273 rough running when warm

[thomas93254]

1966 273 with bbd carb. Runs great cold but as soon as it warms up it starts running rough and has a random miss and then dies. The previous owner has replaced coil, dist, plugs, wires and carb trying to get it to idle warm but no luck so he sold the car to me. Now I plan on doing basic auto 101 on it and double checking the basics, point gap, timing, plug gaps, replace ballast resistor, wires, vacuum lines and adjust the valves. Question is what else should I look at while under the hood? I suspect it might be a vacuum leak but want the other stuff ruled out first. Ideas or random thoughts welcomed.

Thomas

 

[A383Wing]

adjust yer valves also

 

[thomas93254]

Took a closer look at the engine tonight. When the choke open is when it goes to crap for running so I think it's got to be a vacuum leak. Tomorrow I'll block off all vacuum ports and see if that helps to narrow it down.

Thomas

 

[rsd859]

My big block runs kinda crappy once it gets hot and im blaming the cheap gas.

 

[thomas93254]

Got the vacuum lines all plugged and now it idles in gear at least. I can tell the timing is off and everything needs to be reset. The green vacuum regulator has a major leak in it and as soon as I bypassed it the engine ran better. Now to the engine tune up 101,

 

[thomas93254]

Tonight I got the timing light on the engine and found out it was more than 20 degrees retarded. Now that is fixed now I can tune the carb

 

[rsd859]

Good work!

 

[terzmo]

could be burnt valve/valves as they act up when warmed up

 

[thomas93254]

**Update**. Finally got a vacuum gauge that worked on the engine and the vacuum is steady at 16 psi. So no burnt valves, thank God! Choke on runs great, choke off falls on it's face and will not fatten up. Have plugged all vacuum lines from the carb and no leaks at the carb or manifold.
I did noticed that clear fuel filter was empty and it took a bit to get the fuel up to the carb when we were starting it after only sitting a day. I'm thinking that the mechanical fuel pump might be getting weak and not getting enough fuel to the carb for it to run right after it warms up. The kid I bought it from did say that it "suffered" from vapor lock once in a while and insulated the fuel line. I wonder if that "vapor lock" was really lack of fuel from the pump. What should the pressure be from a stock pump and how much volume should it put out?

Thomas

 

[Funship32]

Most "stock" pumps run anywhere from roughly 4 to 6 PSI of pressure. As for your problem: Honestly it does sound like a vacuum problem but you've done your homework (good job!) and not that I'm one for just throwing parts at a problem but I think a new fuel pump is just a generical cheap investment to just want to replace.

 

[Jonnyuma]

If the diaphragm in your fuel pump is bad, be aware that that will allow gas into your engine oil. Conversely, oil that smells like gas could indicate a bad fuel pump. That doesn't have anything much to do with your engine stalling when hot, just something to keep in mind. Good luck getting it tuned up, I'm battling my own vacuum/tuning issues as well.

 

[thomas93254]

: Honestly it does sound like a vacuum problem but you've done your homework (good job!) and not that I'm one for just throwing parts at a problem .

That was my thought too. The carb is a summit rebuilt Carter 2bbd (replaced by po), which are known for lean running and tuning issues. I'm trying to not just throw more money into parts but the thought has occurred to me that there may be a problem inside this rebuilt carb. I have blown the idle jets clear with compressed air but if there is a vacuum issue inside the carb the only way to tell is spend money on a different carb, which will be a Stromberg if I do that option. But maybe a few bucks on a new fuel pump is a safe investment.

Thomas

 

[Funship32]

That was my thought too. The carb is a summit rebuilt Carter 2bbd (replaced by po), which are known for lean running and tuning issues. I'm trying to not just throw more money into parts but the thought has occurred to me that there may be a problem inside this rebuilt carb. I have blown the idle jets clear with compressed air but if there is a vacuum issue inside the carb the only way to tell is spend money on a different carb, which will be a Stromberg if I do that option. But maybe a few bucks on a new fuel pump is a safe investment.

Thomas

Well it certainly is a 'cheaper' investment and if it is old it wouldn't be a horrible idea to replace it. Just out of curiosity tho, once it warms up and dies, have you put the choke on again, you know, by manually resetting the stepper assy, and seen how it runs then?

 

[thomas93254]

If I reset the choke it runs great but once it's off it stumbles rough runs then dies. The Idle mixture screws do not seem to effect it at all. Ive made sure the butterflies are shut all the way. Also when the choke opens the engine drops to less then 12 vacuum steady. I have tried the spray around the carb base and on the intake manifold with no change.

Thomas

- - - Updated - - -

At this point I'm going to pull the carb off, check the gasket under it and make sure all is right inside that carb.

Thomas

 

[A383Wing]

OK..I misread the original post..I thought it was a 4bbl, not a 2bbl....

I bet here's what's wrong...the idle pick-up tubes inside the carb are plugged (common problem)...or the float level is low..either way, a rebuild is in order...

Bryan

 

[Funship32]

Hey Thomas, save your $$ on the fuel pump. You can replace it but I strongly suspect you'll have the same problem. If you don't mind more question...if you ramp up the idle while off choke, will it run then or does it still die?

 

[thomas93254]

I found the problem. The carb throttle shaft has more slop than a $2 whore on a Saturday night. The carb may have been a remand but the shafts were not bushed. On top of that the po used the same 1966 carb gasket instead of replacing it. So it looks like a new carb

Thomas

 

[thomas93254]

Well I ordered a Stromberg from Classic industries. If nothing else the sales rep was very nice and answered my questions quickly. One of the questions he had to put me on hold for, which was good because he did not guess at an answer, which makes me feel better about my purchase. Now I will work on the other stuff till it arrives

Thomas

 

[Funship32]

I found the problem. The carb throttle shaft has more slop than a $2 whore on a Saturday night. The carb may have been a remand but the shafts were not bushed. On top of that the po used the same 1966 carb gasket instead of replacing it. So it looks like a new carb

Thomas

Nice work on your part, sloppy work on the remanufactures part. But good troubleshooting. Would like to see a pix the Stromberg once you get it on.

 

[thomas93254]

you got it. I'll take some off the car and on with the bbd next to it so we have comparison pics

Thomas