Its just new to me that you can simply bolt on a vacuum advance diaphragm and it magically works..... most of the dist's I've seen the vacuum advance was integral to the dist, and not simply 'added' to it.
Which year truck Shop Manual and Operator's Manual are you using?
The vacuum advance unit is shown in all the Shop Manuals. And, it is shown in all the Operator's manuals. You do not need the vacuum advance but it does increase the gas mileage & possibly the driveability.
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I don't understand the concept of not needing one.
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That is the way it was designed to run.
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to answer the original question, yes the engine should have a vacuum advance, which will be the same for any 235, and very simple to install
I think that all 235 engines had a vacuum advance unit, but I am not sure about 235s on COEs. On some GMC trucks that used their 248/270/302 6 cylinder gas engine, there was no vacuum advance installed.
Also,
there are at least two styles of vacuum advance units that were used on 235 engines. The illustrations in the truck manuals that I posted above are of the car's advance unit - this incorrect illustration was oddly used in all the truck manuals. The car's unit has a mounting plate that mounts the vacuum-diaphragm at a different angle than the angle of the vacuum-diaphragm on the mounting plate used for the truck's unit.
