The Stovebolt Site Forums The Shop Area Engine Shop spark plug question

anyone know whether the 1960ies (?) AC plug C43 is the same as the 1950ies AC 43-COM? I want to run the colder plugs because I do so much long distance, and found a few these in my stack of NOS plugs.

The COM is a heavy duty-version of the AC-43.
Should have a larger center electrode and wider ground tab, making it last longer but otherwise the same.

It was used in 2 to 2-1/2 ton trucks with 261 and V8 engines for city operation.
Also recommended for the smaller truck 235 in continous heavy duty operation.

My drivers never need colder plugs than AC-44, even when driving on the freeways for hours during the hottest summer months, around 2500-3000 rpm.

alright, thanks. I got plenty of 44's, so I guess I'll stick with those

The parts stores only have the 45 plugs for our engines, for several years now.
AC doesn't even make the colder plugs any longer.

It has gotten more difficult to get accurate reading from the plugs with todays gas anyway.
But I believe colder than 44 should not be necessary for average driving habits on a mostly stock or slightly built street/road engine, provided it is well tuned.

C43 plugs were made for trucks running full throttle constantly. Back when these trucks were used to work with, they were under powered an constantly driven at full throttle. Hotter plugs would cause preignition. I seriously doubt that anyone works these old trucks the way we did 50 years ago. 44 is a good choice for highway as well as some city driving and 45 is probably better for most people's driving habits. AC 44 plugs appear on eBay quite regularly. C44 appear very rarely.

I actually run my truck like they used to. an empty 12' U-Haul trailer pulling with an all-stock 1959 3800 panel, doing 145 miles in 3hr6mins including a break. and 8 hrs later the same trip back home with the trailer full with NOS car and truck parts, and then some in the back of my truck..
I'm lucky enough that I have 20 AC44 plugs, and unfortunately 5 (!) C43 plugs. but maybe I have a similar plug of another brand, that would work, right? like a Champion UJ-6 (I don;t have one, but it's the first book on the stack)?

Glad to hear somebody is really using his old truck.
How do your plugs read after the trip?
Is the ignition/timing/carburetion all in tune?
Does the gearing run your engine within the power band of your cam at sustained rpm?
How is the coolant temperature?

If all is in tune, you should be fine with 44 plugs.
I wouldn't mix and match spark plug brands, but you probably won't harm anything.

well,I overheated last week, not sure what the reason was. I've hauled a lot over long distances, and this was my first breakdown. I mean, 2 months ago I pulled a car hauler loaded with a 1950 Buick. I guess that was a LOT to pull.
but after I overheated I decided to take the thorough route. ordered a carb kit from the carburetor king (so not a budget kit), will replace manifold and exhaust gaskets, adjust valve lash, check timing, and finally repair the speedo. it's a lot of work but it'll be good for the truck. and since I actually use it for real, it'll be worth it for sure.
I'll post something soon about my progress and findings.
thanks for all the input!

You sure need to address your overheating problem. This is one of the the old timers are not forgiving. I think it would be money well spent taking your radiator out and taking it to a reliable radiator shop or possibly recoring it with a thicker core. Does it have a fan shroud? If not you should consider getting one or making one. I see you were in Austin. I have been in Fredericksurg all my life and operated trucks 45 years. All the things you mention above except possibly timing will help your performance but are not the cause of your overheating.

I sure agree with that! There is a root cause and the culprit is almost always a radiator issue...either plugged or rotted away to nothing.

Stuart