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What's the correct master cylinder for a '70 manual front disc 442
I'm thinking about replacing the master cylinder on my October '69 built '70 W-30 (manual front disc). The brakes have always been really hard to push (more than I would think a manual car would need). I've attached a photo of the master cylinder that was on the car when I bought the car in '96. Note the lack of bleeders. I've seen many references to the correct master cylinder as one with a casting of 5470409 and a stamp code of "EB". It also appears the assembly date would also be stamped on the pad. Of course they also have a Julian date on the casting in the back. The assembly manual shows a part number of 5470662 with a rounded body but I don't remember seeing a rounded master cylinder on any of my 1970 cars, I recall them as all being "squared off". Also the Olds faq from ages ago says there were two types; an early dual bale and a later single bale. Finally, there is also reference to bore diameter in many posts. Where manual brakes should have a 1" bore with a long actuation, while power brakes should have a "1 1/8" bore with a shorter actuating rod.
The master cylinder casting number that is currently on the car looks to be "5470408" with "1 1/8" followed by "D67". The casting data is "194" followed by what looks like "71" or perhaps "77".
Any insight or recommendations would be greatly appreciated.
Thanks for the quick response. Any more information on this elusive master cylinder? Is the casting number 5470662 like the part number in the ASM? Are you aware of this master cylinder being used on other GM cars. Any ideas what the code is? Perhaps NX as described in the ASM? I'd like to hunt one down and put the correct one back in.
The casting number is not he part number, unfortunately. Yes, it is unobtanium. Most 1970 cars you see will have the incorrect rectangular M/C as a replacement.
I think I have a master cylinder that has the correct appearance. It likely came off a power brake car though. Joe, could one from a power brake car be made to work on a non-power brake application? John
I think I have a master cylinder that has the correct appearance. It likely came off a power brake car though. Joe, could one from a power brake car be made to work on a non-power brake application? John
What I believe to be correct is the Moraine casting 5470409, single bale, EB stamp with 1/1/8" bore, power or manual front disc for the 442 cars of 1970.
I should add that the OEM M/C is a 1" bore, not 1 1/8".
If you change to the correct 1" bore, you will reduce the brake pedal effort by 20%.
Many of the high performance, manual transmission cars of that era had manual front discs because there wasn't enough engine vacuum to operate the brake booster.
I had two of those manual brake cars, a 1970 Corvette LT-1, and a 1970 W-30. The brake effort was higher than a power brake car, but it was not something my wife couldn't drive. I remember those systems had nice brake feel--very direct with no lag.
What I believe to be correct is the Moraine casting 547049, single bale, EB stamp with 1/1/8" bore, power or manual front disc for the 442 cars of 1970.
Thanks for the responses. I wonder how other folks have handled the manual brake problem. Maybe they just live with the high pedal effort. I know it takes everything I've got to lean on them enough to lock the wheels up. I guess I need to look for one with a 1" bore, long "throw", and residual pressure valve for the back while having the correct line fitting sizes. Maybe as was suggested one of the 409 EBs can be modified from 1 1/8 to 1.
2blue442/John,
Could you post or send a picture of the master cylinder you have, particularly the casting number and size information that's cast into the side.
Your car already has the correct master cylinder. That picture in the assembly manual is inaccurate and the GM parts books is incorrect for the 1970 Manual disc brake car. The "EB" master cylinder was the same regardless if it was manual disc brakes or power disc brakes (bore 1 1/8).
The only “W” car with manual disc brakes with a 1 inch bore was 1971/1972.
Part of your braking issue may be the brake pads and brake shoes. These cars used special pads and shoes.
This is from the January 1972 edition of the Parts Book. Yeah, I realize that same edition also calls out the dimpled front fenders for the 1970 cars. Also note that 5458522 is the same M/C called out for the 67-69 drum brake cars. I suspect this is a case of the best replacement part available at the time.
OP yet another reason for your hard braking could be caused by the condition of your wheel cylinders. If you are not sure show long it has been since this maintenance has been performed you may want to address it. The brake distribution block should be free of corrosion and gunk. Too, the rear shoes should be adjusted so that you feel some resistance from the shoes when you spin the rear tires by hand.
I have the original rectangular Moraine EB master with the 1-1/8" bore on my '70 W car (4-speed, so no power brakes), and the braking capacity is just fine.
Part of your braking issue may be the brake pads and brake shoes. These cars used special pads and shoes.
Good observation, Joe.
Back in the day, my 1970 non-power brake, disc cars that stopped well still had the original pads and shoes. If a previous owner put in million-mile pads and shoes, their hardness doesn't allow good braking.
This is on a 1970 Olds 98. I've got another of this style loose in the garage or shed. I'm losing my daylight so I'll try to get more details this weekend. It does have a code stamped into the pad, I don't think its EB. It looks more like one of the letters is a W or if read from the other direction an M. If tnswt has a rectangular one having the right application code may be more important for correctness than the shape of the master cylinder. John
Thanks for taking a look. The one in the picture looks like an RA. The other writing with the RA is likely the assembly date. The CSM shows RA, CT, and EB as the correct codes. As was pointed out earlier the EB code is listed in the CSM but the parts book and ASM seem to be in conflict with the CSM. The CT looks like what the service replacement would be looking at Joe's parts book. I'd be interested if the one in the shed looks rebuildable. See if you can read the code on the pad and if there are any casting numbers on the body. The casting code should be seven numbers. The bore size, I believe, is also cast in as 1 1/8 or something like 1 - 0 - 1 and would be in the same area as the casting number and the casting Julian date. In any event it sure looks like what Joe's example looks like and what the ASM shows.
This is the mast cylinder off my 70 w30 with 62,000 miles..I replaced last year, kept this and I believe it to be the original..hope this helps. If you need other pics let me know..
This thread about the M/C for 1970 manual disc brakes, not power.
JP, are the pics of my believed to be original MC off my w30 no power disc brakes helpful, do you need to see any other pics? It does have a 1 1/8” bore. 4 speed car, 62,000 miles
JP, are the pics of my believed to be original MC off my w30 no power disc brakes helpful, do you need to see any other pics? It does have a 1 1/8” bore. 4 speed car, 62,000 miles
I was actually responding to all the photos of cars with power brakes. I appreciate your photos, but of course the problem is "believed to be original", right? I'm looking for "known to be 100% original". These cars are over half a century old - a lot has happened. That's why I'd love to find photos taken in the early 1970s if possible. I've checked all the period magazine articles I have and the photos are either power brake cars or don't show the M/C. There is obviously conflict in the factory literature. The M'C on my 70 MT W30 was replaced long before I got the car, so that's certainly not the original part (and the replacement is an EB). The parts book page I posted above clearly shows 1" bore for the 1970 manual disc cars.
I was actually responding to all the photos of cars with power brakes. I appreciate your photos, but of course the problem is "believed to be original", right? I'm looking for "known to be 100% original". These cars are over half a century old - a lot has happened. That's why I'd love to find photos taken in the early 1970s if possible. I've checked all the period magazine articles I have and the photos are either power brake cars or don't show the M/C. There is obviously conflict in the factory literature. The M'C on my 70 MT W30 was replaced long before I got the car, so that's certainly not the original part (and the replacement is an EB). The parts book page I posted above clearly shows 1" bore for the 1970 manual disc cars.
Joe, this Is a picture of my car from 1979, second owner sent me this picture when he first bought it he said. If you look at that master cylinder, it’s exactly the same one that’s in my pics that I sent earlier I believe it to be the original one..in fact, I’m sure of it.
This is from the January 1972 edition of the Parts Book. Yeah, I realize that same edition also calls out the dimpled front fenders for the 1970 cars. Also note that 5458522 is the same M/C called out for the 67-69 drum brake cars. I suspect this is a case of the best replacement part available at the time.
The drum brake master cylinder will not work. If I recall correctly it has internal check valves that will not allow the caliper piston to retract. Unfortunately, an error from Oldsmobile since the beginning with the parts book. My September 69 book is also not accurate.
Actually, you can easily extract the residual pressure valves. They are in the outlet ports. I agree that a drum brake M/C is not ideal, but I assumed it was to get the 1" bore. Yes, errors in the parts book are not unheard of, but I find it interesting that they specifically pulled out the manual disc cars and listed them separately. I'd be interested in seeing a parts book dated sometime in 1970.
.....The M'C on my 70 MT W30 was replaced long before I got the car, so that's certainly not the original part (and the replacement is an EB). The parts book page I posted above clearly shows 1" bore for the 1970 manual disc cars.
It looks like you have the original mc on your car, no?
December 6th, 2023, 09:50 AM
