D17 Series 4 spark plug confusion

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   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:

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!

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Rusty Allis Members Profile Send Private Message Find Members Posts Add to Buddy List Bronze Level Access Joined: 16 Jul 2020 Location: Rhode Island Points: 166	Post Options Post Reply Quote Rusty Allis Report Post Thanks(0) Quote Reply Topic: D17 Series 4 spark plug confusion Posted: 4 hours 32 minutes ago 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: 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!

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KJCHRIS Members Profile Send Private Message Find Members Posts Add to Buddy List Orange Level Joined: 21 Dec 2015 Location: WC Iowa Points: 963	Post Options Post Reply Quote KJCHRIS Report Post Thanks(0) Quote Reply Posted: 3 hours 22 minutes ago 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,