Master Cylinder - AC Delco 174722 or 174723

[sparg93]

I'm finally working on my hydroboost and should finish it by tomorrow!

My question - our OBS vacuum brakes came with Master Cylinder 174723. The hydro 3/4t trucks came with 174722.

I have the "hydro" (174722) in front of me and it's identical in every way to the vacumm MC on my truck.

I then looked it up on rock auto and 174722 is definitely for the hydro 3/4t, but ALSO lists 1/2t vacuum trucks as other applications. In my experience, if AC Delco has seperate part numbers, there is some difference...any ideas??

 

[SunlitComet]

I am guessing the the stroke displacement.

 

[sparg93]

Sunlit - that's what I was thinking when i took it out of the box.

What's throwing me though is that rock auto's part number next to each MC states the same applications (when you click on it)..meaning they are interchangeable amongst 1/2t and 3/4t trucks.

With that in mind - I'm thinking of using my current MC and simply saving this new one...it would save me the time of bench bleeding it and worrying about seals. However, if the internal springs are different, I would rather go with what Chevy designed b/c if they made an adjustment, there's usually a reason.

Hmm...another mystery

 

[SunlitComet]

found the difference sort of 722 is for the police package. 723 is not.

 

[retorq]

Police package had the bigger pistons in the calipers didn't it?? That probably means that master has a bigger bor to move more fluid ... wild guess though.

 

[BluHoe96]

When I did my hydroboost retrofit it was the bore of the MC that was too big to fit into the hydroboost . I bought an MC for the hydroboost so that it could fit into the HB. If I were to do it all over again though they say if you can find a way to fit an NBS MC the piston is a bit longer so your pedal travel can be shorter.