equivalent spark plugs to AC 46 for FI

[Ian G.]

Can anyone confirm what the equivalent NGK, Denso, Champion and/or Autolightspark plugs would be to the AC 46? I read on another thread that NGK B4 would be equivalent to a AC 45 (maybe also AC 46?). NGK also makes a B2, but unsure if that would be too hot or even fit...

ACDelco makes an R46SZ plug with a .060 gap. Could this be safely bent down to .035 to work for my 1959 FI?

All in all, I'd like to know the closest plug to the old AC 46 to use for my 1959 FI car...

Thanks very much!

[Dennis C.]

Equivalent spark plugs to AC 46 for FI

What is it you have against the AC45 ?

[Joe L.]

Re: equivalent spark plugs to AC 46 for FI

Can anyone confirm what the equivalent NGK, Denso, Champion and/or Autolightspark plugs would be to the AC 46? I read on another thread that NGK B4 would be equivalent to a AC 45 (maybe also AC 46?). NGK also makes a B2, but unsure if that would be too hot or even fit...

ACDelco makes an R46SZ plug with a .060 gap. Could this be safely bent down to .035 to work for my 1959 FI?

All in all, I'd like to know the closest plug to the old AC 46 to use for my 1959 FI car...

Thanks very much!

Ian-----


Use Champion J11C. There may be other brand equivalents but if it were me, I'd use the Champion J11C.

[John D.]

Re: equivalent spark plugs to AC 46 for FI

Ian, I hear this question a lot over the phone. I would say if you bought one set of NOS AC 45 or 46 for your FI car that set would last forever. Now if you foul those out then you have FI problems for sure. Possibly you could use the AC 45S or AC 46S as long as they don't hit your pistons. Gap is .035. Completely forget the R46SZ.
The AC plugs are on ebay all the time. Once in a while you can snag them cheap if the last of the big time spenders don't get in on the bidding. The Champions are for Fords. John D.

[Michael H.]

Re: equivalent spark plugs to AC 46 for FI

The Champions are for Fords. John D.

What would you say if I told you that AC plugs were made by Champion? Wyadda think the C in AC stands for?

[John D.]

Re: equivalent spark plugs to AC 46 for FI

Mikey, AC originally stood for Albert Champion of France don't you know. The founder of the AC spark plug. His baby. Somewhere in the files I once wrote a paper an eon ago on AC spark plugs.
But still Champion plugs in a Corvette are not my forte. Especially a rare real deal fuel car.
Don't you ever sleep? Me either. JD

[Michael H.]

Re: equivalent spark plugs to AC 46 for FI

Mikey, AC originally stood for Albert Champion of France don't you know. The founder of the AC spark plug. His baby. Somewhere in the files I once wrote a paper an eon ago on AC spark plugs.

Yup, that same Albert Champion was the founder of the Champion spark plug company. He was eventually voted out, or bought out (can't remember which) and the Champion spark plug continued without him.
He then formed a new company, the Albert Champion company, or AC.

If ya get the heat range correct, there really isn't much difference in performance among the major brands of spark plugs. There's nothing mysterious about spark plugs.

I would never use AC-46's in a C2 car if it's driven on the street. If ya can't keep 44's or 45's operating properly, there's something wrong with the engine/fuel system.

[John D.]

Re: equivalent spark plugs to AC 46 for FI

Michael, I agree with you. It was once said to me by an old pal that too much emphasizes was put on the heat range of the spark plug and not enough about the ignition coil. The fuel cars had a nice hot coil with lots of juice. The 57 to 62 107's were a very heavy duty coil borrowed from the off the road equipment line in the olden days. Old school buses and big trucks, etc used this coil. I learned that from old Dale Pearman. Anyhow if the gang would use a nice original 107, 087, 091, etc. FI coil then the original 44's would work just fine. But for the trailer queens and cars that sit and collect dust and varnish in the gas tank the 46 plugs are the way to go. I used to drive a 63 all year long except in the snow and all I ever ran was AC 44. But my traier queen has AC 46. Now I have to change the coil on it from 087 to 091 as CC, you, and his crew of writers for the new manual gots it right this time. That was the first thing I looked at when I got the 5th. Yeah I picked up a nice NOS 091 on ebay which set me back a bundle but its worth it. Course I am off the subject as usual. Where's our pal??? JD

[Robert D.]

Re: equivalent spark plugs to AC 46 for FI

I may have to check, but I believe Autolite 295 is a direct replacement for the AC46.
Bob

[Duke W.]

Re: equivalent spark plugs to AC 46 for FI

Here is the actual answer to your question.

The NGK B4 and Denso W14-U are approximately equivalent in heat range to the AC 45 according to the NGK and Denso cross reference charts. These two plugs have been run successfully by many Corvette owners.

As far as the 46 is concerned NGK sticks with the B4 but they do offer a B2, which is hotter than the B4, and Denso says W9-U, but I would not recommed either unless you do mostly short trips in town with no freeway/highway driving.

All these plugs are non-resistor, non extended tip.

Do not attempt to reduce the gap on a "wide gap" plug.

You should also be able to cross reference plugs at most plug manufacturers Web site.

Duke

[Michael H.]

Re: equivalent spark plugs to AC 46 for FI

Here is the actual answer to your question.

The NGK B4 and Denso W14-U are approximately equivalent in heat range to the AC 45 according to the NGK and Denso cross reference charts.

Yup, key word here being APPROXIMATE equivalent. Just because the cross reference chart shows one of their plugs as being the replacement for a specific heat range for some other brand doesn't mean it's the exact SAME heat range. One range may be at the bottom of the temp scale for that range while the other may be at the top of the scale.
You may find that a slight adjustment of one heat range higher or lower is required after a few test runs.

Agree 100% on the use of plugs that are too hot, such as AC-46's for C2's. (ok for early lower C/R C1's I suppose) If the engine and fuel system are operating properly, (no oil burning and correct A/F ratio) there's no need for 46's, especially with todays no lead fuel.
There's a real good reason why GM didn't just recommend hot heat range for all engines under all driving conditions. There are a few definite negatives involved in using incorrect heat range spark plugs.

[Ian G.]

equivalent spark plugs to AC 46 for FI

I saw a lot of this info on previous threads, but I wanted to be sure there wasn't something closer to AC 46. A set of no-stripe AC 46 went for $112 on ebay a few days back. I'll stick to the ones recommended for the AC 45. Do spark plugs get judged? I couldn't find them in the yellow judging guide...

So...equivalent to AC 45:

Champion J11C
NGK B4
Denso W14-U
Autolight 295

thanks for the replies everyone!

[John D.]

Re: equivalent spark plugs to AC 46 for FI

Ian, Do spark plugs get judged you ask. On my 63 the judges did look to see if the car had AC plugs. THat's all. Didn't look any further. Judges don't follow a manual page by page. Judge use it for an occasional reference manual. $112.00 is a waste. I don't blame you for not wanting them. Check with NAPA Ian. They may have some R45's left for peanuts. Call Car Quest. You might be surprised. John D.

[Ken A.]

Re: equivalent spark plugs to AC 46 for FI

Yup, that same Albert Champion was the founder of the Champion spark plug company. He was eventually voted out, or bought out (can't remember which) and the Champion spark plug continued without him.
He then formed a new company, the Albert Champion company, or AC.

If ya get the heat range correct, there really isn't much difference in performance among the major brands of spark plugs. There's nothing mysterious about spark plugs.

I would never use AC-46's in a C2 car if it's driven on the street. If ya can't keep 44's or 45's operating properly, there's something wrong with the engine/fuel system.

I believe you have that reversed. Albert first started AC spark plugs which was later aquired by "Boss" Kettering of the newly formed General Motors. Albert then later opened the Champion Spark Plug Co.

[Michael H.]

Re: equivalent spark plugs to AC 46 for FI

I believe you have that reversed. Albert first started AC spark plugs which was later aquired by "Boss" Kettering of the newly formed General Motors. Albert then later opened the Champion Spark Plug Co.

Yer probably right Ken. I knew it was one way or the other but not sure of the details.