buzz,

Aluminum can be a real bitch to tap, I have always had good luck putting grease on the tap. That help to catch the chips that would normally fall in the hole and gall the new threads, that and backing it out and cleaning the tap often.

 

Since I will be doing this in the engine bay small chip collection and control will be a top job. Tape up and tarp the easy to drop into valley area, etc.

 

shop vac

 

Buzz....sorry to read of your troubles, but please keep sharing your experience. They are very instructive. I really do appreciate it and am sure others here do as well.

 

Amen on shop vac and some small clear hose.

wednesday progress - bought milling machine (Armstrong) and filed out the slot. Would have gone faster if I could get the pipe nipple off, but at this point I worked around it. Question will be how much I have to take off on the narrow face of the slot, will refit to check for that.

Noticed that hole I helicoiled (Fix a Thred) was drilled (per package) to 25/64ths.

Tap drill for the 7/16 is "U", which is 0.3680 inch; the 25/64ths is 0.3906 inch. So now I will not have good results with a 7/16... The Fix A Thred package is giving the drill size for steel, and does not consider aluminum, even though it is a product of Alcoa. Note pix of hole, insert was screwed in until flush, tang removed. It stripped out and spun, you can see the tapped area extends further into the hole. I am tempted to use another insert, with loctite, to the area of the hole where threads remain. Or I suppose I can make this larger than 7/16.... but running out of meat for it to go into.

I have the multi-volume set of Murphy's Law.

 

Buzz, I want you to measure the depth of the hole, the thickness of your manifold flange and the length of your bolts. Your bolts should almost bottom out with a lock washer installed. Now once you've determined the correct length of your bolts if you decide on using inserts they should be almost the same length as the bolt holes your inserting them in. I know they have longer inserts than the one you first used. Clamping force in aluminum isn't by size but by length, the amount of threads your engaging. More thread surface/contact equals higher clamping force. Remember your only shooting for 28 ft/lbs. A larger bolt isn't needed, a longer one is. You only achieved 25 Nm in the insert installed hole because it was the short style, the common type.

 

Well, with respect to the one hole that has the insert, it is now threaded on the bottom section of the hole, and stripped out on the top section. So putting in a longer insert (or stacking short ones) may not have anything to grab. It was drilled out to 25/64ths, so drilling with a "U" bit for tap of 7/16 won't work. Go to long insert for 7/16 and drill the appropriate hole?

With respect to the others, was planning not on inserts but just drill and re-tap for 7/16, no inserts.

 

Make sure the bolts you're using are long enough, they look a little on the short side.

 

Pix of bolts (original vs the 7/16th planned but not drilled for yet). Close enough?

Any ideas on what to do with one hole that has generic helicoil that stripped out?

 

how about filling the hole with JB Weld, let it cure, them drill and tap to the stock size, it not a lot of pressure and JB Weld claims it is drill and tap able.