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Vacuum Diagram 1978

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Old 07-09-2010, 03:54 PM   #1
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Default Vacuum Diagram 1978

I just bought my first Corvette and am ready to get it up to speed. The body and interior is in GREAT condition, but it had been parked and forgotten until discovered 23 years later. Its motor, trans, and exhaust were rebuilt and now run, but I believe that's where they shut the hood and walked away until I bought it. The Vacuum system is a total disaster. Lines are in clusters not hooked to anything, some capped, some not. Lights don't flip, nothing plugged into cluster near the wiper motor, heater blower, nadda, zero, zip. I think the plan will be to rip the whole system out (tube wise) and start from scratch, line by line. I am not mechanically inclined, but I am surrounded by those that are. My main help is laid up in the hospital after an accident, but I would like to start getting prepared. A couple things to note on what diagram I need (because I am being told some things may not be stock, but sounds like it just might be after reading some threads here).

1978 Silver Ed. Annv Corvette. Its a 350 so I assume the L-48. I thought the L-82 was the 427, but now I am confused after seeing threads here referring to L-82 350s. I am told the Carb is a Q-Jet and appears to be missing linkage to be able to open all doors. It also appears to have a EGR, but I am told it may not be stock because there was no EGR in 1978, but not sure how accurate that is. Would love to get this thing back in better working condition vacuum wise as soon as possible. Have not even seen the lights up yet. LOL

So if anyone knows were to get a good diagram and list of the vacuum system for this car, I would be very grateful.
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Old 07-09-2010, 04:29 PM   #2
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In 1978 there was L-48 and L-82, both were 350s. I believe that the L-82 had a smog pump and dual snorkle intake, where the L-48 does not. Check out the VIN.....

Position Description Code
1 GM division 1 = Chevrolet
2 Car line or series Z = Corvette
3 & 4 Body style 3 & 7 = two door coupe
8 & 7 = two door coupe(1978 to 1980)
6 & 7 = two door convertible
5 Engine type 1972 -> K = base, L = LT1, W = LS5
1973 -> J = L48, T = L82, Z = LS4
1974 -> J = L48, T = L82, Z = LS4
1975 -> J = L48, T = L82
1976 -> J = L48, X = L82
1977 -> L = L48, X = L82
1978 -> L = L48, 4 = L82
1979 -> 8 = L48, 4 = L82
1980 -> H = LG4, 8 = L48, 6 = L82
6 Model year GM decided to give the car 2 = 1972, 3 = 1973, 4 = 1974, 5 = 1975
6 = 1976, 7 = 1977, 8 = 1978, 9 = 1979, A = 1980
7 Assembly plant or location S = St. Louis
8 to 13 Production sequence number 400001 -

I will see if I can find a good vacuum diagram
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Old 07-09-2010, 04:46 PM   #3
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Default Let there be lights!

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Old 07-09-2010, 04:52 PM   #4
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Originally Posted by wc5b View Post

So if anyone knows were to get a good diagram and list of the vacuum system for this car, I would be very grateful.
If you have nothing but hoses, you may want to visit Dr. Rebuild's site. The headlights have one vacuum system...

...and the A/C system has another...

You also have vacuum for the power brake booster, the cruise control, distributor vacuum advance and a couple of connections on the carburetor.

Not sure where you want to start.

Last edited by pewter99; 07-26-2010 at 10:03 AM. Reason: NSV link removed
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Old 07-09-2010, 05:14 PM   #5
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Oh! This is good stuff... I can see this forum and community going to be a big help. As for where to start, time to get with the guys and answer just that. Thanks for all the info to this point, Including that VIN breakdown. It does in fact prove that it is the L48. Speaking of stock motor, can someone inform me if the Q-Jet and EGR were stock, or could have been stock?
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Old 07-09-2010, 05:49 PM   #6
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All 78s had q-jets and egr. Many had a smog pump all had 2-1-2 exhausts, catalytic convertors, efe, pcv, charcoal cannister. The l-48 had the single snorkle air cleaner.
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Old 07-09-2010, 06:26 PM   #7
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You'll need this too.

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Old 07-09-2010, 06:49 PM   #8
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Would help to know what year, engine, transmission and state you live in.
Some states do not allow any modifications to anything EPA related.
All 78's had EGR valves and air pumps on automatics.

Good luck, start driving, but after your sure the brakes are prefect. The rest will just happen in time.
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