I don’t believe it to be original since it doesn’t have the machined code pad. Also, the casting number appears to be 408 rather than 409. Of course there’s the 1 1/8 vs 1 inch bore diameter issue. It has a 1 1/8 bore.

I hate to go further down the rabbit hole, but I wonder if the correct master cylinder can be inferred using the parts book and looking at MC cover and bail replacements.

Scott

 

I will probably get scolded here but thats ok, I think it’s possible they used a couple different MC during production. Every picture I pull up of very very low mile w30 non power disc brakes has the squared off MC. I posted pics of my w30 from 1978-79 with 48,000 miles and it has that same greasy MC that I pulled off it last year..EB 5470409. And it’s a 1 1/8 bore. I mean MC don’t usually wear out that quickly. I posted a barn find and a 17,000 w30, same MC, pics of early w31, same squared off MC. My cars brakes worked fine with the EB 1 1/8 bore MC, its was leaking is the reason for the change. From a statistical standpoint how can most every w30 in 1970 show eb with 5470409 as the master cylinder yet not be considered original. Steve Minore calls them correct.. Is it possible GM used different ones mid year?

 

 

The evidence is overwhelming for the EB mc application on '70 A-Bodies for both power and manual brakes, and the evidence is clearly shown right here on CO.

All one has to do is spend time in the Major Builds & Projects forum and there are countless examples to support the usage of the EB mc.

As far as I'm concerned--case closed

 

Well--almost closed!
Do you think 442Fred would put the wrong mc on his pedigrees?

https://classicoldsmobile.com/forums...der-id-150827/

 

I went to a local old car salvage yard last year that was closing down.......a MC on a Cutlass (71/2) caught my eye and I pulled it. It was a "BE" stamping which was correct for at least '71's w/power disc brakes. Kept checking other Abody cars there and by the end of the day I had 4-5 "BE" master cylinders and 1 "EB" master cylinder. Must have been original to the cars I pulled them from IMO.

I'm in the "category" that the "EB" master is correct for the OP's manual front disc car and, of course, correct for power front disc '70 Cutlass's, 442's, etc.

The first paragraph I typed above is merely an observation/opinion that plenty of these original master cylinders lasted a long time and didn't need replacement (as Andy mentions in his posting [#42] above).

 

All

I really appreciate all the responses. I didn’t mean to stir things up but was confused by the factory literature. Looks like EB is carrying the day. I’ll assume everyone with EBs on their manual brake cars find pedal pressure acceptable and can lock up their brakes without applying Herculean pedal effort. I guess I search for an fall of ‘69 EB.

Thanks
Scott

 

Stirring things up is good. I wouldn't get too hung up on the date code.....your "challenge" will be to find one with a nice/legible "EB" stamping on the machined pad on the front of the master cylinder. VERY COMMON for the two letter code to be rusted/pitted away.....very common. Sure, the date code matters for a "super exact" restoration but getting a decent two letter code stamping is usually the bigger challenge.

There's a discussion on a Buick site right now where a guy is looking for an original master for his '70 Stage 1 w/power discs. Those cars used the large oval double bale "EA"-stamped masters like a lot of 1969 cars used.

The Buick stuff is more "cut and dried" with no conflicting info on useage for 1970.

Just be aware of one thing.....you'll need REAL GOOD PICS of the two letter code stamping and stamping area if you're buying one online. No use in spending a lot of $ on a core that has a crappy or illegible two letter code stamping.

Now the search for the most "super survivor" '70 cars continues......to see what MC's they have. Jason Stritesky had a survivor '70 W30 (4 spd I think) awhile back (he brought it to MCACN a year or two ago). He advertised it for sale and did a YouTube video (at least one)......not sure if it still had an original MC but may be worth digging a little to see what photos, etc of that car might show.

Don't know if Fred still has the "Uncle Bob" '70 W30......but I don't recall what trans it had (ie - thus the brakes....manual or power).

Good thread.....thanks.

 

Uncle Bob's car.

 

Can you elaborate on (Uncle Bob's) car?

 

I think I sort of "coined" that name.....the car was for sale A LONG time ago on ebay. Not necessarily the earliest days of ebay but still, not remotely recently or even with the past few years.

I think whoever had it for sale then was related to the original owner and they kept referring to their Uncle Bob in the extensive description of the car. I believe this dude I refer to as Uncle Bob may have been the original owner (not 100% sure but at least their Uncle Bob was the owner that the sellers got the car from or were related to).

So.....from then on I'd call it the "Uncle Bob W-30" car when discussing it w/Oldsmobile friends. It seems like it was one of the "earlier" survivor Oldsmobiles to showed up on ebay. People weren't chasing survivor Oldsmobiles at that time as hard as they've been doing so in more recent times. To me at least, it was one of those ebay cars you really remembered....being a survivor and in REAL nice condition at that....again, at a time when there hadn't been a whole bunch of them out there for sale, etc. I want to say this may have been back in the early 2000's but not 100% sure.

 

Not to fuel the fire but I am with Joe. Pictures fron the 2000's?? So many things were changed day one. Especially drag only cats.

I think we have all learned that books diagrams etc are just that. GM did whatever to keep a car going down the line. Assembly manuals say this and that.

My car came with an OAI hood. Dash code paint color. Spirt mirrors and a dual gate. Nothing else. Open rear. Fixed fan.


Books can say whatever. GM wasn't by the book always. At least from what I have learned.

 

The "books" are conflicting.

 

EB. Joesw31 is correct.