Heli-coil size for ea81 exhast manifold bolt

[7point62fmj]

When I got the brat from the guy before me it looks like he stripped the bolt and there was just enough pressure left in the thread to keep the bolt from falling out. So I need to install a heli coil. The only problem is I have never used them before so here I am.

I am guessing you tap the the metal for the size coil you are going to use then some how thread that coil in to your new hole? Am I getting this right? Then the new bolt will just thread in to the coil. So my questions are what size should I get and what does all the gear intell.

Thanks

[skishop69]

It shouldn't be a bolt, it should be a stud. Bolts tend to rip the threads out due to the turning pulling force whereas studs stay in place and just pull. I believe the thread size is 10X1.25. Go to Napa and buy the kit. It will have the tap and coils and instructions on what size hole to drill. I would recommend using stainless steel studs to avoid future install and removal issues. I use stainless on all my exhaust systems.

Edited December 23, 2010 by skishop69

[7point62fmj]

yep the wrest are studs this one is just a bolt due to the last owner.:-\

[ShawnW]

Ive got a helicoil kit that is used. I moved on to Timeserts and won't go back. Make offer if you can wait a few days for the mail.

[maozebong]

ive replaced my exhaust studs with a fine pitch metric bolts. helicoil is all good and fine, but bolts are cheaper than helicoil and studs.

 

fine threads are good for something you dont want to rattle loose or have high loads on it. the more threads there are, the more surface area there is for holding.

[7point62fmj]

Is this a coarse or fine thread. I need to know because they sell both kits in the 10x1.25

[lostbrat]

1.25. Is fine thread

1.5. Is coarse thread

[MilesFox]

The metric thread reflects 1.25 threads per millimeter, hence the 1.25 pitch.

 

Do the helicoil. It will come with the right size drill bit, and will work so long as the holes have not been previously drilled out. Only drill to the original depth of the hole. going any farther and you will end up in a water jacket!

 

The helicoil kit comes with a bottom tap(flat on the tip)

 

Studs are ideal vs bolts. When you turn a bolt, ithits bottom, and any more torque starts pulling out the threads.

 

Studs go in till they bottom, and the nut then takes up all the torque, while the stud sints nice and snig in its thread.

 

You can use a thread locker when installing the studs if you do not forsee the need to remove them later. Sometimes when dropping the exhaust for other service, the stud may want to come out with the nut. Threadlocker, and clean threads will help prevent this.

 

it may not be an idea to use a thread tape on the nut side, or at least some anti-seize, to prevent the stud from backing out if the threads get corroded.