6coupe4

I've looked at the old posts and still can't decide what plugs I should be using. I have a 64 327/300 with a mild cam. I'm running R43 now and have a slightly rich idle. The carb has been rebuilt and I'm still rich. I've been told by my engine rebuilder to use a HOTTER plug. From what I can see in previous posts the R43 is cold, the R44 which is not available is HOTTER and the R45 is the HOTTEST.

The owners manual says something like the R43 is for the standard engine and the R45 is for the performance engine. I know there is a 250hp engine, which would be the standard. But would the 300hp be considered high performance?


What is everyone using?

Thanks for any comments.

Craig

Ironcross

Use R45, 43`s are TOO cold.....

Any auto parts store that sells AC plugs.

46 is the hottest but basically used in the old 6 cylinder chevies.

Trophy Blue

Whose sells the R-45's?

magicv8

You don't mention the wires, but using resistor plugs AND resistor wires will overload the original coils. Most came nonresistor plug AC44

piper

I got mine at Auto Zone

Trophy Blue

Thanks.

ucc2ic65

I run R45's and I bought them through my local Chevy dealer (past March). The parts guy has been with the dealer for quite awhile (as I learned since I did not know him) and was so excited that someone was looking for / talking about cars and parts from the good old days (I have a 65 coupe 327/365 hp). I didn't think I would ever get out of there.

He had to order them (from I believe Michigan) and it took about five days. He indicated that GM had alot in stock. He gave me a 10% discount for ordering them from him so each plug cost me less than $3.00.

rongold

Running a hotter plug will not make the engine run leaner, but it might enable the plug to run hot enough not to foul out. If you're idling too rich, turn the idle mixture screws in slightly. Try running R45S plugs--Extended nose plugs will run cleaner--much talk about that on the forum.

RON

Kensmith

I agree R45's

rongold

I think you mean R45S's. The plug number ends with an "S", meaning extended tip.

jerrybramlett

I suggest the answer is "none of the above".

Autolite still sells an equivalent to the AC 45 non-resister plug. This Autolite plug is their number 295. That is what I use.

JoesC5

I run NGK B-4's(stock #3210) in my 300Hp '64 and my 56. They are the same heat range as the AC 45. They are not resistor plugs(neither were the plugs that came in these cars originally) and are high quality plugs. I purchase mine at O'Riellys Auto parts, but you should be able to find them just about everywhere.

6coupe4

MagicV8 brings up another question. As far as I know I have standard wires, nothing special. Do I need some type of special resistor wires?

dmentzer

Same here.

RoadVettes

Worked for me. Just make sure you don't have dome pistons though.

Charlie

Allcoupedup

Check this out.....
Same motor, same driving conditions - only difference was the plugs.

R43 - fouled quickly



R45 - looked nice



Brian

Kensmith

Not for my motor as I have the high compression pistons. I run the R45 no S.

sub006

NGKs actually have a much broader heat range than most iron or copper-core plugs.

Back in the day, I read about a San Francisco Ferrari dealer who would put them in the V12's so they could idle in city traffic, then wind out to 150 in the country.

I tried 'em in my 327/250. Plug life increased from 8,000 miles (Champion or AC) to 15,000!

Paul L

I guess each engine is different (mine a 327/300). I tried the NGK B-4s and they fouled. Too cool. Went back to AC R-45S and all is well.

Ironcross

The real problem by using the "S" plug. It may be too close to the dome in high compression versions {11+-1} and the solid lifter engines. If in doubt use the R45 to be safe. Many are getting away with it however. I wasn`t one of the lucky ones. My 61 FI piece did hit the electrodes and it was a real bitch changing the plug shields and air cleaner twice because I tried the "S" version of the 44`s sold to a fraturnity brother that was picking them up for me sold by a dumb parts counterman. 90 degree Miami heat and now a hot engine too as I ran the engine and discoved problem. Funny now but not then.....