Trouble with '66 300

[Justin Heydon]

All,

Just finished up a full engine bay restoration on my 1966 300 convertible. Engine completely rebuilt, new Edlebrock carb with a heat spacer, all new wiring, new MSD distributor and coil. It ran great a couple of weeks ago once the weather broke but now we can only drive a couple of miles and the engine stalls sputters and then eventually dies. After it dies we have to wait several hours before it will start again. After it dies, we check to see if there is any gas still in accelerator pump and there is not.

My question is are we experiencing vapor lock? We have 93 octane in the tank. The timing is set to 16 deg BTDC. Could that be too much causing an overheating problem?

Justin WV

 

[cbarge]

Your timing is advanced. Retarded timing causes overheating. Answer is no.
You could be experiencing vapor lock.

 

[69Ragtopfury]

When it dies, you say there is no fuel at the carb. Have you checked for fuel flow when trying to restart it?
How many miles is a few miles of driving before it dies? Just a few miles shouldnt get THAT hot under the hood. After the addition of the new carb, is the fuel line running up against the block/head or really close to the exhaust manifold - to cause vapor lock? Crud in the tank getting sucked up in the sock, and eventually falls away allowing gas to flow again? Fuel pump failing and not keeping up at higher rpms?

 

[Ripinator]

All,

Just finished up a full engine bay restoration on my 1966 300 convertible. Engine completely rebuilt, new Edlebrock carb with a heat spacer, all new wiring, new MSD distributor and coil. It ran great a couple of weeks ago once the weather broke but now we can only drive a couple of miles and the engine stalls sputters and then eventually dies. After it dies we have to wait several hours before it will start again. After it dies, we check to see if there is any gas still in accelerator pump and there is not.

My question is are we experiencing vapor lock? We have 93 octane in the tank. The timing is set to 16 deg BTDC. Could that be too much causing an overheating problem?

Justin WV

In addition to the other suggestions made here, you should also check the vent tubes at the gas tank. If the tank doesn't vent properly, there will be a vacuum created that could prevent the flow of fuel forward to the fuel pump. Also check the fuel filter for clogging / flow.

 

[Justin Heydon]

When it dies, you say there is no fuel at the carb. Have you checked for fuel flow when trying to restart it?
How many miles is a few miles of driving before it dies? Just a few miles shouldnt get THAT hot under the hood. After the addition of the new carb, is the fuel line running up against the block/head or really close to the exhaust manifold - to cause vapor lock? Crud in the tank getting sucked up in the sock, and eventually falls away allowing gas to flow again? Fuel pump failing and not keeping up at higher rpms?

We have not checked while trying to restart. We will do that.

A few miles being around 5? Really nothing. The fuel line is still the original hard pipe from the mechanical fuel pump which runs over the valve cover. We wrapped it in heat tubing but still no avail.

We will check the sock. The fuel pump is brand new.

Just discouraging.

 

[detmatt]

After it dies next time remove the fuel line from the carb and stick the end in a water bottle, next crank the engine and see what comes out into the bottle while cranking.

 

[69Ragtopfury]

The fuel pump is brand new.

Start here when you find you have no fuel flow when cranking.

 

[detmatt]

Start here when you find you have no fuel flow when cranking.

And when you pull the pump next because of the lack of flow check the length of the fuel pump pushrod before just replacing the pump.
Did you replace all of the rubber hose between the tank and the engine? You could also be sucking air into the system through old rotted hose or bad connections.

 

[mr. fix it]

Start here when you find you have no fuel flow when cranking.

I had a defective $15 B/N fuel pump too. (AZ Special I guess...)

Changed it out and been running great since

 

[Mike66Chryslers]

And when you pull the pump next because of the lack of flow check the length of the fuel pump pushrod before just replacing the pump.
Did you replace all of the rubber hose between the tank and the engine? You could also be sucking air into the system through old rotted hose or bad connections.

I was going to say the same thing about the pushrod. Sounds a lot like the symptoms I was having when my fuel pump pushrod was wearing down.

 

[Justin Heydon]

I was going to say the same thing about the pushrod. Sounds a lot like the symptoms I was having when my fuel pump pushrod was wearing down.

What should the length be? It's a brand new pump?

 

[Mike66Chryslers]

What should the length be? It's a brand new pump?

3.2"

 

[Big_John]

Have you checked for fuel flow when trying to restart it?

This is a very basic diagnostic procedure that an awful lot of guys ignore. All it takes a piece of hose and a coke bottle.

 

[detmatt]

What should the length be? It's a brand new pump?

Your fuel pump and your fuel pump pushrod are two separate things. The fuel pump pushrod is located behind that Allen headed pipe plug just below the pump itself. And yes 3.2” or 3 3/16”. The first one that I discovered was worn after a long time of troubleshooting was a full quarter inch shorter than it should have been And then the same engine ate another one Which I caught it just under 3 inches. I run new ones that are properly hardened now.

 

[Ripinator]

. . . the same engine ate another one Which I caught it just under 3 inches. I run new ones that are properly hardened now.

So true. . . A hard rod is a happy rod. . .

 

[BLUPORT]

So true. . . A hard rod is a happy rod. . .

Mine's not happy until it's finished pumping.

 

[Trace 300 Hurst]

Did you replace all of the rubber hose between the tank and the engine? You could also be sucking air into the system through old rotted hose or bad connections.

I've seen this twice. The short hose at the tank doesn't leak gas (yet) because there's very little pressure, even with a full tank. But the slightest minuscule crack in that hose will allow the car to start and run just fine, but will suck air when engine speed and load (fuel) increases in the highway.

Also...your tank vents are not obstructed with mud or insects or whatever?

 

[Trace 300 Hurst]

So true. . . A hard rod is a happy rod. . .

Not if it's only 3.2 inches.....

 

[Justin Heydon]

Awesome thanks guys. I have a lot to look in to. I'll keep you posted.

 

[Cazman]

I always wondered - do we need to have the OEM style distributor cap with the vent? Many replacements do not have it. Can moisture accumulate without the vent?