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Home » Public Forums » GMCnet » Re: [GMCnet] Different models of P-30 master cylinders?
Re: [GMCnet] Different models of P-30 master cylinders? [message #248379] Thu, 24 April 2014 15:24 Go to previous message
Tom Whitton   United States
Messages: 235
Registered: February 2004
Location: Paducah, KY
Karma:
Senior Member
Does anyone know if the following sent to me several years ago is still true? Are there still three different models of P-30 master cylinders and, the main reason for my question, do they all take the same length pushrod? There is quite a bit of travel on my brake pedal before the brakes engage and I want to reduce the travel if possible. The brakes are new and the rear drum shoes are adjusted tight. My brakes are excellent but I don't like the travel.

(I think Emery Stora might have written this):

"The are three different P-30 master cylinders. Two of them have a 1 1/4" bore and one has a 1 5/16" bore. I used the one with the 1 5/16" bore which is for a 1972-76 Chevrolet P-30 chassis which has 15" drums and 4" wide brake shoes. Carquest 20-1583 (rebuilt) or E84058 $122.43 (new). Price from year 2000. This one has about 10% more volume (or 10% less stroke for the same volume than the 1 1/4" bore on the other P-30 models.

It will be necessary to make a pushrod that is 3 11/16" long. Use a steel rod of the same diameter as the original and round the end on a grinding wheel or adjustable pushrods can be purchased.

Since the master cylinder is longer than the original it may be necessary to grind a reinforcing rib on the inside of the front fiberglass door the clear the bail on the master cylinder or washers can be placed between the hinge and the door to make the difference."

I made my pushrod 3 11/16" long as suggested. I don't want to unbolt everything, including the vacuum pump and connections if there isn't a possibility of reducing the pedal travel. I will appreciate your thoughts.

Thanks,

Tom Whitton
26 foot updated GMC
Paducah, KY


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