Let's play "Diagnose this symptom!" (Six Pack-related)

[jhaag]

Plugs look good. Find it very hard to believe it is electrical, as you stated it runs very well other than hard staring when warm. My 2 cents would be fuel related. Fuel percolating in carbs when engine is hot and shut down. Or internal fuel leak in carbs when warm. Shut the car off after getting it to operating temp. Have the air cleaner off, and look down the carb throats for any leaks. Also listen for fuel boiling, and smell around for abnormal smell of fuel. Make sure float bowl screws are snug. Todays fuel is not good. What are you running in it? Does the car have the correct anti dieseling solenoid connected and curb idle set correctly? For what it is worth my 340 t/a six pak had the same problem 40 years ago. I never did figure it out.

[Grec]

Idle solenoid?

You mean this thing?: http://www.ebay.com/itm/252271840140

No. I don't have one of those. Not even sure what it does, exactly... ?

As for my idle... Pretty sure I have it set right. I set it to be as low as I could get it without it stumbling. It's got a nice, kinda-lumpy idle. Sounds good. Like a well-tuned BB with a pretty hot cam. 

(As for RPMs... not sure. My tach got fried somehow  but I'd guess it's around 800)

I'll do some checking of the carbs next time I take it our and get it up to temp. 

[734406pk]

Plugs look good. Find it very hard to believe it is electrical, as you stated it runs very well other than hard staring when warm. My 2 cents would be fuel related. Fuel percolating in carbs when engine is hot and shut down. Or internal fuel leak in carbs when warm. Shut the car off after getting it to operating temp. Have the air cleaner off, and look down the carb throats for any leaks. Also listen for fuel boiling, and smell around for abnormal smell of fuel. Make sure float bowl screws are snug. Todays fuel is not good. What are you running in it? Does the car have the correct anti dieseling solenoid connected and curb idle set correctly? For what it is worth my 340 t/a six pak had the same problem 40 years ago. I never did figure it out.

  The plugs look good. Are you running pump gas/ethanol blend? If so the boiling point is very low. This isn't a problem on EFI systems, but on a classic muscle cars with carb(s) it can be. Check out this product:::http://www.coolcarb.com. It is recommended to remove your intake manifold and block the exhaust cross over ports. They can drive the carb temp over 250 deg when you shut down. The down side is your factory bi-metal choke won't work correctly, but there is an electric heated one that can be modded to work if you need a choke.

[Grec]

As far as what I'm running... 91 octane. Not sure what, if any, Ethanol blend is in it. I'm wanting to say it doesn't have any, as I don't recall seeing the big label on the pump at the place I go to all the time.

[dfrazz]

Check out this product:::http://www.coolcarb.com. It is recommended to remove your intake manifold and block the exhaust cross over ports.

I had starting problems on my 440 in the Charger due to fuel in the bowls boiling off. I added the a new valley pan to block the heat cross-over (gasket set 1215), a Cool Carb spacer, a return line and re-routed the lines from the block with DEI insulation to cool things down.  Good to go now!

[Chryco Psycho]

I would block the heat crossover in the intake using a 1215 gasket & use an electric choke if you feel you need one at all as most of these cars are driven only in warm weather anyway /

[734406pk]

As far as what I'm running... 91 octane. Not sure what, if any, Ethanol blend is in it. I'm wanting to say it doesn't have any, as I don't recall seeing the big label on the pump at the place I go to all the time.

91 octane may be a bit low for this beast (i have one too). With 915 iron closed chamber cylinder heads, your CR may be beyond pump gas. I blend VP C12 @ 108 octane with high test pump gas (92 octane)to get 98 octane +-. You should be able to push your total timing to 36 deg with this mix. This is closer to what the engine was designed to run on back in the day.

[Denison636]

Did you ever check to see if you have low voltage after it runs a bit. I had this issue before changing over to MSD Box

[jhaag]

You mean this thing?: http://www.ebay.com/itm/252271840140


Yes that is what I was referring to. That solenoid was used to properly set curb idle on Mopars with 6 paks and hemis. After thinking about more, it probably has no effect on your issue. It was energized when you started the car, and contolled the idle speed. When you shut the engine off it would de-energize and allow the throttle blades to fully close so the engine would not run on, or as we used to say "diesel". Anyone reading this younger than about 35, probably never heard of this phenomenon. (They were also used on other vehicles with ac to kick up the idle when the ac was turned on) Any way after all said and done I think your issue is related to poor fuel and engine heat. Good luck and let us all know if, and when you solve this issue.

[Grec]

As luck would have it, I ran into an old-school mechanic buddy of mine yesterday while out and about.

I told him about my starting issue, but that otherwise the car was running great. His 1st response was "It's probably the fuel, dude. The gas that was around when this car, and those carbs, was designed is totally different than the crap we're forced to run today."

Which is what a couple of you have suggested.   

His fix for the starting issue? "Don't pump it, but give it about 1/4 - 1/3 throttle as you're starting it." Sure enough. It starts up MUCH better this way. Still not as crisp as that initial cold start, but it definitely isn't the embarrassing display it has been. Lol

Also, find some better gas if possible.

As for my CR, I'm running dished pistons w/ those 915s, but it's definitely on the edge of what you should be running on pump gas. I think I need to track down some higher octane

[73440]

http://www.racegas.com/fuel/compare

http://www.vpracingfuels.com/master-fuels-table

http://www.exxonmobil.com/aviation/productsandservices_aviation-fuels_avgas.aspx

[Grec]

Heh. Yeah... I've been reading up on avgas. :-)

[jhaag]

stay away from av gas. completely different formulation for air cooled airplane engines.

[HP_Cuda]

So suffice to say that your pump shot is flooding your ride?

Looks like it's time to do some tuning on that carb based on what the engine wants.

[Grec]

Actually, the issue seems to be the lower boiling point of the gas we have to run these days... cooking in the fuel bowls.