Thermostats/Spark plugs/ Wires

[BLKCOMPG]

I am wanting to install a new thermostat, but want to keep it SLP because of my Factory warranty. SLP says that they make a thermostat for 97-03, but will it work on a 04 GTP?

I heard that on the 04 GTP that putting the cooler spark plugs and bigger and better wires is pointless. True???

[BNaylor]

Originally Posted by BLKCOMPG

I am wanting to install a new thermostat, but want to keep it SLP because of my Factory warranty. SLP says that they make a thermostat for 97-03, but will it work on a 04 GTP?

I heard that on the 04 GTP that putting the cooler spark plugs and bigger and better wires is pointless. True???

The SLP 160 or 180 thermostat will work in a '04 GTP. Hypertech also makes one. See link below:

http://www.pfyc.com/store/merchant.m...y_Code=04UNDER

There is no need to go to a colder spark plug unless you run an under sized pulley for more boost. The '04 is not immune from knock retard (KR) and the only way to tell is by running Autotap or get an auto scanner with KR readout to verify. The '04 GTP does have a bigger throttle body and the Gen5 supercharger which helps reduce any possible KR compared to the '97 - '03 GTP. The bottom line is it depends on your SC pulley size and total amount of boost.

The issue of the AC Delco OEM 7mm plug wires is they are the best and there is no reason to use any other aftermarket brand such as MSD or Taylor.

[BLKCOMPG]

You said just what I thought from reading the other forum posting. Thanks. What are the advantages/disadvantages to using a 160 thermostat over the 180?

[BLKCOMPG]

and plugs..... is it worth it?

[BNaylor]

It really depends on how you are modded or plan to mod whether to use a 160 or 180. The theory behind using a 160/180 thermostat is the engine runs cooler when you run an underdrive pulley 3.4 and less. By keeping combustion chamber temperature down it may reduce knock retard. The SLP and Hypertech TS have holes drilled in them so some coolant is always flowing regardless of the thermostat opening once the right temperature is reached. I know it would be safe to use a 180 degree even if you were close to stock. I would not recommend using a 160 unless you have a re-programed PCM and even a 3.25 or smaller SC pulley. The fan turn on point is normally altered to 185 degrees versus over 220 degrees in a DHP or Intense PCM. The other problem with a 160 is you may get a undertemp condition whereby a DTC error code is generated and a SES Mil light. The engine must get to at least 145 degrees to switch into PCM closed loop mode within a certain period of time. The major problem if your Grand Prix is heavily street driven is the lower temp. thermostats will cause a longer engine warm up time and your feet will be cold until the heater starts producing after engine warmup. Not to mention poor fuel economy.

Running colder spark plugs is also based on SC pulley size. With a 3.4 one range colder. 3.25 or less 2 to 3 ranges colder, etc.. If you are stock there would probably be no benefit of running colder spark plugs.

[BLKCOMPG]

Thanks again for letting me pick your brain!!! I think I'm pretty informed now. I am confused about the lower temperature thermastat causing poor fuel economy? Lower operating temp were a good thing I thought?

[BNaylor]

Originally Posted by BLKCOMPG

Thanks again for letting me pick your brain!!! I think I'm pretty informed now. I am confused about the lower temperature thermastat causing poor fuel economy? Lower operating temp were a good thing I thought?

The lower temp. thermostat in itself will not give you poor fuel economy per se. However, you may get poor economy running something other than the stock 195 until the engine properly warms up. But it does take the car longer to warm with a 160 or 180 during the winter time. The best thing to do is experiment and see what happens.