Changing SC Pulley on GTP

I'm considering changing my pulley out on my 97 GTP to a 3.4 Pulley. What should i do (if anything) to make sure there is no knock after i change pulleys? Can i just make a clean swap without adding anything else tothe engine?

I'm considering changing my pulley out on my 97 GTP to a 3.4 Pulley. What should i do (if anything) to make sure there is no knock after i change pulleys? Can i just make a clean swap without adding anything else tothe engine?

Just stick with good quality premium fuel and drop one range colder on the spark plugs to start to minimize any possible knock retard (KR). Good luck!

so there are no other negative effects of switching pulleys without any addition modifications?

so there are no other negative effects of switching pulleys without any addition modifications?

You really won't know for sure unless you run a KR test with an autoscanner gauge or with a program such as Autotap. After review of the data a further determination can be made if other mods are necessary. Intake and exhaust mods have a positive effect on KR by reducing or eliminating it. A lot of us go to a re-programmed PCM because it will have provisions to modify timing and spark advance to take advantage of an undersize pulley. I currently run a 3.25 SC pulley have about 1 degree of KR at WOT. However, it is not a necessity to do this with a 3.4 pulley. Sometimes you may have to go 2 colder on spark plugs.

BTW - There may be a reduction in fuel economy both in city and highway. But it will depend on how you drive after the mods. IMO a 3.4 pulley is the best street mod you can do for the cost.

what heat range are the stock spark plugs so i know what "colder" plugs would be.

what heat range are the stock spark plugs so i know what "colder" plugs would be.

Good question.

The regular OEM AC Delco spark plug is a Rapidfire 14. The AC Delco Iridium counterpart is 41-101. Not sure what the colder AC Delco plugs are for stock Rapidfire or Iridium.

For AC-Delco "double platinum" plugs:

Stock..........41-921
1 colder.......41-932
1-1/2 colder..41-919
2 colder.......41-913

Most of us with GTPs running smaller pulleys use Autolite spark plugs due to cost (cheap) but they are very effective and the numbering system is easy to remember:

1 colder......605
2 colder......104
3 colder......103

My recommendation is to use the Autolites.

bnaylor3400,
Any recommendation for plugs on the 04 GTP's Series III V6.

bnaylor3400,
Any recommendation for plugs on the 04 GTP's Series III V6.

For '04 and up it is similar. If you are modded most '04 and up owners use Autolites just like us '97 - '03 owners. Same heat range standards are applicable depending on mods such as pulley size, etc. The only problem you will run into is they do not last as long as the Platinums or Iridiums. They are copper core. Great price at Walmart though.

If you are stock it is hard to beat the stock AC Delco 41-101 Iridiums which incidently were made by NGK.

Also the multi-electrode Platinums, especially from Bosch don't work too well so I would stay away from them. However, the dual electrode AC Delco Platinums work fine and a lot of GTP owners used them or did at one time or another.

Most of us would probably use the colder AC Delco Iridiums if they even exist but I don't think they are available at least to my knowledge.

Good luck in your choice.