VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1929-1932 timing set at18deg BTDC

Hi Guys,I have set everything as directed concerning the points, timing and plug gap and car is running good.My question is,if the timing is set at 18 Deg BTDC at idle speed(400-500rpm) ,when engine is at speed(1500-2000rpm) what does the timing advance to then.It seems that it would go to like 25-30 deg BTDC as the dist.weights advance the timing,is this correct? If this correct,wouldn't the plug be firing when the piston is like only half way to full compression?
As you all know,I am a true rookie at this,so please bear with me here! What about the "spark" advance on the dash--do you ever use this? Also,is there a coil available that has more voltage for these cars when the gap is set at .40 or.45 does it not require more voltage to jump that big gap to fire? Thanks,the rookie!

I can't answer all your questions, but the "spark" control at the dash is for retarding the timing and should always be used when starting.

Hello jay32249,
Your questions are good ones. I cannot say that I know the answers though, but here are some thoughts. I believe that the "Spark" knob is used to retard the distributor for cold starting. I do not know how much advance (degrees) at high RPM the distributor weights apply. My thought about the location of the piston at full advance is that it is still close to the top of the cylinder. If you could see an engine on a stand with a degree wheel bolted to the crankshaft and the cylinder head removed, you could visually see the piston's location at the time of spark. I think that there are a number of degrees that go by as the piston approaches TDC and after TDC before you see the piston move. I believe this is due to the swing of the piston rod as it crosses over TDC. As far as the coil being taxed or underpowered, I don't think that that's the case. Stock coils produce a set voltage that appear to handle the wider gap at the spark plug without issue. Coil overheating causing missfiring is a breakdown in the coil not related to the spark plug gap, in my opinion.

The automatic advance is 26 degrees so total would be 44 deg.

Theoretically yes but the delay in flame propagation takes care of the advance in timing.

Only when hand cranking to start. Actually pulling out the knob retards the spark up to 15 deg.

Modern 6 volt coils are perfectly capable of generating enough voltage to jump the gap. Too many of us have proven that over the past 10+ years.

Taking Notes Myself...

I acquired this information 1929-30 Electrical Diagragm & Info from somewhere, not sure, but looks like it was published in "Standard Auto-Electrician's Manual" by Standard Engineering & Publish Company ??

Look in the Bottom left Corner for relevant info about Timing Advance vs RPM. Seems to correlate to Chipper's info as usual :)

Ok,now I am rally confused!! According to the link that BearsFan posted to help me,timing AT IDLE (600rpm) should be 0-2 degrees on flywheel and at 1500rpm should be 12-14 deg. advanced.The jump from 2 deg. at 600rpm to 18 deg. at 600rpm just sounds CRAZY to me.Looking in my manuals from other mid to late 30's motors,they call for idle speed timing to be set at 4 deg.btdc. Then at 1500 rpm they would advance to 12-18 deg.
If i start at 18 deg BTDC at idle,is my timing going to 40+degBTDC at 1500-2000 rpm----that just sounds crazy to me---but then again---i am still wet behind the ears guys!!!THANKS TO ALL,JAY

The automatic advance on a 1930 - 1931 engine is maximum 31 degrees , PLUS the initial setting at 18 degrees equals 49 degrees of total advance. ( not including the dash spark control)
The total distributor advance is 15 1/2 degrees , because the distributor rotates at half engine speed.
A poorly functioning distributor may not get that amount of advance due to poorly lubricated advance weights etc.

The distributor advances the ignition 0 degrees at 700 rpm engine speed , and climbs to 31 degrees advance at 2600 engine rpm and then advances no further.

The link to the 1929 and 1930 Standard auto electricians page is very small , so I have used the 1930 and 1931 , so 1929 may be slightly lower RPMS as stated , but are the same distributor 933-G .

Hope this helps.

Hello jay32249,
(Ok,now I am rally confused!! According to the link that BearsFan posted to help me,timing AT IDLE (600rpm) should be 0-2 degrees on flywheel)
Jay, I think that you may be reading the information incorrectly. The way I read the link is: begin with a manual setting of 15 degrees advance. Then: when the engine is running at certain RPM's, these other advance degrees appear which add upon the manual setting. Example: 15 degrees manual setting-start engine-600 idle RPM adds 0 to 2 degrees advance= 15 to 17 degrees advance at 600 RPM.

Jay,
The '33 and later engines had a vacuum advance in addition to the mechanical advance. Late '27-'32 had a mechanical advance with a retard mechanism.

Jay: Set your timing at the recommended 18 degrees and gap your AC spark plugs at .040" and you will be just fine.