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OBX and KOOKS questions along with primary size pros/cons???

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Old 07-27-2012, 12:27 PM   #1
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Default OBX and KOOKS questions along with primary size pros/cons???

Alright fellas,
I'm curious about a couple of things. The OBX header are supposed to be an exact replica of the kooks headers correct? I just heard recently that the OBX collector on their 1-7/8 header (only option they have) is 2.5" while the kooks come with a 3" collector on both their 1-3/4 and 1-7/8 headers. Is that true?

I suppose thats not too big of a deal to have a 2.5" collector if you are running 2.5" exhaust but if you're running 3", that complicates things a little.

At what point (power wise) do you actually benefit from the 1-7/8 primaries over the 1-3/4? I've been dealing with a clearance issue with my OBX 1-7/8 headers and my steering shaft and i have about had it! I dont want to cave in the primary to make it clear although i have been very tempted to do so. Instead, I ground on the steering shaft a bit and it seems to have helped a bunch but its still not 100% yet.

Do the kooks 1-7/8's have this same issue with clearing the steering shaft as well due to the size in general or is it OBX specific??

The reason im asking is because I'm getting tempted to pull these off and sell them and just go with a set of 1-3/4 kooks headers. I had the 1-3/4 on my old V with no problems at all. I just don't know if i'd be working in reverse to go from a 1-7/8 primary to a 1-3/4 primary on the headers. If the kooks 1-7/8 clear with no issues, i'd be tempted to go that route as well. Anything to get me away from having to clearance the primary on the header!!

I am unsure of how accurate this information is but I was initially told that the 1-3/4 primaries would be plenty on this car when N/A and 1-7/8 were beneficial on FI applications. Does FI include nitrous???? I wouldn't think so because its not boost like with a turbo or blower but in my case since i spray the car, i really don't know which size primary i'd be better to run.

So... Pros and cons when comparing 1-3/4 to 1-7/8?
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Old 07-27-2012, 12:36 PM   #2
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I think your spray would benefit from 1 7/8 headers.

I found a solution to the steering shaft problem.
I used a dremel with a sanding wheel and moved the groove that the bolt goes through back so that the shaft can be mounted just slightly farther up the stub. (if that makes any sense.)

Basically, the goal is to back the steering shaft off the stub slightly. I've had no troubles with angles or anything afterward.
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Old 07-27-2012, 01:12 PM   #3
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Ok. I was unsure how nitrous would effect the exhaust flow or if it would even make a difference between 1-3/4 and 1-7/8 on a nitrous car. Are the primaries in fact 2.5" as opposed to 3" though? I know I can take the header apart measure myself but trying to avoid the work if someone here can confirm it.

I may have to try your steering shaft solution. If that works for me, I'd be happy.
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Old 07-27-2012, 01:41 PM   #4
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1 7/8 kooks no issues with steering shaft rub
cs motor/trans mounts installed prior
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Old 07-27-2012, 01:59 PM   #5
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Good to hear. I hope all kooks 1-7/8 don't have issues and you're not just a lucky candidate. Lol my obx issues got worse when I put the UMI solid mounts in because they are slightly shorter than stock.
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Old 07-27-2012, 02:03 PM   #6
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Quote:
Originally Posted by NeverSatisfied02 View Post
Good to hear. I hope all kooks 1-7/8 don't have issues and you're not just a lucky candidate. Lol my obx issues got worse when I put the UMI solid mounts in because they are slightly shorter than stock.
My mechanic is installing OBX 1-7/8 and UMI mounts next week. What should I warn him about, besides saying that a small dent in the headers may be neccessary for steering shaft clearance? I guess I'm asking, how much more compressed is in in there with UMI mounts?

Thanks yo.
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Old 07-27-2012, 02:22 PM   #7
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The UMI mounts aren't that much shorter than stock but enough to make the clearance a little tighter. If u plan to dent the header, ur fine. I'm just trying to get around having to do that if I can. I did some grinding on my steering shaft but I've taken off as much as I feel safe removing so now it's time to dent the header if anything unless I decide to swap to kooks.
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Old 07-27-2012, 02:26 PM   #8
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Quote:
Originally Posted by DACTARI View Post
My mechanic is installing OBX 1-7/8 and UMI mounts next week. What should I warn him about, besides saying that a small dent in the headers may be neccessary for steering shaft clearance? I guess I'm asking, how much more compressed is in in there with UMI mounts?

Thanks yo.
Breaking spark plug wires, most replace them and the plugs during the install as they need need to be removed anyway.
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Old 07-27-2012, 02:29 PM   #9
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Oh yeah... My stock wires ripped during install. I have MSD's now. If u have MSD's, u should be fine. Just tell them to grab low on the boot when removing them.
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Old 07-27-2012, 02:34 PM   #10
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I was under the impression that the OBX were 1 7/8" with 3" collectors, just like the Kooks. The Kooks neck down to 2 1/2" at the converters (or tuning pipes) anyhow, so not really any difference.

1 7/8" primaries will make power everywhere when compared to 1 3/4" tests were done on an LS1 with varying mods, the bigger headers made more power everywhere, not just up top as with typical SBC results. This has been found true for smaller displacement 5.3 motors as well.

I installed Kooks 1 7/8" and had to beat the **** out of one drivers primary b/c it contacted the steering shaft. I wrapped mine about 3/4 of the way down, have not had any problems with them at all.
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Old 07-27-2012, 02:40 PM   #11
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I assumed the OBX were 3" as well but since I've been told they are 2.5", it made me curious which is why I posted here. I know the kooks connector pipes neck down to 2.5 where it connects to the exhaust but at least on those having the 3" collector, u can cut and re-weld the connector pipe to make it 3" all the way. Nothing you can do with the collector size to change it if it's only 2.5".

So are the OBX in fact 2.5" at the collector? If so, is there any performance advantage to having 3" collectors with a 2.5" exhaust? Any benefit to having the 3" collectors with a 3" exhaust?

I know back pressure plays a role somewhere. I was going to run a 3" B&ab catback but it the OBX collector is 2.5", i might as well stay 2.5" because the exhaust will only flow as much as the smallest point will allow it to. Is there even an advantage to going full 3" on these cars?

And it makes me feel a little better that u had clearance issues with your kooks 1-7/8. If 1-7/8 make better power, I'll just pull my drivers side header off and dent the primary enough to clear. Guess that's the only way to get around this issue. I just hate denting my headers if I don't have to.
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Old 07-27-2012, 02:47 PM   #12
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Ill get a picture for you of the OBX header collector size after work.
As DMM mentioned, there are no CONS (power wise) other than having to beat on the one primary for clearance.
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Old 07-27-2012, 02:49 PM   #13
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Perfect! Thanks!! I just didn't wanna go yanking mine all apart just to get a measurement.

I wish there was a side by side comparison of the Kooks and OBX. I'm just hoping the OBX collector is indeed 3". And if it's not, I'm hoping there is no performance loss from that considering the rest of the exhaust is 2.5" anyway unless you go with the 3" B&B setup.
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Old 07-27-2012, 02:53 PM   #14
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Stainless works and B&B headers are both 1 3/4 with 3inch collectors. Nobody seems to make the all around big pipe like a 1 7/8 or 2 inch primary to a 3 inch collector.
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Old 07-27-2012, 03:02 PM   #15
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Kooks headers are 1-7/8 with 3" collectors but you're right about those other two coming in only 1-3/4. Kooks and OBX are the only two making 1-7/8 primaries that I know about. And if what I've been told is true about the OBX collector being 2.5", then kooks is the only one making the 1-7/8 with 3" collector.
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Old 07-27-2012, 03:31 PM   #16
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Quote:
Originally Posted by NeverSatisfied02 View Post
Oh yeah... My stock wires ripped during install. I have MSD's now. If u have MSD's, u should be fine. Just tell them to grab low on the boot when removing them.
No, still on stock wires. Are MSDs really that much better? What is it about them that's so special?

Sorry for the threadjack. I will try to keep my head down.
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Old 07-27-2012, 03:51 PM   #17
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I prefer stock wires... why?
Long needlenose pliers around the metal jacket indent, squeeze hard so no slip... use long screwdriver and pry against side of head and the pliers (just push the screwdriver towards engine (so pushing pliers outward away from plug)... pop... next plug... pop. Takes 30 seconds to pull all plugs, and you will never rip or pull apart. This works well because there is no side angle when using your hand or just pliers.
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Old 07-27-2012, 03:52 PM   #18
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Ill have your pic in less than 2 hours NeverSatisfied02
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Old 07-27-2012, 04:37 PM   #19
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That is a good way to remove wires. I always use my hands or pliers but I'll try that next time.

And thanks bud! I appreciate it!
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Old 07-27-2012, 06:30 PM   #20
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Enjoy
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OBX and KOOKS questions along with primary size pros/cons???-obx1.jpg   OBX and KOOKS questions along with primary size pros/cons???-obx2.jpg   OBX and KOOKS questions along with primary size pros/cons???-obx3.jpg   OBX and KOOKS questions along with primary size pros/cons???-obx4.jpg  
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