Conventional plug or Surface gap plug

[PierBridge]

I was wondering about substituting the "normal" kind of spark plug in place of the surface gap kind in my Mercury engine.<br /><br />I was thinking maybe the conventional plugs would run hotter and not load up as much when I'm just puttin' around? Those surface gap plug just have to be about as cold-running as possible, don't they?<br /><br />Any takes on whether or not this would be a bad thing to try - as long as there is clearance in the cylinder for the different plug, that is?

 

[Perfidiajoe]

Re: Conventional plug or Surface gap plug

The projected nose on plugs don't have much to do w/ heat range. Heat range is the plugs ability to transfer heat from the combustion chamber to the head, colder plugs transfer heat faster, hotter plugs transfer heat slower. Too hot a plug will cause preignition due to fuel burning from the plugs heat. See if there is a surface plug 1 step hotter than your recomended range, if you do a lot of low speed running. Good luck Joe

 

[PierBridge]

Re: Conventional plug or Surface gap plug

Hmm that's strange I thought the primary means of adjusting heat range were by varying the length of the core nose and the alloy material used in the electrodes. Hot plugs have a relatively long insulator nose with a long heat transfer path. Cold plugs have a much shorter insulator nose and thus, transfer heat more rapidly.

 

[PierBridge]

Re: Conventional plug or Surface gap plug

Bump

 

[Perfidiajoe]

Re: Conventional plug or Surface gap plug

So any projected nose plug is colder than any surface gap plug?

 

[PierBridge]

Re: Conventional plug or Surface gap plug

Originally posted by Perfidiajoe:<br /> So any projected nose plug is colder than any surface gap plug?

I don't know, just trying to clear up the contradicting info that I have heard.