Old Shep

CORRECT JULIAN DATE CODE ON MASTER BRAKE CYLINDER

I ordered a reproduction brake master cylinder with julian date coding for my 1967 Stingray.

The original build date for the master cylinder is September 30, 1966.

Upon receipt of the part I was expecting the stamped julian date code to have a 5 digit number of “66273”. The first two digits representing the last two digits of the year or “66” and the remaining 3 digits representing the julian code for the month and day.

Instead the part was stamped with only 4 digits of “6273”.

Before I install it I want to make certain the stamped date is proper.

Which is correct?

JohnZ

Neither. That tiny stamped julian date on the machined spotface area around the forward outlet isn't judged on 67's, as it's not typical of '67 production; that date stamping didn't begin until 1968.

Old Shep

Reply to JohnZ

Thanks for your very interesting response in which you make two separate observations:
1. You indicate that julian dating on corvette master brake cylinders did not start until 1968. I don’t dispute that but I am confused by the fact that major suppliers of original reproduction parts such as Eckler’s-Mid America-Long Island and others advertise and sell these julian dated parts and readily supply them as witnessed by my situation which involved prior telephone conversations and culminated in a subsequent order where it was clearly stated that my vehicle is a 1967. I feel victimized in what could be considered a scam or false advertising. If you could point me to an authoritative source that could be helpful in pursuing this issue it would be appreciated.
2. In my 5 digit-4digit question, if the master cylinder was a 1968part would the three digit julian date be proceeded by “68” or “8” or neither?
3. You stated that julian dates on 1967 brake master cylinders are not judged. Are you referring to NCRS judging? Are you an NCRS judge? This is also of interest to me even though my vehicle has never been judged by any person/group and is not likely to be judged while I own it. It is a very original survivor in excellent condition and I simply want to keep it that way.

JohnZ

1. Many vendors sell items that aren't judging-correct for a particular application; you have to know what's really correct or not for your car before you buy. The best reference is the NCRS 1967 Corvette Technical Information Manual & Judging Guide, available from the NCRS on-line store at www.ncrs.org. The current manual is the Fourth Edition, and the new revised Fifth Edition will be available in August.

2. There were several different formats for Julian dating over the years, but none were used on 1967 Corvette master cylinders; I have little experience judging 1968-up Corvettes.

3. Yes, I'm referring to NCRS judging (and Bloomington Gold judging, which uses the same criteria). Yes, I'm an NCRS 200-level Master Judge.

Old Shep

To JohnZ
Thanks for your informative response. I was seeking the creditability of a reliable source and I am pleased that I have found it in you. I have the 1967 Technical Information Manual & Judging Guide Third Edition and on page 105 it describes everything except a julian date stamp. Now I know why it was not mentioned in my Third Edition-the date stamp didn’t exist on 1967 corvette master cylinders.

I am the perfect example of your statement about needing to know what is really correct before you buy a part from a vendor. In my case a new repo master cylinder is in my garage ready for installation and sports a four digit stamp that doesn’t belong on it. The vendor who supplied this incorrect part is Eckler’s who advertises the date coding for 1967 corvettes as a $50 additional option and I fell for it assuming I could trust them. When I received the master cylinder I corresponded with their customer service department asking for them to confirm whether the code was supposed to have four digits provided or the five I expected. The response was that one of the digits could have rubbed off. When I pointed out that the numbers were stamped into the metal and asked the customer service person to discuss her “rubbing off” comment with her supervisor, the supervisor emailed that it should be four digits. I then asked what source was used for this and the supervisor responded that she looked it up on the internet and couldn’t remember where she found it. In the response under her name appeared Eckler’s Industries with Industries misspelled. I now have a totally different feeling about this vendor than I have held for many years. In contrast, Mid America Motorworks catalog offers julian date coding only on 1968-1982.

This has been an expensive and time consuming lesson for me.

Thanks again for your help.

gbvette62

A couple things to think about.

First, when you call one of the big catalog companies, your going to get an order taker, who's sitting at a computer screen. In most cases, they don't own a Corvette, and have likely never worked on one either. This is often the case with their supervisors too.

Some companies have technical departments, that are much more knowledgeable, than their sales people. If in doubt, ask to talk to someone from the technical department, and if they don't have a technical department, then try a company that does.

Also, just because a company offers a service, like Julian dating, doesn't mean it's correct for your car or part. I've encountered people who insist that something is right for their car, when I know it isn't. If someone has to have Julian dating on a part, that shouldn't have it, I'd tell them it doesn't belong there, but I'd sell it to them if they want it. Remember, "The customer is always right".

Some companies are better than others, but it really pays to educate yourself, and not rely on information from vendor's catalogs or sales people.

Besides the 67 Judging Manual, the NCRS 53-67 Specifications Guide, is an invaluable tool too. Between the two books, you will have access to information on just about every number, detail, finish, part, etc; that applies to your 67.

A quick word about John Z. John worked for GM for 20+ years. Among other things, he was a Production Foreman and was part of the build out of 67 Corvettes, and the 68 start up. John is the go to guy, when it comes to early Corvettes, and especially 63-67's!

Welcome to the Forum!

keri45

I thought 6273 I meant the 273rd day of 1966 year.I believe it is done correctly.

JohnZ

Julian dating on the 509 master cylinder by Delco-Moraine, the manufacturing source, didn't start until the 1968 model year.

vettebuyer6369

How come they dated the '63 master cylinders?

When did they stop before re-starting in '68?

EDIT: looking at my 63-64 JG, the '63 #389 M/C was dated in MDDY format. The '64 #264 is weird, with a 3 digit Julian date with no year on the non power, but with a MDDY on the power units. Thats just odd. Both made by Delco-Moraine.

big block ken

What about the Julian date code stamped on the small tab of power brake boosters? The vendors charge $50 or $100 additional for this. Does this apply to all mid-years?

keri45

I agree 100%. What I meant was If it was ever done the 4 digit date code would have in line with what was stamped.,even tho never done at the factory...As opposed to the 3 digits used on The Booster that was more common?..