Heli-coil questions

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7duce swinger

7duce swinger

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So does anyone use heli-coils here, or are they(heli-coils) a cheap/quick (half-a$$) way to do something? From what i have seen they work pretty well, and some companies, say they are even better than the old threaded hole?(please let me know why they say this). I have seen friends/family use them on blocks with stripped head bolt threads, and they've held up so far. So what i am wanting to know is , is it worth heli-coiling something? Now the reason i want to know is that my heads bolt holes for the exh. Manifolds, have stripped. I fixed two, and one just went all wrong for me. The tap broke inside the hole, i drilled the tap out, and the hole was enlarged (big time). So i have since drilled it out to 29/64 ths, tapped it for 7/16" threads, and have installed a stainless heli-coil. Will it leak is a major concern that hit me? I also used high-temp red rtv on the threads of the heli-coil, and am planning on rtv'ing the bolt as well. Will this hold up, or will i be pulling the head again in the near future?
 
heli coils are a good long term fix for a bad thread. They are fine.
 
Oh the heli-coil is now going to need a bolt with 3/8" threads, i think? Its not going to be the 5/16"ths size anymore.. I was also reading and someone here mentioned threading in a plug, like the ones with the allen head in it. Threading it in, then drilling the middle of the fitting out and tapping it to 5/16th's threads, so that it could use the same size bolts like before. Would the fitting like that work, or would that be half-a$$ed?? It seems smart to me to drill and thread a fitting like that, then you can use the 5/16" bolt again.. Sorry for the rants, just looking for input. Thanks
 
Thanks krazykuda, i was just a litlle scared of it leaking.. What about the other thing, as in drilling the closed fitting and tapping it? I already heli-coiled it ( bout an hour n a half ago), just wondering how the fitting would do.. Thanks for the input.
 
Heli coils are okay if done right and if your not constantly removing the bolt. Rather than drilling out a set screw (Allen head plug) check out a product called an ez lock. I prefer to use them at work if I have the extra material to drill and tap but if there isn't enough material I use a heli coil. Oh and there is a broken tap extractor tool. I've never seen anyone drill thru a tap or easy out. If I break a tap in a hole that not blind I punch it out from the other side. Was you using tapping fluid?
 
According to my drill and tap chart at work for a 5/16-18 ez lok (spelled correctly) you would need to drill to 27/64 and tap to 1/2-13.
 
Easy outs need to take the easy way out...in the trash can.

Use a tap aligner next time. No more broken taps.
 
The box the heli-coils came in, said to use a 29/64" pilot drill bit.. and the 7/16-14 tap for the install.. I already did it, was just wondering about how the allen head fitting/plug whatever would work if i drilled the center out and tapped it for 5/16".. The heli-coil is already installed, just dont want to pull the head and redo something if it fails. One more question, do you pull the little tang, in the heli-coil after install or leave it there? Yea, my dad has some bada$$ drill bits. I "borrowed" one, and drilled through the broken tap. But the hole was enlarged, and piece of the head cracked (inside the hole) which is the cause for the big ol' hole lol. thanks for all the input guys, it jus scares me a little since it leads into the water jacket.
 
The little tang on the heli coils break away with a tiny punch on most. If you have another heli coil from the set look for a line near the tang. I use pipe dope on exhaust studs rather than rtv but that's me. If you chose to try drilling out a plug make sure its not pipe thread and grab two. One to do a test piece in a vise before you install one in your head.
 
Dennday67 no i wasnt using any fluid at all, the cause of the tap breaking i guess... My stupid fault.. Ive drilled through both taps and easy outs. On my brother in laws tri-power 6 in his mustang, he had snapped the bolts off for the water pump. He asked me to fix it, but when i seen it, there wasnt any material to grab onto or weld a nut to turn it out. Worst of all, he broke an easy out, from napa in one of the snapped bolts... I drilled through the eazyout, and the bolt, then tapped the holes again, bamm good as new lol.. Again same "borrowed drill bits" from dad. I have also drilled through a 1/2" caterpillar bolt, it took about 30-40 mins, but i did it lol. where can i get those ez locks you mentioned?
 
Haha, i bought two as i thought of it at the parts store. I already drilled it and tapped it. I wrapped the plug in a towel to not damage the threads, and tapped it for a 5/16" bolt. It came out okay, i just want opinions on it if its kinda a half-a$$ job if you know what i mean... Im still deciding on leaving the heli-coil in there or taking the head to a machine shop and see if they can weld it and redo it..
 
The tapped plug is the same concept as an ez lok. I would as a machine shop if its acceptable.
 
It should work. We did this sort of thing in the textile mill often. the cheap cast iron pumps they used to move liquid latex eventually has a bushing and stainless stud with a nut in every hole. The outer threads were 1/2-20 NF because the casting was less than 1/2" thick. Fine threads equals about twice the surface contact. Just something to consider next time. Anyway..
The plug was staked to the casting, final thread scored and such to prevent the bushing wanting to turn with the stud next time the pump needed a new seal.
 
Redfish, Are you saying, the allen head plug, with the center drilled out and tapped should work, or the easy out i installed should work you mean??
 
If the heli coil is installed correctly, it will hold the load just fine.

If you need to seal the hole, go to the parts store and pick up a tube of the "world's best stop leak" which is the silver powder in the tube and pour a little in your radiator before you start up the engine. Run the engine for 30 - 40 minutes and it will stop all leaks around the bolts to the water jacket. You don't have to use the whole tube, 1/4 of the tube will be fine.
 
To clean out any debris out of the hole before heli coiling, use a blow nozzle on an air compressor to blast it out of there.

You can also use penetrating oil while tapping for lubrication next time.
 
7duce swinger said:
Haha, i bought two as i thought of it at the parts store. I already drilled it and tapped it. I wrapped the plug in a towel to not damage the threads, and tapped it for a 5/16" bolt. It came out okay, i just want opinions on it if its kinda a half-a$$ job if you know what i mean... Im still deciding on leaving the heli-coil in there or taking the head to a machine shop and see if they can weld it and redo it..
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I worked in an engine factory. They used heli coils or similiar (kean-serts) to fix bad threads all them time. No need to weld and try to retap. If you weld, It will be harder to drill and tap than the "regular metal" around it.
Welding will be more difficult and not give you any extra benefit, the heli coil will work fine.

I'm not quite sure what you are talking about using a pipe plug for....
 
7duce swinger said:
Redfish, Are you saying, the allen head plug, with the center drilled out and tapped should work, or the easy out i installed should work you mean??
Click to expand...

Helicoils will work and they are recommended in factory service manuals for places like the flexplate to torque converter bolts.
I'm saying handmade hole bushings will work too. We didn't have helicoils on hand for every application so a handmade 1/2-20 to 1/4-20 bushing for example was the only option.
 
You have to be careful using pipe plugs for "tap adapters" as there are different kinds of pipe threads. They make pipe threads in tapered and non-tapered. If you use a tapered pipe plug tap and go too deep, the hole will be too big and there won't be enough interference to hold the adapter in.

Chrysler generally uses standard straight pipe threads on the holes and tapered pipe thread for the "plug/male" so the taper works like a cork and jams up the straight thread hole with the taper.
 
Worked in the machine tool industry for 11 years & Heli Coils are used in all applications from automotive to defense to you name it. Both heli coils & ez coils are are excellent fixes for not so excellent situations.
 
Yea, my bad, i had an eazy-out on my desk and was staring at it at the time lol. I meant heli-coil.. Well my dad had bought a whole bunch of fittings to plug the extra holes for the temp gauges and so on on his performer manifold for his chevy. So i took one, and drilled the center out and tapped it for 5/16" threads and it turns into the threads i tapped into the head, but i wanted opinions on it first if the heli-coil is to fail.. well ill see soon enough.
 
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