When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Hey new to the C3. I just bought a '69 L46 350/350 and wanted to replace the plugs because it's missing. Owners manual said original was R44 original and city was R45, so I thought I bought an AC R45 Gold from ACDelco Store on Amazon. What I received was "17" marked on the plug and B000C9MZJS on the box along with "ACDelco Gold R45 Conventional Spark Plug". It also has a barcode number 1111597056. I haven't pulled the plugs out, but they don't look like Amazon picture. In fact they look pretty long. Please advise, Thanks.
The Delco 17 plug is completely wrong and will not fit your engine. Just go down to your local Autozone / Advance / Oreilly for plugs. There is no sense trying to order this kind of stuff on Amazon.
I did all the local auto parts in addition to Rockauto and they all come up with R43S, which is highway with extended tip. If I put in R45 (city) they say will not fit.
Neither the regular R44 or R45, nor the R44S and R45S are available from AC anymore. AC's current suggested replacement plugs for 69 350's are the 7 (GM part no. 19360570), the R43S (19362248), and the 41-833 (19360569). Unfortunately, nothing I have tells me what the heat range is for the 7 or the 41-833, or if either of them are equivalent to the R44 or 45. I suspect that the AC Delco # 7 may be the correct replacement for the R45, and you got the wrong plugs because somebody mixed up 7's with 17's? But this is just a guess.
R44's and R45's are available as reproductions from most Corvette parts vendors. While they work well in show cars, I don't have any experience with them for a Corvette that's regularly driven.
Be aware that AC Delco still offers an R44XL and R45XL, but don't buy them, the XL's are longer thread plugs used in Chevrolet big blocks, and won't work in your small block.
What's the heat range on the NKG? I'm looking for occasional city driving. What's the p/n and suggested source?
First, you need to make sure that the heads on your engine indeed take the original plug as far as an o-ring crush seal or a tapered seat and match what's there.
Here is a screenshot of the NGK cross-reference PDF. NGK's heat range is opposite of the AC Delco though it's not at all a 1:1 correspondence (Delco gets hotter from 43 to 45 whereas NGK gets colder from 3 to 5). A Delco 45 is roughly equivalent to an NGK 5; a Delco 44 would be ~NGK 6, etc.
Last edited by barkingrats; May 13, 2022 at 07:21 PM.
They will work fine, the R means resistor - which is in there to suppress AM radio interference.
The number on the plug is the heat range, so higher the number, higher the heat range.
So a 45 is one notch hotter than a 44.
A hotter plug is more resistant to fouling than a colder plug.
If you really want a non-resistor plug, you should be able to get Autolite 295s locally.
Hey new to the C3. I just bought a '69 L46 350/350 and wanted to replace the plugs because it's missing. Owners manual said original was R44 original and city was R45, so I thought I bought an AC R45 Gold from ACDelco Store on Amazon. What I received was "17" marked on the plug and B000C9MZJS on the box along with "ACDelco Gold R45 Conventional Spark Plug". It also has a barcode number 1111597056. I haven't pulled the plugs out, but they don't look like Amazon picture. In fact they look pretty long. Please advise, Thanks.
What I ordered:
What I received:
just throwing it out there .. Is it smart to try and find NOS plugs ?? Will they still perform well even though they are 45+ years old ?
Replacement Spark Plugs
Mine has never had a smoother idle since changing...
