1969 brake MC 5480346

[Kenneth K.]

Hi everyone-

My TIAJM (Ver 3) says the 1969 power brake MC casting number is 5480346.

Most of the posts I have read says the casting number should be 5460346.

Can someone check the most current version of the TIAJM (version 6) to see if it clarifies the casting number? Are both casting numbers correct?

Thanks,
Ken

[Joe L.]

Re: 1969 brake MC 5480346

Hi everyone-

My TIAJM (Ver 3) says the 1969 power brake MC casting number is 5480346.

Most of the posts I have read says the casting number should be 5460346.



Can someone check the most current version of the TIAJM (version 6) to see if it clarifies the casting number? Are both casting numbers correct?

Thanks,
Ken

Kenneth------


The casting number for the master cylinder is 5460346. The third "6" is often confused for an "8". I assure you that it's a "6". Casting number 5480346 never existed for anything.

[Kenneth K.]

Re: 1969 brake MC 5480346

Joe-

Thanks for the clarification. I have two of the 346 MCs that both have the two bleeders. One is casting 5460346 and the other is 5480346. The 8 sure doesn’t look like a 6. What also confused me is the ver 3 judging manual that says the casting number should be 5480346 not 5460346. So I am going to conclude that the ver 3 manual is in error and will order the latest ver 6 so I am current.

Also if you do a google search on “brake master cylinder 5480346” you will get lots of hits and some of the sites that are selling the 5480346 seem to be reputable sites. Even more mysteries about the existence of the 5480346 and from what you said if GM never made a 5480346 there is a lot of misinformation out there. Do you think that some how during the casting process the 6 turned out to look more like an 8?

Over the years I have either replaced or rebuilt my original MC. I remember the first time I had problems with the MC was in the late 70s. I thought I replaced it with a new one and stored the original and then a decade later had another problem. What I can’t remember now is at the time if I rebuilt my original I had in storage or the replacement. The 548…. is in my parts supply while the 546…. is on the car. I was almost certain the 5480346 was my original MC and the ver 3 of the judging manual confirmed it!

So now my MC again needs some attention and I want to rebuild my original which is apparently the 546…not the 548…..Geez I am glad you clarified that for me as I would have for sure rebuilt the replacement MC.

Ken

[Joseph W.]

Re: 1969 brake MC 5480346

Ken,
Here is my rebuilt one for my 1969 with power brakes.
The 6 does look like an 8
Curious if you can read your Julian date?

IMG_5725.jpgIMG_5724.jpg

[Gary B.]

Re: 1969 brake MC 5480346

6th Edition reads... "The brake master cylinder is Delco Moraine. The casting number and the Delco split-circle logo are on the engine side. Power-brake master cylinders are 5460346 and standard master cylinders are 5455509. It mounts to the booster or to the body with either two natural-finish nuts and split-ring lock washers or two natural-finish washer-head nuts without lock washers."
Gary Bosselman

[James G.]

Re: 1969 brake MC 5480346

NOS PG with what I believe is the date on same front pad. 1267
PG_mastercylinderdate.jpg

My 1971 PG with date on front outlet milled boss 20th day of 1971?
100_9224.jpg 100_9227.jpg

[Kenneth K.]

[Mark F.]

Re: 1969 brake MC 5480346

Ken,

If these were used on other GM products, my guess is 100's of thousands of these were made...lots of wear and tear on the male molding parts that press the figures into the receiving sand mold.

Look how "wavy" the cross bar is on the first 4...a lot different than the 2nd 4 with a bar that looks perfectly straight.
My guess is that part is cast in the same position as shown in your photo - molten metal is poured in from the top and flows out to sides (where your numbers are) and then fills up to the lid mating surface. The recesses for the numbers - if not crisp - can allow the molten metal to sag before solidifying. maybe that's what happened to the "wavy" 1st "4" cross bar.

Also to my eye, the "4803" look to be leaning a bit to the right...maybe that one was made at the end of many runs before it had to have the numerals replaced ?

[Gary B.]

Re: 1969 brake MC 5480346

If you crop out the part number and blow the picture up, the first "8" and the last "8" look different. The first "8" is really a 6. Smaller upper circle than the lower circle.

Is this getting to the point of picking fly poop out of pepper?

Gary Bosselman

5480348 Master Cylinder-1.jpg

[Joe L.]

Re: 1969 brake MC 5480346

Mystery solved - here is a picture of what looks like a 5480346 MC. The 8 does not look like a 6 but it does look like the last “6” at the end of the casting number. This is what Joe Lucia mentioned… that the third "6" is often confused for an "8”. This MC does not have a date code and it does not have the double bleeders as I recalled from memory that I thought it had =-). Sorry for the confusion but it’s clear to me that this MC was the service replacement MC that I bought in the 70s and the 5460346 MC on the car is the original which is the one I am going to rebuild.



Thanks for all the help,
Ken

Kenneth------

PRODUCTION and SERVICE master cylinders of this casting number after about mid-1973 deleted the bleeder valves.

[David B.]

Re: 1969 brake MC 5480346

GM 5480346 was/is (1984) a reserved number. It was originally assigned to the Frigidaire Division Ltd. England

[Kenneth K.]

Re: 1969 brake MC 5480346

Mark - your explanation during the casting process makes perfect sense to me. And back in 1969 the QA/QC program didn’t pay much attention if a 6 looked like an 8. That is probably why there are so many “5480346” castings out there that has lead to so much misinformation. Joseph now you know that your beautifully restored “5480346” is actually a correct 5460346.

Very interesting that the 5480346 was/is a reserved number. David - amazing that you would know something like this! And that explains why Joe Lucia said that the “casting number 5480346 never existed for anything.” To me this is the last piece of the puzzle!