Ford 800 (172 engine) Mechanical Advance Question

Brett24 · Oct 12, 2019

My advance is not working properly. The timing advances a little, as RPMs increase, but not very far.
The weights move freely.
I've attached some pictures of the weights.
In one picture I pushed the weights all the way out.
I then let the weights return as far as they would on their own (just the springs pushing them).
In the third picture I pushed them in against the shaft as far as they would go, which was quite a bit farther than the springs managed to accomplish.
Am I correct in assuming that the springs on my weights are not doing their job properly?
Brett

Dean · Oct 12, 2019

The cam and advance mechanism must rotate easily on the concentric distributor shaft.

You may be able to use penetrating oil to loosen the mechanism.

If not, you may need to remove and disassemble the distributor.

Caveat: Cannot see the advance mechanism weights properly. If springs are broken, replacement is necessary. Replacement parts are (or at least were) available from the aftermarket.

Dean

showcrop · Oct 12, 2019

I see a very big potential for a lot more friction than there should be there. You may need to remove it to clean it out but you may be ble to get it cleaned up good with some carb cleaner and paper towels.

Brett24 · Oct 12, 2019

The cam was free on the shaft. The cam and weights were moving quite freely.
I removed the retaining ring and was able to pull the cam-and-weight assembly off of the shaft. I'll attach a picture of the bottom of it, showing the springs.
I'll certainly clean it up while it is off.
Do the springs look the way they should? I have this feeling that the springs are worn/bent, and as a result, the weights do not return to correct position at lower RPMs.

WayneIA · Oct 12, 2019

The weight advance I see you have posted only has one spring on each side! There should be two on each side. That weight advance assembly is not available after market and it costs two arms and a leg at NH. You can buy a complete distributor after market cheaper than the assembly at NH

Brett24 · Oct 14, 2019

My 800-series tractor is an 850.
The serial number is 70***, so from what I could find, it was produced in 1955.
On the current distributor, there is a plate that has only a few markings (I'll attach a picture).
Based on this information, I found that it should take an FDN-12127-A distributor.
The sellers of these list a distributor (part #86588846) that replaces both the FDN-12127-A, and 311185.
Are these two distributors the same? I wondering because the parts manual lists the FDN-12127-A as being used in model-years 55-57, an 311185 in years 58-64.
Brett

Ford 800 (172 engine) Mechanical Advance Question

Brett24

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Dean

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showcrop

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Brett24

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WayneIA

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Brett24

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