Sun Distributor Machine Manometer - Old Hot Rodder

[Jimz Bird]

Thanks for letting me in.
Greetings all - New "old" guy here from Norfolk, VA.

I found this while looking for information on the specific gravity of Sun Manometer Fluid. I saw other discussions on manometers. Hopefully, I am not intruding.

To make a short story long---
I have a Sun 506 Distributor Tester Machine which in a nutshell checks and allows for calibration of centrifugal and vacuum advance on old points style distributors at various RPMs of the engine.

Vacuum advance on most distributors is fairly easy to check as it changes in fairly large increments.
For example on a 1957 Ford Y-Block the vacuum advance is as follows:
With the Sun DT at 1,000 Distributor RPM.
There will be 0-1 degrees of advance at 5 inches of vacuum.
There will be 5-7 degrees of advance at 10 inches of vacuum.
There will be 11-13 degrees of advance at 15 inches of vacuum.
There will be 11-13 degrees of advance at 20 inches of vacuum.

Prior to 1957 Ford used a Holley Pressure type of distributor called a Load-O-Matic. It had NO centrifugal advance and only vacuum advance. This vacuum advance operated at a substantially lower vacuum amount.
For example a 1956 312 with a 4bbl the vacuum advance was:
At 300 Distributor RPM: Advance would be 0 - 1/2 degrees at .16 Inches of vacuum. Note that is "point" 16.
At 400 Distributor RPM: Advance would be 0-1 degrees at .29 Inches vacuum.
On up at 800 RPM: 5-1/2 - 6-1/2 degrees at Inches vacuum: .88
at 1200 RPM: 8-1/2 - 9-1/2 degrees at Inches vacuum: 1.27
at 1600 RPM: 11 - 12 degrees at Inches vacuum: 1.73
at 2000 RPM: 13 - 14-1/2 degrees at Inches vacuum: 2.19
Those are inches of Mercury.
Very little vacuum is need to advance the breaker plate.

Sun offered an accessory Manometer for those style of distributors which used Sun Manometer Fluid of an unknown specific gravity for which their Manometers were calibrated. Even Google doesn't know it. At least not now as it has not been available for decades as the Sun DT has not been made for that long. Besides, who but old school hot rodders cares about 1956 Ford distributors? The Sun Manometers are also quite rare and high dollar if one is to be found.

I have two 56 Fords with the LOM distributors. One a 272 and the other is a 312 in a Thunderbird.
Here is my thinking on a viable replacement manometer to allow me to work on these distributors.

I converted the inches of Mercury to Water Column. Here are the numbers I came up with:
272 - 2v
RPM Advance --In Hg --In WC
200 0 --0 --0
300 0+/- 1/2 --0.15 --2.04
400 .25-1.25 --0.28 --3.80
800 6.5-7.5 --0.96 --13.05
1200 11.5-12.75 --2.21 --30.05
1600 14.5-15.5 --3.41 --46.35
2000 16.0-17.25 --4.6 --62.54

272-292-312 - 4v
RPM Advance --In Hg --In WC
200 0 --0 --0
300 0+/- 1/2 --0.16 --2.18
400 0-1 --0.29 --3.94
800 5.5-6.5 --0.88 --11.96
1200 8.5-9.5 --1.27 --17.27
1600 11-12 --1.73 --23.51
2000 13.0-14.25 --2.19 --29.77

I used 1 Inch Of Mercury to 1 Inch Of Water = 13.5955 as the conversion factor.

I am considering using the Dwyer 1211-72 Slack Tube Manometer. That should give me up to the 62.54 WC I need for the 272 2v. I think.
That manometer runs about $100. I have seen how to build one with plastic tubing and making a scale which is a consideration. It may be better to buy one due to the height along with the preciseness and durability that is needed. That is the other consideration.

So, with all that said, my questions are:
1. Do my numbers look correct?
2. Does the Dwyer 1211-72 sound like the best way to go or are there other recommendations?

Jim

[DaveMcLain]

I think your conversion from inches Hg to water looks right. To build or buy a water manometer to measure to about 30 inches should be easy. We have a Sun distributor machine but I don't know what the Sun manometer looks like.

[Jimz Bird]

Dave,

Thanks, that's the encouragement I needed.

Here is what it looks like attached. From a Sun Manual.
Also a pic from an old eBay ad. It is 35 inches tall and the scale goes from 0 to 6.5 Hg. It has a glass U tube in it.

Thanks again,

Jim

[jfholm]

I just went to Harbor Freight and bought a 48" Drywall square. Cheap! $14.99

http://www.harborfreight.com/48-drywall ... 69244.html

John

[Tony]

My tallest water manometer is 72 inches, and it has a water reservoir at the bottom, so it reads directly.

For an inch scale, I just cut a suitable length from a cheap retractable measuring tape.
Cheap, simple, and very easy to read.

[1960FL]

You might want to save yourself the headach and buy one of these at it has more uses than a 5ft stick with tubing.

http://www.amazon.com/gp/product/B005FU ... E8TPMG9W1M

Rick

[Tony]

Rick has a point.
And an electronic manometer can usually measure in a variety of different pressure units at the push of a button, saving you the effort of converting units.

But sometimes the cheapies can be in error by quite a fair bit, especially after it has been abused, and there is no way to really know for sure if the reading is lying to you.

I think you need both, a digital manometer for ease of use and convenience, and a big clunky water manometer hiding over in the corner to check it against, every now and again.

[Malvin]

Or you can buy this one cheaper http://www.ebay.com/itm/301331703403?_t ... EBIDX%3AIT

Member here at PTS forum JFHolm has one I think just like it he can tell you more about that hand held
digital manometer

[jfholm]

Malvin just ordered one also. It is the same thing as the Pyle only not red and no name logo. I have used mine and seems pretty darn nice. Rick brings up a good point and these things have 11 different units of measure and one of them is inHG

[Jimz Bird]

Thanks to all for the input.

So it appears to me that a reasonable way to go would be to build a large U tube using the HF Drywall square suggested by John along with getting an inexpensive electronic one suggested by others.
The large one could be used to check calibration on the electronic device and for the times when the deferential exceeds the electronic device's range.
In most cases I will just need to go up to about 30 WC for the 312 4bbl distributor in the Thunderbirds which falls within the range of the electronic device.

Thanks again. I have been fussing internally with myself for a couple of months on this so it is good to have some direction now.

Jim