I wanna get spark plugs that are 1 stage colder for my 8 Iroc - 305TPI. I currently have NGKs with the standard heat range = 4. Does anyone know if NGK makes these plugs in the heat range of 3. If so, do you know the part number? I checked their web page, but could not find them. Do any other companies make a heat range 3 spark plug for these cars.

The reason I want to switch is b/c I think the knock sensor may be pulling back the timing. My car was @ 8* BTDC iginition advance. My father rebuilt the distributor and reset it to the factory 6*, but it felt a little flat. So we bumped it up to almost 9*, and now I think the ECM may be pulling back the timing. Sometimes I take off and the car fly's, but other times it feels flat. I think the colder plugs may help prevent the minor preignition a little. (I'm assuming there's slight preignition causing the ECM to pull back timing, but I can't hear or feel any pinging).

One more question - after we set the timing to about 9*, when we plugged the brown wire back in for the distributor advance, the timing came down to about 2 or 4*. I thought that by moving the distributor, the ECM couldn't lower the base timing. Could someone please explain.

Thanks - David

 

If you cranked up the initial timing and it is seeing knock, you need to retard the timing, not add colder plugs. The plugs are not causing your problem, the timing is. If the combustion temps were so high that the end of the plug began to glow and it was starting to ignite that way, a colder plug would help. However, since you stated that you cranked up the base timing to get the car to "feel better" it seems that you have more timing than the motor is able to use. A chip designed for more base timing and less advance may work for you, but I suspect that you need to take 1-2 degrees of timing out of the distributor.

Good luck!

My thoughts.

 

I always see 1 stage colder spark plugs listed under the "free mods" posts, but what brand and part #'s are you guys using? Thanks.

 

I give up.