1963 timing jumping 2 to 4 degrees at idle

[Jeff C.]

I have rebuilt the distributor there does not seem to be any play in the shaft and I shimmed the vertical clearance to .005. The breaker plate seems good. The mechanical advance weight are free and appear to be working. I have checked with the vacuum advance blocked off. What should I check next?
Thanks,
Jeff

[Joe L.]

Re: 1963 timing jumping 2 to 4 degrees at idle

I have rebuilt the distributor there does not seem to be any play in the shaft and I shimmed the vertical clearance to .005. The breaker plate seems good. The mechanical advance weight are free and appear to be working. I have checked with the vacuum advance blocked off. What should I check next?
Thanks,
Jeff

Jeff------

How old is your timing set (camshaft sprocket, crank sprocket, and chain)? Is it the original Morse type chain and sprockets?

[Duke W.]

Re: 1963 timing jumping 2 to 4 degrees at idle

What engine? Stock or modified? What is idle speed and vacuum (in neutral if a manual, in Drive if an auto)? What is the data stamped on the VAC bracket?

[Jeff C.]

Re: 1963 timing jumping 2 to 4 degrees at idle

Duke,
It is a stock 340 HP 327. I have a B28 vacuum advance can that I have verified with a vacuum tester, idle is set at 800 RPM and idle vacuum is 14 to 15 inches. The carb, intake manifold, exhaust manifolds, and heads are all stock and unmodified as best I can tell. It is for sure a solid lifter cam but whether it is a 097 or a after market I can't tell. the gaps are set at your recommended settings. Spark plugs are new ac43. Initial advance is set 14 degrees with the vacuum disconnected. I am going to do a compression test and buy a new timing light as mine is 15 to 20 years old. The engine does not burn oil and there is no smoke out the exhaust.Thanks for you help
Jeff

[Timothy B.]

Re: 1963 timing jumping 2 to 4 degrees at idle

Jeff,

Could it be possible the ac43 plug is to cold for the engine and you are experiencing some low speed misfires. Also, the idle adjustment may be lean, have you tried to open the A/F emulsion screws a little more.

[Patrick H.]

Re: 1963 timing jumping 2 to 4 degrees at idle

Jeff------

How old is your timing set (camshaft sprocket, crank sprocket, and chain)? Is it the original Morse type chain and sprockets?

Same question I thought of.
If it's the original, then I would suspect that the nylon teeth are on their way OTD.

[Joe L.]

Re: 1963 timing jumping 2 to 4 degrees at idle

Same question I thought of.
If it's the original, then I would suspect that the nylon teeth are on their way OTD.

Patrick------


If it's original, it will have a cast iron cam sprocket. The first use of a nylon-toothed, aluminum sprocket for small blocks was 1966. However, that does not mean that the timing set will be in good shape if it's original. Chain stretch and sprocket wear will have taken their toll. In particular, the powder metal crankshaft sprocket will certainly be worn.

[Duke W.]

Re: 1963 timing jumping 2 to 4 degrees at idle

Thanks for the details. Check distributor end play... tight or sloppy? The more end play the more spark scatter. Even the lazy OE centrifugal that isn't all in until 4600 starts at 700, and with lighter springs (which I recommend) it may start lower adding centrifugal at idle, which may vary. Tie up the centrifugal with a rubber band and see it that reduces idle spark scatter. As Joe said your engine originally had a cast iron cam sprocket - the early "wide" one, but it may have something else now. It's best to eliminate the distributor or centrifugal advance as a cause before you think about opening up the timing cover to check the timing chain and sprockets.

[Duke W.]

Re: 1963 timing jumping 2 to 4 degrees at idle

Never mind about the end play as you stated it's five thou, but do the centrifugal check.

[John D.]

Re: 1963 timing jumping 2 to 4 degrees at idle

Like Tim said the AC43 plugs are a minus factor. What are you using for an ignition coil Jeff?
14-15"s of vacuum is OK. Kick the idle up to 900 and try it. Also use a much hotter spark plug. AC45 or 46 or an Autolight equiv.
In the old days I can remember the issues we used to have with the fiber timing gears in the Model A Fords. That and ignitioncoils and condensers.
Good luck, John

[Mike B.]

Re: 1963 timing jumping 2 to 4 degrees at idle

I had this problem before a long time ago and it was a hairline crack in the cap. I replaced cap and solved the problem. But that was me.

[Duke W.]

Re: 1963 timing jumping 2 to 4 degrees at idle

Two NON-RESISTOR plugs equivalent heat range to the AC 45 - NGK B4 and Denso W-14U. (XR-4 is a resistor type.) In the AC number system the first digit, 4, indicates a 14mm plug. The second digit, 5, is the heat range. Heat range "5" or equivalent in another brand is best for normal road and highway use including high speed freeway driving, say up to 80-85 MPH cruise speed. The OP should also check dwell variation, at idle and high revs since dwell variation causes advance variation. It should not vary more than 2 degrees up to redline. If it does the breaker plate may be wobbly or the shaft bushings are worn.

[Richard G.]

Re: 1963 timing jumping 2 to 4 degrees at idle

I have been able to ascertain the condition of the timing chain by moving the harmonic balancer back and forth by hand.
It will come up against the cam shaft when the slack is removed from the chain as the cam turns harder, much harder, than a used rotating assembly.
This alone will not always account for the timing variations as the slack it taken out on one side while the motor is running. If you complete the test with the timing mark visible you can even report the number of crankshaft degrees of slop. Over the years I have found it to be a pretty solid indicator of engine condition.
Rick