hot start issue

[steve340]

Just a note.
Vapour lock is where the liquid fuel turns to a gas in the fuel line BEFORE it reaches the carburettor. It will cause the fuel pump to not be able to supply fuel to the float bowls.
Fuel percolating in the bowls is NOT vapour lock. But that fuel vapour is trapped in the air cleaner and can cause restart issues. Also if the needle valves are open some of the gassed off fuel can end up in the fuel delivery lines.
If the jets and mixture are correct I advise owners before they crank the engine over to gently tread on the gas pedal and open the throttle blades to about 1/4 or 1/3 and with no pumping of the gas pedal and then crank the engine over.
An engine needs air to fire up.

 

[ksurfer2]

Updates....After adjusting idle mixture and idle speed and wrapping the fuel lines, I drove it for about a half hour today, got everything nice and warmed up. Parked in the garage...while idling, fuel pressure gauge reads 0 PSI. Turned off the car and let it sit for about 20 minutes. Turned on fuel pump....0psi at the gauge. Disconnected the fuel line from the gauge, turned pump back on...plenty of fuel coming out. Maybe a bad gauge, so I just ordered another one. Anyway, car fired right up after sitting. Maybe the issue as the poor idle mixture, maybe the hot fuel lines, maybe I just got lucky. I also ordered heat insulating gaskets for the carbs, but mistakenly only ordered 1, so I'll get those on next weekend when the other one comes.

My issue now is dialing in the idle speed, to find a happy cold idle speed...about 1100rpm, it is pretty high when warmed up....about 1600rpm. How do I get a happy medium where it is not so different between cold and warmed up???

 

[steve340]

You probably will not be able to get that unless you set up the choke fast idle system.
Set the idle speed hot and just work the throttle to keep it running when cold.
As I said earlier an engine with the correct jetting is a bit temperamental when cold.

 

[ksurfer2]

You probably will not be able to get that unless you set up the choke fast idle system.
Set the idle speed hot and just work the throttle to keep it running when cold.
As I said earlier an engine with the correct jetting is a bit temperamental when cold.

Thanks...i'll keep whittling away at this. Btw....how in the world do u read the numbers on the Jets and metering rods for the edelbrock carbs. Even with a magnifying glass it is nearly impossible.

 

[steve340]

Yep I use a glass and a bit of guess work sometimes. I have a powerful desk top light which helps.
They can be a bit tricky. I have confirmed some of the rods by measurement as Edelbrock publishes the specs.
A friend of mine has jet measuring equipment of certified diameters so I use that to make little mods sometimes.

 

[dvw]

Cross ram is tricky. Cold intake, fuel puddles, idles low. Warm intake, fuel vaporizes and the idle and throttle response are much crisper.
Doug

 

[myk r sanchez]

Thanks...i'll keep whittling away at this. Btw....how in the world do u read the numbers on the Jets and metering rods for the edelbrock carbs. Even with a magnifying glass it is nearly impossible.

It's the springs that I cant decipher. They're supposed to be different colors, but in the calibration kit they all look the same to me...

 

[dvw]

Easy to see if it's a spring issue. Loosen the metering rod access plate screw. Rotate the plate just enough so you can see the metering piston. Snug the screw in this posistion. Now start the car. Have someone put it in gear. Watch the piston. If it stays down the spring isnt stiff enough to affect idle. If the piston is dancing up/ down or is up, the spring is to stiff. The springs should only lift the piston (and along with it the metering rod) when engine load is sufficient to need additional fuel flow thru the jet.
Doug

 

[ksurfer2]

Easy to see if it's a spring issue. Loosen the metering rod access plate screw. Rotate the plate just enough so you can see the metering piston. Snug the screw in this posistion. Now start the car. Have someone put it in gear. Watch the piston. If it stays down the spring isnt stiff enough to affect idle. If the piston is dancing up/ down or is up, the spring is to stiff. The springs should only lift the piston (and along with it the metering rod) when engine load is sufficient to need additional fuel flow thru the jet.
Doug

If I am reading this right, at idle IN PARK, the piston should be down. At idle in GEAR, the piston should be up? Is that what you are saying? Properly tuned, this is what the spring should accomplish?

 

[dvw]

If I am reading this right, at idle IN PARK, the piston should be down. At idle in GEAR, the piston should be up? Is that what you are saying? Properly tuned, this is what the spring should accomplish?

Piston should be down park and in gear. Itll raise under load such as heavy brake torque.
Doug

 

[steve340]

The step up spring is working against the vacuum generated in the engine. As the vacuum in the engine drops the spring can overcome the vacuum the piston goes up and exposes more jet. This richens the primary side of the carb.
The piston should be down at idle and cruise.
It is the way the designer of that style carburettor allowed the primary side of the carb to richen up for high throttle/low vacuum operation of the engine.

 

[myk r sanchez]

Piston should be down park and in gear. Itll raise under load such as heavy brake torque.
Doug

Damm I'm going to try that today...

 

[ksurfer2]

I think I got this issue fixed. Here are the steps I took:

1. Wrapped fuel lines in the engine bay heat wrap.
2. Installed heat isolating spacers under each carb. This reduced the float bowl temp by about 20 degrees
3. Re-tuned idle mixture and idle speed.
4. Replaced fuel pressure gauge....I think this could have been a big part of the problem. The old pressure gauge was set to 5.5psi, but would read 0psi once the motor was warmed up. The new gauge read 9psi!!!! I reset the regulator to 5.5psi and it reads fine cold or warm.