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Spark Plug Recommendations

ryan_thompson87

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ryan_thompson87 Enthusiast

ryan_thompson87

Posted
Posted

Ive been wondering what I should be running for spark plugs, as I think thats whats causing my idle and driveabilitly problems. I think I need a higher heat range. The motors a 355 with about 9.6:1 compression, Vortec heads, GMPP TBI Vortec Intake, A Mild Cam, and headers. It idles like crap and surges abit going down the road. Sometimes there is a misfire also.

grimmysnr Enthusiast

grimmysnr

Posted
Posted

I just replaced mine about 500 miles ago and I am not sure if i can recommend what i used. I got the Bosch double platinum which is basically a platinum plug with two prongs that surround the electrode.

 

Initially i saw an increase in get up and go. The truck was more responsive and felt like it wanted to just run over s**t. But now after driving it for a while the power i felt seems to have worn off and it feels like im getting misfires and overall crappy drivability out of it.

 

I am thinking about replacing them again with something else. Picking a spark plug heat range only depends on what type of gas you use. All heat ranges do is prevent detonation. I know this becuz i was working on a Grand Prix Turbo project and i had to deal with this type of thing constantly.

 

If you use regular 87-89 octane gas and just drive like normal then you will not need any heat ranges colder or hotter than stock. If you are getting mifires and such that has nuthing to do with the heat range of the plug. If your plug is too hot then the electrode will detonate the gas before the spark will or if ur plug is too cold then your waiting solely on the spark to ignite the mixture. A failed spark could mean more plug fouling, ignition wires, or ignition coils.

 

Changing heat ranges on plugs is mainly for forced induction applications simply becuz more air+more fuel = an insane amount of heat. Putting a hotter plug may cause more detonation especially with 87-89 octane gas becuz that fuel is easier to ignite. Detonation = chipped piston, spun bearing, and a heap of other problems.

 

If you are experiencing detonation then go with a colder plug or a higher octane fuel. If you are experiencing misfires and s**tty driveability look into changing you plugs but troubleshoot you wires and coils.

 

So my recommendation would be to stay away from Bosch double platinum for now possibly look into Autolite platinums. I used them all the time in my Turbo setup and they run beautifully.

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