D17 Series 4 spark plug confusion
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=208253
Printed Date: 05 Oct 2025 at 3:53am
Software Version: Web Wiz Forums 11.10 - http://www.webwizforums.com
Topic: D17 Series 4 spark plug confusion
Posted By: Rusty Allis
Subject: D17 Series 4 spark plug confusion
Date Posted: 20 Sep 2025 at 9:54pm
|
Well... Long story short is I had to pull a plug and noticed that it had Champions (yuck) in it but the plug was a short reach RJ12C plug. I did find this thread: https://www.allischalmers.com/forum/d17-spark-plugs_topic52040.html" rel="nofollow - D17 Spark Plugs - AllisChalmers Forum But...it seemed to kind of trail off without any definitive answer. The threads are LOT longer, so after some digging it looks like I need the long reach plugs. 1) am I correct thinking it really should have the long reach plugs in it and 2) will NGK BP5ES be ok? and..."while I'm there" can anyone suggest a good set of wires? Delco? Bosch? Thanks!
|
Replies:
Posted By: KJCHRIS
Date Posted: 20 Sep 2025 at 11:04pm
|
we find both short and long reach plugs in them. In theory early D17 will be short 3/8" thread (Autolite 295) and later will be long reach 3/4" thread (Autolite 405). The split is tractor at s/n 75000 / 75001. BUT as D17's are 60+ yrs old you can find some have been pieced back together. Always check the heads thread depth to verify which length plug it should have. ------------- AC 200, CAH, AC185D bareback, AC 180D bareback, D17 III, WF. D17 Blackbar grill, NF. D15 SFW. Case 1175 CAH, Bobcat 543B, |
Posted By: Ed (Ont)
Date Posted: 21 Sep 2025 at 9:00am
Champions will work just fine! Lol.. So will the NGK. Or any plug you can find of the correct heat range. Mine ran all its life on used plugs out of our Camaro's and Chevelles. And ran well and still is 60 years later!! 
|
Posted By: Rusty Allis
Date Posted: 21 Sep 2025 at 6:27pm
|
This does in fact have longer plug threads than the plugs in there now and I'll need to chase the threads. I didn't measure, but they look about 3/4" long. I'll order a set of NGK's and see what happens
|