Stripped out a thread on my intake..... what
 

Hey guys

Not sure what happened here, but when bolting up my surge tank to the intake (Blue thunder MR 2x4)the bottom bolt stripped out the intake threads!!!! It was wierd, I was using a hand socket driver (not an air ratchet) and I didn't have any resistence. The bolt went right in but kept spinning and never snugged up. I pulled everything back off and sure enough there were aluminum threads on the bolt!

So basically I need to retap the hole with a bigger thread, this isn't a big deal, but a few things I need to know before I can call BT on Monday are:

1: Is the depth critical on the lower bolt hole? As is, the depth is only about 1/2" deep, but could I drill a bit deeper since I will have to used a hand tap instead of a CNC bottom cutting tap. Or will I break through into an area inside the intake? How much room do I have there?

2: Does anyone know right off hand what size that thread is, and the next size up that I should tap?

I would suggest not increaseing the size of the bolt but putting a heli-coil in instead. It will be much stronger than the aluminum threads.

I've never done that before, what does the process entail?

Is it the same as a heli-coil?

Sorry wrong spelling. you got it Heli-coil. http://www.helicoil.in/helicoil.htm

That would be better, and I can get those at Sears. That is actually better, that way I don't need to modify the keeper in the surge tank for a bigger bolt.

They come in a set, for the specific bolt thread size , you would need to drill, then use a special tap, and then insert the helicoil with the tool provided , and then you should be good to go.

You may want to do this off the car, as there will be some chips generated.
You can use grease during the drilling and tapping processes to minimize chips flying about.

Steve

Hey Dan you can increase the depth some also. You probably won't need to with a heli-coil. If you do break through the threads can easily be sealed with a bit of silicon, thread sealer or PST on the threads. The tap will say STI on it which stands for standard thread insert then you'll have the thread size (3/8"?) after that. If you feel inside the coolant hole I believe there are bosses there for the holes you'll be able to get an idea of the depth. Pretty straight forward job worth doing to both while you're set up.

i would probably coil both the holes or 3, however many.

I'd helicoil it, or insert it, whatever you want to call it. You should be able to find a "kit" including the helicoil type inserts and the approprite sized tap and insertion tool at any hardware store, or I think NAPA or other autoparts stores. Take your bolt with you ( ? 5/16 ) to get the correct size. It will then specify what drill bit to use, which you have to purchase separately. If you can get to it, I would leave the intake on the car and try to repair it there, making sure you drill and tap it perpendicular. If you screw it up bad, you'll need to take the intake off and have somebody reweld the hole. Good luck.

Permatex automotive thread repair kit is also an option. It is designed for exactly this purpose. And if it doesn't work for some reason, you can still use a heli-coil. No drilling required.

http://www.acehardware.com/product/i...ductId=1295869

Just use the heli-coil kit. Should take about ten minutes. Use a cordless drill. It will follow the old hole easily with a light touch. Depth is non-critical. Any parts store or decent hardware store. 5/16-18 thread

Heli-coil in.... I like these!

simple and strong. I was just worried about breaking through into a critical area.

Atta boy, they're the cats meow for aluminum threads aren't they?

They make a simple Heli-coil tread repair kit (Theree are different names but they are bascically the same)with a couple of average length coils and a tap at the local auto parts store to a full kit with different length coils a special tap, installing tool , tang break off tool ,and remover tool . They never seem to come with the percision drill bit. Once you have the kit, You can buy the coils in bulk in different lengths. The serious kits and souch can be had at a local screw-bolt supply store, hardwhare tool supply etc. A machinist will have the set if you want to just let them do it. I've done this so much, I have the kits in 10x24 through 9/16. The Helicoil tap is special in that it is oversized as compaired to the bolt but the tread spacing is the same. Also the basic heli-coil tap is more like plug tap rather than a starting and finish bottom tap. if you do this enough you may accquire a second tap to make a bottom tap from. Also be sure to use a long enough coil to take the pulling force when used in soft material like alluminum (unless you drill though) in a blind hole. There is no such thing as too much coil. you can shorten the coils that are too long with a cutt off wheel. Make sure you break off the coils tang after installing. make sure that you get that tang as it is Stainless and not verry magnetic and if it gets some where it's not supposed to be as in the case of that tang getting into an FE oil pump and stopping the gears causing evere engine failure.
I pulled two of the Heli-Coils in one head that hold the rocker shaft. Then had to have a machinst install an insert in each of the four rocker shaft holes in both heads . The heads had to be removed as the machinist needed to mount the heads on a machine so to be sure that all four holes in each head are in the same plane so the shaft and stands will slide over them when mounting. The coils wern't enough for this application.