I am currently restoring a 1970 Buick Post Sedan Skylark. The car was built 06/70. It will using the correct original front disc brakes from a donor 1970 Skylark. I have seen both styles of MC... the round type with bleeders and the square type with bleeders. I have heard that the earlier cars had the round type and the later that the square type? Not sure? My question is what type Master Cylinder is correct for my 06/70 built Skylark with disc brakes. Also what would be the correct part numbers for either master cylinder and the proper code stamping? Thanks, Dan.
The correct one for a disc brake car is the round one with double bailing clips and bleeders. I got mine from Then and Now Automotive. http://www.thenandnowauto.com/ Corvettes use a similar looking master cylinder. The drum brake cars, and 71 and up cars use the rectangular master cylinder with single clip.
I am just stating this to be on the safe side. When you say you have "both" kinds of MC's, I assume you mean you have two different "Disc brake" MC's and not one drum/drum and one disc/drum MC as the all drum MC's are rounded as well (so much smaller in fluid capacity compared with the disc MC's), but should not be used with disc brakes.
Ken, I'm not sure, but I believe the Drum Master Cylinders were rectangular in 1970, just the Disc Brake ones looked like this, I might be mistaken. I'm sure Duane can tell us for sure. http://www.v8buick.com/attachment.php?attachmentid=72729&d=1147102970
The drum MC's were round, but smaller (fluid capacity) than the disc MC's. My '70 GS S1 has all drums with a build date of 5/70, all original with small round MC. Unfortunately, it is stored off site, so I cannot just take a photo, etc. My point was just to make sure the drum MC is not mixed with the new/swapped disc/drum setup (the drum MC does not hold nor move enough brake fluid required by the disc MC's). I believe the double bailing clip MC's are all for disc systems and the round drum MC's had one clip.
Ken and Larry, Great advise, I appreciate the feedback. Ken... from the picture your posted, I`m assuming this is a reproduction MC? What I would really like to find is an original Disc/Drum MC, which I can rebuild and resleeve. Is there a part number for the correct MC that anyone can help me locate? Dan.
Dan: I did not post the earlier pic, Larry did. My point is just to make sure a drum MC is NOT mounted to a Disc system as the '70 (4 wheel) drum MC is also round. My understanding is that the all the square MC's (with one chamber visually larger than the other) are disc MC's. The dual bailing/retaining clips may be the BEST distinguishing external visual clue between the round drum MC's and the round disc/drum MC's. In the pic Larry posted, there does seem to be a larger front fluid chamber due to the bulbous external casting contour (indicating a scalloped internal chamber for holding more fluid). Your point is which disc MC is correct for a 6/70 build date and Larry is spot on that Duane could tell precisely which MC is correct for your car and when in the '70 model year Buick changed over, if at all that year. I think the pics posted below should help explain the point I was trying to make (just making sure a safety problem is avoided) that there may have been more than 1 rounded MC used in '70 and they are NOT interchangeable as between all drum and the disc/drum systems. The '70 GS 455 below is all original and has the 4 wheel drum brakes w/ rounded MC showing 1 retining clip mounted front-to-back (longitudinally) and the '70 GSX shown below has the disc/Drum brakes w/ a rounded MC and dual laterally affixed retaining clips. More importantly, the GSX has a build time span from March to June (or July) 1970, which encompasses your build date also. Hope it helps.
Here is a picture of the other disc MC which is squarish and is probably seen most often as most aftermarket ... and maybe even GM ... as this design was switched over to years ago as replacements. This picture is also from an unrestored '70 GSX, but I believe the MC pictured is NOT original, but we know disc brakes were included as part of the '70 GSX package.
Ken, You are right, they both have round covers. I was referring to the look of the master cylinders themselves. The Disc brake master has a sort of flattened look to it (like it was crushed top to bottom) Makes it look wider too. The drum master looks smaller and more rectangular in shape. The 71 and up were bigger and even more sharply rectangular as in the picture posted. Another thing I forgot to mention is the drum brake master cylinders would have residual valves front and rear while the disc brake master would not in front.
Dan, If you are swapping over a disc set-up...make sure you install the hold-off valve that mounts to the master cylinder stud.....if you leave that out...you will have problems.
Ken, Larry and George.... Thanks for your Help. I really appreciate it. Now for my dumb question.....Who is Duane? and How do I get a hold of him? Dan.
http://www.v8buick.com/member.php?u=517 Here you go. A PM will get you what you need. Duane is a concourse judge.
Is the proportioning valve on the side of the frame the same or different for drum to disc brake cars ? I thought it was ? Thanx Dave
I'll second the notion that ALL 70 original equipment master cylinders (PB PDB and Non PB) were round (NO Square) I have all three original units out in the field if you need pictures.:TU:
The reason for my question.....there is no proportioning valve on 70 models. There is the distribution block on the frame rail which is the same for disc and drum cars. The disc cars have other valves.....hold-off and rear delay valve. See my article for details and pics: http://www.buickperformance.com/discbrak.htm
I have the solid brass one in the upper of one of the those pictures on my 70 Power Drum car. I bought a new one through in-line tube. Hope it works as well as it looks? Thanks for the advice George...much appreciated! Dave
Hope this can help someone out. This is my 71 GS350 with 4sp and non power drum brakes. I found this NOS master cylinder about a year ago. Yes it is a factory GM master cylinder with bleeders. George
