So a while back I picked up the ARP 144-1202 header bolt kit in prep for my TTI W2 build, and while these are nice, they are just too short to work with the hefty flanges on the TTIs. These bolts are all 0.750" UHL.

Looking through ARP's catalog I find 641-1000, which is a 5/16-18 bolt but with 1.000" UHL...seems like that's exactly what I need.

Strangely though, ARP does not list an exhaust header bolt kit that is a 5/16" with 1.000" UHL.

So I'm wondering: are these the same bolts as the ones in the kit, just longer?

Heck, these are only holding the headers on, so I can't imagine the materials would need to be all that different...but what do I know about materials sience...LOL, so I thought I'd check-in here.

Thanks!

These are listed as header bolts. Bolts

Summit lists them as header bolts. What am I missing? Summit

...the ARP part you pointed to is a 3/8-18 thread...I need a 5/16-18.

In fact, initially I actually ordered the ARP 100-1209 kit, which is a 3/8-18 x 1" bolt, only to discover that I actually need a 5/16 thread.

I see that. I just searched 5/16 x 1 inch header bolt. To bad your heads were not made with 3/8 threads. 5/16 seems like an odd ball.

Would these work? Bolts
Or these. Hedman

Both good finds, I hit these up as well:

1) Summit Lock bolts - never used this style before so I'm a little hesitant to toss these into a street car where the header to chassis clearance is already tight

2) Hedman - larger 6pt head (7/16) vs 12-pt (3/8) on the ARP, there are a couple of tight spots on this install, like the #7 cylinder, where I literally need every tiny little amount of wrench room, I say this because my old headers were using the shorter 6pt Hedman bolts and it was such a PITA to tighten up a few of these bolts

I'll fire off a quick inquiry to ARP next.

Alright, so here is the update from ARP (two emails actually):

1) my question was: are the materials different in these two bolt kits?

"There is no difference in the material type of the two kit numbers you have provided. They are both the same chrome moly steel. The only difference will be the collar diameter. The exhaust manifold kit has a reduced collar diameter for clearance on the header tubes. If this will not affect you, then you should be good to go."

2) my question was: so what is the actual collar diameter on the 1" bolt, or at least what's the difference between the two of them (so that I can measure out the clearance I need on the headers)?

144-1202 UHL .750” Collar OD .530”
641-1000 UHL 1.000” Collar OD .620”

Bottom line, the 641-1000 is just fine given that the washer that comes in the 144-1202 kit is already a 0.670" side anyways.

Wow!!!

Can't go wrong with that find...7/8" should be fine, I need to measure that out, but it's such a tiny (1/8") difference...and heck, 50 pcs for $6.20???

Awesome find, thank you again, I'll most likely pick these up!

EDIT
Hmm...just realized these are plain steel, which is going to rust in this application, can't do that! damn...

Maybe you'd like these/attached. Or not.

Black oxide will eventually rust too. Stainless won't. Gold zinc won't, if you can find those.

Stainless will gall aluminum threads. Not an issue if your aluminum head has helicoil inserts though. If not use anti-seize.

He's using iron W2 econo heads I think.



https://arp-bolts.com/kits/arpkit-detail-b.php?RecordID=2445

https://www.summitracing.com/parts/arp-612-1000

You're overthinking this, don't worry. I've used Chinesium hardware store SS bolts for exhaust before. These will work just fine.

MarkZ, guys...


Correct, cast iron W2 race econo (long-valve).

I can't do it Mark...my OCD is holding me prisoner: the TTIs are finished in ceramic Black Satin...can't have a shiny steel/chrome bolt heads on those flanges, just can't do it man!!! LOL

(like I said, I'm a prisoner...now you know why my coupe took THAT long to hit the road)

Thanks again to everyone, great suggestions!!!

any time i use stainless hardware i use anti-seize.
stainless will gall in any type of material if anti-seize is not used.
i use the copper high temperature stuff on all applications.
just my life experience, your mileage will vary.