'63 L84 spark plug

[Michael J.]

Which AC plug did a '63 L84 engine leave St. Louis with? Thanks.

[Rick A.]

Re: '63 L84 spark plug

Michael - believe would have left with AC-44's

[John D.]

Re: '63 L84 spark plug

Michael, The 44 plugs are too cold today. Use AC 45 or 46. John

[Rick A.]

Re: '63 L84 spark plug

ChePhart agree they are too cold today, but the question was what did the vehicle leave St Louis with - AC-44's like I stated

[Michael J.]

Re: '63 L84 spark plug

I have 46s for driving, but that takes a hit on judging points, so needed the TFP plug, and I assume the green stripe version too. Thanks Rick.

[Duke W.]

Re: '63 L84 spark plug

Essentially all small blocks from the late fifties to '68 had the AC 44 from the plant, replaced by R44s for '69. I believe there might be some cosmetic differences over the years, and the various year JGs should have the details. The 44s kept fouling in my 340 HP SWC, so I finally installed 45s, which mostly solved that problem, and I installed 43s when I went out to Kent for a day of hot-lapping, and they were just right for that type of service.

[Michael J.]

Re: '63 L84 spark plug

Thanks Duke. That brings up a question for you, I have a couple of sets of R43-XLS AC plugs, are those way too cold for normal driving?

[Duke W.]

Re: '63 L84 spark plug

Those are big block plugs (resistor type) that are modern substitutes for the 43N that was standard in early big blocks, but they're too cold. R45XLS would be a better choice. For all OE engines AC heat range 5 or equivalent in another brand are the best choice for the light duty use that most vintage Corvettes see today.

[Michael J.]

Re: '63 L84 spark plug

Thanks Duke, that's what I was afraid of, more stuff for the trash........

[Rick A.]

Re: '63 L84 spark plug

agree with Duke any AC 45 plugs or another brand that is heat range equivalent will work just fine - something like a Denso W14U or NGK XR4 or maybe even Bosch

[Duke W.]

Re: '63 L84 spark plug

In the NGK line, the B4 is a better choice because it's a non-resistor type, and I think the Denso W14-U is the best choice if you don't need to run AC plugs for judging because it has their "U-groove" ground electrode, which offers more sharp edges for spark propagation. These are small block plugs. Off the top of my head I don't have the number for big plugs, but they would also be heat range 14 and 4 respectively.