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Post by genebobmiller on Mar 27, 2012 19:56:54 GMT 10
Hey all,
I just invested in a dwell meter and am finding that the reading i am getting seems way too low, I have to close the points until I can hardly see the gap to get even 30degrees of dwell angle (aiming for 45).
This is with new points.
Would this behavior be caused by worn distributor cams? I tried two distributors i had lying around and the problem remained (not to say they're not both worn).
Any light shed would be greatly appreciated .
Cheers
Gene.
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Post by genebobmiller on Apr 4, 2012 23:14:28 GMT 10
I've now set the dwell on 3 different engines, 2x datsun a12s and 1 holden 186.
In each case it has been the same, I cannot get the points far enough adjusted to get to the required dwell angle before they are completely closed.
In each case I've taken it as close as possible and each engine has improved performance amazingly.
I'm very keen to learn the cause of not being able to adjust the dwell further, worn distributor cams? would a weak coil effect dwell? Something I'm not thinking of?
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Post by boost on Apr 11, 2012 10:52:09 GMT 10
Just a thought you have adjusted 3 and the only thing they have in common is your dwell meter maybe you have a faulty meter.
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Post by genebobmiller on Apr 12, 2012 9:27:57 GMT 10
yes this had occurred to me the first time I took the measurment, so i went out and bought a new meter. Same result. Just did another 120y and got it up to 40 degrees but no way it could ever be higher.
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Post by mickeyding on Oct 27, 2012 22:15:53 GMT 10
I always set points on my datto 1600 to 16 thou gap and set timing to 10 degrees btdc static. (Engine not running). I don't use a dwell meter. only a 12volt light to help figure out when the points open. Typically the points will open about halfway up the cam lobe. When the distributor shaft bearings wear you will get weird behaviour as the cam flaps about while it is running. Usually it will fire too early. You should not have any sideways play in the shaft as any play will translate to variable ignition timing. I usually set the points on the first cyclinder tdc but you can check your gap and timing on the cyclinder 3. (The flywheel advance marks also line up when firing cylinder 3). If there are discrepancies you may have worn shaft bearings or a bent shaft.
I would advise checking that the vacuum advance doesn't leak air. Take off the vacuum hose and suck on the pipe. Place your tongue on the pipe and see if the vacuum holds your tongue. The other advance is in the flywheel weights under the points plate. As the engine revs the centrifugal weights pull against a spring to advance the timing. On older engines the spring wears through the hole in the weight. You should be able to twist the distributor shaft and feel the spring twist the shaft back. If not all these systems are working properly the engine will not perform well. I doubt that the distributor cams have worn as they are hardened steel but they may be dirty with dry grease and road dust. Also make sure that there is a good spring return on your points and that the points rotate freely on their pivot. You also need to check when sucking on the vacuum advance that the points plate rotates on its bearings. The tiny bearings tend to wear grooves in the plate that make it stick. There are two braided wires inside the distributor which need enough slop to allow for the plate advance. I have been timing my vehicles this way for 30 years and am always happy with the performance I get out of them.
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