I started on the passenger side and the header slid right up into place, no problem. I got the two end bolts in so i could slide the gasket in place and then started to install the rest of the bolts. Well the fourth header bolt wouldn't go in for anything. The head of the bolt won't clear the #3 primary. I've got the ARP 400 1209's...1" long, so i tried grinding a couple threads off and i still can't get it to go in.

The same thing happens when I try to get a bolt into the driver's side header that isnt even installed yet...it just hits the primary and wont go through the flange.

I don't know what else to do...this thing is driving me crazy! Anybody have any suggestions?

 

Yes you need to pull the header back from the head then put the bolts into the hole on the header next to the problem primaries to get them started.

Try loosening the bolts you have started and back them out as far as possible without removing them completely from the head, now pull the header back and put those problem bolts through the header hole, you might have enough room doing that. If not you will need to pull the header back further even if it means removing the bolts you already have started.

I hope you didn't jack your threads grinding them down. Test those bolts on a hole that is easy to access.

Edit,

I notice you said the other bolt won't even go through the flange. What size head is on the bolt?

 

I tried all of that..The bolt wont go through the flange of the header even when it isnt installed. I've been messing with it most of the day and still can't figure out what to do.

The bolt is a 5/16th 12 point hex head.

 

That's what I used, the 12 pts. Will the bolt at least line up straight with the flange hole or is it at a slight angle? Did you try to put the bolt in from the head side of the flange to see if it will go through at all? That's a shame considering the price of the headers.

 

The bolt won't line up straight because of the primary. I put it into the flange from the head side and it'll go in all the way, no problem. The only thing i can think to do is either open the hole in the flange a little with a drill or break out the mallet and dent the header in a little so the bolt will slide in. Neither of which I really want to do...but i don't know if I have any other choices. This is just ridiculous...

You hit the nail square on the head.

 

This might sound stupid.. but couldn't you find bolts with smaller heads?

 

Well the ARP 12 pts. I have now have a really small head on them and they dont even come close to clearing the primary. I don't know of any other bolts with a smaller head that would be good. The head of the ARP's is already smaller than the threaded section of the bolt....I would be scared to go with something smaller than 5/16 in fear that it would easily strip...