Rotten Running 300. Now what? Suggestions

[Buick2]

Sorry if this is a duplicate:

I have a freshly rebuilt '64 300 in my '34 Pickup. It runs fine when cold, even just warmed up. When completely warmed up it begins to miss and seems to load up at idle and lower rpm (700-1100). It smooths out over 1500rpm but around town it gets to be a hand full! I've switched out the carb (currently using an Edelbrock 1406), installed a 1/2" Edelbrock spacer, new plugs, rebuilt distributor (points, vac. adv., condenser), new coil, re-timed it, and even put in a 160º thermostat. Even put in a leaner metering-rod kit. Problem persists. It runs worse on plus, it seems, than on premium.

I thought it was boiling the fuel in the carb. fuel bowl at first but even cooler weather and the adjustments I've listed above, don't seem to help.

Now what? I'm open to any and all suggestions.

Typical scenario: I take a run to the parts store about 4 miles away, then on the way home stop at Safeway to satisfy the grocery list and 10 minutes later head home. Runs like crap and dies on the uphill corner as I make an unceremonious entry into the local neighborhood.

Rich (Buick2)

[telriv]

If we had a CLUE on where you lived you never know there may be a member close by willing to give a hand. Like has been said, "two heads are better than one".

[Buick2]

If we had a CLUE on where you lived you never know there may be a member close by willing to give a hand. Like has been said, "two heads are better than one".

Tom,

I'm in Oregon so it would be great to have some wisdom from CT!

I've had a good bit of help and still can't solve the problem. It seems like carburator or timing but both have been replaced, checked out, adjusted, cursed at, and most of the other usual operations/solutions. The issue that seems to aggravate smooth running is heat of some sort, when it get really warm it runs worse. Not good!

Rich

[bob k. mando]

carefully inspect the routing of the fuel lines, both before and after the fuel pump. the carb is not the only place that fuel can gain too much of a heat load.

you might also want to try getting some kind of a fuel gauge on the output side of the pump. it may be that after everything gets warm and loosened up the pump is just getting too much slop in it and is losing pressure.

make sure the fuel return line isn't kinked or plugged.


installing an in-tank pump never hurts if you've got low fuel pressure problems although upsizing the filter would be a much cheaper fix.

if all else fails, drop the tank and check the sock on the fuel pickup and clean the tank. it MAY be that sock is just getting crudded up and that it doesn't really show until after the car has been running for a while. i doubt this, but cleaing the tank on one of these old cars is never a bad idea.

[Buick2]

carefully inspect the routing of the fuel lines, both before and after the fuel pump. the carb is not the only place that fuel can gain too much of a heat load.

you might also want to try getting some kind of a fuel gauge on the output side of the pump. it may be that after everything gets warm and loosened up the pump is just getting too much slop in it and is losing pressure.

make sure the fuel return line isn't kinked or plugged.


installing an in-tank pump never hurts if you've got low fuel pressure problems although upsizing the filter would be a much cheaper fix.

if all else fails, drop the tank and check the sock on the fuel pickup and clean the tank. it MAY be that sock is just getting crudded up and that it doesn't really show until after the car has been running for a while. i doubt this, but cleaing the tank on one of these old cars is never a bad idea.

Bob,

Thanks for your suggestions. I had wondered about the routing of the fuel line, especially between the fuel pump and the carburetor. Also, the idea of installing a fuel pressure gauge in that line might be revealing. The fuel tank and fuel pickup are new so shouldn't be the problem.

I didn't mention in my original post that when it starts running rough it also occasionally backfires through the carburetor at low rpm when I try to accelerate, even only slightly.

Thanks a million for the reply. Will let you know when I find the culprit(s).

Rich (Buick2)

[jmk1955]

Just for the heck of it,check the vacuum advance on the distributor. Maybe?

[Kiwijeff]

Sorry if this is a duplicate:

I have a freshly rebuilt '64 300 in my '34 Pickup. It runs fine when cold, even just warmed up. When completely warmed up it begins to miss and seems to load up at idle and lower rpm (700-1100). It smooths out over 1500rpm but around town it gets to be a hand full! I've switched out the carb (currently using an Edelbrock 1406), installed a 1/2" Edelbrock spacer, new plugs, rebuilt distributor (points, vac. adv., condenser), new coil, re-timed it, and even put in a 160º thermostat. Even put in a leaner metering-rod kit. Problem persists. It runs worse on plus, it seems, than on premium.

I thought it was boiling the fuel in the carb. fuel bowl at first but even cooler weather and the adjustments I've listed above, don't seem to help.

Now what? I'm open to any and all suggestions.

Typical scenario: I take a run to the parts store about 4 miles away, then on the way home stop at Safeway to satisfy the grocery list and 10 minutes later head home. Runs like crap and dies on the uphill corner as I make an unceremonious entry into the local neighborhood.

Rich (Buick2)

Hi Rich, Did you check the Intake manifold was straight, it could be sucking air when it gets hot? with it running squirt soapy water around the joins & see if it either bubbles or improves it's running! may help,Thanks,Jeff

[killer66]

Hi Rich, Did you check the Intake manifold was straight, it could be sucking air when it gets hot? with it running squirt soapy water around the joins & see if it either bubbles or improves it's running! may help,Thanks,Jeff

When I first baught my Lesabre, I drove it around everything was fine, then it started sputtering, choking, and smoking. I talked to a friend and he told me to change the PVC valve, it was stuck. Evidently it cause a lot of back pressure I guess. Anyway my problem was solved. I would also get rid of the points and go with an electric ignition. I intalled mine over 6 years without a problem. Also do you have a fan shroud on your car?
Ken

[Buick2]

When I first baught my Lesabre, I drove it around everything was fine, then it started sputtering, choking, and smoking. I talked to a friend and he told me to change the PVC valve, it was stuck. Evidently it cause a lot of back pressure I guess. Anyway my problem was solved. I would also get rid of the points and go with an electric ignition. I intalled mine over 6 years without a problem. Also do you have a fan shroud on your car?
Ken

Thanks Ken. I'll give both solutions a try. Now that we have much cooler weather it is running better but not ideal yet. I did think about the PCV valve so will change it now that you have encouraged me. Nope, no fan shroud. In fact it has been running nice and cool this Fall without a fan. How about that? I'll solve the problem for sure before the hot weather returns in June.

Rich

[telriv]

Make sure the heat riser is not closed/partially closed. This could very well be why it runs better when the engine is cold & with the cooler weather.