Thread: Spark Plug Questions for Truck Mount Carpet Cleaning Machines & Trucks

Recently I needed new spark plugs for my White Magic Triton LS 59 hp fuel injected Ford carpet cleaning machine engine. They are very hard to find since an auto parts store does not have a cross reference for carpet cleaning machines. And let's face it some of these engines are used for industrial purposes and then adapted to our industry. So after a thorough search I came across some plugs but they were not a 100% match but the auto parts store said they will be fine. The machine runs better but now it takes a little longer to start. So here are my spark plug questions. I know some may be obvious but for anyone else hunting it may help in the future.


1) What's the difference between a hot & cold plug?

2) How important is gap?

3) Are not plugs pre-gapped from factory?

4) As long as they are the same size won't they work fine?

5) Is it ok to put a little grease on threads when installing? (Mine were VERY hard to get out?)


Thanks
Rob

Cool site!

Thanks Kevin.


Rob

Use anti-seize on the threads. It won't melt away like grease. Different plugs have different gaps, it is fairly important. You really just don't want the gap collapsed or massive. The larger the gap the better, IF you have enough coil to fire across it.

Rob, hot or cold plugs are concidered a type of heat range that make up the plug itself. Or for lack of a better term "thermal conductivity". Hotter plugs do not dissipate heat well and contain heat at the tip. these types of plugs are used for lower RPM and can sometimes cause pre-ignition when running high. A cold plug has more ceramic insulation inside the plug on the electrode. This type of plug carries the heat away when engine temps climb and higher RMP. The plugs do not affect engine temp but rather the temp of the plugs. Plugs are generally gapped at the factory but that does not mean they are always going to be the same or perfect. Always regap or inspect new plugs and regap if nessesary. David says the larger the gap the better. This is the case and usually creates a cleaner burn. Too large of a gap and the plug can misfire at higher RPM and also means that you will need to change or regap them more frequently. Most engine specs come with a gap range. Lets say .020-.030 I like to adjust my plugs somewhere in the middle of that range. On my truck I set my gaps recently to the shortest spec because I was experiencing pre-ignition/detonation on hot starts I did this because I knew it would take more cranking to fire the cylanders and allow more fuel to enter so it wasn't so lean rather than replacing the fuel solenoid which will be done at a later time. One disadvantage most have with fuel injection is control of stoichiometrics air/fuel ratio without additional computers to change the ratio. Very upsetting stuff if you are aware the technical side of things. So these car manufactures now days are leaning out the ratios sooooo much that they obtain these wonderful MPG's. Very bad for the motors in the long haul. Even carburated engines that need to pass emission fall way into the lean side just to pass. More fuel in the chamber will assist in cooling the plugs also. I was discussing with a friend over the weekend and he was saying how Nitro methane fuel can actually buildup inside the chamber and ignite blowing off the heads and intake. This only leads me to believe that a lean mixture which is the number one culprit for detonation or preignition is not the only thing that can cause detonation but a fouled plug or matter inside the chamber will cause detonation as well. That being said a rich mixture will not cause preignition or detonation.

Thanks Dave. Anti-seize makes sense.

Ara that was a great explanation. Your the man.

Rob

Originally Posted by davenjai

BTW anything with an aluminum head should have anti-seize on the plugs. Thanks Ara, that hot cold stuff has always confused me. You sure it is not a timing issue?

Are you asking about my truck? If so good guess but its fixed timing. No adjustment on a 96 gm yukon.