Ray Schmidt

I need help with carb vacum lines is a California car different?
The carb on the car is part number 7040502.
Decode as this
4 70/74
0 1970
5 4 bl California only
0 Chevy
2 Auto
Part number states it is for a 300 hp THM/ECS Rochester modle MV4
Car is 1970 build date of car is 12/10/69 it is a 300hp auto with air.
Build date one carb is 2069.
206th day of 1969. This was July 25 1969.
Is this a correct date for this car?
The motor numbers do match the car along with almost everything else.
I did buy the car from California.
The problem is the car did not have the TCS switch on the motor.
The problem is the vacum port in the back of the carb where the vacum hose from the TCS switch goes has a plug in it. Did someone put a pulg in it to eleminate the TCS switch or was it different for Calinfornia cars?
If this car should have the TCS switch can I take the plug out and find a metal nipple to go in the port? Thanks for veiwing this I have been scratching my head over this one!

Crimson Thunder

I don't think your build date is correct. They didn't start building 70's until January of 1970. GM was still building 69's in December of 1969 due to the extended 69 year model run.

What is the date code on your trim tag in the drivers door jam? A=Jan70, B=Feb70 etc.

Ray Schmidt

Car is not here at my house. I will check tomorrow and let you know.
Just kinda of weird the carb part number matches everthing the car is.
Thanks, Ray.

Alan 71

Hi Ray,
I think this 502 is a carburetor for a car with automatic transmission and that was equipped with EEC and built for the 70 Model Year.
Cars that were destined to be delivered in California had the EEC system, but I 'believe' it could be ordered on other cars too.

Have you looked for other signs of the EEC system on your car?... the charcoal canister mounted to the rear side of the left side front apron and a steel line running from the canister back to the fuel tank on the inner side of the left frame rail? It runs parallel with the brake line.
Regards,
Alan

Here's the location of the EEC canister.

Ray Schmidt

Allen, My car does have that part. I need to check the build date I think I might have it wrong. Just trying to figure out why the carb that is on the car does not have the vacum port on the back for the TCS switch, it has a metat plug in it. As always thank you for your information and help.

Revi

All 1970's had the TCS system installed and in theory CA cars were required to have the EEC system installed as well. One of the differences between a Federal carb and a CA carb is that the CA carb has an additional vacuum port located on the front side to connect an EEC vacuum hose.

Your car does not need the TCS system installed to run properly. Most people disconnect the TCS system and run a vacuum hose from the TCS port on the carb directly to the distributor.

Additional FYI - Your carb should have the letters "ET" stamped after the part number (7040502). If not, your carb may be an over the counter exchange dated 2069 (1979). Factory installed 68-72 carbs did NOT have this cast triangle, circled in the photo below.

Ray Schmidt

Thanks so much for all the information and pictures. They are a great help.
After trying to figure this thing out I come up with the following. My carb does not have the triangle on it and the place on the back where the TCS switch vacum port is is smooth and never drilled. I am thinking this is a carb for a 69 because if I am thinking right they did not have TCS switches. I am trying to put car back together as correct as I can but have no plans on having the car judged. I think I am going to look for a correct carb I don't know if I will a date correct one. Sad thing is I sent the carb I have to be redone about 11 or 12 years ago when I started this project. Also build numder for the car on the trim tag is A07 the vin is 194370S400401 so I guess a early car in 70. Thanks again to everybody for the help.

Ray Schmidt

Thanks for point out wrong build date.
Number one trim tag is A07
Vin is 194370S400401.
A early build in January.

Revi

Your car was built Jan. 7, 1970 and is the 401st Corvette built in 1970.

A 1969 carb would have a different part # and different letter code.

Does your carb have the "ET" stamped on it? Better yet, post some pics of it.

Ray Schmidt

Carb does have the ET after the number. The thing that it is missing is the vacum port on the back for the TCS vacun line to plug into. Thats why I think it was for a 69 I dont think they had the TCS switch. We tried to post a picture of the back of the carb in the original post and had a problem. Still trying to figure that out but will try and get some on. Thanks for the help.

RonR80

Mine was built not long after yours , VIN 194670S400613 ,
I think it was Jan 12th .

Ray Schmidt

It is kinda a cool the information you can learn about these cars. When I am working on mine I wonder if anybody that worked on the line thought these would taken apart and put back together?

kansas123

And how many of those line mechanics were named 'Bubba'...

Crimson Thunder

Very early 70 build. My car is two months and a day behind yours(3/8).

I'm wondering, does your car have a red light(instead of blue) indicator for the high beams on the dash. I've heard very early 70's have a red light but I've never seen one.

Ray Schmidt

Boy I dont rember. The cars interior is completly out. I sent the speedo and tach out to be rebuilt. I am guessing it is in one of those. It will be interesting to see when it is back together.

Alan 71

Hi Ray and CT,
The NCRS 70-72 TIM&JG describes the red high beam indicator as being used through the first month of the 70 model year production.
So about the first 2200 +- cars had red before the change to the blue indicator.
I'd think Ray's car would likely have the red.
Regards,
Allan

Ray Schmidt

Interesting! Thanks for the update.

Alan 71

Hi Ray,
I think it's interesting too.
It's fun to understand why one car is a little DIFFERENT than another... and so often it has to do with changes made during the production year for various reasons.
It's also interesting to note how SIMILAR cars can be too. That's especially true for cars built relatively close to each other.
Regards,
Alan