Farm Equipment - Spark plugs

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Spark plugs

Printed From: Unofficial Allis
Category: Allis Chalmers
Forum Name: Farm Equipment
Forum Description: everything about Allis-Chalmers farm equipment
URL: https://www.allischalmers.com/forum/forum_posts.asp?TID=199496
Printed Date: 24 Sep 2024 at 3:26am
Software Version: Web Wiz Forums 11.10 - http://www.webwizforums.com

Topic: Spark plugs

Posted By: Smiling John
Subject: Spark plugs
Date Posted: 26 Jan 2024 at 12:48pm

I have a WD45 with a D17 head, Series 1 or 2. What spark plugs should I use? Thanks.

Replies:

Posted By: Brian G. NY
Date Posted: 26 Jan 2024 at 2:12pm

From the manual:

The early D-17 engines use a 3/8" reach plug eg: A-C 45, Autolite A-7 or Champion J-8.

Begining with "engine" Ser. #17-17293, a 3/4" reach plug was used eg: A-C 45XL, Autolite AG-5 or Champion N-8.

I don't know if those plug numbers are still available but can probably be cross-referenced.

You may not know the engine number from which your head came.....in that case, I guess the depth could easily be measured. Or..... someone here may know the head casting numbers.

Posted By: DrAllis
Date Posted: 26 Jan 2024 at 2:31pm

3/8" plug heads have smooth cylinder head castings front and back. 3/4" plug heads have a core plug in each end of the head. Delco R45 plugs for 3/8" reach and R45 XL for 3/4" reach plugs. If the plugs currently used are 3/4" reach and they aren't SMASHED they are correct length.

Posted By: Lars(wi)
Date Posted: 26 Jan 2024 at 2:39pm

Take a plug out, and see what you got.

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I tried to follow the science, but it was not there. I then followed the money, and that’s where I found the science.

Posted By: Smiling John
Date Posted: 28 Jan 2024 at 3:09pm

Thanks. The plugs in it were in it are RN11YC4. Have no idea where I got them or why. Don't know if they have some unique feature.

Posted By: Ed (Ont)
Date Posted: 28 Jan 2024 at 4:40pm

If they are in reasonably good shape just clean and reuse. Don't need anything fancy in those motors. Set the gap as well.