (permalink) Old 02-22-2019, 04:02 PM
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With 4-2-1 headers it is easy to make 2 & 3 the same length. #1 is usually an inch or two longer and #4 an inch or two shorter. " better" depends upon what you are trying to achieve. Equal length are probably best when you are looking for the highest peak HP.

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post #78 of 126 (permalink) Old 02-22-2019, 05:25 PM
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Personally, if the headers are not even why the heck were they made in the first place. It's just laziness, or cost cutting if not even.

If you were after compromise you would have left the original manifold on
Pete

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post #79 of 126 (permalink) Old 02-23-2019, 04:01 AM
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did you know that Hans Deen drove this car also? just once, when dady Huisman was angry on his son Patrick and he didnt let him race that weekend so Hans was there and raced this car, he told me that personally like he visits me every summer.
Daddy Huisman was angry earlier, he did not allow Patrick to race, so Patrick rented e Squadra from Peter van Veen (one of the founders of the B series). at least, word is it happened like this how he got into the SB.
SB was a THE reason I started racing . Not only that, started a new series just because SB was allready way to expensive for me at that time (mid 90`s)..
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post #80 of 126 (permalink) Old 02-24-2019, 12:47 PM
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Just an image showing the difference in primary diameters on GTA headers, 1st and 2nd pipes are larger then 3rd and fourth, go figure. Notice especially where 1 meets the 4th, as far as I know they all came this way..
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post #81 of 126 (permalink) Old 02-24-2019, 03:03 PM
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Just an image showing the difference in primary diameters on GTA headers, 1st and 2nd pipes are larger then 3rd and fourth, go figure. Notice especially where 1 meets the 4th, as far as I know they all came this way..
While strange, this could be to equal up the pulses. Ducati and Alfa (with the 156v6) did/does this but I always thought it was to save cost.

Would be a fascinating dyno back to back test! Although to be fair, extractor design has come a long way since GTA's were racing for real (and no classic racing can never be real racing, no matter how some try).
Pete
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post #82 of 126 (permalink) Old 02-24-2019, 04:07 PM
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David Vizard's comments on header length:

Headers -- Primary Pipe Lengths

Quote:
Misconceptions concerning exhaust pipe lengths are widespread. Take for instance the much-overworked phrase "equal-length headers." More than the odd engine builder/racer, or two, have made a big deal about headers with the primary pipes uniform within 0.5 inch. The first point this raises is whether or not what was needed was known within 0.5 inch! If not, the system could have all the pipes equally wrong within 0.5 inch! Trying to build a race header for a two-planed crank V-8 with lengths to such precision is close to a waste of valuable time. Under ideal conditions it is entirely practical for an exhaust system to scavenge at or near maximum intensity over a 4,000 rpm bandwidth. Most race engines use an rpm bandwidth of 3,000 or less rpm. If the primary pipe scavenging effect overlaps by 3,000 rpm then it matters little that one pipe tunes as much as 1,000 rpm different to another. Since this is the case, then all other things being equal, pipe lengths varying by as much as 9 inches have little effect on performance. A positive power-increasing attribute of differing primary lengths is that it allows larger-radius, higher-flowing bends and more convenient pipe routing to the collector in often confined engine bays.
Feom Vizard's How To Build Horsepower:

Quote:
So far, we have discussed basic manifold configurations based on all the primaries dumping into a secondary. This gives us the commonly seen 4-into-1 system used on V-8s and high-RPM four-cylinder engines. If the engine is a four-cylinder unit, and is not likely to see the top side of 7,800 to 8,000 rpm, then a 4-into- 2-into-1 system is the way to go. Such a system has the advantage of fitting the confines of the engine bay easier and produces more torque up to about 6,800 to 7,000 rpm. At the lower speeds (2,000 to 4,000), such a system can be up by as much as 12 ft-lbs per liter (0.2 ft-lbs per cubic inch). Above 7,800 to 8,000 rpm, it’s a clear-cut advantage to go with a 4-into-1 system.

Jim . . . '72 Super 1300, '70, 1750GTV, 2nd series,
'62, Lancia Flaminia Zagato3c, 2nd series

Last edited by 180OUT; 02-24-2019 at 04:21 PM.
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post #83 of 126 (permalink) Old 02-24-2019, 04:27 PM
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Here is a copy of an email that was sent to me in 2014 from Steve Johnson who was on the ABB for a while. It was in response to a request for advice for the exhaust system on my 2L Spider. Please excuse the lack of puntuation:

Quote:
by the way... these header guys spend a lot of time pushing these " merge
" collectors and they are expensive.... and are useless in any real sense.

i manufactured and raced cars called sports 2000's . 1100 lb sports prototypes powered by 2l ford motors that were , essentially stock but with
small mods allowed. an average one made 138 hp most made 142 to 145 and
the best one in history was 150. in racing , hp equals downforce and
downforce is what wins you the races. so... people would kill their
mothers for 2 hp. and exhaust systems were the first magic bean that
everyone worked on. lola manufactured cars for this category which
started in 1978 and ended last year . their cars arrived with a 4 into 1
header with the 1.625 primaries , 32" long into a 2.25 pipe that was roughly 40 " long . ... this is 1978 ...

in 1980 when i really started building these cars in mass, i did a dyno
study on the exhaust on my own dyno. two motors , 5 days , hundreds
and hundreds of pulls, scientific methodology. i made 4 sets of headers
using 4 different primary diameters , segments that allowed me to change
the primary lengths an inch at a time and create stepped designs. 4
different sized exhaust pipes and the ability to change those lengths.

i started on day one with motor #1 with the box stock lola exhaust system and established the baseline curves...

5 days later after every permutation of design and configuration including
4 2 1 designs that showed any promise at all which was probably about 100 or more different types and sets as some were just garbage immediately so
the were investigated no further , the results were crystal clear. the
box stock, plain jane absolutely ordinary lola design using the same math
and theory that had driven header design from the 50's was the best.

other designs would move the power around some ... gain one or two at 7000
lose 4 or 5 at 5000 sort of thing but the simple fact was that the area
under the curve of the std set was always the best. every single time.

now... fast forward to 2003 when i won my last championship. i build that
car and while im doing it i get calls from header guys with all the new
magic ****. and they send it all to me for testing... LOTS of magic
merge collectors... i was retired by then and the dyno was gone so we
just took them to the track and ran them with full instrumentation...
none could get within a 1/2 second of the std lola set at mid ohio no
matter what tuning exercise they tried. i started on pole and won that
race by 15 seconds with headers and exhaust that were designed in 1978.

i don't figure that these 2l alfa motors are meaningfully different in any
way. same power. same torque, same rev range , the only thing different
is the fact that the head is al and cools a bit better and is less prone to detonation so you can run a couple more degrees of timing if you want ...

i would keep it as simple as possible.

Ed Prytherch
79 Spider
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76 Suzuki GT500
2011 Jaguar XKR

A little government and a little luck are necessary in life, but only a fool trusts either of them. - P.J. O'Rourke
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post #84 of 126 (permalink) Old 02-24-2019, 04:42 PM
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Quote:
Quote:
Originally Posted by VabeneGTV View Post
Just an image showing the difference in primary diameters on GTA headers, 1st and 2nd pipes are larger then 3rd and fourth, go figure. Notice especially where 1 meets the 4th, as far as I know they all came this way..

Here are the primary diameters of my GTA headers. This might explain why Classic Alfa offered "big tube" 40mm headers (presumably from CSC). When I get a chance I'll measure my Alfaholics headers for comparison.

#1 40.08 mm
#2 40.11 mm
#3 37.00 mm
#4 37.00 mm

Jim . . . '72 Super 1300, '70, 1750GTV, 2nd series,
'62, Lancia Flaminia Zagato3c, 2nd series

Last edited by 180OUT; 02-24-2019 at 04:46 PM.
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post #85 of 126 (permalink) Old 02-24-2019, 05:15 PM
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180OUT and alfaparticle,

2 very interesting posts. I guess it all comes down to "the best overall compromise" makes the best racing car, and if making a dead even length exhaust system compromised something else or required ugly bends, then as your posts says "relax" and find a better solution

I think the best race cars are designed from a grip and handling perspective, but reality is many of us spend hours chasing hp ... I wonder if we spent those hours on handling, would we have a better race car? I think so, but its hard to chase handling improvements with a beer in one hand and your mates standing around your car ...
Pete

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post #86 of 126 (permalink) Old 02-24-2019, 05:47 PM
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Perhaps this is the reason the common recommendation is to use the stock early two piece cast iron headers. Practical results do show that there is only tiny benefits at narrow rpm ranges that only sometimes are suitable for a specific track. The "casties" are much easier on heating the brake fluid and steering box.

In the early SCCA club racing days I did notice that most very fast cars used the cast iron ones, just adding larger pipes beyond their connections. Fancy "bundle-of-snakes" headers are more ego than effect, and a well hit apex exit will beat all of them every day. I agree that handling will beat small HP or Torque gains often. We've all seen that fresh tires run amazingly fast, and aren't even connected to the exhaust.

I love the look of the Darstan Headers (and other similar ones), but I do really know that they don't matter for an AX or TT car, and they do roast the engine bay every day on the street times.

Robert
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post #87 of 126 (permalink) Old 02-24-2019, 07:22 PM
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From the Alfaholics site:

Quote:
Superb quality, unrivalled on the market for quality, fit and performance! Primary & secondary lengths and bores optimised on the dyno. With this system fitted the engine will rev much freer with higher rev capability and in the region of 10BHP increase and 8lb/ft torque.

Jim . . . '72 Super 1300, '70, 1750GTV, 2nd series,
'62, Lancia Flaminia Zagato3c, 2nd series
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post #88 of 126 (permalink) Old 02-24-2019, 08:05 PM
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It is easy to get a gain of about 10 HP if the comparison is with the one piece manifold that was standard from 1975 to 1989. Fitting a two piece manifold from a pre '75 or a post 89 will achieve most of that. Headers with longer primaries will usually work better than the two piece manifold at higher rpm.
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Ed Prytherch
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A little government and a little luck are necessary in life, but only a fool trusts either of them. - P.J. O'Rourke
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post #89 of 126 (permalink) Old 02-25-2019, 02:42 AM
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Tri-Y headers were popular for small block Ford V8s. Not sure how that would apply to 4 cylinders.
what do you think factory stock, gta or spruell and durstan alfa headers are? they are Tri-Y meaning 4-2-1 or 3 Y junctions. the attributes in the 4-2-1 header are in the secondaries in which the gas velocity is much higher than a 4-1 before the collector. this should be the area of focus for tuning the lengths and size rather than the primaries which are more forgiving. the secondaries are also a detriment to high rpm running since the nice mid range velocity it becomes a restriction but on street nord motor that isnt much of a concern due to its low rpm celling.

like i said, it all depends on what your intent is. for a 4 cylinder, most inline's run a flat crank. however in the 2000's yamahas race bikes ran odd 90 degree crank on their inlines 4's along with a 4-2-1 headers with merger pipers rather and a typical secondary while kawasaki ran an even stranger flat crank with a big bang firing order lighting off both cylinders at once exiting out of expanding individual headers with and inversion cap. these are extreme examples of course. motorcycle motors at least 5 to 6 generations up on the antiquated nords and arent not so much interested in hi-peak hp specific output which they have achieved for decades. the motors are now focused on throttle responds and traction out of the corners for circuit speed rather than the drag strip.

i ran john shankles decades ago and now have a sperry TS header that i havent got use yet. i just kept my bored out stock cast system though im probably losing out 10hp or more with my mod motor. I relate to it running a dcoe 40 vs 45 on street car on pump gas. off the track, is that 5-10 hp worth it when the 40s run so much better at the lower end? still i get a kick at seeing all you BB'ers trying to get blood out of this stone :-)
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Last edited by davbert; 02-25-2019 at 08:07 AM.
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post #90 of 126 (permalink) Old 02-25-2019, 06:40 AM
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i ran john shankles decades ago
What do you think of them?

Ed Prytherch
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76 Suzuki GT500
2011 Jaguar XKR

A little government and a little luck are necessary in life, but only a fool trusts either of them. - P.J. O'Rourke
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