Found a heli coiled spark plug
02-18-2018, 10:26 AM
#1
10 Second Club
Thread Starter
Found a heli coiled spark plug I was taking apart a friends trans am for a cam swap and found a autolite plug with a heli coil destroyed still on the plug on number 1. After freaking out a second I screwed one of the tr55s in and it tightened up fairly well and felt good. Somebody tell me for sanity’s sake if it had a heli coil that’s now removed how is a oe plug going in what seems to be fine. I assume they’re a reason it was there should I go ahead and try to put a insert in I just don’t want a plug to blow out later on
02-20-2018, 07:03 PM
#6
10 Second Club
Thread Starter
It was definitely a heli. What doesn’t make sense is a normal tr55 will thread right in the hole the heli coil came out of and tighten up. It’s like they were never anything wrong with the hole to begin with but how did a heli come out and a normal plug go right back in without another heli. I don’t have pics. I only get to touch the car on Saturdays and it was pouring rain when I found it.
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02-20-2018, 09:27 PM
#8
TECH Addict
Just a side thought...
When repairing spark plug holes, there are some aviation versions that are a iconel (I believe) thread in sleeve, much tougher than a heli-coil style repair.
They typically require a slightly larger overbore, but especially if the heads are off then thats really no big deal.
Yes they are more expensive,, and not as easy/quick to install but they provide a lot of support for the plug and hole.. Seen them preemptively installed don engines that get their plugs checked/changed a lot (Sprint/midget/Sand toys..)
When repairing spark plug holes, there are some aviation versions that are a iconel (I believe) thread in sleeve, much tougher than a heli-coil style repair.
They typically require a slightly larger overbore, but especially if the heads are off then thats really no big deal.
Yes they are more expensive,, and not as easy/quick to install but they provide a lot of support for the plug and hole.. Seen them preemptively installed don engines that get their plugs checked/changed a lot (Sprint/midget/Sand toys..)
02-21-2018, 07:08 AM
#9
That may very well be the case. The strength of the heli-coil is dependent on its length (the company has published pull strength data for their installed lengths in different materials). They come in lengths of "d", that is multiples of the thread diameter. For a spark plug, I would want a full length helicoil if you go that route. Whoever did it, might have just picked up a helicoil from a local box store.
02-21-2018, 08:18 PM
#10
10 Second Club
Thread Starter
I bought a insert kit today. Part number 5334-14. I’ve used them in 5.4 fords before so hopefully I can get it in there without pulling the head. This has definitely made a no big deal job a pain. Hopefully it goes smooth.
02-22-2018, 03:23 PM
#11
I used a kit similar to these https://www.ebay.com/i/152538849809?chn=ps with a shoulder at the top of thread, worked very well. I used compressed air into the tailpipe and grease on the tap. But the install tool that I used was much better, It had a guide and cutter on the end then the tap section. It did a perfect job, I was truly impressed with it, may have been a KD kit. Been a while .