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06-30-2013, 04:24 PM | #1 |
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Join Date: Dec 2012
Location: Little Falls NY
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Distributor cam
Hi, just got done restoring 30 coupe have 350 miles clicked off and all is well. When I rebuilt the distributor I replaced the points cam with a new B style cam that is said to give hotter spark because it increases dwell time. When putting together a travel kit of spare parts I included a condenser, points and coil as suggested. The coil on my car is an original and works well. Yesterday just for fun I changed the points cam back to stock and went for a ten mile sprint with my wife. The car ran great she asked what I had done because it seemed to run much smoother. I'm going to leave it this way my thoughts are that the increased dwell with the B cam may very well reduce miss fire and help with quicker starting but won't it also lead to more stress on the points, condenser and coil leading to less reliability? Any thoughts on this? Maybe I'm just over thinking it.
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06-30-2013, 05:34 PM | #2 |
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Re: Distributor cam
That's all I use with many miles and no problems.
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06-30-2013, 10:24 PM | #3 |
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Re: Distributor cam
Some of the repro B cams are not machined very well and may be no better, or worse, than a stock A cam.
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07-01-2013, 12:37 AM | #4 |
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Re: Distributor cam
From what I have found with the distributor cams purchased from Sacramento Vintage Ford, Brattons, and Snyder's, the stock cams have more dwell time than the "B" cams. And, like you, have discovered that the car runs much better and gets better fuel economy on the stock distributor cams.
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07-01-2013, 05:41 AM | #5 |
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Location: Aiken, South Carolina
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Re: Distributor cam
Do any of the vendors offer the original A cam? Looks like they all sell the B cam.
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07-01-2013, 07:34 AM | #6 |
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Re: Distributor cam
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07-01-2013, 09:16 AM | #7 |
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Re: Distributor cam
I think that all of the distributor cams that are now produced are the B profile. The B cams have an ocean wave profile. The model A dist. cam profile is more pronounced. With the A cam, its easier for me to tell when its on high cam, when prepairing to adjust the points. The B cam gives more dwell for hotter spark. Bill Stipe makes the best cam. Some other vendors sell a dist. cam that is rough and wears out the rubbing block on the points fairly quickly.
More than likely, the reason that it ran better after changing back to the previous cam is that you got the timing set better. |
07-01-2013, 09:21 AM | #8 |
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Re: Distributor cam
The B cam gives longer dwell time than the A cam. I compared them using a degree wheel. With a point gap of 20 mils (.020 inches), the A cam dwell was 32 degrees and the B cam was 43 degrees.
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07-01-2013, 10:17 AM | #9 |
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Join Date: May 2010
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Re: Distributor cam
From A ... experience. I have seen many repro cams are not machined with true same lobes all around.. there is a big varience.. Use a degree wheel as mentioned or a caliper. Like ford said; GYP parts..
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07-01-2013, 10:20 AM | #10 |
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Re: Distributor cam
Right- the cam that looks like "ocean waves" is the one that works best. My catalog has it backwards, I thought that was the A cam. My sincere apologies for the mixup!
You MUST polish the cam before use, and also check that all 4 lobes provide exactly the same gap. You may ruin 1 or 2 before you get the hang of it and polish up a real good one, so buy a couple extras. |
07-01-2013, 11:06 AM | #11 |
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Re: Distributor cam
Or get one from Bill Stipe and no mods required. I don't know if this number still works 920-467-2895 . the part number is SMC 0033 This cam has 10 more degrees of dwell.
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07-01-2013, 12:30 PM | #12 |
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Location: New Jersey
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Re: Distributor cam
Can someone post or refer us to a photo so we can see the difference between the A and B cam? Also, when P.S. talks about polishing the cam, what type of procedure is being used and what are the items needed?
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07-01-2013, 02:01 PM | #13 |
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Location: Spooner, Wisconsin
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Re: Distributor cam
Increased dwell time will put a higher load on the coil and it will run hotter temperature. Don't know if that would effect the life of the coil significantly.
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07-01-2013, 02:43 PM | #14 |
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Re: Distributor cam
I would like to see these on a tester and a lab scope to really tell whats going on. Would make a nice post on the actual value etc.
I would do one at no charge if anyone would like to ship me the parts etc??? |
07-01-2013, 02:52 PM | #15 |
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Location: Mpls, MN
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Re: Distributor cam
Here you go. Notice the A can has 8 distinct lines, while the B cam has 4 sharp lines.
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07-01-2013, 03:18 PM | #16 | |
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Location: Southern California
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Re: Distributor cam
Quote:
My thanks to Tom W. for posting the photo and explaining the difference between A and B. I have a whole bag full of discarded cams. I went through them trying to determine the difference. The "ocean wave" description didn't help me. The 4 and 8 lines better explain it. I found the difference in the collection I have, but thought the reverse was true. Tom Endy |
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07-01-2013, 03:52 PM | #17 |
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Re: Distributor cam
Thanks for the photos Tom & Tom. Does anyone know the proper way on how to clean up these old cams so they will not chew up the points block?
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07-01-2013, 04:28 PM | #18 | |
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Re: Distributor cam
Quote:
As Richard mentioned, I've also found about 32 for the A and 43 degrees of dwell for the B cams. |
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07-01-2013, 05:03 PM | #19 |
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Re: Distributor cam
Tom, have mercy, what is crocus cloth and is it sold in grades like sandpaper?
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07-01-2013, 05:10 PM | #20 |
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Location: Mpls, MN
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Re: Distributor cam
You might find it on a long roll about 1" wide at an auto parts store. I think I bought my roll at a swap meet years ago. It's a redish color fine grit. No reason a fine sandpaper wouldn't work also, but with the cloth backing, the crocus cloth lasts much longer.
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07-01-2013, 09:43 PM | #21 |
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Location: SW Wisconsin
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Re: Distributor cam
also known and sold as plumbers tape
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07-01-2013, 10:07 PM | #22 |
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Location: Anchorage, Alaska
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Re: Distributor cam
Don't think that's quite correct. When I look up the definition of "plumber's tape" this is what I get:
There are two common types of tape that are referred to as plumber's tape. The first should more accurately be called "Teflon tape", and the second is more correctly referred to as "metal strapping". In both cases, the product is most commonly used by plumbers. On the other hand, Crocus Cloth is described as: Crocus cloth is an abrasive sheet similar to sand paper or emery cloth but covered with a layer of very fine loose iron oxide particles rather than with bound grains of abrasive. "For final metal and gemstone finishing." It is available in various grades (particle sizes). What is being described here is the abrasive sheet, available at industrial hardware stores.
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07-02-2013, 12:22 AM | #23 |
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Re: Distributor cam
Wouldn't trust any sort of abrasive paper on a distributor cam. I use a Dremel tool with a buffing wheel on it and some metal polish instead of compound. You want to polish the cam, not cut away material and chance changing the shape or size of the lobes. You just want them mirror finish smooth.
The last polished distributor cam I installed in my Tudor with a brand new set of (old style) points, I set them at .020 and in a couple thousand miles, they are still at exactly .020, no wear at all. Typically, a new set of points will have to wear in, requiring re-adjustment around 500 miles after installation. With a polished cam, zero wear on the new points. |
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