How do you find out the right heat range for spark plugs for a 72 chevy 350 engine 120 psi of compression?

Question

I'm having problems with it carbon fouling , loosing cylinders, rough idle in gear. Thinking it was a vacuum leak replaced the intake gasket and still having the problems. I'm thinking its either the spark plugs (R44T) or putting a hotter coil to fix the problem.
Before I go buy something I don't need , Can anybody help me please.

Answer 1

If your plugs are carboning up you must not run the car very hard very often to keep the carbon from building up or your carburator needs attention such as it's too big for the engine or the jets need to be smaller in it as it sounds like it's getting too much gas, also check your plug wires for being bad and if you don't have a HEI distriburator in it and still have the old point distriburator get rid of it and put the HEI in it, any junkyard carries them and it will give you a lot hotter spark and you will never have to worry about changing points again and your engine timing will stay stable all the time.

Answer 2

A sparkplug doesn't make heat, therefore it can't heat up the engine. Sparkplugs can not and will not make an engine run hot (or cold). The fire in the cylinder heats up the plug, not the other way around. Heat range simply means how hot the plug itself will be. If the plug is too cold, it won't be able to burn off the oil and fuel deposits that collect on it and it will foul. If it is too hot, the electrode can't cool fast enough and it may start to melt away. On high compression engines, there is more cylinder heat so a colder plug is usually used. Sometimes the heat on race engines is so great, even cold plugs melt-off the electrodes. This is a common problem when running nitrous oxide. Some top fuel engines don't even run electrodes. The ground electrode is simply cut-off and removed because it will melt-off! The spark from the magnetos on those kind of race engines has no problem at all jumping from the center electrode to the edge of the plug. The bottom line is, you want to run the hottest plug you can without melting the electrode. This just assures a clean plug that yields a good spark. Hope this helps.....

Answer 3

Some good info on these links for proper plug heat range determination. Too cold of a plug will allow more fouling as will an overly rich carb adjustment or settings. Too hot can cause problems also. Stock engine? call a Chev dealer or parts store for what is normal plug for it....usually, you can go one size hotter with no problem. as in, R44T to R45T. Are you sure it's carbon fouling and not oil?
http://www.centuryperformance.com/spark.asp
http://www.ngksparkplugs.com/techinfo/spark_plugs/overviewp2.asp?nav=31000&country=US

Answer 4

120 lbs of compression is not that good. As for your question of heat range if you get a repair manual it will tell you what type of plug to use.

Answer 5

"Low Compression, Rebuild Time!"