68 Master Cylinder casting number
 

Anyone know the proper casting number for a 68 GTO with power drums?

Or ... how to identify what I have. Looks like 29863, has a faint what appears to be 4231A3, a random "G12" and a random 75.

I think the one I have came off a 68 Lemans with power drums, but was probably not OEM.

My 68 GTO has power drum brakes. I'll take a look at the master cylinder this weekend when I ride over to the shop.

Thanks. Might be a pain, it's probably on the bottom of the master. Maybe stick a phone camera under there :)

5460465
It is on the bottom. This one is with bleeders which I believe is for power brakes. Manual brakes didn't have the bleeders but i think the casting number is the same.

Casting number for manual drum brakes is different.
5452310

So whatever I have is not even close to "correct". Came off a power drum brake car, no bleeders. Says made in the USA .... so probably an old parts counter replacement from decades back.

Thanks guys.

I have a 68 GTO with manual drums. Casting number 5452310, with CT stamp.

Can you just add the booster? Can someone post a picture of an original 1968 GTO power drum booster and master?

I have a 68 manual and power drum master cylinder. My 68 GTO came with the power drum. The manual came off a 68 LeMans .

Both of these master cylinders have 5452310

The 2310 is the non-bleeder version. As I understand, that was intended for manual drum and the bleeder version for power drum. I think they thought the bleeders were needed because of the angle the master cylinder is at when mounted on the booster vs when it is mounted directly on the firewall (level). Like everything else, there are no absolutes with the way these cars were built and I have seen original cars at the yards were this rule did not hold.

The masters look identcal other than the bleeders.

Can you use either version for either application...yes. You have to make sure you have the correct piston, as indicated by the hole depth, to match the rod coming through the firewall (and booster if power). I believe the shallow hole piston is for power and the deep hole piston (maybe 1 inch) is for manual.

Looks like I would be safe looking for a 5460465. Just went through my reference pictures and I'm seeing quite a mix and match on "original" cars. Most of the power systems showing the bleeders, many of the manual systems showing the same MC but with just the bleeder bosses but no bleeders. But there are exceptions to both.

What is the funny looking valve setup bolted to the MC on some 68's with power brakes? Disk brake proportioning valve? It's not the one I've seen on the right side of the MC, this is on the left side bolted to the MC mounting bolts.

This is what I have now (after bead blasting) Looks like the right casting for non-power drums ( I have power) but the casting number doesn't appear to be GM at all.

The actual 2310 non-bleeder casting does not have the casted bumps where the bleeders would go. Looks similar otherwise. Not sure if you are looking for exact correct or just reasonably close.

If it's obtainable I'd like to get exact correct. Wouldn't think common old MC castings would be too expensive.

But then I just saw an ebay listing for a used 68 "Ram Air" timing cover for $750 :) So I could be wrong.

They should be cheap as they were used on several GM cars. Easy to rebuild but likely will have pitting in the cylinder. If the pitting is more than minor then should have it sleeved.

Well, look what I found in my parts collection .... if not for the virus lockdown I would have probably never taken the time to look so thoroughly for it and bought another one somewhere.

Looks like I might have already rebuilt it some decades ago, has original Delco cover and seal too. Found various other things I need also.

Chucked the other one in the recycle bin already :)

http://forums.maxperformanceinc.com/...1&d=1588667417

http://forums.maxperformanceinc.com/...2&d=1588667422

Dataway, I have a non-bleeder GM master (2310) I removed from my 68 Lemans if you need it. It worked well. I removed it to upgrade to a disc/drum master.

If it has an April date and Data doesn't need it I may be interested.

I'm good to go with the 0465 I found so have at it.

Where would the date code be? Happy to post some pictures.