does anyone know what size gap to use on a 99gst? and also what would happen if the gap was bigger then the normal size.

do .030 for moderate boost (stock-16psi)
do .028 for high boost

increasing the gap is only going to make it harder to jump, and under high boost you may get misfires. Bigger gap is only good with big ingition system.

There is a sticker under the hood that says your engine size,specs, and gap.

i know that this is alittle off the subject but i found somewhere online that you take your sparkplugs and mark them in the same spot so when you put them in turn them facing the same way and it will boost your hp some

ORIGINAL: mirageracer23

i know that this is alittle off the subject but i found somewhere online that you take your sparkplugs and mark them in the same spot so when you put them in turn them facing the same way and it will boost your hp some


I've read about that too - it is called indexing the plugs. The only way it works is if you face them all the RIGHT way - with the open side of the gap facing towards the intake valves, and the negative electrode facing towards the exhaust valves. That way the inrushing air/fuel mixture is exposed to the maximum amount of spark and doesn't have the negative electrode between it and the spark.

The way I've read to do it, since the plugs all have to be tightened down all the way, and to the proper torque spec, is to get a bunch of thin copper or aluminum washers to use as shims and use however many or few it takes on each plug to make it face the right way when it is screwed down tight.

Never quite made sense to me that it could possibly make enough difference to even be noticeable, but seems simple enough to be worth trying. The only hard part is getting your hands on the right size thin copper or aluminum washers to use as shims.

wouldnt t be easier to just get like the bosch 4+ plugs

ORIGINAL: 99clipsgst

wouldnt t be easier to just get like the bosch 4+ plugs


Well, with the Bosch +4 plugs, it doesn't matter which way they are turned, you still can't make the gap face towards the incoming air fuel charge from the intake valves So basically you can't index Bosch +4 plugs, and you can't get whatever benefit there is, small as it may be, from indexing the plugs.....