08-11-2012, 10:02 AM | #1 |
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Dwell Angle
Is there a dwell angle for a model A point setting? I cannot seem to locate anything but gap.
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08-11-2012, 10:55 AM | #2 |
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Re: Dwell Angle
I never was able (probably out of ignorance) to measure the dwell (the angle through which the distributor cam rotates while the points are closed) on my standard distributor using my Allen-Tune Model 50-514 Dwell/Tach meter, although when I ran a Mallory distributor, the Dwell/Tach meter would work, albeit I had (as memory serves) to divide (multiply?) the reading by 2 inasmuch as the 50-514 was only set up for 6- or 8-cylinder engines. As I recall, at least on my SBC's (283's and 327's, always in a Chevy and not a Model A) the dwell specification was 28 to 32 degrees, so, depending on the distributor cam profile and the point gap (reducing the gap will increase the dwell) if you did want to set your point gap by measuring the dwell, it ought to be somewhere around 45 +/-degrees. (If this isn't correct, someone more knowledgeable will chime in.)
However, (a) I wouldn't rely on this and (b) as fordgarage correctly pointed out above, set the gap and then the timing. It isn't that difficult and works pretty well. And, lastly (and depending on the quality of your distributor cam, the tightness of the upper distributor plate and the condition of the distributor bushings) do not rely on just one lobe to set the points. Instead, pick a lobe, set the point gap (after ensuring the points are reasonably clean and "polished" and are parallel to each other when closed) and then measure the resulting gap at the other three lobes. You might be surprised to discover the variance from lobe to lobe.
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Skip Keyser Napa Valley A's Olympic Vintage Auto Club (1980-1982) MARC of San Diego (1977-1978) MAFCA (since 1978) MARC (since 1977) ---------- Model A owners belong in their Model A’s; Model A’s belong on the road. Last edited by Napa Skip; 08-11-2012 at 11:10 AM. Reason: typo |
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08-11-2012, 11:18 AM | #3 |
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Re: Dwell Angle
Dwell also depends on whether you are using an A cam or a B cam. The B cam is the only one sold and it gives about 9 or 10 more degrees of dwell when the points are set at .020".
I measured the dwell years ago and seem to recall it was about 35 for the A cam and 45 for the B cam. |
08-11-2012, 11:49 AM | #4 |
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Re: Dwell Angle
I agree there is no "spec", per se. I carefully set the gap on some new points with a feeler gauge. Then, when the engine is running, I measure the dwell, just to see what it was (for future reference).
I use that number to do a quick check for point "follower" wear. Every time I change the oil, I connect the dwell meter just to see where it's at. It is quick and easy to do. If the dwell has fallen too much from my initial reading, I open up the distributor and set the gap back out to spec with a feeler gauge.
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08-11-2012, 01:33 PM | #5 |
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Re: Dwell Angle
Vince , you should find you an old school pencil box like us geeks carried back in the day .
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08-11-2012, 01:51 PM | #6 |
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Re: Dwell Angle
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I would think you could chuck the pencil up in a lathe then bore out the center and then slide the new guts in with a little Loctite to hold it in place. Bob Last edited by Bob C; 08-11-2012 at 02:15 PM. |
08-11-2012, 02:05 PM | #7 |
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Re: Dwell Angle
Bob and Vince,
I was thinking the same thing Bob. BUT, were are dealing with Vince, a crafty kind- a-guy, soooo, Vince you have any photos of this project? |
08-11-2012, 02:31 PM | #8 |
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Re: Dwell Angle
After you follow the procedure in the service bulletin ,put it away and set the timing where the engine gives you the best performance with out rattling ( pining ).
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08-11-2012, 02:45 PM | #9 |
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Re: Dwell Angle
"Anyway, does anyone have any advice or info on how to modify and convert these into a plastic bodied style, with gel ink cartridge, and a rolling ball tip? "
Hmmm! Let me DWELL on this for a bit. Yep, keep it simple and just set them at .020" and enjoy the drive. |
08-11-2012, 05:59 PM | #10 |
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Re: Dwell Angle
Thanks for the info. It is set at .20 and runs fine, I was just curious is there was a dwell reading.
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08-11-2012, 06:42 PM | #11 |
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Re: Dwell Angle
Hmm! Pencil upgrades/conversions?? I think I'll write this one OFF and go scratch the dog. (More productive!) Bill W.
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08-12-2012, 10:55 AM | #12 |
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Re: Dwell Angle
There once was a Model A distributor,
Which required point-gap setting by feeler. "I tried gapping by dwell," "But the ignition went to hell," Proving the old way is often times better.
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Skip Keyser Napa Valley A's Olympic Vintage Auto Club (1980-1982) MARC of San Diego (1977-1978) MAFCA (since 1978) MARC (since 1977) ---------- Model A owners belong in their Model A’s; Model A’s belong on the road. Last edited by Napa Skip; 08-12-2012 at 11:03 AM. Reason: typo |
08-12-2012, 12:46 PM | #13 |
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Re: Dwell Angle
I have some assorted old shop literature that all call out 31 degrees dwell... 31 would be for ORIGINAL distributor cams. the ones available now will run 41 - 47 degrees (my measurement). forget about the dwell and just set the points as previous posts state. I think Napa Skip supplied an excellent summation !
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12-14-2015, 04:34 AM | #14 |
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Re: Dwell Angle
My dwell machine must be 40 or more years old. Just thought I would have
Some fun using it again, you know for something to do? Was easy on old chev motors just connect the leads, start the engine and,adjust distributor with a Allen key. Next big project I might remove the small stones from the tire treads! Fredski |
12-14-2015, 06:43 AM | #15 |
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Re: Dwell Angle
That is not a measurement you need to waste your time on for keeping the A happy. I think there is a pun in there...
What you do want to measure is the amount of slop between your upper plate and the center bushing area of the dist in the normal operation area. If there is too much play here you get a variation in timing as the plate moves. I measured mine with a dial indicator about where the points would be. Then slid the top plate back and forth to determine the movement. A couple of thou is not too bad, but at some point beyond that you can start altering the point gap enough to change how the engine is running. More importantly it can vary as the engine runs giving some inconsistancies in the engine running. A fix is to use a peen and expand the metal a bit near the edge where the hole is larger. This will reduce the movement, but depending on use the points of the squeeze will wear faster over time. |
12-14-2015, 09:35 AM | #16 |
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Re: Dwell Angle
One day I had more time then projects. Sooo... I took dist. out and bench set the pionts to .020. Then I used a VOM to check the rotational angle that the points were in contact. I am not sure what I measured but I think you could determine the dwell by this methed. My brain cells leak after a time and it was quite a while ago that I did this so I am not sure what I found the dwell to be. Seems like it may have been about 38*.
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Steve Hanna, Polk City, IA Last edited by sphanna; 12-14-2015 at 09:45 AM. Reason: Brain may have kicked in. Not 100% sure. |
12-14-2015, 10:57 AM | #17 |
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Re: Dwell Angle
Doesn't seem as though it would be too hard to do. Set the points and then check the dwell. If you're like me, you'll have to write it down and then forget where you put it.
Last edited by Patrick L.; 12-14-2015 at 11:20 AM. |
12-14-2015, 11:08 AM | #18 |
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Re: Dwell Angle
I have one of these that I have had for 40+ years.
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Alaskan A's Antique Auto Mushers of Alaska Model A Ford Club of America Model A Restorers Club Antique Automobile Club of America Mullins Owner's Club Last edited by CarlG; 12-14-2015 at 11:23 AM. |
12-14-2015, 11:18 AM | #19 |
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Re: Dwell Angle
Here's a thread about Model A and B distributor cam dwell angles.
http://www.fordbarn.com/forum/showth...ht=Model+Dwell |
12-14-2015, 11:26 AM | #20 |
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Re: Dwell Angle
I used the B cams in both my cars purchased from brattons / swapped out the A cams... Very high quality and a noticeable improvement as well
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12-14-2015, 12:57 PM | #21 | |
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Re: Dwell Angle
Quote:
If distributor do have to modify b cam to fit. Not understanding this quite. Fred |
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12-14-2015, 01:02 PM | #22 |
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Re: Dwell Angle
Okay to all , will give up dwell adjustment on the A .
It does work well on my 1963 (xxx) . Fredski |
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12-14-2015, 01:04 PM | #23 |
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Re: Dwell Angle
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12-15-2015, 06:38 AM | #24 |
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Re: Dwell Angle
A dial indicator setup on the back of the points is rhe most accurate way to set them. You can also check the variation in the cam lobes.
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