Farm Equipment - D-17 spark plugs

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D-17 spark plugs

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Category: Allis Chalmers
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URL: https://www.allischalmers.com/forum/forum_posts.asp?TID=10308
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Topic: D-17 spark plugs

Posted By: David Maddux
Subject: D-17 spark plugs
Date Posted: 30 Mar 2010 at 6:58am

What spark plugs do you guys like for the D-17? Can I use the Autolite 295's or would the 303's be a better plug? Or is the reach on those plugs wrong? Dave.

Replies:

Posted By: Jeff Z. NY
Date Posted: 30 Mar 2010 at 7:03am

The 295 is the crossover match from the Champion J8 which Allis used for heavy duty use.

Allis used the Champion J11 for medium/light duty which crosses to the Autolite 306.

I don't think the Autolite 303 crosses to anything Allis used but I could be wrong.

I know alot of people use the 303 in Allis engines.

The Autolite 303 crosses over to the Champion J5 J6 J6J J7 & J7J

Posted By: DanD
Date Posted: 30 Mar 2010 at 3:27pm

The 295's and 303's are correct for older D17's. Newer D17's had the 3/4" reach plugs and I believe the correct Autolite number is 64. You'll need to verify that however. This would be for the engines that took the AC 45XL plugs instead of the regular 45 plugs. I don't know if there is an easy way to tell the heads apart from the outside or not. Can anyone help?

Posted By: Rick
Date Posted: 30 Mar 2010 at 4:17pm

I believe that the heads that used the 3/8" reach plugs only had 3/8 of an inch of threads in the head and the ones that used the 3/4" reach had 3/4 of an inch of threads in the head. Just pull a plug and measure the threads in the head and that will tell you what reach plug to use. Rick

Posted By: Lester
Date Posted: 30 Mar 2010 at 4:19pm

You can put a little tape measure in the spark plug hole to check the thread depth.

Posted By: Lester
Date Posted: 30 Mar 2010 at 4:37pm

I would not rely on the plugs one takes out of your D-17 s or 45s because I have seen on several occations that they have the wrong length plug put in . When I got my D-17 it had the short plugs in it with deep threads holes. Had to ream out the inner threads, I also got a 45 that had the long thread plugs in it but had it's factory 45head on it. They were very hard to get out of head.

Posted By: mlpankey
Date Posted: 30 Mar 2010 at 5:20pm

If its a gas engine thats run on gas and is in good condition it can benefit from 3/4 reach plugs . if youre running it on tractor fuel or kerosene use the 3/8 reach plugs. You can even run the 3/4 reach plugs on the short head just have to stay away from the projected tip plugs.jmho

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people if they don't already know it you can't tell them. quote yogi berra

Posted By: Steve in NJ
Date Posted: 30 Mar 2010 at 5:51pm

Dave,
To try to answer your question, and try to be accurate, when it came to the D17 in particular, I think AC went by the serial number of the Tractor to determine what it had for the correct application for spark plugs. Autolite lists 5 different numbers of plugs in the Autolite book for the D17 in particular for its different fuel & combustion chamber applications. As the guys mentioned with reach, spark plug number 64 is used when a 3/4" reach cylinder head is used. The 295's are used with a 3/8" reach cylinder head. A D17 using low grade fuel is supposed to use a 306 which is also a 3/8" reach plug. If the D17 runs on LPG, the 303 number plug is used which also is a 3/8" reach plug. There's also an optional plug for the D17, which also is for the D19, a 2540 plug number. Sooo, that tractor took a lot of different spark plugs to say the least! As far as the reach is concerned, the 64 Autolite which is a 3/4" reach plug has 14mm threads as does the 3/8" reach 295, so the reach is not determined by the size of the spark plug hole. The reach is determined by the length of the threaded shank and how shallow or deep the plug decends to the combustion chamber of the cylinder head its designed for. This obviously is super important to know being it determines the performance of how the engine will run. HTH BTW, I carry ALL the different numbers in stock that pertain to AC engines and their applications.
Steve@B&B

Posted By: mlpankey
Date Posted: 30 Mar 2010 at 6:01pm

steve they all had the same style of combustion chamber . it was the piston below the block deck . The head is flat and the under side has a hole drilled verticle then the spark plug hole on the outside is drilled horrizontal intersecting . So the 3/8 plug acts as a antifouler so you can run distilate or kerosene without fouling the plug. The gas engines used the 3/4 reach plugs. filling up the hole the most with a 3/4 reach plug and having the plugs electrode exposed in the verticle hole really helps with spark and compression unless youre engine is in need of rings and in that case the 3/8 reach plugs will not foul as quick . you can search pankeys new project and see the actual underside of a d17 head to give some visual aid of what I am explaining. the autolite 306 cross references to a champion j11c the 303 cross references to a j6c . Champion the lower the number the colder the plug so the all fuel got the hottest shortest plug to keep fouling down .jmho

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people if they don't already know it you can't tell them. quote yogi berra

Posted By: Steve in NJ
Date Posted: 30 Mar 2010 at 6:59pm

Mitch,
Thanks for the history lesson on the D17 cylinder head. I've never seen one off an engine, just going outta memory of what my book references, and the needs of my customer's. I understand different piston dome configurations can make a big difference also. Just like in racing engines. I just pulled an Autolite book off the shelf cause' I was curious of how many plugs for the AC gas engines have a 3/8" reach. Most, according to the book it looks. There's only a small handful that are 3/4". I've been an Autolite dealer for over 30 years, and its been a while since I looked up plug profiles, & construction. I always try to be aware of the heat ranges and the applications they can effect mostly.....
Steve@B&B

Posted By: mlpankey
Date Posted: 30 Mar 2010 at 7:07pm

yes the lp had the highest cr.

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people if they don't already know it you can't tell them. quote yogi berra

Posted By: ChuckLuedtkeSEWI
Date Posted: 30 Mar 2010 at 8:08pm

I have a D17 Series 4 gas, serial number 83495. What plug should I have in it? When I went to NAPA and they looked it up, they gave me an Autolite 404. Is this the wrong plug? Since I changed plugs it has been running like crap, but I haven't isolated exactly what is causing it. Might be points and condensor as I haven't replaced them, or could be junk in the carb, as I have been having problems with that also. I put an inline fuel filter in the fuel line to help eliminate that, but I am probably going to drain and flush the tank also to try and get most of it out.

Posted By: Steve in NJ
Date Posted: 30 Mar 2010 at 8:20pm

Good question Chuckles. I just happen to have one of my books on my desk here when I was looking @ plug reaches. According to my book, the 404 is listed for the D19, as well as the 301 engine and 250 cube engine in the Combine. The 404 is listed as one of those few 3/4" reach plugs......
Steve@B&B

Posted By: ChuckLuedtkeSEWI
Date Posted: 30 Mar 2010 at 8:25pm

Well, the plugs I took out were 3/4 reach plugs so I figured these were right, so will they work?

Posted By: mlpankey
Date Posted: 30 Mar 2010 at 8:42pm

Take one out and see if its hit the back portion of the verticle plug hole . If it has the electrode will be bent reducing the plug gap from what you set it at . If the plug has a gasket and is not a projected tip it shouldnt have hit the backside of the hole. The only plug that i have seen in 3/4 reach that would do this was ac for the bodies of ac plugs are generally longer . autolite is a tic shorter and champion is the shortest of all 3/4 reach plugs. if you really like the projected tip plugs .708 reach plugs but they have a tapper seat. so i use either two gaskets or one index washer and gasket with the 3/4 pretruded tip and a have ran gaps up to .045 without bending the electrode against the back side of the verticle plug hole. the reason is i dont like champion but i do like the easy to figure out heat range better than the autolites .The plug doesnt protrude out of the head so the piston will never kiss the plug electrode . the piston would kiss the valves and the flat side of the head first having to bust the head before striking the plug.

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people if they don't already know it you can't tell them. quote yogi berra

Posted By: David Maddux
Date Posted: 30 Mar 2010 at 8:58pm

Thank you very much Gentlemen, this has been an education for me. Now if I could only retain. Dave.