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rotorwrench · 02-23-2021, 10:04 AM

I found a photo of a Lincoln distributor from a 317 and it does appear to be a Load-O-Matic but it has a large dual diaphragm vacuum spark control similar to the 1956 Ford design. The Mercury distributor appears to be a single diaphragm control so there is some difference in the way these two designs are controlled.

Load-O-Matics generally all have a venturi vacuum ported carburetor in order to get full advance in normal load conditions with a change in vacuum for load conditions to get the proper amount of retard for the engine design. Manifold pressure decreases under load due to the change in throttle plate position which allows for enough retard. If the two systems use different vacuum signals then it will affect efficiency of the automatic spark control.

A lot of folks abandon the Load-O-Matic systems for 8BA flatheads in favor of modified Chevy/GM distributors so that they can use the vacuum spark control along with the centrifugal mechanical advance. The vacuum source from the intake manifold is tuned by use of an adjustable vacuum diaphragm canister. It takes a while to tune one but it can be done. On the small Y-blocks, the 1957 and up 312 T-bird system works that way. The Load-O-Matic was adequate for lower power requirement applications but became increasingly problematic when larger higher power engines like the FE medium blocks and the MEL big blocks came out in the mid to late 50s. The 1957 Thunderbirds with higher perfomance 312 Y-blocks used this new system to good effect. Sal is correct though. Ford kept the Load-O Matic system around as long as there was still an application where it would work effectively.

Bottom line is how well the OPs engine functions for his use. If it works for you then use it. If it is inefficient, ie, uses a lot of fuel, or has a tendency to run hot or there is noticeable pinging under load then those are indications that the spark control is not as effective as it should be. A carb jetted for a 317 Y-block may run a bit on the rich side for a 256 Merc Y-block but that could be changed if needed.

02-23-2021, 10:04 AM	#9
rotorwrench Senior Member Join Date: Jun 2010 Location: San Antonio, Texas Posts: 16,436	Re: 1954 Lincoln Shop Manual I found a photo of a Lincoln distributor from a 317 and it does appear to be a Load-O-Matic but it has a large dual diaphragm vacuum spark control similar to the 1956 Ford design. The Mercury distributor appears to be a single diaphragm control so there is some difference in the way these two designs are controlled. Load-O-Matics generally all have a venturi vacuum ported carburetor in order to get full advance in normal load conditions with a change in vacuum for load conditions to get the proper amount of retard for the engine design. Manifold pressure decreases under load due to the change in throttle plate position which allows for enough retard. If the two systems use different vacuum signals then it will affect efficiency of the automatic spark control. A lot of folks abandon the Load-O-Matic systems for 8BA flatheads in favor of modified Chevy/GM distributors so that they can use the vacuum spark control along with the centrifugal mechanical advance. The vacuum source from the intake manifold is tuned by use of an adjustable vacuum diaphragm canister. It takes a while to tune one but it can be done. On the small Y-blocks, the 1957 and up 312 T-bird system works that way. The Load-O-Matic was adequate for lower power requirement applications but became increasingly problematic when larger higher power engines like the FE medium blocks and the MEL big blocks came out in the mid to late 50s. The 1957 Thunderbirds with higher perfomance 312 Y-blocks used this new system to good effect. Sal is correct though. Ford kept the Load-O Matic system around as long as there was still an application where it would work effectively. Bottom line is how well the OPs engine functions for his use. If it works for you then use it. If it is inefficient, ie, uses a lot of fuel, or has a tendency to run hot or there is noticeable pinging under load then those are indications that the spark control is not as effective as it should be. A carb jetted for a 317 Y-block may run a bit on the rich side for a 256 Merc Y-block but that could be changed if needed.