JB Weld on accessory bolt studs in aluminum heads?

[JeremyNH]

98 Z71 with a new 383 (390 technically - 3.8" stroke 0.040 over). It has AFR 190cc heads with a little more than 100 miles into break in. Runs perfect. Issue came up on final assembly two weeks ago that one of the accessory bracket bolts (AC bracket top outboard) started to pull out the aluminum threads on torqueing. It's not stripped as I stopped as soon as I saw the torque reduction, backed it out, used a longer bolt to chase the threads and re-installed without a torque wrench but could feel the threads grips are soft. Left it snug but not torqued. AFR 190s have accessory bolt and valve cover center bolt holes tapped short and they say in the install instructions to reduce the length by 1/3" to keep them from bottoming out which I did (1/4" about as 1/3" seemed too much). Obviously on retrospect the reduced thread contact wasn't going to allow for high torque (32 ft-lbs, not all that high but too high here). Went to the treasure yard and picked up four accessory bracket studs thinking I could bottom them out using the full pitch of the threaded holes and replaced the four bracket bolts with studs (two in the alternator bracket, two in the AC bracket). The offending bolt hole is still soft so I again left it snug but not torqued. My plan is to let it be for now and see what happens. Probably it will be fine and riskier to try to do something about it until I have evidence that I need to. My thought was to use JB Weld to permanently affix the stud in the head. The threads are present and the studs thread in and out just fine so epoxy them in to keep them from turning and continuing to damage the threads and let the remaining metal keep the stud from pulling out. If it's an issue in the future I can always just cut them off and swap the heads to use the still fresh holes now in the back. I have little experience with JB Weld but it seemed this may be a good application for it. Thoughts?

 

[kennythewelder]

If you JB weld that bolt, you will never be able to remove it, with out damaging the head. A much better choice would be a helicoil kit. Drill out the damaged bolt hole, and install the helicoil. If you not sure how this works, just do a YouTube search, in helicoil.

 

[JeremyNH]

If you JB weld that bolt, you will never be able to remove it, with out damaging the head. A much better choice would be a helicoil kit. Drill out the damaged bolt hole, and install the helicoil. If you not sure how this works, just do a YouTube search, in helicoil.

Right, but I've replaced the bolts with studs on the accessory brackets in the head now and the studs can stay in the head forever so far as I'm concerned. I don't have any interest in removing the head over something like this. As mentioned I have fresh holes on the back side so would just swap the heads vice drilling into them as they are.

 

[kennythewelder]

Right, but I've replaced the bolts with studs on the accessory brackets in the head now and the studs can stay in the head forever so far as I'm concerned. I don't have any interest in removing the head over something like this. As mentioned I have fresh holes on the back side so would just swap the heads vice drilling into them as they are.

Your choice. I see your point. Yes JB weld should work fine.

 

[Supercharged111]

No need to remove the head to install a helicoil.

 

[JeremyNH]

No need to remove the head to install a helicoil.

Looking through Youtube on comparisons it looks like EZ Lok would work well. Helicoils have a center spar that need to be punched out and since these are blind holes maybe better with a brand that doesn't. I do wish AFR would either warn about the bolts pulling out or, given the cost of the heads, simply included coil inserts even as a pay option. Youtube video shows 8mm bolts in aluminum yielding at about 320 in-lbs. Accessory bolt torque is 32 ft-lbs so coupled with the reduced engagement despite the slightly larger diameter they will predictably pull out. Their testing of spring inserts put the pull out at north of 500 in-lbs. JB Weld is barely a third of that. How do you ensure the drill bit is perpendicular to the head when drilling out the old threads? I have a spare set of accessory brackets I could use as a jig and do them 1 by 1 if there isn't a special tool. I would say "I'll have a shop do it" but my stroker was 13 months in the shop to get it done. Transmission had a cracked bell housing discovered when I pulled the old motor which added 7 weeks to the operation before the shop could weld the ear back on (I'm 4L80e swapped). Point being that having a shop do more than brakes and oil in Southern NH is largely theoretical.

 

[Jeepwalker]

Did you ever put a tap in there and clean the threaded area out well? And shoot a bunch of carb cleaner to make sure it's crystal-clean in there?

JB Weld works great and I could tell you some really good personal JB Weld stories. You would be able to get those studs out if you epoxied. Just heat up the studs real hot with a torch, the epoxied end will get hot and you can walk it out with a vise grips. And if you just put 'enough' but not too much heat on them (and your bolt threads were real nice to start with) you might be able to do it w/o damaging the JB Weld threads. But then again, like you say, you might never need to. See how it goes in the meantime with the studs you put in.

 

[Vikingdude]

I would definitely do the helicoil or timesert repair over JB weld, but that's just me.

 

[Supercharged111]

The fact that the hole is blind is irrelevant, the insert won't be seated all the way down so you'll have no trouble removing that piece after it's in place.

 

[JeremyNH]

The fact that the hole is blind is irrelevant, the insert won't be seated all the way down so you'll have no trouble removing that piece after it's in place.

You stated earlier it can be done with the heads installed. I'm thinking make a simple jig to keep the bit perpendicular to the head and let it self center on the hole. Use a right angle attachment and drill it out to depth of 0.6" then tap and set the coil. Sound right? I'll check with AFR as to a safe drill depth but the coil is 0.52" deep which about matches the tapped depth presently.