8-100a Point Synchronization and Performance Question

  • geojunkie
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15 Jul 2004 19:11 #1956 by geojunkie
geojunkie created the topic: 8-100a Point Synchronization and Performance Question
Question 1: What is the proper procedure to synchronize the dual points on an 8-100a engine?

Question 2: When I received the car it had no power at all and vibrated severely under acceleration. The idle wasn't bad. The car had been fitted with a 1934 intake/exhaust manifold and Stromberg EE1 downdraft carb. Otherwise it is stock and in excellent condition (was a #1 not long ago), but has suffered from sitting for a while.

Found one main jet plugged in the carb and cleaned that. It run much better but still ran out of steam above 2200 rpm (a tach has been fitted). In second gear it just wouldn't rev much above 2500 no matter how patient you were. Vibratiion under acceleration was almost gone.

Decided to check the plugs and found 1,2,3,4 looking lean, rest pretty much good. Don't know why. Regapped plugs and points and reset timing. Plugs were wide and points fairly wide too. Timing ended up off, but point gap changes probably caused that. Now it pulls much better, but still doesn't want to wind out much past 2500, yet HP rating is at 3200 rpm. Also, vibration under acceleration returned after all this. So this is why I am speculating that point sync has something to do with this.

Any comments would be much appreciatied!!

Dan Ellis

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03 Aug 2004 01:05 #2027 by geojunkie
geojunkie replied the topic:
I ordered a reprint service manual which provided good detail on how to synchronize the points, but it required a special tool. I finally decided to construct one using parts from a Craftsman protractor fitted to a hub which drops into the distributor shaft oil wick area with a fabricated key to lock it into the standard rotor cutout. I used the plastic degree wheel off the protractor, which is almost the exact diameter of the distributor housing. Using this I could now accurately read distributor shaft rotation in degrees over 360 degrees.

I then used a 6v bulb across the points one at time to determine exactly at which degree of rotation a particular point set opened. I stuck some cardboard into the opposite point set to ensure I was getting an accurate reading as they do overlap a bit. I used the starter to get in the ballpark and found that by using the slop in the centrifugal advance I could rotate the distributor shaft to determine the exact point of opening with ease. This little trick saved me from removing the distributor, which with the anti-theft interlock would have been fairly time consuming. Then I just adjusted per the manual to ensure the points were opening 45 degrees apart.

After this adjustment the engine ran MUCH smoother, idled beautifully, and pulled stronger. I still detect a little vibration when applying a good bit of throttle at low rpms in second. It judders the car a bit, so I want to resolve it. Anyhow, it is worth it to do this synchronization and each time you regap the points, if you are not very careful to get them exactly the same, the synch will be off. This throws the timing to 1/2 the cylinders off, so it is no small issue. It isn't hard to do if you have the right tool.

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03 Aug 2004 01:57 #2028 by Mike Dube
Mike Dube replied the topic:
Don't think you really need that tool, just use a timing light. If you use a modern 12 volt light with an adjustable dwell, its pretty easy. Just park near something with 12 volts to power the light. Mark the top dead center line and 12 degrees btdc (3-1/4 teeth) on the flywheel before you start, with a high viz grease pen or paint. Time the stationary set first, them pick another plug wire and time the moveable set. Involves taking the cap off a few times to adjust the points, but no big deal.

Mike
8-100A

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  • MICHAEL S SMITH
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03 Aug 2004 03:10 #2030 by MICHAEL S SMITH
MICHAEL S SMITH replied the topic:
DAN
COUPLE OF OTHER THINGS TO CHECK.
A CRACKED DISTRIBUTOR CAP COULD BE LOSING FIRE WHICH WOULD PRODUCE THE SAME PROBLEMS YOU DESCRIBE.
ALSO DISTIBUTOR AND/OR CAPACITOR COULD BE GROUNDED.

MICHAEL S SMITH ACD LIFE MEMBER #40
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  • John Trittschuh
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03 Aug 2004 21:20 #2031 by John Trittschuh
John Trittschuh replied the topic: Rough Running
Had similar problem on my 1933 which ran beautifully before it was shipped to me. Ran rough after two weeks transport to me from Seattle. After playing with everything else, I found the distributor wire from the coil was not seated into the coil firmly. It had jarred loose and was a nest of wire originally so a new wire and end cap solved my problem.

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03 Aug 2004 23:42 #2032 by Mike Dube
Mike Dube replied the topic:
Also check all the mechanical connections inside the distr. There are a lot of connections in that small space, and none are supposed to be anything other than tight.

Mike
8-100A

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