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On my 350 SBC I have a Edelbrock Performer manifold with a 600 Holley, HEI dizzy and the cam is 214/224 @ .050 (272/282).

I've set the timing at 900 rpm to 12 btdc with the vacuum disconnected. When I connect the vacuum it jumps to about 18 to 20 degrees.

Is that normal or too much?

I'm using the vacuum on the front of the carb's base. I also tried the vacuum point on the side of the metering block which seems to do the same thing. Could it be the vacuum can on the distributor giving too much advance too quick?

I don't know what the total advance is as I only have a "standard" timing light.
 

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The first thing to do is establish a 36° mark on your balancer so you don't need a special timing light. Measure the diameter of your balancer, multiply by .314 and use this measurement to make a mark CW from your existing TDC mark. Use this to set your total mechanical advance.
The amount of vacuum advance that gets applied and at what vacuum is peculiar to every engine. What VA can do you use?
 

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That`s about the normal amount with the vacuum connected to a manifold source, some advance higher such as mine, it advances to 24 degrees.
 

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Discussion Starter #4
onovakind67 said:
The first thing to do is establish a 36° mark on your balancer so you don't need a special timing light. Measure the diameter of your balancer, multiply by .314 and use this measurement to make a mark CW from your existing TDC mark. Use this to set your total mechanical advance.
The amount of vacuum advance that gets applied and at what vacuum is peculiar to every engine. What VA can do you use?
So the value from the measurement must be marked clockwise from the TDC mark?

The VA can is the standard one that came with the motor. Do they have any markings as I didn't yet check for any?

DoubleVision said:
That`s about the normal amount with the vacuum connected to a manifold source, some advance higher such as mine, it advances to 24 degrees.
That makes me feel more at ease. From this I gather that the mechanical will in the end account for the rest to give a total of the ideal 36°?

This weekend I'll try to establish the 36° mark so I can check how much I get in total. What's the typical rpm where it should happen by?
 

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So the value from the measurement must be marked clockwise from the TDC mark?

It must arrive at the timing tab before the TDC mark, so you put it CW from the TDC mark.
There may be marks on the can that you can reference, but if it's the stock can it was meant for a stock motor.
 
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