Spark plugs for a 1x4 1956

[Alexander C.]

I'm going after a set for judging and also a set for driving.

AC-43s I believe are correct for judging right? I see different ones on eBay though, Acniter, Fire Ring, etc. Which are correct? I think the Fire Ring are but I want to be sure before I buy a set.

I am considering AC-46s for everyday driving. I mosty do country & mountain road driving & I have a 180 degree thermostat. Rebuilt engine and summer temps here reach 115 in the summer. Should I maybe use AC-44s instead?

Thanks!

[John S.]

Re: Spark plugs for a 1x4 1956

1955 used ac43-5r. from what i read most 56 and 57 had ac44 plugs until march of 1957 where they went to ac46-5 plugs. the ac46-5 plugs did not fit on boots correctlly so later in production they went to ac46. as for driving ac-46 city, ac44 town and country driving.

[Bruce B.]

Re: Spark plugs for a 1x4 1956

I like to use AC45 or AC 46 in my 340 HP 62 Corvette.
They are hot plugs and since my engine runs on the rich side and with either of these plug types I never have fouled a plug.
I would think a AC44 or AC45 would be good in your setup.

[Alexander C.]

Re: Spark plugs for a 1x4 1956

Perfect, so then I can run AC-44 for my country driving and still be correct all the time. I know my 1x4 won't be nearly as rich as a 2x4 setup.

Any idea exactly how I can know which AC-44 plug sets are eBay for *correct* though since there are different series and changes over the years?

Thanks!

[John S.]

Re: Spark plugs for a 1x4 1956

Perfect, so then I can run AC-44 for my country driving and still be correct all the time. I know my 1x4 won't be nearly as rich as a 2x4 setup.

Any idea exactly how I can know which AC-44 plug sets are eBay for *correct* though since there are different series and changes over the years?

Thanks!

email jeffstuarts@aol.com or call 248-6455953. he is a ncrs member and is in the driveline. he deals with original sparkplugs and headlights.

[Jeffrey S.]

Re: Spark plugs for a 1x4 1956

The plug that came in the engine from Flint was an AC44 "Hot Tip" with 4 thin ribs with NO green on them. The "Fire Ring" was introduced in 1960 and the green rings were added. As John said 1957 started out with AC44's but switched for a short time midproduction to AC46-5's which had smooth porcelain which was problematic and then to AC46's. This also had thin ribs, no green.
Jeff

[Alexander C.]

Re: Spark plugs for a 1x4 1956

Thanks for the info!

Also, as far as my daily driving plug, could I just run a brand new set of AC 44 plugs, if AC Delco even makes them?

[John H.]

Re: Spark plugs for a 1x4 1956

Thanks for the info!

Also, as far as my daily driving plug, could I just run a brand new set of AC 44 plugs, if AC Delco even makes them?

Alex -

I had occasional fouling issues with 44's in both of my '57 2x4's (270's), and switched to R45S plugs - never had a fouling issue again; that's what I run in my '67 300hp and in my '69 Z/28. Any auto parts store has them for less than two bucks apiece.