Planning to install an electric fuel pump in my 68 327. Do I need to bypass the mechanical pump, or can it be used in conjunction?
Not looking for hi-performance, just to alleviate vapor lock.

 

you can use them together. I did on my 68

 

I'd just get a block off plate and get rid of the stock pump, added benefit of less drag on the cam.

 

Thanks for the replies. I hadn't looked into blocking off the mechanical, but I will.

 

The mech pump is a 'blow-thru' item, meaning the pump can be blown through on its inlet.
You could add a 12-801 Holley pump to fill bowl of carb without removing mech pump. Use relay for powering pump.
If you chose to use elec pump continuously, you will have to add the regulator.
My '67 does the same symptom, long cranking on first start after sitting for some time.
Then after, starting, cranks right up through the next couple days. Use it or lose it.

You can remove air cleaner and use a ketchup squeeze bottle or a syringe and fill bowl using its vent tube.

 

My issue isn't on startup. Mine starts first try, every time. My problem, I think is with vapor lock when the engine is hot. It quits when I'm at idle with a warm engine. I think I need a full time electrical pump, very low pressure, just to alleviate the loos of prime at the mech pump.

 

An engine should run all day long at hot idle.
Fuel pump should be pumping more than enough fuel for this.
You can fill carb bowl and fill a quart jar and time the filling, should be no less than 15 seconds.
You could remove gas cap in seeing if cap vent is not working allowing air into tank as fuel is drawn off.
Or, if driving, the heat generated during driving, pressurizes the tank and when removing gas cap, pressure would be released.
Or, an air leak in fuel line allowing air in fuel intake to pump.
Or fuel pump is bad, leaky check valve.
An external clear fuel filter between pump and carb is a good troubleshooting tool as pump should keep filter full at all times.
Good luck.

 

Thanks, I'll look at these things before adding a pump. I haven't looked at the quality of the fuel lines. Bought the car about a year ago, so I have no idea how old the lines are. I guess that's a cheap first step. I appreciate your help!!!

 

You're welcome, no problem.
If you believe vapor lock, you can clip on spring-loaded clothes pins on the fuel line between pump and carb for heat dissipation, every inch if you like. Old school trick.

 

Read your other post about stalling and you found bowl empty while running.
Suggestion: you should check exhaust valve at pass side exh manifold ensuring it does open and not stuck in closed position.
This closed position diverts exhaust gas through bottom of intake manifold for heating up choke and carb.
The valve has a bi-metal spring keeping the valve closed when closed, then open as spring heats up.
Make sure valve is not installed upside down, I don't think it can be as gasketry would be really a cumbersome affair, one side is flat for manifold mating and other side is chamfered for exhaust donut with exh pipe.
You also might look for a non-metallic spacer in fitting between manifold and carb in reducing conduction of heat from manifold to carb.
Install 180° thermostat to keep engine compartment temp lower than using a 195°.