l48 timing question

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Jul 23, 2011 | 08:18 AM

#41

mr.beachcomber

Burning Brakes

Joined: Jan 2003

Posts: 755

Likes: 32

From: Roswell Georgia

Quote:

Originally Posted by scottyp99

The distributor spins at half the speed of the crankshaft. Ha! I bet you knew that, just didn't occur to you, tho!!

...

Thanks! I did overlook that crucial fact as well as thinking that the poster was recommending 52 degrees of mechanical advance (which would be possible is the mechanical advance stops were modified) rather than a combination of initial (lead) advance, mechanical advance, and vacuum advance.

Jul 23, 2011 | 08:24 AM

#42

mr.beachcomber

Burning Brakes

Joined: Jan 2003

Posts: 755

Likes: 32

From: Roswell Georgia

Quote:

Originally Posted by petes74ttop

If you set your initial timing at 12* before Top Dead Center it means the spark plug fires when the crankshaft is 12* BTDC.
When you hook up your ported vacuum advance you ad 16 more degrees-your spark plug now fires (12* + 16*=28*) when your crankshaft is now 28* BTDC.
When the distributor is turned CW or CCW the spark is fired earlier or later (advance or retard).

Does that help or is it more confusing?

Not confusing. Just good, solid information. However, my error was twofold. First I thought the original post was recommending 52 degrees of mechanical advance, and second, I forgot that the distributor was turning 1/2 crankshaft speed so therefore 45 degrees of distributor movement equaled 90 degrees of crankshaft movement. (Thanks Scott!)

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