Possible Replacement Spark Plugs

[Stuart F.]

Have chance to pick up a set of NGK B6S spark plugs from a friend. I have a 63 L-76 in which I have always used AC-44 heat range plugs, be it AC or Champion. As best I can tell, by my cross reference chart, the B6 is the equivalent heat range. My question is does the "S" designate power tip like it did with the Ac's, and can/should I use them on my next plug change?

Stu Fox

[Duke W.]

Re: Possible Replacement Spark Plugs

B6S is equivalent to AC 44. The "S" indicates a "standard 2.5 mm center electrode". I recommend the B4 or Denso W14-U (both equivalent to the AC 45) for your application.

Duke

[Stuart F.]

Re: Possible Replacement Spark Plugs

OK Duke, Thanks. Exactly what I wanted to know.

Stu Fox

[Frank D.]

Re: Possible Replacement Spark Plugs

I've found the NGK XR-4 plugs are excellent in both my '61 and '63 original motors... The '44s are too cold in my cars...

[Stuart F.]

Re: Possible Replacement Spark Plugs

Frank;

My cross reference list is from many years ago, but I thought it contained all the pertinent information that I needed to deal with my 63 L-76. I do not see a listing on it for NGK XR-4 spark plugs. Could you fill me in as to what they compare to in AC or Champion equivalents?

Thanks for posting.

Stu Fox

[Frank D.]

Re: Possible Replacement Spark Plugs

Frank;

My cross reference list is from many years ago, but I thought it contained all the pertinent information that I needed to deal with my 63 L-76. I do not see a listing on it for NGK XR-4 spark plugs. Could you fill me in as to what they compare to in AC or Champion equivalents?

Thanks for posting.

Stu Fox

I stumbled across the alternative plug about 5 years ago when trying to find something a little hotter than the AC-45S for my rich-burning dual quad '61. The NGK-XR4 is cheap, available anywhere and burns beautifully in both my C1 and C2. One of the few times I've ever changed to a new plug brand and noticed smoother idling and better burning characteristics -- see attached. Although its a cross-over for the whole range of AC plugs for our small block vettes it seems to burn just a tad hotter than the 45S (don't even try to find original 46S plugs)...

[Stuart F.]

Re: Possible Replacement Spark Plugs

Frank;

Thanks for the infirmation.

It seems different engines, even if the same configuration, can and will run better with certain spark plugs vs. another. In your situation, if I read your signature data correctly, you have two engines with 9.5 to 1 compression ratio (if stock). The 270 hp's I recall were all that ratio, as were the 327 base 250 hp engines. I imagine you therefore are able to use both power tip and resistor type plugs. I believe that with mine, having advertised 11.25 to 1 (said to be closer to 10.5 to 1) compression, I have the domed top Pistons and to use power tips with it they have to be indexed upon installation. In my experience as well, since I have adopted the use of electronic ignition many years ago, my engine runs sweet all around with the 44 heat range plugs. I have yet to have a need to consider going up to the 45 heat range. I have had a number of hot soak starts, even some with percolation caused flooding, but after re-start a little rough running, my 10 year old AC44's cleared right up and were followed by highway on ramp runs back up to redline without missing a beat. What more could I ask for?

I too was looking for an alternative plug that was/is readily available at a reasonable cost. I'm currently in the midst of rebuilding my original tach drive distributor so figured now is as good a time as any to change plugs before our winter meet next month. We have to travel a few more miles down I-4 this year to get there.

Stu Fox

[Duke W.]

Re: Possible Replacement Spark Plugs

The XR4 is a resistor type, extended tip plug equivalent to the AC R45S.

Duke

[Stuart F.]

Re: Possible Replacement Spark Plugs

Duke;

Thanks. The "X" is what threw me. My cross-reference list is very old. The heading shows it as being from "The Holley 1976 Performance Parts Catalog"! Wow! Guess I better get with the times. Just shows you how often I change plugs, I guess.

Stu Fox

[Frank D.]

Re: Possible Replacement Spark Plugs

All quite true (I think the 250hp is actually 10.5:1 strangely enough) but I'd have to get out my manuals to confirm.
I run Pertronix III in both cars. You should use whatever works in your particular situation of course.

Lars rebuilt my tach drive distributor for the '63 a month or so ago for a VERY reasonable price and its like new and needed custom machining...he recurved it too as it was all messed up...

Yes Lakeland is more of a hike for me too...about an hour south of Orlando....maybe I'll see you there...

[John D.]

Re: Possible Replacement Spark Plugs

The XR4 is a resistor type, extended tip plug equivalent to the AC R45S.

Duke

I have the ACR45S in my 67 350hp. The R44's were too cold and prone to fouling in my opinion..

[Stuart F.]

Re: Possible Replacement Spark Plugs

Frank;

I don't know why I didn't recognize your name and information, but you and I are neighbors. I live just east of the airport just a couple blocks from spitting on the 417.

I have been using the Pertronics II for many years, and Prestolite for many years before that. I only changed away from the latter due to not liking the external control unit and they had chicken connectors made of rolled brass that tended to break internally without warning.

I opted to rebuild my own distributor as I had it out to redo my plug brackets. It's not that I'm too cheap to go to an expert, but I got that old back yard "can do" spirit. It's like a curse that causes me all kinds of grief and expense. In the midst of a project, I tend to replace or buy a lot of new tools to do the job better. I spent nearly $150.00 yesterday on a couple of drills and taps. It seems that old tach drive housing gets hardened over the years from a lot of heat cycles, or something. I just couldn't even scratch it with my old Chinese and even older Japanese drills! Had to hunt all over for a good 1/4 - 28 tap too (lots of 1/4 - 20's out there though). Then too, as I have posted before, I lost a number of important parts by using Corvette shops so I am paranoid I guess.

Stu fox

[Stuart F.]

Re: Possible Replacement Spark Plugs

John;

Maybe your problem with the R44's was the "R". If you already have resistor plug wires it seems to me the use of a resistor plugs is redundant, except for concerns for your radio reception perhaps. Straight 44's have served me well over the years - simpler the better I guess.

Stu Fox

[Frank D.]

Re: Possible Replacement Spark Plugs

Frank;

I don't know why I didn't recognize your name and information, but you and I are neighbors. I live just east of the airport just a couple blocks from spitting on the 417.

I have been using the Pertronics II for many years, and Prestolite for many years before that. I only changed away from the latter due to not liking the external control unit and they had chicken connectors made of rolled brass that tended to break internally without warning.

I opted to rebuild my own distributor as I had it out to redo my plug brackets. It's not that I'm too cheap to go to an expert, but I got that old back yard "can do" spirit. It's like a curse that causes me all kinds of grief and expense. In the midst of a project, I tend to replace or buy a lot of new tools to do the job better. I spent nearly $150.00 yesterday on a couple of drills and taps. It seems that old tach drive housing gets hardened over the years from a lot of heat cycles, or something. I just couldn't even scratch it with my old Chinese and even older Japanese drills! Had to hunt all over for a good 1/4 - 28 tap too (lots of 1/4 - 20's out there though). Then too, as I have posted before, I lost a number of important parts by using Corvette shops so I am paranoid I guess.

Stu fox

I've just reinstated my NCRS membership (circa 2007) so I'm sorta new on here. I live over in West Orange in Oakland - a small town between Winter Garden and Clermont. Good on you for working on the distributor. I just didn't know anything about them being a C1 driver (tach drive off the generator) so I sent it off to Lars....IIRC it was $150 and the 63 runs like new now... He found major problems and the cross shaft housing was close to failure. All fixed now.

Nothing against points but the Pertronix III rev limiter feature won me over....had an ugly situation in 2008 with the '61 linkage caught in the ignition shielding and it buried the tach. Only quick action saved the motor. Don't want that to EVER happen again!

[Frederick N.]

Re: Possible Replacement Spark Plugs

Duke, I would like to use your reply to Stu Fox on the Possible Replacement Spark Plugs in my Dec 24th Indiana Chapter Newsletter.

Fred Neitzel (9201)