eBay headers are 1-5/8” primaries
I recently ordered a set from DNAmotoring and thought I'd add my measurements. Mine are pretty much identical to the OPs measurements. Overall quality of the headers are impressive for the price. I cut off and welded shut the AIR flanges and EGR because I didn't want to run the risk of it breaking off/cracking over time.
true, but check out ds98formula's build thread link above. he got pretty good results with these things on a stock motor. 1 5/8 is fine for a mild old school small block, and also true for our ls1's. the difference is that these ls1's breath heavier and want to rev more so the bigger primaries do help, but the smaller cheapies still do pick up some decent hp. they prob arent ideal for a head/intake/cam car, but in any case they are a signifacant improvement over stock. what bugs me is why cant people just make true 1 3/4 that would cost a tad more than the 1 5/8? what would the step up really cost? annoying.
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Joined: Aug 2007
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From: Turnin' Wrenches Infractions: 005
Almost all if not all headers are measure OD. You're wasting our time with this foolish thread. And, you're eating $60 to send them back over 1/8". Foolish number 2. Then you will order a brand name header and find out it is measure OD too. Then you'll start another thread bashing them. Foolish number 3. 
Almost all if not all headers are measure OD. You're wasting our time with this foolish thread. And, you're eating $60 to send them back over 1/8". Foolish number 2. Then you will order a brand name header and find out it is measure OD too. Then you'll start another thread bashing them. Foolish number 3.
People report better numbers after switching from 1 3/4" to 1 7/8"s. Like these guys:
+32/21 - BBK's/Y-Pipe/SLP Dual to Kooks 1 7/8"s/Kooks Dual Exhaust
https://ls1tech.com/forums/dynamomet...l-exhaust.html
+20/15 - Kooks 1 3/4" to Kooks 1 7/8"
https://ls1tech.com/forums/dynamomet...l-exhaust.html
The difference was only 1/8". I may seem miniscule but going from 1 5/8 - 1 3/4 is an increase of 8% [(1.75-1.625)/1.625]= 8%. Going from 1 5/8 to 1 7/8 is an increase of 15% [(1.875-1.625)/1.625]=15%. That is a modest increase.
Thread Starter
Joined: Jun 2003
Posts: 7,128
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From: Pittsburgh, PA
What is the gauge of the tube wall. Have you measured it? If its presently 16, and they go to thin wall 18ga on there new race version then they will flow very close to 1 3/4 . They can keep the the same OD , but by going to a higher gauge they will be increasing the ID and they will flow close to 1 3/4 But the end result is a cheaper product .
At the end of the day, we need to determine the honest size of the primaries and the gauge of steel they're using. This it the only way to compare the brands at this point since now even a sponsor is advertising 1-3/4" primaries that are actually 1-5/8". I'd love for someone to measure their TSP primaries...
EDIT: I should have thought about this before, but we can determine the gauge because I measured the OD and ID of the collector. At 3.002 OD and 2.862 ID, that leaves us at 0.14/2= 0.07" or 15g ( http://www.engineersedge.com/gauge.htm ).
Last edited by demonspeed; Jun 12, 2013 at 12:21 PM.
Thread Starter
Joined: Jun 2003
Posts: 7,128
Likes: 5
From: Pittsburgh, PA
Almost all if not all headers are measure OD. You're wasting our time with this foolish thread. And, you're eating $60 to send them back over 1/8". Foolish number 2. Then you will order a brand name header and find out it is measure OD too. Then you'll start another thread bashing them. Foolish number 3.
Did you even read the original post? I measured OD. The brands listed at the beginning of the thread (yes, even a sponsor who advertises 1-3/4") are 1-5/8".
Further, it's not about the $60. It was about how one can save +/-$500 over name-brand 1-3/4" headers by going with -- what we assumed -- were super-affordable eBay headers of the same size..... which we now know are 1-5/8".
With this thread, I think we've determined (in context of price):
Budget: 1-5/8" eBay headers (this includes Speed Engineering for the time being)
Middle-of-the-pack: 1-3/4" Pacesetter, hooker, or even TSP (or used name brand)
All-out: 1-7/8" TSP or name brand
At the end of the day, if one is saving this much money by buying on eBay, they're getting the smallest primaries available, which is 1-5/8" OD and 14g steel
Last edited by demonspeed; Jun 10, 2013 at 09:32 AM.
I wouldn't necessarily call TSP middle of the pack. They're definitely well ahead of Pacesetter.
ARH measure their headers by OD as well.
Again, tubing (less than 12" diameter) is measured by OD. Pipe (greater than 12") is measured by ID.
ARH measure their headers by OD as well.
Again, tubing (less than 12" diameter) is measured by OD. Pipe (greater than 12") is measured by ID.
Thread Starter
Joined: Jun 2003
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From: Pittsburgh, PA
Joined: Aug 2007
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Likes: 89
From: Turnin' Wrenches Infractions: 005
I understand ARH and Kooks are top of the line, so with an exception to those two brands, ALL others will not measure true to the stated specs I'd be willing to bet. Its been like this FOREVER. Carry on.
Thread Starter
Joined: Jun 2003
Posts: 7,128
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From: Pittsburgh, PA
If it's been like this forever, then please provide empirical evidence.