| Re: JC-4 Vacuum Pump?? [message #364214 is a reply to message #364212] |
Sun, 23 May 2021 14:43   |
rjw
Messages: 697
Registered: September 2005
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RF_Burns wrote on Sun, 23 May 2021 14:45I posted this about a year ago on the operation of the JC-4 vacuum pump. Its not a great pump, about 8-9" of vacuum is all you can expect from it.
I bypassed the internal circuitry so now it only acts as a vacuum pump. Then I wired it through a relay controlled by Dave Lenzi's vacuum switch assembly. Best I can get is about 15" of vacuum. Not great but better than nothing.
http://www.gmcmhphotos.com/photos/data/6785/JC-4_vacuum_pump_operation.pdf
I might have kept my JC-4 pump had I known about the mod to use an external switch and some sort of reserve vacuum storage container. I thought a lot about the possibility of losing brakes while I was driving down to Death Valley from California and was happy I had the upgrade over the JC-4 pump. That trip caused me to decide to go with Dave Lenzi's disk brakes (I already had a 4-bag system). During the installation of the disk brakes I found out that I had a badly leaking drum brake cylinder that may have contributed to my less than great brakes during that trip down to the valley.
Richard
76 Palm Beach
SE Michigan
www.PalmBeachGMC.com
Roller Cam 455, TBI+EBL, 3.42 FD, 4 Bag, Macerator, Lenzi (brakes, vacuum system, front end stuff), Manny Tranny, vacuum step, Tankless + OEM water heaters.
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