63 340hp, best spark plug?

[William B.]

Working on a 63 340hp, need to clean or replace plugs, using R45, no judging driver car, what is the best plug for around town driving?

[Thomas B.]

Re: 63 340hp, best spark plug?

My 63 - 340hp car had AC Delco R45 installed when I bought it last year. The best reasonably priced option I could find is AC Delco R43S. Runs great with those.

[Chuck G.]

Re: 63 340hp, best spark plug?

I've been using NGK B4's for years.

[Duke W.]

Re: 63 340hp, best spark plug?

The original plugs were non-resistor type . If you're not involved in judging I recommend the non resistor NGK B4 or Denso W14-U. Those are both equivalent heat range to the long out-of-production AC 45.

And the above applies to ALL pre-'69 small blocks with gasket seat heads. The required heat range of a plug has NOTHING to do with its peak horsepower rating. It has everything do do with the average load the engine sees. In normal road driving Corvette engines see low average load, including freeway driving, so you need a "hot" plug to keep the plug insulator hot enough to burn off deposits.

Back in the sixties when I hot lapped my 340 HP SWC at Kent I installed AC 43 plugs because the engine would be operating at very high average load and needed a "cold" plug to avoid overheating the plugs and getting the engine into preignition and detonation.

Duke

[Leif A.]

Re: 63 340hp, best spark plug?

Denso 14-U...terrific plug that I've used for the past nine years. BTW, the R43S is a pretty cold plug. Unless you're going to be doing a lot of highway driving, It would not be my recommendation...too cold a plug for normal driving.

[John D.]

Re: 63 340hp, best spark plug?

AC Delco R45S (S=extended tip) on my 67 L79 for many years. I had 43's but they were more prone to fouling.

[Duke W.]

Re: 63 340hp, best spark plug?

Most of us who have driven these cars since the sixties learned that even the OE AC 44 was too cold and would quickly foul out in around town driving, and the answer was the AC 45, one heat range hotter.

Even though the 44 and 44S were OE on millions of small blocks, GM discontinued the 44 along with all non-resistor plugs, and now the parts books list the 43. There were many other ill-advised parts consolidations over the years including vacuum advance controls and accessory drive belts.

Also keep in mind that GM has not manufactured spark plugs for decades. AC Delco is just a marketing outfit that contacts out for parts. I have no idea who or where "AC plugs" are now manufactured.

Duke

[William B.]

Re: 63 340hp, best spark plug?

Thank you everyone , will purchase some NGKB4's

[Bill M.]

[Thomas B.]

Re: 63 340hp, best spark plug?

Where do you buy them?

[William B.]

Re: 63 340hp, best spark plug?

Is there more to the spark plug number NGK B4, local flaps can not find them?

[Chuck G.]

Re: 63 340hp, best spark plug?

Here are 2 links, Bill. I use the copper core ones. They also have a nickel core model.

https://www.oreillyauto.com/detail/c/copper-core/ignition---tune-up/spark-plugs/b14eb31b13d7/ngk-copper-core-plug-number-b-4-spark-plug/ngk1/3210

https://shop.advanceautoparts.com/p/ngk-standard-spark-plug-b4-3210/19650314-P

[Thomas B.]

Re: 63 340hp, best spark plug?

I’m not disputing the use of the NGK B4 plug since it looks like they do the job but a 63 corvette is not listed as correct fitment at Advance, O’Reilly or Summit Racing. The R43S is listed for 63 corvette. It’s an extended tip plug if that makes a difference I don’t know. I haven’t had any fouling issues. I’ve read on a couple of forums that the extended tip prevents fouling at low rpm but some of you have had that problem.
NGK has other plug options for 63 corvette on their website.
Finally, Ive learned from this that AC is not made in the US. Says China right on the box. However NGK is made in Japan. Not campaigning for one over the other just sharing the info I’m finding.

[Duke W.]

Re: 63 340hp, best spark plug?

Go back and read posts #4 and #7, carefully!

Duke

[Mel S.]

Re: 63 340hp, best spark plug?

Call me "old fashion", which I am (76), but in 1964 I had a 327/340 in my 56 Chevy. I did a lot of racing. I used Auto lite A-42.
Just my input
Mel