the dealer shows that i need rts45 plugs ..i would like to run 43's instead..

will i have any detonation problems?

 

the 45s are the hotter of these 2 numbers, you can run the 43s just find, although going to a colder plug you may wind up with problems fouling the plugs out. are you having problems with it over heating or burning the plugs up?

 

the car in general runs hot... i would like to lower the heat range at least one point

 

the plugs won't much if any effect on enigne temp, i would check the other things, fans, radiator, cap, good air flow, t-stat, water pump, air deflector.
how hot is it getting?

 

The only reason you'd want to run a colder plug would be if you were having problems with detonation under load.

 

in traffic on a 90 degree day with the air on the car stays around 210

 

i got that last time i ran the car at the track it broke up a little above 3500 rpm....

 

Was it because of detonation?

 

Plug heat range has nothing whatsoever to do with casting temperatures.

210 isn't hot for your car. That's exactly what it's done since the day it was new. I know, I have one too, have had it for quite some time now. Your fan doesn't even turn on until 230-some odd.

A too-cold heat range plug will tend to carbon-foul at low speeds, like in traffic or whatever. Not a good idea for an otherwise stock motor driven on the street.

Run the right plugs for your car, you'll have less trouble in the long run.

Find out what's really wrong with your car if it "breaks up" at moderate RPMs. Changing the plug heat range won't fix it. You might as well change the tire pressure or the interior color to try to get the engine to run better, it will have about the same amount of effect.

 

it did it once...when i was testing different secdonary metering rods and hangers..

 

What, the "break up" thing?

If so, I believe I wouldn't use that hanger/rod combo.

Usually, that means a lean condition. Try adjusting the air valve tension. About 5/8 turn is usually a good starting point for a strong-running 305, might even work for a mostly stock L69. If it's too loose, no amount of fiddling with the metering parts will cure the lean-out.

 

the break up thing happened when i had too rich of a rod with a shorter power tip...so i jumped back to the previous setup i had...

i had the carb re worked by a local shop...

he knocked out the plugs that cover primary rich/lean stop..cleaned out the bowl..put in a new TPS, new springs and a float..he also changed the choke pull off for a faster one...then he tuned the carb once it was back on the car.. he also loosened the air valve so it opens quicker..i have not run the car since he did all this work...

im going to change my plugs before i go and am wondering what to use....

GM told me R45ts...