ZR-1 Mark

I'm looking at a '75 L-82 4-speed vette next weekend.
I went to http://www.idavette.net for some info and I saw 4 possible
engine codes for L-82 4 speed. Does anyone know why they
would have done this ?? It is confusing me :crazy: ,
which obviously doesn't take much :lol: :lol:

Thanks in advance, :seeya
Mark B.

page62

Don't worry about the engine codes -- they're just casting codes. If you want matching numbers, make sure the VIN and the engine block stamping match. Also make sure the VIN has the correct code for an L82.

BTW: The '75 L82 was not produced in large numbers. GM had a hard time getting this engine to conform with smog regulations.

Jim Shea

Actually the three letter alpha codes are stamped on the engine pad and are not casting codes. They keep track of running changes that were made on the engine during that year's production. They might have had something to do with emission calibrations.

I have some sketchy notes that say that the CHC code (L82 4-speed) was released for production in March of 1975 as engine part number #361446.

My L82 4-speed was built the beginning of July and still had the same CHC alpha code stamped on the engine.

This is how you read the engine stamped code.

15S4XXXXXV0603CHC

1 = Chevrolet
5 = 1975
S = St. Louis build
4XXXXX = V.I.N. #
V = Engine assembled in Flint
0603 = Engine built on June 3
CHC = Alpha Code

ZR-1 Mark

Thanks guys,

I was trying to figure out why multiple codes were used...
One other question, this car might be a Z07.
How do I tell that without the tank sticker ??
It does not appear to have power steering or brakes....

Thanks men,
Mark

GTR1999

I like the 75 L-82 4speed cars. I gave one to my son last year for HS graduation and he rebuilt it over the summer. Nice car I would like another one someday.
Gary

page62

Only 144 of those made in 1975!

Paul Borowski

Z07s had the "dual pin" front calipers, heavier springs front & rear, HD shocks, heavier than stock front sway bar and a rear bar. Z07s also had to have power brakes + M-21 close ratio trans(even though it was a Borg-Warner, NOT a Muncie).

If it's the car I'm thinking you're refering to, it's a cool car-love those all manual cars :yesnod: Less stuff to go wrong :yesnod: If I had the room, I'd be bidding on it too :yesnod:

Only 2372 '75 L-82 cars were ever made, 2006 coupes & 366 convertibles. I've been doing a 1975 L-82 Survey for the last 6 yrs and have over 66 cars in it. Of those, about 7 cars seem to be true Z07 ones. ONLY 144 of those were ever made in 1975.

If I'm not mistaken, the reason for the different codes could have been for the motors that had A/C brackets, PS pump brackets, etc. The motors themselves would have been the same. In my "1975" research, I also firmly believe ALL '75s came with smog pumps from the factory, especially all '75 L-82 cars.

In my survey, my earliest car is #19634 out of 38,465 and has like a March 19th build date.

hunt4cleanair

[

Quote:

Z07s had the "dual pin" front calipers, heavier springs front & rear, HD shocks, heavier than stock front sway bar and a rear bar. Z07s also had to have power brakes + M-21 close ratio trans(even though it was a Borg-Warner, NOT a Muncie).

Paul:

Double check your survey notes on the rear sway bar for Z07. My notes show "rear bar equipped per base suspension" which indicates big blocks came with rear bar because they normally do while smallblocks did not.

Paul Borowski

Tom, yeah, you're probably right-I guess I just assumed this for '75. I've even seen 4 of these "Z07s" in person, just did'nt think to check. :banghead:

Jim Shea

Paul,
I have been researching my records for a description on the three letter alpha codes.
___________________
If I'm not mistaken, the reason for the different codes could have been for the motors that had A/C brackets, PS pump brackets, etc. The motors themselves would have been the same. In my "1975" research, I also firmly believe ALL '75s came with smog pumps from the factory, especially all '75 L-82 cars.
___________________

I don't think that the codes are tied to the accessory brackets on the engine. Here is my reasoning. In 1975 you could order your Vette with or without: air conditioning; with or without power steering; with automatic or manual transmission; with L48 or L82 engine; Federal or Calif emissions. I don't believe that there were any restrictions on any options, trans, etc. (Although California could be an exception).

Not even considering Fed vs Calif emissions, this gives a possibility of 16 different combinations of engines. There aren't 16 alpha codes in 1975. I think that the engines came to the assembly plant without accessory brackets. AC and/or power steering along with the proper pulleys and belts were added at the assembly plant to match the vehicle build sequence.

Also, the fact that I was told that my alpha code, CHC, was released in March 1975, would indicate that there would have to be even more than 16 alpha codes used in 1975.

I still think that the alpha codes were tied to something that was on or in the engine that could affect emissions, interchangeability, durability, warranty, etc. (i.e. changing the ignition curve, changing camshaft material, changing something in the carburator, etc.)

Paul Borowski

Jim, I understand what your saying. What's odd is out of 66 L-82 cars in my survey(I know this is a small part of 2372 L-82 cars) ONLY two of these codes have surfaced, CHC or CKC. Every manual car has "CHC", every automatic car has "CKC" :confused:

Jim Shea

I will bet that of the 66 L82 cars that you have surveyed, a lot of them did not have AC and a few may not have had power steering. Yet the manual trans cars still have the same CHC code.

I think that you just have to find some early build 75s in order to find some of the other alpha codes. It is amazing that all of your survey cars start in March (half way through production).

You know, it is possible that engineering could have pulled a particular alpha code and the plant may not have implemented it. Or there could have been a very few engines actually built before another change with another alpha code came along. From my information, you should not find a CHC code on vehicles built before March.


[Modified by Jim Shea, 9:42 AM 4/29/2004]

KenSny

I think one of the reasons Paul's survey cars only start in March is that his survey is for L82 optioned cars. I don't think any L82's were built much earlier in the production run.

Jim Shea

I know that the two letter alpha code that Saginaw used to identify its components did not follow any order. In fact, if there were two steering columns going to the same assembly plant, they tried to use very different letters between the two, so as to minimize assembly plant errors.

That having been said, if you look in the Corvette Black Book, you will note that Chevrolet obviously didn't use that philosophy when identifying engines.
When you look at the three letter alpha codes for the 1975 Vette, you find that there are very distinct sequences (i.e. CRJ, CRK, CRL, CRM). So it appears that there were series of engines released with adjacent alpha letters.

So the fact that the CHC L82, 4-speed was released in March, it could have been the first actual L82 engine introduction in the 1975 model year. Just because there were codes for CRL and CRM (L82 4-speed & auto) maybe there never were any of those engines actually installed in production.

I wonder if there is any time sequence as to how the engine codes are listed in the Black Book? In other words, possibly CRJ, CRK, CRL, CRM could have been released before CHA, CHB, CHC.

KenSny

The only way we can even get a glimmer is if everybody with a '75 chimed in with the build date and the code. But let's not highjack this thread. Then maybe we'd see a pattern of some kind. I doubt if it has anything to do with accessories. More to do with minor engine and/or casting changes during the production run I'd suspect.

BTW: My car's trim tag is for April 21 and it's a CHC also. I have the paperwork showing the original owner picked up the car from the dealer on May 1.



[Modified by KenSny, 4:23 PM 4/29/2004]

page62

Basic question: Is the car you're going to look at justify such close attention to detail? Is the seller asking a premium price for a '75? Just curious...

hunt4cleanair

Quote:

Not even considering Fed vs Calif emissions, this gives a possibility of 16 different combinations of engines. There aren't 16 alpha codes in 1975. I think that the engines came to the assembly plant without accessory brackets. AC and/or power steering along with the proper pulleys and belts were added at the assembly plant to match the vehicle build sequence.

Also, the fact that I was told that my alpha code, CHC, was released in March 1975, would indicate that there would have to be even more than 16 alpha codes used in 1975.

I still think that the alpha codes were tied to something that was on or in the engine that could affect emissions, interchangeability, durability, warranty, etc. (i.e. changing the ignition curve, changing camshaft material, changing something in the carburator, etc.)

I've concluded after much study that the code refers to the application but then the challenge is to define "application" which is what I think your (Jim) are trying to get at. The variables I see that factor in is A/C, rear Axle, emission application, and transmission. All of which calibrated to the specifications you outline above. I also believe they played with options or eliminated options to reduce the number of codes required which is a pattern we see from 1969 through the end of C3 production.

Brackets were thus installed (bottom brackets) to prepare for receipt of the components installed at the Corvette factory. The AIM describes rather precisely what was installed and what was not.

1975 was an easy year for the packageteers in contrast to the early years like 1969. Further contrast to 1982 when few options factored in to engine codes...effecively all these variables were eliminated by 1982. All got A/C, one engine RPO, auto tranny, one of two axles choices dependent on wheel (of all things!) and two emission choices...one for CA and one for everybody else. Thus, three codes for 82 with one early and one late both of which were head for CA. Thus only one code for 49 states!

If you think about logically from a manufacturing planning perspective, they would have planned on changes before production began and therefore reserved the various codes for the entire production year. I've course, that may be giving more credit than one should but having worked in a manufacturing environment...this is what I would expect happended from an engineering perspective.

I don't know if this helps but perhaps it puts code assignment into perspective.

Paul Borowski

I personally talked to Dave McClellan out at Corvettes@Carlisle a few years ago and asked him if he "remembers" the '75 L-82 being a "late" production car. He said he surely remembered this and told me it was'nt released due to the emissions AND first year for a catalytic converter. This concours with many "original" '75 L-82 owners I've spoken to have said they did not receive their car until sometime after March/April of '75. Many told me they had waited 6 months or more for their car. :yesnod:

Jim Shea, out of my survey, probably 90% DO have A/C. Most of these cars are "loaded", not bare bones minimum options.

ZR-1 Mark

page62,

The car is an original paint 20k mile car.....
I would never consider buying a "non-matching-numbered" car,
unless it was very cheap....
And yes, he is asking a premium :yesnod:

Thanks,
Mark