Spark Plug CHOICES? What heat range? any 18mm choices?

My fastback likes to run a little hot. I want to try using a colder plug but I cant find any that fit and are colder! I’ve read that you should have the coldest spark plug that self-cleans properly. I’ve also read that
"if you want your car to run colder use a colder plug; hotter, run a hotter plug- its that simple" I don’t know if these are both true, but I would like to try, but cant find one to try! Any part# you might know would be much appreciated!

I’ve got at *least* 600 miles on Autolite 45 spark plugs. They are completely clean and white. They appear brand new except for the tiny carbon build up near the threads.
The Engine ran its first 2,000-3,000 miles on splitfires,
changed to bosch platinum & sparks 'leaked' out of the wires, and EVERY spark plug boot. Thats when I went to Autolites!
Info on the Autolite 45's:
18mm, .468" reach, 13/16" hex, tapered seat, resistor
Info on my engine:
1970 302, Crane HI-6 ign box Mallory unilite dist.
9.23 sec in 1/8 mile

Find a local Motorcraft dealer & have them special order a BF-32C. It won't make the engine run cooler though. A different heat range plug just allows for faster or slower heat dissipation thus keeping a little more or less in the combustion chamber. I have a cross reference for spark plugs someplace. I believe Champion still makes a colder plug as well... maybe Aurolite/Bendix
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I believe the readly available Accel 375 is even colder than the BF32.
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THANKS for your help

I finally found someting to try out at a local NAPA dealer

Champion 409 RF9YC $2.24
The cross-over # for my Autolite 45's was a RF18YC

Now the car wont idle until warm, and seems a little underpowered....however the change in the temperature is remarkable. before the autometer mech. guage would read 205-220 when its now 185-190.
Tonight driving around on the street the temp 170 max, (this with revving the car whenever I could and avoiding overdrive)

Maybe I should try the inbetween plug RF11YC!!

Yikes! Details Details ...........

Years ago had a neighbor that bought a new air cooled '71 NSU Prince. It needed new plugs at 15k mi, so he went to the dealer for a new set. The ones they sold him were too hot, burned the valves in less than two weeks time. After the valve job(still with the same plugs), it burned a piston. Finally the dealer realized the mistake and installed the correct plugs, no more prob.

I knew spark plug heat range would affect cylinder temps in a air cooled engine, but didn't think it would make any real difference in a water cooled engine.
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Ya start geting the cylinder pressures up, it do make a difference. My last iron headed 466 was almost 14 to one & hated anything but the coldest plugs. I'm just glad I had made adapters to run a 14mm plug [img]/phpBB/images/smiles/icon_biggrin.gif[/img]
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was running the car all over today on the freeway. I felt a torture test was needed so I drove the car fast on my standard commute route to work (a repeatable test) hit freeway for ~10-12 miles, then exit right up to a stop light (you always hit) which leads directly to another stop light (you will 80/100 hit) onto a main thoroughfare, drive 2 miles down and stop in the workplace parkinglot.

The area of most trouble has always been those two stops directly off the freeway where my car would heat up from 180-190 freeway temp to 215-235
I suppose it is the residual heat built up from the recent high speed effort, but the new plugs must shed the heat or block it because the temp stayed within 5-7 degrees of when I was moving at high freeway speeds... hmmmm

<font size=-1>[ This Message was edited by: 67fastback on 1/17/04 3:54pm ]</font>