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73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: fiddler on July 09, 2020, 09:58:50 pm

Title: Vacuum advance unit change.
Post by: fiddler on July 09, 2020, 09:58:50 pm

So my truck went suddenly sluggish.  I checked the timing and when I gunned the engine I did not get as much of an advance as I remember seeing so I checked the vacuum advance and when I plugged the line to the carb the engine smoothed...Oh oh.  So I put my vacuum pump on the vacuum advance and I can't pull any vacuum.  The diaphragm unit needs replacing.  Is it possible to change that while the distributor is still in the truck or do I have to pull the distributor?  Have any of you done that?   Thanks for any inputs.

Title: Re: Vacuum advance unit change.
Post by: fiddler on July 09, 2020, 10:00:49 pm

Sorry,  I forgot to post the truck specs.  1974 chevy C10 stepside.  350 engine with automatic transmission and factory air....  And yes the air works.   

Title: Re: Vacuum advance unit change.
Post by: bd on July 09, 2020, 11:18:23 pm

The vacuum advance diaphragm can be replaced with the distributor in the engine and clamped down tight.  Two screws.

Title: Re: Vacuum advance unit change.
Post by: fiddler on July 10, 2020, 01:27:24 am

Tomorrow then.  Thanks much...