Wayne64 wrote:Charles, since I no doubt have a non re-designed unit, and from what you have mentioned I have two questions. I'll bookmark this thread for when I have the time to do it up right. First question, after installing the module should I use molding clay to check the clearance between the inner cap to the module? Also while we are talking clearances what would you look for as a clearance between the bushings and the new shaft after reaming? And thank you for all your valuable input.
You can easily tell if the interference issue is in play by simply placing the top cover on the housing and pressing down lightly by hand. If you notice the top cover does not easily go down against the o-ring seal, you have the issue. A little trimming on the inner cap screw boss will relieve it.
We ream all our shaft bushings to .501" This must be precisely done in order to prevent an out of alignment situation between the 2 bushings. If the shaft is worn smaller than, .500" od, it should be replaced.
Damn Charles I had no idea the content this would generate... You are obviously taking these distributors to a new level and coming from a guy who does vintage Pontiacs and not much else it is very impressive to see the two different camps positions on a points or pointless system!
Wayne64 wrote:Charles, since I no doubt have a non re-designed unit, and from what you have mentioned I have two questions. I'll bookmark this thread for when I have the time to do it up right. First question, after installing the module should I use molding clay to check the clearance between the inner cap to the module? Also while we are talking clearances what would you look for as a clearance between the bushings and the new shaft after reaming? And thank you for all your valuable input.
You can easily tell if the interference issue is in play by simply placing the top cover on the housing and pressing down lightly by hand. If you notice the top cover does not easily go down against the o-ring seal, you have the issue. A little trimming on the inner cap screw boss will relieve it.
We ream all our shaft bushings to .501" This must be precisely done in order to prevent an out of alignment situation between the 2 bushings. If the shaft is worn smaller than, .500" od, it should be replaced.
Thank you Charles, I have a new shaft for the distributor and the bushings I'll ream after installing for .001 running clearance. Now Robert get used to the way some of these threads wind around. But as usual with the Internet it's your final decision after weighing all the posts, both pro and con.
If you at least review the overhaul manual (TM 9-1825B) for the Group 3 waterproof Auto-Lite distributors the above specifications and methods are all listed there. I have PDF copies of this manual section loaded on my web sites for members to use. The civvy Prestolite service manual specifies fitting new bushing/bearings to 0.0005" which of course equals the bore diameter posted above of 0.001 over 0.500 if you have a 0.500 shaft. I would not discard my shaft unless I could not maintain the actual required clearance. IE if your shaft is straight and 0.498 and the bushing can be reamed to 0.499 then you do not have a problem with the shaft.
cuz wrote:If you at least review the overhaul manual (TM 9-1825B) for the Group 3 waterproof Auto-Lite distributors the above specifications and methods are all listed there. I have PDF copies of this manual section loaded on my web sites for members to use. The civvy Prestolite service manual specifies fitting new bushing/bearings to 0.0005" which of course equals the bore diameter posted above of 0.001 over 0.500 if you have a 0.500 shaft. I would not discard my shaft unless I could not maintain the actual required clearance. IE if your shaft is straight and 0.498 and the bushing can be reamed to 0.499 then you do not have a problem with the shaft.
If this web site manager would like to make these available to this web sites members he can contact me anytime.
Actually you do have a problem with the shaft in the above mentioned situation. That problem would be that the shaft does not wear on areas that are not in the bushings, thus these areas on the shaft that are not worn will still be .500" diameter. The unworn shaft area must go through the bushings in order to install it. Last time I checked, you couldn't put a .500" shaft through a .499" bore. You must have at least a .501" bore in order to insert the shaft, regardless of whether it is new or used, the areas that don't wear simply will not go through a bore if it's under .501".
First off thank you Wes for posting those pages. I was thinking all afternoon how to explain gracefully how your reasoning on the shaft wouldn't work, but Charles bet me to it. I will offer a thought though that if a new shaft wasn't available, in my case I would dust off my tool post grinder and bring the entire shaft down to the .498 that you used as an example. Then finish ream the bushings to .4985-.499". As a side bar I was very fortunate in my 30s that a neighbor was the head lathe operator at Grumman in Bethpage (he made parts for the Lunar limb). This was before CNC machines and everything was done with holding fixtures and purpose built jigs not to mention skill. He taught me well and certain jobs just need to be done with the right tools and by a machinist, and this in my opinion is one of them.
The "problem" of maintaining and adjusting mechanical points ignition systems comes up every now and then, and I have to chuckle to myself at how such a simple system that has been nothing but reliable for a hundred years can be so difficult for today's mechanics to understand.
Perhaps you missed the word straight in my post. I suppose I should have expounded on straight 0.498 shaft. At any rate it looks like it did make ya'lls gears turn a bit. The more important idea to take away here is when determining bushing ID's to ream to always measure the shaft in question, clean it up if necessary and then ream the bushing to the shaft size + 0.001. Don't just ream to a nominal 0.501 and hope the sahft you are using is actually 0.500.
cuz wrote:Perhaps you missed the word straight in my post. I suppose I should have expounded on straight 0.498 shaft. At any rate it looks like it did make ya'lls gears turn a bit. The more important idea to take away here is when determining bushing ID's to ream to always measure the shaft in question, clean it up if necessary and then ream the bushing to the shaft size + 0.001. Don't just ream to a nominal 0.501 and hope the sahft you are using is actually 0.500.
I believe you may be missing several points, the procedure you describe is generally correct in a machining process, however with a distributor shaft it will be difficult to hold the shaft in the chuck in a way the entire length could be turned, simply because of the shaft make up. Of course a shaft that can't be held true can't be turned true, this 1 would be a challenge. Another issue is this, if you were able to be successful in getting a true undersized shaft, you would have to turn a new shaft retainer collar to fit the now undersized shaft because the original only fits a .500" shaft diameter. Having done many such similar projects in the repair and upgrade of various components, the one you are describing in this case of the distributor shaft is quickly falling into the catagory of "going around the world only to cross the street." The only sensible solution here would be to obtain a new original shaft or a good take out shaft. No way would the expense involved in the machining process you speak about be justifiable when compared to simply obtaining a new shaft.
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