Any Helicoil pros out there ?? Help
 

:( OK, getting ready for some A/C install action and I went to swap out the heads from my Sanden 508. I believe I have amassed every part and item and I was very pumped. I also got ROLLGUYS kit, very nice !:)

Took a bit of mojo to get the old head off. This is a NOS Japan original, not a Chinese clone knock off. I got the pump, et cet from Secondaries over a month ago. Now, it's too hot for any more delays.

Then, per the spec's, 24-27 ft pounds, I went to the install. Guess what ? threads pulled right out ... poop. So, I am thinking my only hope is to helicoli the 5 bolts. Right now, I removed the thin metal star-like plate too. I am down to the pistons, so I am good for the clean up and re-install. Need to order the gaskets tonight.

So, any ideas or caution about helicoiling this? If it's a loser from the beginning, please let me know so I don't waste my evening or tomorrow in the early AM before Mr. Sun rises.

Thanks in advance.

If the are 8mm and grade 8.8, then it should be only 18 ft/lbs or more accurately 225 in/lbs. Smaller bolts would be less torque. Also make sure your torque wrench is accurate. At these low torques I prefer a beam type, as the click type has too soft of a click at the lower end. Also, if it has been left set for more than a few hours it will not be accurate, and the further you are from the center of the wrench's range the less accurate it will be as well.
Using a helicoil or similar will be a good fix, just make sure you drill straight, tap straight and keep chips out of the moving parts.

I can't really see which bit you are planning to fix - but so long as there is enough metal a helicoil will probably do just fine. You have to oversize the hole anyway before running the specially made tap (can be bought in a kit - drill, tap, inserts and insert tool) and fitting the insert. Very simple process - try to drill the hole straight!

You're thinking 6mm.

An 8mm can to to 30-35 lb.-ft. before it fails. I routinely run the 5/16 screws to 28 lb.-ft. with plenty of room above (by feel).

Are we talking the bolt or the threads in the aluminum? I am sure the threads in the aluminum will give out before the bolt will break. Also, are both heads the same thickness? If the new head is thicker, longer bolts will be needed. A short bolt ( only a few threads in the aluminum) will surely pull a few threads out.

According to this, I am thinking of 8mm-
Metric Bolt Torque Table - CNCexpo.com
Do you have a reference to qualify your statement, or is it just the calibrated elbow?

I would recommend Time Sert insted of Heli coil.

Yes, I see you are correct for the hex heads. I only have the SHCS which can handle significantly more.

I also only torque in steel with sufficient length (1.5X diameter), so my figures are going to be higher than any other charts.

You're probably much closer to the mark in aluminum.

In aluminum, the numbers are significantly less. In fact, I'd guess they are 1/2 the figures that I quoted above. Aluminum can't take any torque and, typically, the screw isn't of sufficient length (1.5 x diameter in the threaded length) to even make the table values.

Aren't Time Serts quite a bit larger in diameter? They are great for something that gets put together and taken apart fairly often, but I couldn't see the expense on something that would just be put together once. You are looking at nearly three times the cost of a Helicoil-

Well, I totally chickened out because the pistons in the pump looked a little too close for me. I drilled them out and re-tapped 9mm x 1.25, which took out very, very little aluminum.

Any ideas on whether the torque will remain the same, e.g., 24-27 ft pounds. That is, with new bolts which are 9mmx1.25x40mm?

This was going to be my recommendation. Good job!

I'd use the rated torque, or less and loctite. The alum threads are the limiting factor, not the bolts.

OK ... news at 11.

No such thing as a 9mm bolt. So, need to go up another hair in sized bolt. Why in the world would you have a 9mm tap and die and NO bolt on the market. This is turning into a royal PITA !

Does the tap say 9x1.25 on it? It might be a 5/16 tap if you eyeballed it.

Make sure you pick the "right" pitch for a 10MM bolt. One is really common and the other is rare (I *think* it's 1.5)

No, it's M9 x 1.25. I am not the only dufus to have done this. It's all over the forums for different cars. There are options, e.g., a Polaris speciality bolt, et cet. I am lucky because I removed so little material, that I am going the helicoil route tonight. Keep in mind that I have to keep the bolt shaft size down since the head has pre-bored holes and I am not messing with those no matter what. Worst case scenario is that I am forced to buy a Chinese clone 508SD compressor for my a/c. My gaskets should be here by Wednesday or Thursday, just in time for the 4th weekend. Poop !