mmesa005

Hello All,

I am new to this forum having last owned a Corvette @ 20 years ago. After getting married and having kids I had to trade the Vette for an SUV.

I just purchased a 74 C3 with @ 93k miles. The engine was recently rebuilt and has a replacement carburetor as well. Two immediate issues are the brakes and the headlights.

The brakes feel flat as if the brake booster is not working? The headlights turn on and the drivers headlamp came up once or twice then stayed closed.

Are the two problems vacuum related?

Also, any recommendations for a local Vette mechanic? I am located in Cameron Park, CA.

Thanks!

bluedawg

I would guess there vacuum related.

mmesa005

I just ordered a service manual so I don't have anything to reference right now but I suspect something may not have be re installed properly after the engine rebuild? I hope someone can point me to a vacuum diagram to reference?

bluedawg

You said it was recently rebuilt. If the camshaft was replaced it could have reduced vacuum ccausing vacuum issues.

gahaegele

For the brakes, I would start with bleeding the lines. If that does not help, have someone press the brakes while you obt serve the rubber brake hose at the wheel to be sure that it is not bulging. Next step would be to test the vacuum at the booster then replace the master cyclinder.

For the lights, start testing the vacuum from the manifolds to the actuators. You have a vacuum issue somewhere along way. I ended up replacing all the hoses for my headlight system. Not expensive, but took a time working in and around the dash switch. Now they work like a charm! If after that only one or the other works, you will have to test the vacuum at the relay and actuator at the headlight doors.

ddawson

You have some really nice people near you.
http://www.cameronparkcorvettes.org/index.htm

PeteZO6 is also in Cameron Park. See if he has any recommendations.

Peterbuilt

http://www.corvette-101.com/vacuum.htm

mmesa005

Everyone,

Thank you for the great advice, very much appreciated! I will start the troubleshooting process and see where it leads me.

I have taken some photos thinking others may see something out of place?

Thanks again!

ddawson

What is the fresh air intake for the PVC doing?

What is the other SS hose going to?

mmesa005

Sorry, what is the PVC? The SS Hose is from the fuel pump. Why they used an aircraft grade hose I don't know?

Oldguard 7

Leery of the "fly's eye" air cleaner..... one plume of flame through carb..... and fire!

aussiejohn

mmesa,

Congratulations on your new car!!! I have three '74s and AM NOT AN EXPERT on them, or anything really, but have picked up a lot of good information on this Forum relating to '74s.

First off, that fuel line!!!! Get rid of it and buy a stock steel pump-to-carb line from Willcox, etc. As you're not running a Qjet, you will have to either buy a Qjet or modify the new fuel line. Obviously the latter process is cheaper. The main reason is to get rubber fuel lines out of the engine area, especially near the fan belts and exhaust manifold. A short piece a few inches long between the steel line and the carb is acceptable, but not ideal.

That vacuum line going to the right exhaust manifold is part of the EFE system, Early Fuel Evaporation. It is designed to keep the flapper valve under the right manifold open so that exhaust gases travel through it to the pass. side muffler and out of the car. However, when the engine is cold, the switch closes the valve and forces the gases through the driver side head. It is triggered by a Thermal Vacuum Switch on the thermostat housing and, as you can see, the switch is there, but no hoses.

I suspect that at idle and light throttle applications, the vacuum will hold the valve open, but when you floor the accelerator pedal, the associated vacuum drop will allow the valve to close (under spring and counterweight pressure). This forces the passenger side exhaust gases to back up and flow through the central exhaust passage on the pass. cylinder head through the inlet manifold and into the driver side head before exiting the engine via the driver's side exhaust pipe.

Just when you need maximum power, you are strangling half the engine's cylinders. My suggestion is to remove this valve and replace it with a short piece of exhaust pipe or at least weld it in the open position. Then remove that long piece of steel vacuum line and plug the opening at the fitting that's on the inlet manifold.

I would suggest that you procure a factory Cold Air Induction air cleaner system for a factory look. These allow you to use the outside air via the solenoid operated valve in the hood to feed air to the engine. It's probably good for another five horsepower, but it won't rob you of any.

Do those three things and your car will run cooler and have more throttle response and better fuel economy.

Regards from Down Under.

aussiejohn

aussiejohn

mmesa,

The driver side rocker cover on your car has a PCV valve and a hose correctly connected to the carb. Its purpose is to suck up oil fumes and "inject" them into the low pressure area under the throttle valves and into the cylinders where it is burnt. However, when sucking this air and oil mist mixture OUT of the engine, a low pressure area in the crankcase is initiated and the engine wants to suck ambient outside air INTO the engine. It does this through the fitting in the opening on the passenger rocker cover.

The cars came from the factory with a rubber hose connecting this fitting with the steel air cleaner and has its own filter inside the AC. This ensures that only filtered air is sucked into the engine, thereby protecting it from ingested stones, dirt, etc. As said earlier, if you buy a correct '73-'75 AC assembly, this opening will be there.

I should have said earlier, buy an Assembly Instruction Manual, AIM, for detailed drawings of all these components. You will learn heaps as you travel the Corvette highway and we're here to help you.

Regards from Down Under.
aussiejohn

mmesa005

aussiejohn,

Thank you for all the great recommendations!
Since posting this request for help I have gone through the headlight vacuum system and found the Vacuum Check Valve to be defective. I was able to blow air in both directions. I have also found a sticking relay valve. I have new parts on order including all new vacuum lines and should have them changed this weekend.

As the car has an Edelbrock 1400 series carburetor I have ordered an Edelbrock hard line/filter assembly. What I have to figure out is a mounting solution for the Mr. Gasket Fuel Pressure Regulator. I also want to add a fuel pressure gauge into the line.

I do have a manual and will look further at your recommendations.

Thanks again!

PeteZO6

PM sent to OP.

Pete

mmesa005

Forgot to add in my previous response that the brake booster was bad and has been replaced. That really amplified the vacuum leaks in the headlight system as the car didn't want to idle in gear. Fortunately my son was watching me and told me that the headlights were winking when I tried to restart the car.

PM replied to PeteZO6 - Thanks!

aussiejohn

mmesa,

That's a nice looking fuel line. You should still try for a solid steel line from the pump to the filter in that photo and perhaps you could plumb a FPR between them, but don't worry about a FPG. If the pump and the FPR are both working well, then the engine will get all the fuel it needs. You don't need to know what the FP is, as long as the engine isn't stumbling, then it's getting the right amount. A FPG (and even a FPR ) is just another potential leak source.

Regards from Down Under.

aussiejohn

mmesa005

aussiejohn,

I read elsewhere that the Edelbrock 1400 series requires a fuel regulator , not so much an option?

Any recommendations, photos of a solid line would be greatly appreciated!

PeteZO6

Call the Edlebrock tech line and ask them. Most street carbs are happy with the more or less standard ~6 psi most fuel pumps deliver. I would go with what they recommend.

Solid fuel lines are pretty easy to make if you have a flaring tool and a simple tubing bender. I used stainless tubing which is harder to work with as it is a hard metal. But not at all difficult.

Yep, I was at the Airpark show last month.
http://www.cameronparkcorvettes.org/...NShine2013.htm
Not the '69 with all the chrome in the engine room.


Pete

CaseyJones

My POS '77 has been running a 1400 series Edelbrock for years with no issues without a pressure regulator. I've never heard that myself.