Cold-blooded 340

[DartSportDude]

I hope someone can give me advice regarding my Dart Sport 340. My engine was rebuilt about a year and a half ago, and it still has the original Thermoquad carb (carb was rebuilt, too). The car has always been cold-blooded (tough to start on cold mornings), and lately this problem seems to have gotten worse. After the car has been sitting in my garage for 4-5 days, you have to pump the accelerator to the floor at least 5-6 times to get it to fire up. At that point, the carb seems flooded (it loads up a bit) and there's a fair amount of white/blue smoke from the pipes until the engine warms up. Once warm, there's no smoke and the engine idles and runs fine.

I've had a local mechanic tinker with the carb a few times in an effort to ensure easier starting and less flooding, but the issue has only gotten worse. I'm about ready to throw in the towel on the Thermoquad and go with a newer carb (I hate to do that, since the TQ is original).

Any suggestions? This is driving me nuts! Thanks.

 

[wish4hemi]

Do you get fuel on the first few pumps? Had this trouble on my 440 and found out that somehow either the fuel was draining back or evaporating out of the carb. I put on an electric fuel pump and it solved the problem. Just flip the electric pump on for 4 or 5 seconds before you crank it to make sure the carb is full of fuel and mine starts right up just about every time.

 

[1968FormulaS340]

What intake?

Does it have a working choke?

Is the heat cross over blocked?

It could also be the craptastic winter gas blend.

 

[DartSportDude]

The 340 still has the stock intake. Choke appears to be working (at least, it will kick on to high idle after just a minute or so). I know it's getting gas to the carb when pumped; for some reason, it just seems like it takes a lot of gas to get the engine to fire, and at that point, it acts flooded until you rev it up or it gets warm.

 

[Snake]

Yep your intake is not getting warm fast enough.Your crossover in your intake could be plug up with carbon.Do you have a hose for your exhaust manifold yo your breather.Up here in Canada that hose is used to warm the air going into your carb.i know you say its geting worse so could be your intake is too cold at start up.Try heating your intake with a tourch first that try it,worth a try.

 

[DartSportDude]

Yep your intake is not getting warm fast enough.Your crossover in your intake could be plug up with carbon.Do you have a hose for your exhaust manifold yo your breather.

Hose in is place. I'm wondering if it could be the fuel pump? My mechanic has looked at the carb, and just doesn't seen any problem with it.

 

[1wild&crazyguy]

initial timing and ignition are probably to blame.jmo

 

[1968FormulaS340]

initial timing and ignition are probably to blame.jmo

Yes.... All the normal tune up stuff should be checked and set first.

 

[66fs]

All good answers above. Thermoquads are set lean. As I remember, the choke must shut closed all the way, even when warm. Then set the choke pull off to what the factory says. Adjust slightly from there. Choke pull off could be bad and not working. Is the electronic delay gizmo still on the electric choke? Vacuum advance could leak and not advance when it starts. I also use an electric fuel pump. You always have plenty of fuel when you start cranking. I lived in South Dakota for 5 years, now I can't stand to be cold...

 

[MopaR&D]

Actually I think your choke might be working a little too much... I ran an '83 ThermoQuad on my mild 318 without a choke and it would start and run fine cold (not winter cold, but I'm sure it would've still worked). Like has been said though also check the crossover in the intake/heads and make sure the timing is correct.