Looks like I'll need to repair my spark plug threads on my 37 Flathead. These heads take a 18mm plug. My local machinist isn't much help on getting this helicoiled. It looks like some of the options are expensive. Anyone have any thoughts or suggestions?
You may want to check the depth of the pitting before going too far. And a machinist who can't helicoil a plug hole ????
Put the offending cylinder on exhaust. Take your shop vac and put it on blow. Let it clean itself for minute or so and then install it on the exhaust pipe. While you are working , drilling tapping etc all chips a debris will be blowing out into your face probably but that beats into the cylinder. Works perfectly. The reason machinist don't want to do it is the possibility of getting chips and debris into the cylinder making a simple job into a nightmare. I tried this about 20 years or so ago (I am a mech by profession)and have used it many times since. How do you know when you are on exhaust? Wind will be coming out the hole from the shop vac blowing into the exhaust system. Otherwise follow the instructions on the repair kit exactly and you will be fine.
Look into dreracecar's source. These will be 'bushings', rather than loose-coiled 'helicoils'. I have been in the aluminum engine German car biz for 57 years, and only use helicoils when a permanent stud will be inserted, NOT spark plugs which get removed and replaced with decided regularity.
Heli Coil makes a sleeve type of spark plug repair kit that works very good. The kit is a little pricy just to do one plug. I would call another machine shop and ask them if they have this type of insert.
Every auto parts store sells thread inserts for spark plug holes. Another tip is to grease the tap so it will catch the chips.
That is probably the "worst case scenario" kit if its what I think it is. It has a larger outer thread that takes the helicoil insert. We used them on boat engines years back.
I may have found a solution. http://www.amazon.com/TIME-SERT-Metric-Insert-M18X1-5X15-0MM-18157/dp/B003WN1BZA
Time sert are by far better than any thing i have ever used GM sends them to every dealer as a required special tool.
My God, good heads (in better overall condition) are almost a dime-a-dozen. You've already done the hardest part in removing the boogered head. DD
I believe you could but 18-14 or 10mm adapters in steel. Coat them with JB weld and screw them in. Then use commonly available plugs.
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