What intake is on it?

How hot is it getting?

Sounds like it is rich at idle when hot and flooding carb..

When eng is hot turn fuel mix screws on carb out 1 turn then in 2 turns then out 1 turn to orig position. Set these screws so idle is highest.

If it still has problem set float level to 1/8" below inspection hole and tell us where it was before adjustment.
If there is no sight window loosen screw on top, lift nut to break seal to gasket, drop nut back down, turn nut counter clock wise 1/2 turn, tighten screw.

Gasket might break during this process causing gas to leak while running.

Are you running that e 85 junk gas?

 

Yep, sounds like a percolation problem. You might try a different spacer, maybe a SuperSucker or a wafer-style. You could also cut and bend some heat shield material and install under the spacer to keep the heat from the manifold off the bowls. Last, but certainly not least, find a "hot idle compensator", which is basically a thermostatic valve that installs in the PCV line that opens a controlled vacuum leak when hot to increase idle speed.

 

I'm ahving the similar problem but it only takes about 3 miles (get it up to temp) and it stalls and has a hard time starting up. Check your ignition coil voltage and fuel line to make sure it's getting fuel when it stalls.

Hopefully we can figure them out so we can enjoy our pony's.

 

thanks for the replies so far. I don't know the intake manifold brand. From the VIN I know it was born a 2 barrel and was converted to the 4 barrel. I am running only 93 octane gas but cant avoid the ethanol add-in down here. It ran hot with the old radiator, but the new alum 3 row has it cool as a cucumber, so the engine is not running hot. Even idling after hwy running on a 94 degree day, the temp needle barely moves. Carb was just rebuilt about 4 weeks ago; I 'presume' the mix was properly adjusted but I will have that checked. thanks and keep the suggestions coming!

 

Had a similar problem on my recently completed (off topic) hot rod... chasing the problem I would swear it was fuel related... i finally ended up narrowing it down to the china mfg. ignition coil (which was new with 600 miles) getting hot and breaking down the ignition....

My problem was the Accel SS coil, was proper design for my ignition system and would test out fine cold, but after 25 miles would run rough, then not at all (seemed flooded from percolation)....
Tom

 

I understand your engine is not running hot, so does your intake manifold and/or air cleaner feel hotter than they should be? Similar problem a day ago found the intake and gasket was installed without the exhaust block off plates. It heated the manifold and carb to the point it would boil off the fuel. His engine was cool.

 

Sounds kind of simple but my 347 with 355 gears runs about 3800 rpm at 65 mph. After about 25 miles on the interstate it will run out of gas. Let it sit a few minutes and it's good to go for a while. Replaced tank fuel lines (larger) and hi cap fuel pump. Still did it. Found the gas
cap which also serves as the vent was not venting fast enough. It actually sucked the bottom of the tank up and I had to use an air hose to pop it back into shape. New cap still doesn't help I guess I need a filler tube vent kit.

 

Is the intake aluminum or iron?

Does it have a carb spacer?

You need to adjust the fuel mix screws when it is hot as i suggested. Calling the "guy" to see if it was done doesn't cut it.

Lower the float level as i described.

Second time now, is your gas E85? yes or no.

Suggestions will not help you if you don't do what is suggested.

What is your ignition timing at idle with no vacuum?

 

Mine had a problem where the fuel line (rubber) was lying on the water pump and would cause a vapor lock.
Another suggestion is to get a clear (glass type), fuel filter so you can see if there is any crud in the filter. Mine had a really dirty gas tank and the filter would constantly get clogged up, easy to swap out the little tube filters with a clean one.

 

Intake is iron; fuel is 93 octane - 10% ethanol. Moroso plastic spacer. No float adjustment on a Holley 80457-S carb. Timing was just set a month ago. Confirmed mix was set last month when carb rebuilt but that will be the first thing looked at. New clear fuel filter - still clean no debris or rust present. Didn't feel like the carb/air cleaner was 'excessively' hot, but it was hot. Read SA70's post about the exhaust block off plates. I am also running an Accel coil, so will look at that as well.

Going to mechanic in the morning with these suggestions. If you think of more, please pass along. Will report what works. Thanks!

 

When the car "does it's thing" and runs poorly/stalls, grab ahold of the coil (be careful) and if it is really hot, it probably is your issue.....I chased my new Holly SA carb as the culprit for many 100's of miles on my 327 Chev last month (and last fall) until I googled for coil issues after I layed a hand on mine.....

My Coil was the Accel Chrome coil....replaced it with a stock one as a last resort... problem is 100% gone, i would have bet the carb was percolating.....
Tom

 

Did you happen to replace the gas cap? My buddy had a 67 with same symptoms. Took a while to figure it out, but the gas cap he used did not have a vent in it. I happened to pop his trunk for something and the top of the tank was collapsed, basically after 20 minutes the fuel pump had pumped all the air from the tank and could not pump fuel. Had him drill a small 1/8" hole in the cap and ran fine ever since. Simple to check, maybe you get lucky.

 

We need to know what timing is

Is 10 ethanol e 85? If it is e 85 it will say on the pump.

i bet he won't touch the float level and gives you some reason why that can't be the problem. If he does you need a new "tuner" not a mechanic.

 

Is 10 ethanol e 85? If it is e 85 it will say on the pump.

He is not getting E85 which is like 85% ethanol.
I buy it for my company car, the pump prompts
you to push another button so you don't get it
by mistake.

 

No it is not E85. It is 'premium' gas that 'contains up to 10% ethanol. Will have new mechanic check time. As odd as it sounds, there is no float adjustment nor is there a sight window in a 80457-S Holley carb.
Go figure.

http://www.holley.com/data/Products/Technical/199R7948-5rev6.pdf

 

No it is not E85. It is 'premium' gas that 'contains up to 10% ethanol. Will have new mechanic check time. As odd as it sounds, there is no float adjustment nor is there a sight window in a 80457-S Holley carb.
Go figure.

http://www.holley.com/data/Products/Technical/199R7948-5rev6.pdf

My 67 also does not have an adjustable float nor a sight glass.
I bought my 4BB carb and installed it myself and it ran fine for over a month. Then I took it on a long drive from Austin to Houston on a relatively hot day, and when I got back home it ran like exactly as you described. Turned out that for some reason, something in the new carb had shifted with the long drive, and I had to adjust the fuel/air mixture. That was about six months ago and it has ran like a champ ever since.
Short story - on a similar car, I also had a new Holly Carb, and it shifted and required adjustment once after the install.
Adjusting the fuel and air mixture is really easy, and your carb probably came with a CD describing how to do it.

Check out this video (the same found on the CD the carb came with) :

 

ok good at least its only half junk gas, lol.

yeah that's holleys budget model, cheap skates.

pre set to some 18 year old hungover kids specs, lol.

 

LOL, too funny. I 'inherited' it!

 

And the answer is......

Bad ignition control module for the ACCEL distributor. When hot, it failed, therefore no spark. Old stuff (ACCEl dist and coil) coming out and new (MSD) stuff going in.

 

I have read many posts regarding this topic but I haven't seen my exact situation. After 20 minutes of highway driving, if I get into stop and go/extended idling, the car stalls when its time to move forward. Shifting into neutral, engine runs smooth. As soon as shifted into D, it dies. Cranks right back up but dies again as soon as D engaged. When it eventually gets rolling, engine has difficulty developing power (runs but stumbles with heavy acceleration). After a while back on he highway, all goes back to normal until back in the neighborhood with numerous stop and go. Bought the car from a bankruptcy auction so I don't know about its history. 289 with Holley 80457-S carb sitting on a Moroso 64930 plastic spacer. When I first got it, I had carb rebuilt, new 3 row alum radiator, new plugs, tune up, new air filter, new fuel pump and a bunch of other stuff that is irrelevant to this situation (ac, suspension, etc...). Does not burn oil; engine runs perfectly except for this issue. Read up on vapor lock, so I installed a heat sheath around the fuel line, but that didn't stop the problem. I am not a mechanic and the guys who have worked on it so far have 'some' experience with non-EFI cars, but not a huge amount. Would appreciate some good suggestions to pass on to them for troubleshooting the prob. Thanks!

Hello I have the same problem did you ever find a solution?