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Username Post: SPARK Knob 1931 Sport Coupe        (Topic#366753)
Posts: 32

Reg: 07-14-19
10-19-21 09:52 AM - Post#2829477    

I'm trying to figure out what / when the SPARK knob is used for and when it should be used. According to the Chevrolet Manual it is used to retard the spark and is NOT to be used at start up. I have done the usual internet searching and have seen (U-Tube) the SPARK was pulled at start up. I can not find any other instructions when this is to be used. Any help would be appreciated.


Posts: 9

Loc: Saskatoon Canada
Reg: 01-27-20
10-23-21 09:11 AM - Post#2829649    
    In response to 1931Harlet

The spark knob was originally not used for starting, and really was only supposed to be used to retard the spark when the engine was pulling hard up a hill (or otherwise heavily loaded) to stop or prevent preignition. This was of course at a time when gasoline octane ratings were much lower than even the lowest available today. With today's gas, and the ignition timed to the "original" specification, there really isn't ever any need to pull the spark knob.
If you advance the timing to take advantage of modern octane ratings, you may then want to pull the knob for starting.

Posts: 32

Reg: 07-14-19
10-29-21 05:12 AM - Post#2829908    
    In response to Stovblt2

Thanks for the explanation on the use of the SPARK knob. I have herd that some drivers do advance the timing above specifications to obtain better performance and better fuel mileage. Thanks again.

Posts: 128

Loc: Virginia
Reg: 12-12-12
11-08-21 04:40 AM - Post#2830432    
    In response to 1931Harlet

per the 1929 manual:

If the motor is laboring in sandy roads or on a hill, at low speed, the spark button ("S") should be pulled out a slight amount, to prevent an ignition or spark knock.

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