Bleed down on vacuum advance question

[Joe B.]

The first new vacuum advance control sent for my stock 8ba loadamatic distributor would not hold vacuum when applied by an Actron hand vacuum pump. A replacement was sent and I pump it to 15# and it slowly bleeds down to 0 in about 15 seconds. Is that acceptable?

[Jack E/NJ]

Does the pump itself hold a vacuum for a longer time if its end is plugged?

[petehoovie]

Originally Posted by Joe B.

The first new vacuum advance control sent for my stock 8ba loadamatic distributor would not hold vacuum when applied by an Actron hand vacuum pump. A replacement was sent and I pump it to 15# and it slowly bleeds down to 0 in about 15 seconds. Is that acceptable?

[Joe B.]

Yes, the pump is new and will hold. I don't know from experience, but am thinking the large diaphragm and crimped construction, maybe that's just the way it is. Then again, making an airtight seal isn't rocket science. I will try a different pump connection. Something tells me that not too many of the carb to advance tubing connections are completely air tight.

[Kurt in NJ]

A good one won’t bleed down

[pistonbroke]

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My old rusty dented stocker doesn't beed down. Tim

[V8 Bob]

Keep in mind that diaphragm only works with about a 6" max vacuum level from the loadomatic, so try testing at a lower value.

[Joe B.]

Good point. I have 3 Made in china from a popular 49-51 mail order place and they all leak down regardless of the vacuum applied. Finally got smart and ordered one from a local napa. Echlin made in Mexico. The website said it would not fit my '50, but it looked identical. Put the vacuum pump on it at the store counter, low and behold, it held rock steady at 6 lbs. There is a slight difference. I needed to drill a tiny hole in the arm in a different location for the retaining clip. It's in and all is good. For any 49-51 guys out there, I suggest getting the Napa ECH VC915. PS, I also checked the vacuum at the carb fitting and it varies from 2-6# as it should depending on rpm's.

[petehoovie]

Originally Posted by Joe B.

Good point. I have 3 Made in china from a popular 49-51 mail order place and they all leak down regardless of the vacuum applied. Finally got smart and ordered one from a local napa. Echlin made in Mexico. The website said it would not fit my '50, but it looked identical. Put the vacuum pump on it at the store counter, low and behold, it held rock steady at 6 lbs. There is a slight difference. I needed to drill a tiny hole in the arm in a different location for the retaining clip. It's in and all is good. For any 49-51 guys out there, I suggest getting the Napa ECH VC915. PS, I also checked the vacuum at the carb fitting and it varies from 2-6# as it should depending on rpm's.

[Planojc]

Good to know, thanks.

[JayChicago]

Look at all the helpful info in JoeB’s post. Info that everyone else would have to learn the hard way. Now they don’t have to.
This is what makes these Internet forums so great to have.

[Bill OH]

With the vacuum control on the distributor and the vacuum line disconnected, I advance the point plate by hand, then put my finger over the vacuum connection and the release the point plate and if the plate does not fully go back, the diaphragm is good. If the plate goes back to zero, then the diaphragm has a leak.