Wrong spark plugs

[JT1]

So today I decided I should replace the plugs in the Caprice, all went well and it's running as good as ever. Turns out though that I looked up the plugs for the police engine which are 2 heat ranges colder than the ones for the civillian engine. Do you folks see a problem in running a colder spark plug? The engine is completely stock.

 

[MrBeachcomber]

Time will tell; however, if your old plugs were clean (no oil or carbon fouling) and the engine isn't using that much oil, you should be okay. Prolonged idling in stop & go driving is the real culprit for fouling spark plugs in most engines next to oil fouling. If you start to get a miss after a lot of in town driving, a quick blast down the nearest open road ought to clean the plugs!

I use colder plugs in my daily driver '89 Vette because I auto-x the car at least once at month and haven't had any problems over the years.

 

[ARCOgraphite]

AC Delco? IMO stocks are usually too hot, 1 heatrange colder is good, just keep an ear out for misfire counts. I think most FI cars run leanest A/F on 1/4 throttle on stoic just before enrichment, this is where you get unsulator overheating/blistering. Most everything runs dead rich at WOT. Keep and eye on fuel mileage - this is tell tale.

 

[01rangerxl]

Since the colder plugs are the correct application for a 9C1, I wouldn't worry, especially if the car is running fine now. I can't imagine that a 350, even with EFI, is going to be terribly picky about plugs.

 

[mechtech2]

2 heat ranges colder is a lot.
I wonder what the reasoning is, as police cars often idle and drive slowly. Full bore power for extended times is not the norm.

Extended tip spark plugs have wide heat ranges today.
I would use the stock ones for a civilian car, or maybe one colder.

 

[yeti]

arco -- would a 1 range colder plug affect mileage enough to notice ? thank you.

 

[JT1]

Engine is 305, runs smoother than with the correct heat range accel plugs, which were about .030 over gapped at .065.

I'll keep an eye on fuel econ, but I'm betting it will be an improvement.

 

[eljefino]

I'm running 3 range colder autolite 3923 vs the stock 3926 in my saturn. It doesn't burn much oil so it's doing just dandy.

 

[01rangerxl]

When a Saturn doesn't burn/leak much oil something is wrong.

 

[JT1]

Originally Posted By: eljefino
I'm running 3 range colder autolite 3923 vs the stock 3926 in my saturn. It doesn't burn much oil so it's doing just dandy.


My caprice doesn't use oil either so I'm sure mine will be fine.