67 master cylinder

[Gary 38683]

After installing a rebuilt 509 master cylinder, I cannot get it to bleed. I
have been told that I need the 348 for power brakes by the co. that the cylinder
came from. Checked another 67 pb Top Flight and it had a 509. What's the problem? Put a Delco replacement on and brakes bleed and work fine. Does anyone
know what the deduct is for the not correct master cylinder is?

[Craig S.]

Re: 67 master cylinder

Gary - when you say it won't bleed, do you mean it won't bench bleed? It is very important to perform that operation first, with the cylinder off the car usually in a soft jaw vise. This lets you tip the keep the cylinder horizontal to get the bubbles out.

You don't mention how or who rebuilt the cylinder, so it is hard to guess if you have a problem with correct rebuild kit parts or issues with clogged holes between the cylinder and reservoir. I have no faith in rebuilt master cylinders at all unless they have been brass sleeved by someone like White Post Restorations or Apple Hydraulics. Maybe you can elaborate on what you have to help us out. There have been many posts on the boards here about 67 castings, and 509 is the right cylinder. It should also have cast in bleeder ports for 67, later 509's didn't have this feature if I recall from Joe Lucias comments. The non power brake 1" bore cylinders like mine also have a DC stamped on the front flycut area. If I recall, the power brake cars use the later 1.125" bore, and have a different stamping on this pad, seems like a PG if I recall, I am sure this is detailed in the TIM&JG.

[Norris W.]

Re: 67 master cylinder

I probably shouldn't be posting this, because it's based on a REAL foggy memory, but arent't there at least 2 different depths in the piston hole for the actuator rod for the power vs non power cyl's? I wonder if the difficulty in bleeding could be a mechanical problem????

[William O.]

Re: 67 master cylinder

Casting number 5455509 with a "DC" stamp on the front machined area were used for "standard" or J50 power brake cars.

Casting number 5480346 with a "PG" stamp were used for J56 HD power brake cars.

Both master cylinders had bleeder screws.

Make sure of the casting numbers before you buy!

[Craig S.]

Re: 67 master cylinder

Bill - I will amend my post, I sure don't want to convey misinformation. I should have looked in my TIM&JG BEFORE posting!..thx, Craig

[Craig S.]

Re: 67 master cylinder- CORRECTION!

As Bill pointed out, the power brake cars use the 346 vs 509 castings, the PG stamp is correct I mentioned for the PB cars. That will teach me for posting without checking the TIM&JG first!...Craig

[William O.]

Re: 67 master cylinder

The bore for the standard master cylinder is 1" and the HD J56 is 1 1/4"

[Craig S.]

DOUBLE CORRECTION!

509 is correct for J50 manual and PB cars, the heavy duty PB was with 346 cylinder was for the J56 only brakes...Craig

[Craig S.]

Re: 67 master cylinder

Bill - 509 cylinders are correct for both manual and J50 power brakes...most power brake cars were J50 option. The J56 with 346 cylinder was the rare HD power brake option....just got this out of the TIM&JG....Craig

[Craig S.]

Re: DOUBLE CORRECTION!

My post should have said "manual brake and J50 power brake" I wish we had short term edit functions on this board like some of the others....Craig

[William O.]

Re: DOUBLE CORRECTION!

Thanks for the clarification.

Bill

[Norris W.]

Re: 67 master cylinder

I wish somebody would refresh my memory on the hole in the piston depth issue. I recall sending a bare cyl of some type to White Post in the past and them calling to ask if it was manual or power brake application. I wouldn't say for sure that it was Corvette, but I sho' thought it was. I do distinctly remember that in some GM applications there's a rod length issue.

[Craig S.]

Re: 67 master cylinder

Norris - I would like to know too...all I have is my 67 509 manual cylinder. It is stripped so I could compare if you have a handy power cylinder to compare drilling points. I do know when I recently bought repair kits the power was a different part, but I believe this was due to the 1.125 bore vs 1.00, (again, we are talking the 509 cylinders). However, the rod length may also be a difference, and affect drilling....Craig

[Joe L.]

Re: 67 master cylinder

Norris----

There were different depths for the push rod hole in the secondary piston. However, this does not apply to Corvette applications. The "509" master cylinder used for 1967 Corvette standard and J-50 power brakes used the same secondary piston, regardless of whether the actual application was standard or J-50 power brakes.

After 1967, the "509", DC-coded, 1" bore master cylinder was used only for manual brake applications. However, it used the same secondary piston as the 1967 "509" master cylinder.

For 1967 J-56 and all 68-76 power brake applications, the "346" or "309" (68+ only) master cylinders were used. These were 1-1/8" bore master cylinders. ALL used the same secondary piston, but, at the moment, I cannot tell you if the pushrod hole depth is the same for the 1" and 1-1/8" bore cylinders.

The real problem with primary piston pushrod hole depth comes into play when other, non-Corvette pistons are installed in a master cylinder used for the Corvette application. Originally, the "DC" or "PG" codings defined the COMPLETE master cylinder, NOT just the casting. The casting number defined the casting. The only difference between the Corvette master cylinders of the 67-73 period and some of the other GM master cylinders of the same period related to the installed primary piston and the presence or absence of check valves in the outlet ports. So, if someone (like a rebuilder) installs the wrong primary piston in a Corvette master cylinder, then it is no longer a "DC" or "PG" coded master cylinder, even though the CASTING still has this code on it. The master cylinder then may be NCRS-correct, but NOT FUNCTIONALLY correct.

By the way, the bleeder valves were used for 1967 thru about 1973 applications. Afterwards, although the castings were the same through, at least, 1976, the master cylinders were not drilled and tapped for bleeder valves for PRODUCTION or SERVICE (including 67-73 SERVICE).

[Gary 38683]

Re: 67 master cylinder

The master cylinder was bought and rebuilt from CorvettePartsMan in Florida.
With the Orlando show so close I am not going to be able to rebuild it again
by someone else, maybe White, so must use the Delco. How many points is that going to cost? Should I return it for a refund or ask him to rebuild if again.
I don't think he will rebuild it as he has said I need the 346.