there were some posts about spark plugs this last week of which i was part of. there was question as to wether R45 ac plugs could be purchased as they are out of production. i wrote down the Denso and NGZ equiv and went down to the Advance Auto and was totally suprised that the R45 XLS was a stock item and they had them. i was told it was a regular item and they sold a lot of them. bill
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Re: spark plug update on AC R45.....
I don't recall anyone saying that the R45XLS is no longer available. In the past I have said that the SB OE AC 44 is no longer available, nor is the 43 or 45. The only versions of this plug geometry that are available from AC have a resistor and are known as R43 or R45, as there is not longer a R44.
Since engines of this era used non-resistor plugs, I was able to cross reference the non-resistor AC 45 to a non-resistor NGK and Denso spark plug of the same geometry and heat range.
I have not done so for Big Block XLS extended reach plugs. I'll leave that up to big block owners.
When discussing spark plugs you have to give the full designation to avoid confunsion. A 45 is not the same as a R45, which is not the same as a R45XLS.
Duke -
Hmmm...
What era? My '55 is pecified in the original AMA paperwork as requiring R43-45 plugs. Surprised me, I don't think the car has had resisor plugs since the Johnson Administration, if then. I used Delco R43's as part of a complete tune-up, which included new points, plugs, wires, coil, and installation of the long-missing RFI condenser on the outside of the distributor. I don't remember the car ever running this well.
Rivets in StockComment
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Re: Hmmm...
I didn't know that resistor plugs were available in '55, but I'll take your word for it. Non-resistor plugs were OE on most engines from the fifties until they came into general use circa 1969 for additional RFI suppression. It could be that "special" resistor plugs were developed for RFI in the early Corvette years. Then better shielding allowed use of conventional non-resistor plugs of the era in later years.
Heat range 3 is way too cold for normal road use. They were just right for a day of hot lapping Kent. And the OE 44s fouled out to quickly in normal driving. I finally learned from my own experience that 45s were the best choice for normal road use including long highway drives.
Most long time owners will agree with this.
DukeComment
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Yeah,
they are on the cold side, but as long as I don't let it idle much it's just fine. I'll be putting in R45's eventually.
The original AMA paperwork was in the "Restoration Packet" I got from Chevy a few years back, and the original spec was in there. Since this was photocopies of the original GM paperwork, I have no reason to suspect an error.Comment
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Re: Hmmm...
Dave:
The plug specified for your '55 was an AC43-5R. It was a cold plug (3.5 heat range- the "-5" is a half heat range). It was indeed a resistor plug which was used only on that year Corvette. As such they are very rare and virtually impossible to find. In all the years I have been collecting plugs I have only had 1 set of these plugs. The 44-5 supplied in the '53 and '54 are also very rare but they do occasionally show up. The 43-5 (non resistor) is available more readily.
JeffComment
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Well,
that explains the confusion I got from the local Chevy parts when I gave them the number. The closest they could come was the R43, which actually works pretty well, and between that and the rest of the RFI system being intact I have the clearest radio reception I've ever had in the car, in addition to it running as well as it ever has. Thanks for the input about the rarity of the plugs. I think I'll stop worrying about it.
53-55 SummaryComment
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Re: Hmmm...
Jeff-----
I show that the 43-5R was first used for 1953 Corvette.In Appreciation of John HinckleyComment
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Re: Hmmm...
Joe:
My source for the 44-5 application comes from Noland Adams book, page 99, right hand column. It lists 44-5 except for continous high sped operation in which case a 43 Commercial is recommended. Page 104 lists an AC 43-5R Commercial. I also have a 1957 AC specification chart which lists 1953-1954 Corvette as a 43-5 (not R). It lists '55 Corvette as 44-5 for regular service and 43-5R for severe service. I guess you can take your pick. I would really appreciate it if you could share your source. It seems there is a mixed message from reputable sources.
JeffComment
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Re: Hmmm...
Jeff-----
This information comes from early editions of the Chevrolet P&A Catalog.In Appreciation of John HinckleyComment
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