Hello all.
The threads for the exhaust studs on my 89 pu's 3.0L heads were seriously damaged when I was removing the studs. Actually, only two of the threads were damaged, but as I am putting headers on this truck now, a mechanic recommended to me to install hell-coils in ALL of these threads to avoid headaches down the road. I have no experience with these, however, and am just wondering how simple it is to drill out the old threads. The last thing I want to do is screw up my heads after I just got them rebuilt and machined, but I would really like to do this job myself. If anyone has undertaken this project or something similar, I would appreciate any advice or recommendations. thanx yet again...

 

I've done helicoils in aluminum, its not too hard if you have some room to work. You just drill the hole out to the diameter they give you and tap with the tap they give you and screw in the coil. I don't think I'd do them all though unless there is something wrong with them all.

 

thanx dale, yah, i was kind of questioning doing them all too... kinda seems like a little overkill. I was just worried that if i was constantly having to re-tourque these studes to eliminate exhaust leaks at header manifold, i might end up damaging more of these weak threads. Apparently helicoil threads are MUCH stronger and durable. i dunno.. neways, thanx again

 

I certainly would not do them all. If only two are messed up just do them. You can have problems later with the heli coils too just like regular threads and it is a more time consuming and annoying job to fix a helicoil (again) than original threads. IMHO if you do them all now you are removing a quick fix option for the next time there is a problem.

 

I wouldn't say "MUCH stronger", they are still threads into aluminum just a little bigger than before.

 

Hey just remember to knock the tang off when your done, if not you'll unthread your helicoil. I think they'll work just fine, hell I even have one in the block for a headbolt. A drillpress makes life easier but with a steady hand you can do it without one. As for strength it's alot stronger, not only did you retap the aluminum but you put stainless steel threads in it that expand when you put a bolt/stud in it. I did a test out in the shop on a junk head and the helicoil took more torque from the wrench than the stock thread or a retapped thread.

 

went out and checked all the threads, there are two that seem almost perfect, the rest definitely show signs of wear. So ive decided to just go ahead and do all of them. will update after the grand attempt. Thanks to everyone for replies

 

Hey you spent the money on the kit, you should use them. My machineshop kindof family owned wanted more than it cost me to do it, and that's me buying everything. They don't do many yota motors, mainly circle/drag stuff so I was probably a pain in the ass.

 

I would just tap them out to the next size bolt, SAE or metric. I think a 10MM will tap out to a 3/8 or 7/16. Pretty easy, and no drilling.

 

Have you ever been this far before?

 

Google something called time-serts (I think). Supposedly like heli-coils, but better.

 

I stripped out a few of the holes in my heads where the camshaft caps go. I used a helicoil to fix it and it worked perfect. They are super easy to use. At the company I work for we always put stainless steel helicoils in if we tap into aluminum. They are way stronger than just the aluminum alone. Also, when you use a helicoil instead of just drilling out the hole bigger and retapping to the next size up, you can still use the same bolts on all of holes and down the road someone isn't going to wonder why one of the bolts is bigger than the rest.

 

Amen on that brother, nothing like having to use 3 different wrenches on a part or some a$$hole tapped them SAE.

 

Wha?
If you mean have I ever done, this? Yep, on a chevy S-10 v6 exhaust manifold bolt holes, my 89 toyota thermostat bolt holes and the distributor adjustment bolt. Several of them are now SAE instead of metric and vice versa in the chevy. Tapping out one size larger in aluminum was easy.

 

Yeah it's easy, so is tripping over a rock. I know what the size is on every bolt on my engine without looking at it and last time I checked they were all metric. So let's just say I tapped this one for SAE and that one for Metric (oversized) next thing you Know I have to have the whole freaking snapon catalog in my toolbox. You've given good advice to me in the past but I have to say you're wrong on this one. Helicoils (or a something like them) are a proven method and are better than tapping threads the next size up into aluminium. Ask someone at a machine shop what they think. There's alot of U.S. aircraft flying around with Helicoils in them.

 

I got nothing against helicoils, but I am glad all my ideas don't suck. :-)

 

Does anyone know the thread size on the stud? M10 1.25 or 1.5 etc? I have to helicoil 3 on my 1985.

 

M10x1.25

 

Awesome, thank you.

 

I hope you have the head off

I would not wish anyone the frustration trying to drill on the vehicle