Verifying a header's primary diameter
 

Hey guys, a couple of months ago i bought a beautiful used set of what i was told were Kooks 1 3/4" race style LT's (non stepped).

The passenger side install was a breeze and the driver side was a real bitch. (I had thought that Kook's design was to be real easy on both sides...and this wasn't my first set of headers to install, either)

Last night a few of the guys and i were talking at Bob's big boy and joked that maybe the headers were tougher to get in since the primaries were bigger. (the difference from 1 3/4" to 1 7/8th's isn't too drastic so I doubted it)

Then one guy (hitmanws7) looked on Kook's website and said kooks didn't make a 1 3/4 "race style' (no AIR provisions). We then went and looked at our cars. I think they looked similar to my friends 1 3/4" Hookers, but he swears mine look bigger. This all sparked the debate....how do we measure the diameter of a primary? Is it the I.D. of the primary or the O.D.?

I figured I could wrap a shoe lace around the primary, mark it and then measure it for the size, but I dont know what the O.D. should be.

Anyone out there got an idea? Maybe some sponsers who sell them?

Thanks for any help.

99% sure its inside diameter. The outside diameter might be different depending on the brands because some might use a different gauge tubing.

x2^^^ inside diameter. Different vendors use diffferent size tubing thickness so i doubt you can figure it out that way.. I know how... remove the DRIVER side header and check the inside diameter..lol!

Jk... I had problems installing my kooks but after they slipped in they had great overall clearance and mine are 1 7/8.

I believe that larger header diameter headers would be harder to install, atleast in my z06. These 1 3/4 ARHs were an extremely tight fit on the driver side from the top. Would have had to jack the car up higher ( no lift :( ) to get it in from the bottom if they were even a hair larger.

My Kook's have amazing clearance now that they're in....and that #8 plug is EASY to get at from the top! Thanks Kooks! lol.

Mine wouldn't go in from the top... but close. They had to go in from the bottom. We had to disconnect the steering knuckle, bang the firewall, and the heat shield, remove the oil filter, and notch the K.....all for a set of friggin headers. And now I'm gonna be pissed if I've got 1 7/8th, lol. :D

Can anyone with Kooks 1 3/4" or 1 7/8" measure the O.D. of their primaries for me, please?

I should really put this somewhere that people can easily find it :bang:

https://ls1tech.com/forums/11596564-post4.html

D'oh!! :bang:

What can I do to sweet talk you into measuring the O.D. of one of your primaries? :)

Leave the 1-7/8's on, why would you prefer 1-3/4?????? I have 1-7/8 hooker super comps and theyre badass.....

lol, I wouldn't take them off. I'd just be pissed if the 1 3/4 ones were easier to install, lol. Either way, I'm fine, I'd just like to definately know what i've got.

Are your super comps stepped?

Mike I take what I told you back, apparently Kooks makes both a 1 3/4 and 1 7/8 Race header. I just checked their site. but to be sure have someone with 1 7/8 measure their diameter

Weird. I looked on their site earlier but I didn't see anything about race style or non stepped with pictures for me to check mine against. Oh well. So who's got a set of Kook's 1-7/8's race style headers in the Los Angeles area I can look at? :)

I'll check back later today...if you don't have an answer by then, I'll see what I can do. For right now, the car is put up for the winter, so it is under a cover right now. I might be able to get a measurement from the bottom though since it is up in the air. Just kinda hard for me to do while I'm at work :secret2:

I've always seen and measured header primaries by their outside diameter. I've verified this on pretty much every LSx header manufacturer including Kooks.

NOPE, but the driver side was hader to put on than the passenger side i had to remove that little oil bypass/tube thingy on top of the oil filter to get the headers to go in ......

According to my digital calipers, the outside of the primaries on my Kooks 1-7/8" headers is around 1.88"-1.90" - since 7/8" = .875", that sounds about right.

I've got the same headers, Kooks 1 3/4" race style no EGR no AIR. I measured mine before I put them on, inside to inside was 1 3/4". Maybe you could measure the circumference, mine were 5 9/16".

Also my driver side install was a Pain, I had to take off the oil filter and finagle the header around until it slipped in (from the bottom).

Any idea what that number should be? on a 1-3/4 and on a 1-7/8?

Thank you sir, I'll check mine tomorrow. I appreciate it!

Thank you too! ^^ Is that the outside circumference of the primary? Man, for an "easy install header" it sure was a pain in my ass. It seems my friends' Hookers have been the easiest to install on an LS1.

On 1 3/4" that'd come to about 1.75", for 1 7/8" it's 1.875".

Yep, that's the outside circumference.