Timing

[Tcash]

To link to this thread

[RedBaronofRedBud]

Great information! What kind of vacuum reading are we looking for using this method? 5 to 10 inHg?
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[Amskeptic]

[SGKent]

the concepts of static timing, timing by ear, timing by vacuum gauge etc come from a time, 70 - 100 years ago, when engines were not built with the tolerances and compression ratios that came into automotive engines starting in the late 1950's - early 1960's. They did not have automatic chokes, automatic spark advance, fuel injection, ECU's, computers etc. An early 1950's car often had a manual choke, and a manual spark advance. Part of the driver's responsibility was to choke the engine when starting, and to operate the spark advance at different engine speeds by means of a lever on the steering column or dash. Today's cars use computers and knock sensors to set spark timing. The cars like our buses from the late 60's and 70's used mechanical and vacuum means to change the timing. Those systems must be maintained. That said, fuels have also changed. On our buses to reduce heat and possible head failure we set the timing to 28 - 29 degrees BTDC at full advance. This gives good performance and safer engine operation.

Old manual systems:

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[Tcash]

[Amskeptic]

[SGKent]

been there. Never heard the pre-ignition. You can hear detonation because it goes off all at once in a sharp spike. Pre-ignition causes a rise in cylinder temps and pressures but is not always audible. Timing plays a part in both because the more advanced an engine is the hotter the engine runs. The hotter the pistons the greater the pressure in the cylinder and the closer to both the engine is. Detonation is caused when the timing is so far advanced that the additional pressure from the burn sets off the whole cylinder instantly and that causes a knock. Pre-ignition is caused by a lean mixture and something like too hot an area of the head, carbon flakes glowing, a plug tip that carries too much heat from the last cycle etc. You don't hear pre-ignition unless it is combined with detonation. Either way no air cooled engine hold up well to either. The piston crowns melt is usually where the failure is. I agree with Colin that air cooled engines make so much noise you may not hear the damage being done. But if you like to drive like that go for it.
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“Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin

[inhabor]

[inhabor]

[busdaddy]

Any year, with the exception of 68-70 still using the original 205M or K vacuum only SVSA distributor. The mechanical only 009 and all SVDA or DVDA units are best timed with the hoses off at maximum mechanical advance.
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[inhabor]

[busdaddy]

[inhabor]

Thanks again Busdaddy, you are the best.

[Wildthings]

[Wildthings]

[inhabor]

[inhabor]

Can I connect the hose for the retard vacuum here?

[airschooled]

inhabor,

I'm not sure your carb setup would be compatible with the vacuum retard.

When your car is idling, and you take the advance hose off the distributor, does your idle RPM change at all? When you use a timing light at idle and then suddenly take the advance hose off the distributor, does the timing change at all?

Let us know, and we can go from there.
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[inhabor]

[airschooled]