MTFCA Forum

Do I have the wrong spark plug? This is as far as I can get the plug in. I have cleaned the threads. They all seem to do it.

Also what gap? .8mm?

They are tapered threads, so yes. Sparkplugs can vary in depth by brand. Some newer plugs seat higher than original era plugs.

Do I need to put some thread sealer or something? Or just do it up until it's tight?

Do not over-tighten! It is possible to split the head with a tapered thread.
It is a low rpm low compression engine. A slight leak will not hurt much. It CAN allow water to leak in if the plug valley fills with water, whether from rain or car washing. So some care should be made to keep those valleys dry.

No problems. What gap should I make them?

Gap depends on ignition system - stock .025 - .030 with a distributor, around .032 - .035

Pipe thread plugs - tighten them tight !

Don't try to force them tight, not like a water pipe. Turn down tight. It will feel tight with the standard wrench or a handle about 8". If you notice a little oil coming up through or hear a hissing noise, you can wrap the threads with aluminum foil and that seems to seal them and also conducts electricity to the head.
Norm

They need to be TIGHT ! I've installed & replaced hundreds of pipe thread spark plugs with a 1/2" drive ratchet with a 15/16" deep socket - you won't break anything !

UNLESS - you're installing pipe thread plugs into an aluminum head then you need to liberally coat the threads with never-sieze !

Thanks guys. All installed. I was just worried as I could still see the threads.