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Mod | | | Forums66 Topics128,159 Posts1,057,039 Members48,460 | | Most Online14,466
Apr 26th, 2026 | | AD Chevy Trucks  Over 6,000 pictures Brad Allen has an awesome collection of Chevrolet factory pictures that he has set up from film strips. Check them out!
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| | | | Joined: Dec 2007 Posts: 171 Shop Shark | | Shop Shark Joined: Dec 2007 Posts: 171 | Engineering is going on for new brakes on the 1947 first series GMC EC-302 dump truck. Can someone tell me what the bore and stroke length of a stock master cylinder would be? Also, does the stock brake system, on these trucks, have a metering device to prioritize more pressure/flow from the master cylinder to the rear brakes? Or is the pressure equalized between the front brakes and the rear brakes?
Al | | | | | Joined: Nov 2005 Posts: 6,100 'Bolter | | 'Bolter Joined: Nov 2005 Posts: 6,100 | Hy Big Al's, the bore of the stock master cylinder is 1 1/4" as to the stroke that is dependent on the pedal linkage and the brake shoe adjustment, suffice to say that the stroke available was more than adequate for the average driving conditions anticipated by the engineers who spec'd the system, hope that helps. | | | | | Joined: Mar 2004 Posts: 6,233 'Bolter | | 'Bolter Joined: Mar 2004 Posts: 6,233 | Al, The pressure is equal throught the system. The amount of stopping power per axle was determined by the size of the wheel cylinder, the diameter of the drum and the brake shoe surface area. Mike B  | | | | | Joined: Jan 2010 Posts: 120 Shop Shark | | Shop Shark Joined: Jan 2010 Posts: 120 | And as an old timer pointed out to me recently- there is no booster- the "boost" came from the really long foot brake pedal and the short leverage into the master cylinder.
'47 Canadian RHD 1.5 ton truck
| | | | | Joined: Mar 2004 Posts: 6,233 'Bolter | | 'Bolter Joined: Mar 2004 Posts: 6,233 | anyoldiron, FYI, the Hydrovac booster were first introduced in 1939 on the 1-1/2 & 2 ton trucks... Mike B | | |
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