1 5/8 or 13/4 - Team Camaro Tech
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post #1 of 10 (permalink) Old Jul 19th, 03, 04:12 AM Thread Starter
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I am currently building a combo and would likse some suggestions as for the headders.
The Engine is a 355

AFR 195's
Victor Jr.
282s solid cam
1.6 roller rockers
10.5-1 comp
750 holley
2.5 exhaust with 40 series flows

Right now I have a set of headman 1 5/8 on there now but it is still a pretty stock combo. Also I have been reading the posts about the Afr's and people having trouble getting headders for them. So with this new set up would 1 3/4's be too big?

69 Camaro RS, 383ci,10.5-1 AFR 195's ported, Comp 286HR, 4340 forged Crank & Rods, JE Pistons, RPM Airgap, Holley 750 HP carb, 350 turbo w/ shift kit, 3000 Coan, Be cool, caltracs,12bolt 355 eaton posi..Best E.T. 12.22 @ 112

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post #2 of 10 (permalink) Old Jul 19th, 03, 09:41 AM
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Ron
 
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I say stay with the 1 5/8's. The 1 3/4's are great for large stoker small blocks and race 350's. You dont have enough cam or cubes to make though big headers work.

69 Camaro
491/AFR 315'S/Straub hyd roller
TH400/GV OD
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post #3 of 10 (permalink) Old Jul 19th, 03, 12:08 PM
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joseph l clance
 
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If you have the choice, go with the smaller ones, they fit w/ more room and makes an easier install. I v'e had both and didn't notice any difference from a performance standpoint. I stayed w/ the larger ones since they were already installed and massaged to fit!
joe c

69 X-44 base coupe, ZZ4, 16lb nodular flywheel, Center force DF clutch + PP, Holley 600DP, Hooker super comp 1 3/4 ceramics, 2.5" dual exhaust w/ X-pipe, flowmaster 40 series mufflers.
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post #4 of 10 (permalink) Old Jul 19th, 03, 12:30 PM
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SS
 
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I have had the headman headers on a previous build and have been to their factory, They were basically crap, unequal length and thin flanges one of which was warped hence the trip to their manufacturing location. I had a set of custom 1-3/4 made at 32" length tubes with small collectors in diameter and length and was extremely pleased with the results, but I have a stroker. Seems with your combo heads etc that 1-3/4 tubes could be beneficial dependent on collector design etc. The guy who made mine looked at the headmans and stated these flaws and mentioned the large 3" long collector just slows down the scavenging process because they come into a large area. Just some food for thought. SS
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post #5 of 10 (permalink) Old Jul 19th, 03, 02:55 PM
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Here's some tips:
1. Don't worry about equal length pipes on a small block Chevy. They don't matter, the power difference is negliable. A Ford 5.0 is a different story.
2. There is a very simple trick for warped flanges. First, think about the problem. The long, one-piece steel flange gets warped in one area, and it throws off the flatness for the rest of the flange. So, take a hacksaw and cut the flange in between the first two tubes, and between the last two tubes. This way, if warps again, you just re-torque the bolts and the leak goes away!

Matt Jones
Lead Mechanical Engineer
Art Morrison Ent. Inc.
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post #6 of 10 (permalink) Old Jul 20th, 03, 05:46 AM
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Quote:
Originally posted by Silver69Camaro:
Here's some tips:
1. Don't worry about equal length pipes on a small block Chevy. They don't matter, the power difference is negliable. A Ford 5.0 is a different story.
What's the rest of the 'different story'?

"For those that will fight for it...FREEDOM ...has a flavor the protected shall never know."
Semper Fi! L/Cpl Edwin L. "Tim" Craft, B Co 3rd AT's, Khe Sanh Combat Base, February, 1968
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post #7 of 10 (permalink) Old Jul 20th, 03, 07:23 AM
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Equal length headers work best if the cylinder banks are even firing (180* plane). The Ford 5.0 I believe falls into this category.

This is not to say that equal length headers have no effect on our SB Chevy's. They will have a greater effect on high RPM race motors.

Consider a header 'good' if the primaries are all within about 2-3 inches. If you want them to be true equal length, be prepared to shell out some serious dough, and gain very little power.

Matt Jones
Lead Mechanical Engineer
Art Morrison Ent. Inc.
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post #8 of 10 (permalink) Old Jul 20th, 03, 09:10 AM
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Unfortunately, the Fords suffer from the same syndrome as the Chevys, consecutive firings on the same bank twice in the order. In order to get a true 180 header system, you will have to cross the center two tubes from side to side, Chevy or Ford.

There are two types of scavenging, primary and secondary. Primary scavenging occurs at a frequency controlled by the length of the primary tube, so having all the primary tubes the same length would bring the same scavenging intensity to all cylinders at the same time. For a good lesson in primary scavenging, look to the Jr. Dragster folks with the single cylinder motors.

Secondary scavenging occurs as a result of the coupling of scavenging signals in the collector, where the exhaust pulse from one cylinder creates scavenging in another. If the cross-sectional area of the collector is large compared to the cross-sectional area of the primary tube, you will see decreased secondary scavenging. If the timing of the pulses is irregular, you will also see decreased secondary scavenging.

The major drawbacks of most OTS headers are that the primaries are too short and the collectors are too large. A 2 or 3" inequality in primary length won't make a huge difference, but most of the rear tubes I see are about 12" shorter than the front ones. A 30" long primary tube works well with a 7000 rpm motor, but if you are trying to get more torque at 4500 rpm you will need something closer to 40".

A 1-5/8" header with a 3" collector is lacking in secondary scavenging, a 2-1/2" collector is more suited for street use. Ed Henniman of Headers by Ed has some great information on header design and selecting the best collector size. If you go to Rodney Davis' site at headerdesign.com and plug your motor stats into the calculator, you'll get a good street header design.

http://www.headerdesign.com/index.asp

We use LC Engineering 1-5/8" x 2-1/4" merge collectors on our 331" high-altitude road racing motors with great success. Midrange torue is just awesome, and we recently dynoed one of them at 380 rwhp @ 6000 rpm with more than 350#ft rwt from 4500 to 5500 rpm. This was with a set of Stahl 1-5/8" x 34" primaries, a Dr. Gas 2-1/2" XCO and a full exhaust system including Dynomax Super Turbos.

"For those that will fight for it...FREEDOM ...has a flavor the protected shall never know."
Semper Fi! L/Cpl Edwin L. "Tim" Craft, B Co 3rd AT's, Khe Sanh Combat Base, February, 1968
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post #9 of 10 (permalink) Old Jul 21st, 03, 02:07 AM
 
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onovakind67,

He, He!!!

Looks like the name here is STAHL b/c they were first!!

And tonight I will punch in the names you mentioned and do some reading!

pdq67



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post #10 of 10 (permalink) Old Jul 21st, 03, 06:31 AM
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I have the Jan 1999 issue of CHP magazine with a test of various types of headers. The 1-5/8" equal length headers from Ed produced up to 51#ft of torque more than a set of generic 1-5/8" headers in the 3500-4500 range. As most tests done by magazines, it wasn't very scientific or methodical. They simply bolted on one of several sets of headers and tested for power. The fact that they were equal length may or may not have contributed much to the torque increase, because they also had smaller collectors than the generic models. Ed has some thoughts on that.

http://www.headersbyed.com/info1.htm

David Vizard wrote an interesting magazine article on exhaust system design:

http://www.geocities.com/MotorCity/T...92/vizard.html

"For those that will fight for it...FREEDOM ...has a flavor the protected shall never know."
Semper Fi! L/Cpl Edwin L. "Tim" Craft, B Co 3rd AT's, Khe Sanh Combat Base, February, 1968
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