62 Fuel , R45 or R45XLS ??

[William B.]

Parts store tells me they do not have AC Delco R45 and sold me R45XLS, they have a longer tip, will it cause a problem? Should I look further for the R45's. I am running them in a 62 360hp fuel car.

[Joe L.]

Re: 62 Fuel , R45 or R45XLS ??

Parts store tells me they do not have AC Delco R45 and sold me R45XLS, they have a longer tip, will it cause a problem? Should I look further for the R45's. I am running them in a 62 360hp fuel car.

William-------


I don't know what they were thinking of when they sold you R45XLS instead of an R45. The R45XLS is not only an extended tip spark plug, it's an EXTENDED REACH spark plug. As such, it should not be used in most small blocks, including yours.

The AC R45 remains available, so if you want to use it, that's what you should obtain. If it were me, though, and I was going to use an AC spark plug, I would use a 41-833 for your application. This is a platinum plug and it's a little expensive at about 5 bucks a copy but that's what I'd use.

[William B.]

Re: 62 Fuel , R45 or R45XLS ??

Thank you Joe, I do have a 67 427/400, I can use it for 427"s correct or should I return them?

[John D.]

Re: 62 Fuel , R45 or R45XLS ??

Bill, Call me for info on proper plugs. John

[Joe L.]

Re: 62 Fuel , R45 or R45XLS ??

Thank you Joe, I do have a 67 427/400, I can use it for 427"s correct or should I return them?

William------


I think you could use them but this plug was never cataloged by GM for a big block application. As far as Chevrolet engines go, the 45XLS was primarily a spark plug for 60's and 70's 6 cylinder applications.

[Duke W.]

Re: 62 Fuel , R45 or R45XLS ??

Parts store tells me they do not have AC Delco R45 and sold me R45XLS.

Any parts store that offers AC plugs can order ANY AC plug, and AC heat range "5" or equivalent in another brand is best for normal road use. If you aren't having your car judged, then I prefer Denso W-14U or NGK B4, both of which are non-resistor types, equivalent to the long gone AC 45. These are all 3/8" reach, 14 mm thread with a gasketed seat, which is the proper geometry for small blocks until they went to taper seat type plugs in 1971.

I suggest you find another parts outlet. The guy who sold you 3/4" reach 45 XLS for a small block is an IDIOT!

Duke

[Duke W.]

Re: 62 Fuel , R45 or R45XLS ??

William------


I think you could use them but this plug was never cataloged by GM for a big block application. As far as Chevrolet engines go, the 45XLS was primarily a spark plug for 60's and 70's 6 cylinder applications.

Isn't the AC R43XL the modern equivalent of the OE 43N? But the hotter 45XL is a better choice for normal road driving and won't foul as easily, and the R45XLS is the extended tip version. I think many are running R45XLS in big blocks with good results.

Duke

[Joe L.]

Re: 62 Fuel , R45 or R45XLS ??

Isn't the AC R43XL the modern equivalent of the OE 43N? But the hotter 45XL is a better choice for normal road driving and won't foul as easily, and the R45XLS is the extended tip version. I think many are running R45XLS in big blocks with good results.

Duke

Duke------


The AC R43N, aka GM #5612425, was replaced in October, 1988 by the AC R43XLS, aka GM #5613522. The R43N was once cataloged by GM for many Corvette and other Chevrolet big blocks. Through this supercession the R43XLS is thus also cataloged for most 1965-69 Corvette big blocks.

The only Corvette application that GM ever cataloged the AC 43XL, aka GM #5613104, for was 1967-68 L-88. The AC R43XL, aka GM #5613312 was cataloged for the 1969 L-88/ZL-1.

The AC R44N, aka GM #5612321, was cataloged for some non-Corvette Chevrolet big blocks. The R44N was replaced by the R44XLS, aka GM #5613870, in March, 1988.

Of course, the AC R45XLS or R44XLS could be used in any 1965-69 Corvette or other Chevrolet big block. However, neither was ever cataloged by GM for a Corvette application.