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went to time my 65 L79 and found the setting to be 8 degrees btdc, 6 degrees to 12 degrees nominal. What does this mean? I timed the engine at 8 and motor ran very smooth, idled at about 750 rpm but experiened engine run on after shutting it down. What needs tobe done? Thanks for any help.......................Joe
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Re: C2 timing
Joe,
The "nominal" is the range that engineering thought would be acceptable for the range of gasoline octane levels at the time your car was produced. It may be necessary to reduce the initial timing slightly but I wouldn't just because of the run on condition. If you don't experience pinging while driving, the timing may be ok as is. The run on problem isn't new and isn't the direct fault of todays fuel as these cars did the same thing in the 60's with good fuel. The fix? Leave the car in gear and allow the clutch to engage just slightly, enough to drag the idle speed down just a bit, then turn off the ignition. I've been doing this for 40 years. -
Re: C2 timing
Check the function of the vacuum advance, which should add 16*@8". With the vacuum can connected the total idle timing at 750 should measure 8 initial plus 16 vacuum plus maybe a degree or two of centrifugal since I think it starts at about 700 - somewhere near 25 degrees.
The initial timing must be set with the vacuum can signal line removed and plugged at less than 700 RPM. If you set the initial properly and then connect the vacuum can you should read about 25 degrees total idle timing at 750. A non-functional vacuum can reduces total idle timing, which heats up the combustion chamber surfaces, and this can cause run-on when the key is switched off. It can also cause high operating temperatures and will definitely increase fuel consumption, so it's worth looking into at today's gas prices!
Total WOT timing at high revs should be about 38*, which is achieved with 8 initial plus 30@5000 centrifugal.
The OE vacuum can should be stamped "236-16" on the mounting bracket. A proper current replacement, such as the NAPA/Echlin VC1810 should be stamped "B28".
The distributor is probably the most overlooked component on vintage engines. They degrade slowly, but will continue to operate at some level as long as the points open and close. A good "mapping" of the spark advance and comparison to OE specs is in order, and you can search the archives on how to do a "blueprint overhaul" that will make it run like new.
DukeComment
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Re: C2 timing
Duke: went to the garage and checked the number on the vac can and saw 236-16, I remember rebuilding the distributer back 25 yrs or so. You mention removing the can signal line and plugging it, the line or the snout of the can? Thanks for everyones input will try and check everything again, the vac line seems a little loose............joeComment
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Re: C2 timing
If you pull the signal line off the vacuum can the engine should run faster but rougher because it's basically a vacuum leak that leans out the mixture.
If you plug the signal line (golf tees work very well) revs should drop. Either way removing the signal line from the vacuum can eliminates vacuum advance.
If you have a Mighty Vac or other vacuum tester you should check that the vacuum can meets spec. Or you can just apply oral vacuum with a length of test hose and verify the the vacuum can rotates the breaker plate or check using a timing light. You can easily apply 8" orally to check that it pulls all the way.
A quick check is just to measure total idle timing at the 750 idle speed, which should be about 25*. Then pull the signal line and plug it. Revs should drop to 500-600 and you should just see the 8* initial.
There are a lot of cars running around with dead or defective vacuum cans, but they are very easy to test and replacements are about ten bucks.
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