Julian dating of rear ends

[John Rohe]

Does anyone know when julian dating of rear ends started? (That is a number from 001 to 365 identifying what day in the year the rear end was put together, for example 347 is December 13 - the 347th day of the year).

I've got a '67 small block convertible with a rear with a julian dated rear (the rear code is "AOW 347 E1"). The casting date is "L 6 4" so it is a rear for either a '65 or '75 application. I've been told in the past that julian dating started in '71, but I don't know if this is correct because there is no "AO" rear code listed in the '75 literature (that I've seen).

Any help in correctly deciphering my rear date / code would be appreciated.

John R.

[Terry M.]

Re: Julian dating of rear ends

The answer is in the 1970-1972 Technical Information Manual & Judging Guide. My memory is bad & since we don't judge differentials - well anyway: What I do know is 1970 was still the month/day/year date code and 1972 is Julian. I just can't remember which 1971 is, but you may be right. If I remember when I get home I'll check the manual.

Terry

[Tony H.]

Re: Julian dating of rear ends

It appears the Julian date began in 1971 according to the 1970-72 Corvette Judging Manual. So the question remains, what ratio is this rear end? Perhaps you can mechanically verify the ratio by measuring the number of drive shaft rotations vs. tire rotations.

[John Rohe]

Re: Julian dating of rear ends

Terry & Tony,

Thanks for the verification of the julian date. So now I know I have a '75 rear, but, as Tony mentioned, then what ratio is it?? I don't have an AO code listed for a '75 application in the literature I have. Oh by the way, the spring that was on my car was a 7-leafer and looks like it "came with the rear" judging by the rust - I don't know if that helps any.

I'm new to the Corvette hobby (bought my car in May '98) and I'm just starting to build up my bookshelf, but I'm only planning on buying mid-year literature anyway. I wasn't planning on splurging for any '75 literature just because of my rear.

One more question while I'm at it. My 327/300 has a cast iron intake from a 327/275 Camaro/Chevelle application with a Rochester (from an Oldsmobile). I've thought about getting the correct intake/holley setup, but after reading about the troubles with the Holleys leaking I'm not so sure (by the way my car is 100% daily driver). Would I just be making more trouble for myself than its worth?

Thanks, John R.

[Jack H.]

Re: Julian dating of rear ends

Tony's advice is most solid. What code's on the pumpkin has little to do with what lives inside today. Reagan said 'trust, but verify' and it's applicable advice. You need to know what you DO have as well as what it should be. So, spin the rear wheels off the ground and count wheel revolutions against drive shaft rev....

[John Rohe]

Re: Julian dating of rear ends

Thanks for the advice Jack. Right now my car is in "storage" (at my mother-in-law's place - believe it or not) so once I get her back in April I will do that (I have a feeling the ratio is somewhat high - probably 3:70 or so based on where it tachs on the highway). I'm still curious though what the "AO" stamping on the case means for a '75.

Thanks again, John R.

[Joe L.]

Re: Julian dating of rear ends

John----

A few comments:

First, a seven leaf rear spring is unusual for a '75. The 7 leaf spring was generally used only with the F-41 HD suspension option. Very few '75s have this option and there are several other chassis differences for those that do. I've covered this in detail in earlier posts which should be in the archives.

Second, as far as rear ratio goes, I agree with all previous responders who suggested verifying it by doing a rotational check. This is very easy, especially since there are a very limited number of ratios that it could have.

Third, as far as carburetors go, I do not recommend Holley carbs for street applications. I've owned many of them in years past and every one was problematic. I especially dislike the 4160-style models used on '67s. Of course, many folks need to use Holleys to maintain originality. If that's not important to you, the Rochester QuadraJet is the way to go. In my opinion, this is the best 4-barrel carburetor ever manufactured for street use. Of course, like anything mechanical, QJs do have problems from time-to-time and inherent weaknesses. Still, I consider them extremely durable and reliable.