Spark plugs?

[Ulaff]

I have a 1955 Johnson 25 horse that the sparkplug holes have been resized to 18mm anyone have an idea what would be the best plug to use ?<br /> Or where i could find some 18 to 14 mm adapters at?

 

[bubbakat]

Re: Spark plugs?

Just about any parts store will carry the inserts or heli coils<br /><br /><br />Look on the plugs that you took out. I bet the inserts are still screwed onto the plugs.

 

[Ulaff]

Re: Spark plugs?

It had a set of autolites in it (18mm) and i was unable to find inserts or helicoils that would go from 18mm to 14 mm

 

[Paul Moir]

Re: Spark plugs?

Ulaff - If you can't find a couple adapters, I would be looking for a new head if I were you. I don't see any 18mm Champion plugs that have a 3/8" threaded portion at all. <br />Try Twin City Outboards for the head. Iboats carries the head-gasket if they don't. Also try to see if you can find where outboards are junked locally - they'll have plenty of heads.

 

[petrolhead]

Re: Spark plugs?

Isn't this something any competent machine shop could make for you, a pair of simple 18-14mm adaptors?

 

[Ulaff]

Re: Spark plugs?

Not any local machines shops that i know of ,I know that NAPA use to carry the adapters (i used them in several old fords) but cant seem to find them anymore I geuss i will e-mail autolite,NGK,etc and see if they make something<br />that will work

 

[Paul Moir]

Re: Spark plugs?

Ulaff - mabey a left-feild idea, but what about taking an old 18mm plug, removing the innards, and tapping it out to 14mm? Then you could just cut the threaded portion at 3/8" and wind it into the head with a little hi-temp loctite red to hold it.<br /><br />I see a few places are still making adapters, but they're pretty pricey since they seem to be made for aircraft engines.

 

[Scaaty]

Re: Spark plugs?

Originally posted by Paul Moir:<br />[QB] Ulaff - mabey a left-feild idea, but what about taking an old 18mm plug, removing the innards, and tapping it out to 14mm? Then you could just cut the threaded portion at 3/8" and wind it into the head with a little hi-temp loctite red to hold it.<br /><br />Never work...get to a John/Rude chat room/forum (google search) and get a used head...there out there

 

[walleyehed]

Re: Spark plugs?

Try here...<br /> http://www.marinepartsoutlet.com/index.htm

 

[rolmops]

Re: Spark plugs?

Hello Paul.<br />I tried that once or twice and there were always problems with the proper grounding through the loctite.There is a company out there that has the weird size helicoils.I'll see if I can find them.