Farm Equipment - CA spark plugs

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CA spark plugs

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Category: Allis Chalmers
Forum Name: Farm Equipment
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URL: https://www.allischalmers.com/forum/forum_posts.asp?TID=147972
Printed Date: 22 Jun 2025 at 6:18am
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Topic: CA spark plugs

Posted By: allisbred
Subject: CA spark plugs
Date Posted: 26 Feb 2018 at 8:51pm

I noticed that A295 plugs do not make it to the chamber on the CA. Looks like it needs another 3/8" to make it. What would be a good alternative for medium heat range, non resistor? I'm just taking a guess that the 45 could be the same way?

Replies:

Posted By: Bill Long
Date Posted: 26 Feb 2018 at 9:04pm

Get in touch with SteveNJ. He is our resident expert on electrical.
I can tell you when we sold them new we used AC45 - AC48 depending on the engine condition. They worked fine but that was then. Now I understand the AC plugs are not so good. Lot of people on this site like Auto Light.
Hey, if you are from Hanover PA and you are unaware, there are some great Allis People near you. Fred Wilke for one. He has an outstanding collection of Allis and John Deere.
We just had an Mid Atlantic Allis Chalmers Club meeting there.
Take good care of that CA. Neat tractor.
Good Luck!
Bill Long

Posted By: allisbred
Date Posted: 26 Feb 2018 at 9:27pm

Do you by any chance remember how long the original AC-45's were? I was wondering if plugs ever changed length during any rationalizing of part numbers over time? I also looked at some 3/4" reach as well, they are about 1-2 threads too long ( threads exposed in chamber could cause a problem removing down the road). I have met a few AC guys local, all been great people with a lot of knowledge.

Posted By: Steve in NJ
Date Posted: 26 Feb 2018 at 9:29pm

Why do you think the plug should be deeper into the combustion chamber? Just curious...
Steve@B&B

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39'RC, 43'WC, 48'B, 49'G, 50'WF, 65 Big 10, 67'B-110, 75'716H, 2-620's, & a Motorhead wife

Posted By: steve(ill)
Date Posted: 26 Feb 2018 at 9:32pm

The 295 plugs fit in the B and C heads........ why don't they work in a CA ?

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Like them all, but love the "B"s.

Posted By: ac45dave
Date Posted: 26 Feb 2018 at 9:49pm

ca calls for 295 or 303 "3/8" reach plug in auto light.depends on if you want resistor or non resistor plug.the 295 non resistor is a little hotter plug according to their heat range chart. http://www.autolite.com/Productfinder/Home/ModelList?categoryID=HeavyDuty&vehicleTypeGroupID=AgIndustrial&makeID=ALLISCHALM" rel="nofollow - allis application list
http://www.autolite.com/Productfinder/Home/PartDetail?partNo=295&vehicleAttributes=Make||ALLISCHALM;;Model||BCCAD14G1B;;" rel="nofollow - 295 specs w/link to heat range cgart

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54 wd-45gas ; 56 wd-45d N/F w/fact p/s ; 63 d-17 sIII N/F gas ; 60 D14 N/F ; 67 d-17 sIV N/F gas ; 63D15 sII W/F; 39rc#667 ; 2021 massey 4710 fwa ; gravely 2 wheel tractors

Posted By: PaulB
Date Posted: 27 Feb 2018 at 1:38am

NGK. B6S

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If it was fun to pull in LOW gear, I could have a John Deere.
Real pullers don't have speed limits.
If you can't make it GO... make it SHINY

Posted By: allisbred
Date Posted: 27 Feb 2018 at 6:59am

Steve, I have tried several plugs all were 3/8" reach and worked fine(some better than others). I am finally catching up on my winter projects and a valve job on the CA was in line. I noticed when I pulled the head that the 3/8" reach plug is not visible in the combustion chamber at all. Looking at it, there are no clearance issues with valves or the piston. I am far from an expert on this issue, it just doesn't seem to me that the short plugs would be as efficient as a longer reach plug that makes it to the chamber. I remember putting short plugs in my old jeep because that's all I had in a pinch, they ran like crap and fouled out very quickly. I can't post pictures on here from my phone but would be glad to share some if anybody would like them texted. I know many do not like champion plugs on here but I also tried them with good results. Paul-- thank you, I will try the NGK B6. Thank you all

Posted By: DougS
Date Posted: 27 Feb 2018 at 7:44am

Into the combustion chamber? I usually see the thread just flush with the head when the plug is seated all the way. The electrode may extend a little into the chamber, but the threads should always be flush.

Posted By: allisbred
Date Posted: 27 Feb 2018 at 8:19am

Doug, That is what I expexted to see, threads flush/or near to the inside of the chamber. I do not know the thread depth on B/C's or if there is a veriance in head castings on the CA, just going by what I see here on this head.

Posted By: drobCA
Date Posted: 27 Feb 2018 at 9:57am

hmmm... we're igniting a gas cloud here.

I wonder which would be more efficient - an explosion started in the center or one that starts on one edge and ripples through.

of course we are talking about a fraction of a second, here...

pretty sure I can predict which would be more destructive to the spark plug.

just thinking out loud here - anybody know of any testing in this area?

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3 Ford 8N's I loan to neighbors, but the '52CA, '41B and little B1 I do not.

Posted By: DougS
Date Posted: 27 Feb 2018 at 10:37am

It does not explode, drobCA. It burns. I'd say the difference between an explosion and a rapid burning it that with an explosion the entire amount ignites simultaneously. With a burn the burn starts at the plug and rapidly moves away, igniting the mix as the flame travels.

Posted By: Gary
Date Posted: 27 Feb 2018 at 11:28am

A source of ignition within an vapour that will burn results in an EXPLOSION.

A source of ignition at the surface of a liquid that will burn results in a FIRE, not an explosion.

Gary