8BA Distributor VAcuum

[B_man_Al]

Does any one have typical numbers for the vacuum on the 1953 distributor port? I'm getting about 18.5 in. Hg on the manifold port at idle, and about 2 in. Hg on the distributor port at idle. At moderate PRM (actual RPM unknown) it increases with increasing RPM to a maximum of about 6 in. Hg. I just redid the carb and was wondering if these numbers are in the ball park.

Al

[V8 Bob]

Originally Posted by B_man_Al

Does any one have typical numbers for the vacuum on the 1953 distributor port? I'm getting about 18.5 in. Hg on the manifold port at idle, and about 2 in. Hg on the distributor port at idle. At moderate PRM (actual RPM unknown) it increases with increasing RPM to a maximum of about 6 in. Hg. I just redid the carb and was wondering if these numbers are in the ball park.

Al

Those numbers are normal and well in the ball park. A shop manual will give more detail information.

[ken ct]

Dist vacume is taken off the rear port of the carb NOT the same as intake manifold vacume.Will not work right if your getting dist vac. from manifold. ken ct.

[B_man_Al]

Thanks for the response V8 Bob. Ken ct I realize the diffference between the two ports. I quoted the measured manifold vacuum to determine a reference base line for the distributor port which varies between 2 and about 6 in. HG depending on RPM.

Al

[ken ct]

Your post was a little confusing,it appeared you were trying to use manifold vac.My appoligies. ken ct.Happy NY "B Man.

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Originally Posted by B_man_Al

Does any one have typical numbers for the vacuum on the 1953 distributor port? I'm getting about 18.5 in. Hg on the manifold port at idle, and about 2 in. Hg on the distributor port at idle. At moderate PRM (actual RPM unknown) it increases with increasing RPM to a maximum of about 6 in. Hg. I just redid the carb and was wondering if these numbers are in the ball park.

Al

The actual specs for the 53 "load a matic" vacuum only distributor are:

1/2 degree ( 1 degree advance engine) at .30 in vac gauge
10 1/2 (22 degrees engine) at 3.7 in vac

Interesting that all flatheads from 32-53 used approx 11 degrees ( 22 engine) of spark advance .
I have found that its very hard to "tune" a decimal point of venturi vacuum.
This is not (as the others mentioned) manifold vacuum and depending on the carb may use a external spark control valve as well.

More than likely most of these engines just go to max vac when started and the timing stays there ( fixed timing).
A mechanical advance unit makes these much easier to tune ...