[F1147D]

I need some help figuring out what is the correct master cylinder for my 70 GTO w/o power breaks. Right now my car has a delco master cylinder with a part # of 5468309. All the searches I’ve done show this as a 69 chevelle/Firebird/GTO master cylinder (which my car was assembled in the last part of 69). However, I have the Paul Zazarine restoration guide that says that the 67-70 GTO all carried the same part number of 5458522. Anyone out there know what the correct part number is for a 70 GTO?
Thanks

[Keith Seymore]

I know nothing about '70 GTOs, but I do have access to the Delco Moraine engineering charts for 1969 and 1970.

First: disc or drum? They show power disc and also power drum, in addition to one manual system.

Secondly - keep in mind a number cast into the side of a part does not necessarily equate to the part number. It could be a casting number for the raw casting, which could be machined or assembled into a different (or multiple different) final assembly part numbers.

Lastly - I show a master cylinder part number, power booster part number and then an assembly (ie, power booster plus master cylinder together) number, and I don't see the 5468309 or 5458522 number in any of those columns.

K

[F1147D]

Keith,
Thanks for the help. My car is drum brakes without power breaks. Here’s a picture from the page of the restoration guide where is gives the part number.

[Keith Seymore]

For '70 Pontiac A body with manual brakes I show 5468683, assembly code RW, a 1 inch bore master. This is dated 10-19-68, so was probably pretty close to the original release.

That part is common with '69 Pontiac A body manual brakes but does not seem to be shared with any other product or nameplate.

K

[Scott Thelander]

the 309 is a disc brake master cylinder

do you have disc or drums up front?

whats the code on the front pad ?

here is a pair of my 69 disc brake 309 masters

and a 70 manual drum master I pulled off a parts car

[F1147D]

Thanks for all the info.

My GTO was originally build with drums upfront but was converted to disc at some point. I am going to keep the front disc just for safety.

[marxjunk]

309 is 69..

70 uses the square master...heres an orig..

[Held for Ransom]

Mark, are you sure that's not a replacement? There's no bleeders.

[marxjunk]

could be..i didnt notice..but 70 is square is what i was trying to show..the oval ones are not correct for 70..and ya see them on them all the time..i will look thru my stash i have 4 or 5 with bleeders..i will post a pic of one of those..

[pggto]

Originally Posted by marxjunk

309 is 69..

70 uses the square master...heres an orig..

I thought the non power brake cars used the smaller master. The square one was for power brakes I think. Heres a picture of a car I found online with manual brakes.

[Scott Thelander]

manual drum on that red 70 350-2 car..
or at least it has a 70 alternator bracket

[Held for Ransom]

http://www.forums.maxperformanceinc....d.php?t=612266

[Scott Thelander]

70=manual drum and no bleeders ... power drum and bleeders ... seems to be my observation on my parts cars

[OG68]

The stock drum brake, no power assist, master cylinder was the same from 67 to 70 and was shared with Chevrolet. Casting number 5462310 (not the same as part number) This one for my 68 is dated C128 and stamped CT.

[F1147D]

So my car came with front drums (non power) but was converted to disc and I want to keep them so should I use the 5468309?

[marxjunk]

if you keep discs, yes..the disc master..it has more volume that is needed for discs

if you want it to look like a factory set up you need a 70 square reservoir..if you dont care about appearances then the one you have a pic posted will work

[Held for Ransom]

It's not just the master. The proportioning valve and metering block have to be correct too.

[F1147D]

Thanks everyone for all the help