Putting together a junkyard eight lug front disc brake setup for my 66 c20. At this point I've got everything but the master cylinder and prop valve. I'm hoping to find a dual circuit manual brake master cylinder that's set up for disc/drum and that's capable of moving enough volume to operate the big 3/4 ton brakes properly and reliably. So far the closest I can find year-wise is 73 camaro. Would this work? I wonder if it would be stout enough to push brakes bigger than the five lug camaro stuff. All of the truck units for 71 and up seem to be power only, which I want to avoid. Want all manual ideally. Truck and full size car units I've found have all had 1-1/8 inch bores or larger, which I imagine would make the pedal too hard to be useful, not to mention the lack of a deep hole for the push rod. Have searched far and wide for the information but haven't come up with anything. I'm hoping one of you might have the hot tip. Recs for good adjustable prop valves welcome as well. Thanks much in advance.
Stick with the truck stuff. What is the discs out of? Use that master & prop. valve. There has to be a truck with manual brakes. I'd take an Impala or Chevelle unit over a Camaro.
Everything is from a 73 c20. No manual cylinder available for that year as far as I know. I was pretty sure there'd be a dual manual disc/drum cylinder from an earlier truck application (71 or 72) but that doesn't seem to be the case. I haven't been able to turn up anything manual for full size cars either, just the camaro unit--that's the only one I found with factory front disc and a 1" bore. Strange but true.
I should probably add that the rear brakes will stay stock 66 drums. Will need a residual valve in the drum port presumably, which is why I've been keeping my search to mid-70s and earlier. It's my understanding that residual valves went away in the mid 70s with the advent of wheel cylinder expanders.
It's what I use, a 73 non power master from a chev pickup, but I'm told it was marketed for municipal use, wasn't standard on showroom trucks. Least that's what my parts guy says. Anyway, that's whats in my roadster. Vick, get that coupe on the road, I need some drool time.
Would either of you happen to have a part number? I haven't been able to find one disc/drum with the small bore. I don't have the calipers in hand--reman units are in the mail--but they're supposed to spec out at 2.94" bores.
The catalog alone is a fantastic resource 34-4022 I had an 85 with manual brakes. My parts house got it for me the next day.
Thanks, 31. I actually came across thats page in my searching, but the only cylinder definitively marked as "without power brakes" is for a 1/2 ton application. I'm assuming the different stock numbers for the 1/2 and 3/4 ton cylinders mean they're different in some important way. Bore size, maybe? However that 1/2 ton cylinder is probably better than the Camaro unit I was looking at, at the very least. Maybe I'd better give LMC a call and ask if they think it'll work. Spendy, especially with shipping, but what are you gonna do?
Lets say you have 2 identical OEM vehicle but one has power brakes and the other has manual brakes. You'll find the foot pedal is higher off the floor on the manual brakes than the power brakes because if the pedal ratio. The master cylinder MAY have a slightly smaller bore on manual brakes than the power. Also the push rod reciever cup MAY have a different depth bore. So for sure the pedal ratio will be different. Maybe bore size and maybe cup depth
But why the distinction between 1/2 and 3/4 ton specifically, with no clearly marked manual cylinder for the heavier chassis? I know the manual and power cylinders will probably be different within the same model designation, that makes sense. I'm confused as to why there's no specific 3/4 ton cylinder though. Starting to think it doesn't exist as an oem part. Bobs, my understanding is that anything pre-71 will be drum/drum only. I wonder if I could pull the residual valve from the rear port of a drum only cylinder and run the discs that way. I imagine there might be a fluid volume issue.
That's possible. Strange that there would be two catalog numbers though. The calipers for 1/2 and 3/4 ton are listed as same part, same bore size, so that's a useful clue. Maybe I'll see if I can get a cylinder from each model and compare bore and reservoir sizes.
'77 E-250 van has a 1-1/16" bore master p/n 10-1676. Has a deep hole in the piston that fits a manual brake push rod. May be something to look at.
Look at those part numbers and then look at the applications You'll see same same for 1/2 ton and 3/4 ton and a variety of letters. You need to read between the lines and that compare off page text to get what you want. Everything you need is there, get the application and call autozone
Yeah I'm probably overthinking it. Looks like most calipers, truck or car spec, shared that bore size of 2.94" in 1973. Rotors for 1/2 ton are same thickness as for 3/4 ton too. I feel pretty confident that the 1/2 ton cylinder is the same, or certainly will be functional in any case. Thanks for all the help fellas. The HAMB rules.
Gotcha on the pre-1971 thing. Quite possible. What is the bore of the single master? You could always upgrade to power brakes pretty easily. https://www.summitracing.com/parts/...2/make/chevrolet/model/c20-pickup?prefilter=1 Just realized it says disc-disc, but you get the idea. Look at Cardone, they are a good rebuilder. Cardone 50-1023 for a '73 C20 may work. https://www.cardone.com/Products/Product-Detail?productId=50-1023&make=Chevrolet Trucks&model=C20 Pickup&year=1973&info=
Ordered up a Delco disc/drum manual master for a 76 C10. Closest I could find to what I've been looking for. Has a 1" bore, which ought to be small enough to operate manual, and has the larger reservoir for the disc side of the system. I'm pretty sure it'll work, will report back as soon as I get it installed. I'm also going to plumb an adjustable prop valve into the rear line. I figure the way if there's any issue running the big drums I can at least dial a little extra pressure into the rear. The master cylinder is AC Delco 18M117, for posterity. Thanks a ton for talking it all over with me everybody. As for that prop valve, anybody have a specific brand to recommend or avoid? Looking at dial adjustable type, like the ones Wilwood, Baer, etc, sell.
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