Header bolt and Stud/Nut question

[BlackArtemis]

Greetings!

I am in the middle of a BBK Long Tube header installation (YAY!).

Yes, it is as much of a PITA as everyone says it is, but my friend has done his fair share of crazy jobs in his garage, so we elected to do it at his place. Unfortunately, his experience is mostly with Evos and Subarus, so we need your help.

We have everything off the car, and are getting to putting the headers on the side of the head. The bolts we bought (Stage 8 locking fasteners) seems to not enjoy the side of the head. Literally, they have a ton of resistance when going in. They are indeed the correct size (model # 8906, 4.6L and 5.4L FORD w/8mm locking header bolts) and the holes in the side of the head are sparkling clean. One bolt even chewed up the threads a little bit, but luckily our M8x1.25 tap cleaned it up. Note, I cannot finger tighten these locking header bolts at all in the holes.

Interestingly enough, I pick up the old header studs (OEM) and they thread in like butter, no problem at all. I can't reuse the old header studs because the OEM nuts are rusted on, but the fact is that the OEM studs go in so easily.

What's the deal with these stage 8 bolts? What am I doing wrong here? I'm pretty certain I need to go get some new header bolts/nuts OEM and put these fancy-pants stage 8s to the side.

Input and Mustang expertise appreciated!!

(note: the Evo/Subaru mechanic is the guy writing this while Artemis is standing behind me, so be nice to me )

 

[trinity_gt]

Can you compare the threads on one of the Stg8 bolts to the OE threads?

It sounds like you've got a mismatch somewhere: thread pitch is wrong or thread diameter is wrong etc etc. Try putting the threads of the Stg8 up onto the OE stud threads and look for differences. Use verniers to measure the OD of each.

BTW, when done right Evos and Scoobies rock

 

[BlackArtemis]

Pitch is exactly the same. m8 by 1.25.

The problem seems to be that they line up fine but strip the head a bit when they go in. You can only finger them about 1/2 to 1 turn before needing to ratchet them in.

 

[trinity_gt]

If the pitch and diameter is the same then they wouldn't be damaging the threads on the way in.

If you're using a ratchet to turn them in and they're stiff you've probably F'd the threads in the head by now.

 

[BlackArtemis]

Put one side in and the last one was hard. We took em all off and that was the only one that was messed up. We had a tap and fixed this issue. The stock bolts go in fine with just fingering them on both sides. The stage 8's need more than finger strength.

 

[EJZ Evo]

Ok, it's the Evo guy who helped make this thread.

Hopefully I can clear things up a little bit as I was rushed a little in my initial post.

The threads are indeed the same, M8x1.25, and to confirm that, my tap and die kit swiveled over the stage 8 bolts the same way they did over the OEM studs. However, even with my fingers I can't get the stage 8 bolts to thread in properly; they go about 1/4 a turn and just stop, just as if they were the wrong thread pitch. It's almost as if the coating on the stage 8 bolts (or whatever it is) makes it just a hair too wide for the hole in the side of the head.

 

[BlackArtemis]

Stage 8 8906 Stage-8 Locking Header Bolts that's what I bought.

 

[Kornnut]

Re-use the stock studs and bolts.

 

[flstang65]

I agree, use the stock studs/nuts. I have had this problem several times. Even though you bought the right size, thread pitch, ect, for some reason they never fit quite like the stock ones.

 

[EJZ Evo]

Ok, I agree. Unfortunately the stock studs/nuts are pretty rusted on the outside, so I am going to replace them. Anyone know what part # from Advance Auto the studs are?

 

[flstang65]

They are in the help section.