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| | | | Joined: Dec 2012 Posts: 5 New Guy | | New Guy Joined: Dec 2012 Posts: 5 | In my '46 pickup I have a 261 block with a 235 head. I looked at Old Online Chevy Manuals for a 1956 truck and it says I need an
AC 44-5 com plug for the 235 engine
AC 43-5 com plug for the 261 engine
I don't know what "com" stands for.
The plug in the engine now is an AC 43S. What is the difference between the 43, 44 and the 45? | | | | | Joined: Jul 2008 Posts: 1,321 'Bolter | | 'Bolter Joined: Jul 2008 Posts: 1,321 | Read this extensive discussion on spark plugs, Spark Plug Discussion Harold
Harold
Is a restoration ever finished? | | | | | Joined: Dec 2012 Posts: 5 New Guy | | New Guy Joined: Dec 2012 Posts: 5 | Gene Schneider has good information about spark plugs in that discussion. But he doesn't mention the 43S plug and if it is the best one for my engine.
Btw, the date code on the block under the "captain's bars" ends in 2 (so 1962). I can't find a serial number on the block. The head seems to be the earlier low compression head from 1954-55. I'd have to open the valve cover to see more about it.
Last edited by pistachiofarmer; 06/02/2014 8:40 PM.
| | | | | Joined: Sep 2001 Posts: 29,269 Bubba - Curmudgeon | | Bubba - Curmudgeon Joined: Sep 2001 Posts: 29,269 | 43-5 was a commonly used plug, but hard to find; however (I found this after we talked, Ted): 44-FF was the plug listed for later 261s, and the C42-1 plug was recommended in 1962. Gene Schneider also posted that the 44 plug was used in later 235/261 engines and the 44s are hard to find. He indicated that the 45s were the common replacement plug. Gene also suggested to keep away from the long version of the plugs - he had seen evidence that under certain loads (driving conditions) piston damage might occur. http://www.sparkplug-crossreference.com/convert/AC_DELCO/C42-1 | | | | | Joined: Jul 2008 Posts: 1,321 'Bolter | | 'Bolter Joined: Jul 2008 Posts: 1,321 | See this discussion, post #4, at this site. 44s Plug Harold
Harold
Is a restoration ever finished? | | | | | Joined: Dec 2012 Posts: 5 New Guy | | New Guy Joined: Dec 2012 Posts: 5 | That's an interesting discussion on "44s Plug", Harold.
Tim, I'm not sure if the plug is 44s or 445. I think it is the former though since there is no hyphen and it looks slightly more like an S than a 5.
Maybe my best bet is to leave well enough alone. The R43S plugs that are there are clean and not eroded and the engine purrs now that I have new points. Also I don't have any information that one works better than another on this queer combination of head and block. | | |
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