RB30 spark plug thread insert - any ideas????

Hi,
Working on the project card which was running and idling nicely on petrol.
Pulled the plugs which were very old - #4 came out , there was no ground electrode and what turns out to be a thread insert is stuck on the plug.
Compressions are very good on the other 5 cylinders, assuming the same for this one, so trying not to pull the head off.
Am trying to find another insert to use, all of the common ones so fare are 15.7mm
The one that I have is 16.7mm.
Any ideas on what this insert is so that I can try to get another?

Attachment 85588

Maybe ring a head reconditioner or talk to a retailer that supplies helicoil kits.

Quote:

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Originally Posted by mudnut

Maybe ring a head reconditioner or talk to a retailer that supplies helicoil kits.

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Thanks mudnut, I have spent hours trawling the nett, phoning head recon places.
My email to Time -sert in the US was answered and they thought the Helicoil - save a thread inserts were 16.7mm
More searching and I found ProThread kits made by Bordo. I emailed their Oz office and they confirmed the od is 16.7mm

Fingers crossed have ordered them
Cheers

Observations

Thread O/D:
15.7mm / 0.618" Off the shelf inquiry.
16.72 / 0.658" Actual thread insert

5/8" / 0.625"

Maybe use thread gauge to determine if thread angle is 55 or 60 deg . Measure effective dia (a good fastener supply joint or machine shop would have suitable mic to measure). Determine pitch of thread and go from there.

Quote:

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Originally Posted by fazersix

Thanks mudnut, I have spent hours trawling the nett, phoning head recon places.
My email to Time -sert in the US was answered and they thought the Helicoil - save a thread inserts were 16.7mm
More searching and I found ProThread kits made by Bordo. I emailed their Oz office and they confirmed the od is 16.7mm

Fingers crossed have ordered them
Cheers

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I will be very interested in how you go. Number 3 and 4 cylinders have a bit of a weird angle to the spark plug holes. I have started cross threading them a few times over the years. Luckily iI have always felt the difference before any harm was done.

Success!
The Pro thread insert measure 16.72mm v 16.7mm of the old one. Close enough cos I didn't want to stick a tap in there for .02mm.

I put a bit of high temp silicone on the threads(not sure this is absolutely necessary!) I applied some anti-seize to the plug thread screwed the sparkplug into the insert and the whole thing into the block. Initially it didn't require much force, but then after a couple of turns it needed a fair bit but not muscle man like! When it felt pretty tight i back the spark plug out and the insert was flush with the head. It was a bit of a tense moment, I thought that the insert might not seat fully cos I didn't tap out the hole!. I put the plug back in and have taken it out out again and all appears to be good.
Mudnut, I have always put a bit of rubber fuel line on the end of the sparkplug on deeper holes so that I cannot cross thread them - the rubber loses grip as soon as a cross thread starts!

PROTHREAD M14 - 1.25 SPARK PLUG THREAD REPAIR KIT - I got mine for $70 delivered - 6 inserts, but only two 19mm ones.

Glad you got it sorted. I will put a link to this thread in the RB30 sticky thread.