9n followup on rotor to dist.gap issue

pulled the dist.cap off.All four contact points inside the cap were being hit by the rotor cap.When I checked the rotor I found that the contact tip was 45 degrees from its correct straight ahead position !! A piece of the bakelite rotor next to the contact tip was broken off.I am amazed the little tractor would run at all.I examined my old rotor and cap and could find no interference issues at all, so I assume there is not a distr. shaft wobble issue.The cap seems fine as far as cracking, etc.I am going to clean the contacts on old distr. and rotor , put it back on the tractor and see what happens. All the new parts were Napa Echlin.I have the box for the cap and it shows FA350. I don't have the rotor box.You guys seem to swear by the Napa parts so I guess one of these parts got in the wrong box , or they had a bad production run .
 
I've never been a big fan of NAPA parts myself. my guess is the new rotor is not sliding completely onto the shaft. Might want to compare how far the old rotor slides on compared to the new rotor.
 
The rotor was pushed down all the way and seated properly on the shaft. It's a pretty simple thing.just push it down on the shaft until it bottoms out. Where the rotor was hitting the distrib.,was in the proper place along the distrib contact ,just no clearance.
 
It's not NAPA necessarily, it's just the brands they sell. Standard Ignition/Blue Streak/Echlin are definitely the best. Don't recall your model but front mount points are CS-35 for the Echlin brand. Now, some of today's aftermarket rotors I've found do not have the proper broached hole depth and thus the rotor does not seat all the way down, as was mentioned by Bruce. Never have seen any 'spec' for rotor gap -how would you know where and how to measure it? What we need is a spec for rotor tang height measured from distributor base contact face.

[i:654c4848f0][b:654c4848f0]<font size="4">Tim *PloughNman* Daley(MI)</font>[/b:654c4848f0][/i:654c4848f0]<table width="100" border="1" cellpadding="0" cellspacing="0" bordercolor="#000000"><tr><td height="25" colspan="2" bgcolor="#CC0000">
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David, I have a Ford Jubilee, NAA model. 5-10 years ago I experienced what I think was a 'run' of bad rotors. My tune up efforts of what had been a running tractor resulted in the same situation you've experienced. After chasing my tail and wasting way too much time, I discovered my newly replaced rotor cracked with contact tang sitting at a 45* angle. First replacement ran for a couple of minutes; 2nd replacement fired but never ran; third replacement fired up and ran until I was a couple of blocks from my shop and tools. Each time the new rotor was cracked. These new parts were not from the same vendor. I bought from NAPA, TSC, and a local farm store. While I might have failed to properly seat the rotor during installation one time and caused this part failure, I don't think I made the same mistake three times in a row. I cured the problem by reinstalling the original rotor retrieved from my trash barrel.

At the time, there was discussion on this board and other information sites about similar problems. The conclusion by folks far more experienced than I was that many vendors must have sourced rotors from The Land of Almost Right and the same production run, slapping their own label on to the packaging.

I hope we're not in for another bad run of rotors! I'm about due for another tune up. :)
 
The location vertically on the cap contact where the rotor was hitting was half way down which is the same as the old cap I removed. To me that indicates the rotor was located correctly vertically on the shaft. The parts I used had been in my spare parts drawer for years , so if there was a bad production run , no telling when it happened. If a whole run was bad I would think I would have heard about it on this forum.
 
This is not a new issue. This comes up every year or so. I very seldom change a rotor. I just clean up the old one and use it again.
 
I like your idea.I cleaned up my old rotor with 320 grit sandpaper and it looks brand new.I will be going back in the tractor since I know it fits OK with my old cap which I also cleaned up.
 
(quoted from post at 07:38:00 01/30/17) It's not NAPA necessarily, it's just the brands they sell. Standard Ignition/Blue Streak/Echlin are definitely the best. Don't recall your model but front mount points are CS-35 for the Echlin brand. Now, some of today's aftermarket rotors I've found do not have the proper broached hole depth and thus the rotor does not seat all the way down, as was mentioned by Bruce. Never have seen any 'spec' for rotor gap -how would you know where and how to measure it? What we need is a spec for rotor tang height measured from distributor base contact face.

[i:1f7bbf2c20][b:1f7bbf2c20]&lt;font size="4"&gt;Tim *PloughNman* Daley(MI)&lt;/font&gt;[/b:1f7bbf2c20][/i:1f7bbf2c20]&lt;table width="100" border="1" cellpadding="0" cellspacing="0" bordercolor="#000000"&gt;&lt;tr&gt;&lt;td height="25" colspan="2" bgcolor="#CC0000"&gt;&lt;center&gt;&lt;font color="#FFFFFF" size="3"&gt;*9N653I* &amp; *8NI55I3*&lt;/font&gt;&lt;/center&gt;&lt;/td&gt;&lt;/tr&gt;&lt;tr&gt;&lt;td&gt;&lt;img src=http://img.photobucket.com/albums/a379/ploughNman/TPD9N100.jpg&gt;&lt;/td&gt;&lt;td&gt;&lt;img src=http://img.photobucket.com/albums/a379/ploughNman/TPD8N100.jpg&gt;&lt;/td&gt;&lt;/tr&gt;&lt;/table&gt;
1.18 inch on my side mount. Too lazy to measure front mount today. :(
 
OK, I got over my laziness this afternoon and Tim Daley was interested in front mount tower post height relative to cap face of distributor base (actually rotor tip). That range of machined post is 0.050 to 0.070. Rotor tip not much higher than 0.070 and it will hit. Lower than 0.050 and the spark will have a longer gap to jump.
 

am i right to assume that that spark gap is additive with the gap at the plug, and that an oversized gap in the cap could be the final straw that breaks the back of a system with a weak spark but still runs?
 

ps: forgot to add don't worry about the laziness thing. i will cover for u today, and be lazy enough for the both of us :)
 
And following up on your follow up.....

The spec of .006 to .008 for the rotor gap in the Ford literature is a mistake.

JMOR measured a front cap and using the spec for the rotor, the gap would be .015 to .018.

Remember, the gap on a Model A engine, older by 8 years, is given by Ford at .025.
75 Tips
 
(quoted from post at 17:57:16 01/30/17)
am i right to assume that that spark gap is additive with the gap at the plug, and that an oversized gap in the cap could be the final straw that breaks the back of a system with a weak spark but still runs?
ort of.........because at plug under pressure it takes a higher voltage to arc than in distributor at atmospheric pressure. That rotor to cap gap will likely arc over at less than 10% of ignition voltage, but yes, under some cases, it might be the straw.
 
tractor now running perfect with new points, old cap and rotor.By the way I used the jig sold by Windy Ridge Farm to set the timing.great tool. locks everything correctly in place so an ohm meter can be easily used to determine when the points open.
 

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