1970 Master Cylinder Dates?

[Carr C.]

I just purchased a 5480346 / PG core for my '70 454 convertible. I had talked to several people that said they were not dated, and then others that said they were. If they are, where, and what does it say?

The core I just bought only has one unidentified stamping between the two bleed screws that is upside down, and starts with a star or snowflake (kinda like a winters foundry mark)followed by D3 (*D3).

I thought this meant April 1973, but the guy I got it from has 10-12 cores and said they all had D something on them, and that if it was date coded, it would have at least a 4 digit julian date on it.

What are your thoughts?

[Dick W.]

Re: 1970 Master Cylinder Dates?

IF dated it will be on the machined surface around the outside of the threaded hole for the fittings. The characters are very small stampings. They do not occur on all cylinders.

[Carr C.]

Re: 1970 Master Cylinder Dates?

Now that you mention this, I see a very small 3308 that is upside down on the front port boss. I'm guessing the date is March 30, 1968.

Is there any visual difference between the years? Does this one look correct for a 1970 also?

Thanks.

[Jack H.]

Re: 1970 Master Cylinder Dates?

Those MC's stamped on the front boss used a 4-digit, Julian dating sequence XXXY where XXX is the day of the year (1-365) and Y is the last digit of the year. This would make your sequence read 330th day of 1968, a nice part for a '69 Corvette built sometime after Christmas.

[Mark #28455]

Julian date

3308 is most likely the 330th day of year ending in 8 but some say it could also be the 308th day of year ending in 3.
Good luck,
Mark

[Joe L.]

Re: 1970 Master Cylinder Dates?

Carr-----

Usually, the stamping on the machined fuel line boss is in the format of last digit of year followed by the the consecutive day of the year. For example, the coding on my known-original 1969 master cylinder is "9253" or the 253rd day of 1969. The reverse of this may have been used, but I'm not aware of it.

As far as configuration of the master cylinders, the 5460346 master cylinders are pretty much all the same with TWO possible exceptions: first, those manufactured after about 1973 usually do not have bleeder valves. All PRODUCTION 67-72 5460346 master cylinders did have bleeder valves. Second, some do not have the semi-circular machined surface of the forward portion of the master cylinder. However, inasmuch as you say that you have a "PG" coded cylinder, yours must have this feature. "PG" is the correct coding for the master cylinder used on 67-72 Corvettes with power brakes (J-56 only for 1967). The 5460346 (and, yes, the number is 5460346 even though the 3rd digit might look like an "8") casting was also used for non-Corvette master cylinders and these have other stamped codes.

The "D3" refers to the Danville, IL foundry (D) and the pattern number (3). The symbol that you describe as looking like the Winters snowflake is the Central Foundry Division "wagon wheel" casting mark. These are often found on Danville castings. They are also found, irregularly, on castings from other GM foundries, including aluminum.

If your 5460346 master cylinder has the "PG" stamping on the front semi-circular machined surface AND bleeder valves, then it is the correct configuration for your 1970 Corvette with power brakes. The date coding, however, is not correct.

[Jack H.]

Joe's right on!

The sequence is YXXX with Y=year digit and XXX=Julian day of year. In fact the '73-74 Judging Guide calls this out. So, a MC stamped '3308' is a nice fit for 1973, 308th day meaning a '74 Corvette built in the Dec-Feb timeframe.

[Dick W.]

Re: Joe's right on!

Date not judged on 68-72 cars. If you can't see it, you can't judge it

[Carr C.]

Re: 1970 Master Cylinder Dates?

Much thanks to everyone who answered this post!

Carr

[Mark #28455]

it goes both ways!

9302 - obviously 1969
2978 - can't be 1972 - but does exist!
go figure!
Mark

[Dick W.]

Re: it goes both ways!

Mark, the confusion with the codes is another reason not to judge them. Some do not fit any known code arrangement

[Terry M.]

Re: it goes both ways!

You talking about my 1970 with just the number 1 on it? Go figure that one!