Hey guys my 75 slant 6 225 has been having a engine stumble and has to warm up for 5 mins to even get power to pull away with out it dying on a cold starts. Warm starts fire right up and have no trouble with power. If I have to sit in traffic or any place too long (20 mins) the engine gets real hot it will lose power and stumble and spit and want to dye. I have had the carb rebuilt about 8 months ago, did the Valve lash, changed the fuel filter fuel pump about 7 mouths back. Don't know if it might be my idle setting or the radiator! But it really only has this problem in traffic normal freeway driving (65 and up) is fine after warm up. What do you guys think? Thanks

I think your choke is not working properly. Take a look here for carburetor adjustments.

The cooling system needs attention in that radiator may be partially blocked or thermostat not opening fully, or fan not moving enough air when sitting at a stop. Check idle rpm when fully warmed up and reset if needed, flush system and radiator, and test thermostat.


Also when in traffic you can run the heater with fan on high, and increase idle speed with right foot to move more air over radiator. This will help cool the engine.

Letting the engine get hot enough to sputter and want to quit is not good for it. I’m guessing that fuel in carburetor is getting too hot when over heated and causing fuel delivery problems.

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67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

When was the last time you flushed your cooling system?

I would pull the radiator, reverse flush it, and then flush the block.

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82 D150-225/727
02 Dakota-3.9/5 speed
87 GMC C7000-8.2 Detroit Diesel/5+2

Also make sure the lower hose to your radiator is not collapsing when hot. I tried everything before I noticed this was happening, and since then: cool runnings.

Also make sure the lower hose to your radiator is not collapsing when hot. I tried everything before I noticed this was happening, and since then: cool runnings.

Well I reset the idle a little higher cause it did seem to low to me after I had adjusted it last. What is a good gage to use to see the rpm's and to help set the idle speed? I have never flushed the radiator and engine and don't know when if ever it has been done being only the second owner. The coolent does not look old but I'm sure its not great. I plan to flush out the cooling system and clean it. Then changing all the hoses and heater hoses and the thermostat it all does not look bad just normal wear but I'm sure it could use replacing. So I'm hoping that will fix the car over heating. I might also sense my car does not have a fan shroud run a electric fan in front of the radiator to help cool down when in traffic or driving at less then 25 mph. Should any of theses changes keep my thermostat in the cool running range? Thanks for all you help guys -R-

[quote]Well I reset the idle a little higher cause it did seem to low to me after I had adjusted it last. What is a good gage to use to see the rpm's and to help set the idle speed?[/quote]


Setting idle speed is best accomplished by using a tachometer, but adjusting up in steps will work as well to get close. If transmission engages with a clunk and car wants to move along (more than a creep) when idling, than idle speed is too high.

[quote]I might also sense my car does not have a fan shroud run a electric fan in front of the radiator to help cool down when in traffic or driving at less then 25 mph. Should any of theses changes keep my thermostat in the cool running range?[/quote]

You have to keep in mind that when new these six cylinder cars did not over heat as a general rule. I believe only some of the air conditioned cars had fan shrouds. With that in mind, electric fan won’t correct a deficient cooling system.

I would bet that both radiator and heater core are partially plugged. Plugging could be crap from block, or corrosion from bad chemistry, or both.

Disconnect lower radiator hose at radiator and run some water down through the radiator. Do the same with the block with thermostat removed, and passenger’s side drain plug (between oil pump and fire small ¼â€￾ square threaded plug) wall removed

Is there any white stuff festering out from radiator’s fins?

[quote]I have never flushed the radiator and engine and don't know when if ever it has been done being only the second owner.[/quote]

If coolant looks good, that is; no black scum, rusty color, or opaque, than it is a good bet that someone changed it recently, probably for that same reason you are experiencing now, over heating.

_________________
67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC