JRoy91RS

I was torquing down my TPI intake today, and as I was torquing down the front driver's side bolt, I felt it give. I pulled it out along with a bunch of rust, and a couple of threads from the cylinder head. Boy, I was ticked! I mean, there was a LOT of rust that I pulled out of that hole. This happend to me on three bolts--the two bolts at the very front on each side, and the very back bolt on the passenger's side. I was able to use some longer bolts to grab enough threads to torque them all down to spec.

My question is--will I most likely leak coolant anyway, even though they are all torqued to spec? I think maybe one thread per hole was stripped out--maybe two threads on one of them. Is there anyway to fix this other than buying new heads (like rethreading the holes)? How do I know if I rethread the holes that this won't happen again? Finally, what do you think cause this?

Thanks.

Vader

You can remove the intake again and install thread inserts. A lot of people like HeliCoil types, but they don't do well where a seal is required. You can drill up to 27/64" and tap the "bad" holes for solid inserts, like these:

JRoy91RS

That's probably what I should do. I was afraid I'd have to take off the stupid intake manifold again. There goes another pair of new gaskets....

Do you think it will leak if I don't put inserts in? I know, I know, why risk it, but it was only one or two threads, I think.

Thanks, Vader.

If I do drill, what size and type of bit should I use?

Dialed_In

iTrader: (3)

Always, always, ALWAYS run a tap through holes like that before you try to assemble anything. Lesson learned I guess. Also, never run a bolt in dry. Especially aluminum. Use sealer (if required) or motor oil to lube the threads.

Take Vader's advice and use the solid thread inserts to repair the holes. Be sure not to get any metal into the ports or lifter valley.

Sonix

iTrader: (1)

I've never had to use a threaded insert, or knew there was a solid type compared to a helicoil. helicoils you need to buy their special tap size, and get their special install tool, etc. So a helicoil kit can be pretty expensive, and it only works for the one size.
Is this any different?

89gta383

iTrader: (5)

I've helicoiled 4 intake bolt holes, 1 valve cover bolt hole and 1 front of the head accessory holes on these afr heads, never had a problem with any of them.

Vader

Yes, HeliCoils can get expensive, and require the special tap. They do have their place, however. Many applications do not have adequate material surrounding the hole to install a larger solid threaded insert such as these.

Another down-side of HeliCoil inserts is the fact that it is very difficult to seal the threads against leakage while still being able to remove the fastener without backing the HeliCoil out with it. That will wreck your whole afternoon.

These inserts are available in multiple sizes and types. Those that a locked in place by driven pins never loosen or back out. Those with anerobic epoxy sealant are also very resistant to backing out, and seal very well even under extreme pressure.

These inserts use standard size taps as well. For example, the 3/8-16 insert that would be necessary for the intake flange repair would have a 1/2-13 external thread, and costs about $1.15 each. They are also available in other external thread sizes, even metric (with fractional internal threads), and in various lengths.

I've had fairly good success with them in heads for spark plug holes, cast aluminum and zinc, and even in plastics.

JRoy91RS

Well, I guess I'm going to go with Vader's suggestion. So, a 27/64" drill bit, a tap and some inserts is all I need?

Where do I get all this stuff?

I guess I should consider this a rite of passage. I suppose everyone has to drill out some threads at some point!

Vader

Don't drill anything until you get the inserts. You may decide on a different size. You can get them at any well-stocked hardware store (NOT a home center, but a real hardware store), industrial suppliers, catalogs, or online at places like Fastenal, McMaster/Carr, Austin Hardware, etc.

JRoy91RS

Well, I finally found some inserts. SHould I be using a drill press for this or will a hand drill do the trick? My 18v cordless drill just doesn't seem to be cutting.

Vader

Umm, Yeah. A cordless might be good for a few holes here and there, and running some screws in and out, but leave the real machining to real tools. Cordless tools are getting better all the time, but just don't equal the power of a corded model. A drill press may not be necessary, but a drill guide would be handy. You could redrill the holes with the engine in the cradle that way. It's going to be important to tap them straight, too.