3 replies to this topic

[308 Sunbird]

Hi Team, has anyone had any success with repairing a damaged spark plug seat and thread

with one of those insert kits?

 

It's on my HZ Kingy 202 I'm restoring to stock and I'm not keen to spend heaps on reco-ing

or replacing the head unless necessary. It runs ok but when I replaced the plugs, #2 had

been botched up with an aluminium washer and what looked like exhaust paste to seal it. 

The seat looks a bit sus and when I sprayed CRC around the plug it is definitely gurgling a bit

of air. I would rather repair it better had that if possible.  

 

I tried to find out the exact plug thread specs but couldn't and the only inserts that seem available

and close are M14 x 1.25 but I would of thought these old girls would be imperial threads?

 

Any information would be greatly appreciated. Thanks.  

[Dr Terry]

Metric threads have been used on most spark plugs since or before WWII. All Holdens since FX have had 14mm spark plugs.

 

However from HQ onwards (HT onwards for V8s) their seats are tapered with no washers.

 

There shouldn't be too much difficulty in cleaning up the 14mm thread, but cleaning up the seat might be moreso.

 

If it needs an heli-coil insert you'll need a dedicated tapered seat spark plug style.

 

Dr Terry

[claysummers]

If you are trying to avoid taking the head off you won’t want to be getting any swarf from the clean up in the combustion chamber. Being cast iron it won’t burn, and will cause preignition. You may be able to clean up by inserting a magnet through the hole.


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[308 Sunbird]

Thanks Doc that is the information I was looking for.

Thanks Clay I you-tubed a few ways of minimalising the swarf and if I can

get a tapered seat insert I will give it a go.