Throttle bog..

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Dogdish95

Dogdish95

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Obviously learning as I go. Posted on Facebook with minimal results. I have a slant six that’s stock. I have been having an issue when I put my foot to the floor it stalls and won’t accelerate. When it’s about 80% -1% pressed it zooms on along. When at 80% and I slowly release the throttle it stumbles but accelerates all the way as my foot goes back to 1% off the throttle my I have tried adjusted valves, new plugs, wires, rotor, cap and played with timing and mixture screws the best I understand. The fuel tank and filters are clean. Fuel pump fills the carb an filter without issue. It idles good and starts good. I have had this issue since day 1 over a year of owning this car. This is my only issue any thoughts? Carb float has been changed and raised, Carb gone through, new plugs wires, distributor works new vacuum pod..
 
Which slant, what carb and what is your ignition system and current timing?
 
In what gear? what rpm/what roadspeed? and is it always the same?

Help me understand this;
Lets say you are in Second gear at somewhere near 2000rpm. And you slam it to 80%. And the engine gets to work no problem. You hold it there for a bit, but as the shift-rpm approaches, you back off the throttle to 1%, and this is when the stumble shows up?
I mean this is what I'm thinking as I read your words.

If yes,
then pressure test your exhaust system.
If no,
Please clarify
 
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AJ/FormS said:
In what gear? what rpm/what roadspeed? and is it always the same?

Help me understand this;
Lets say you are in Second gear at somewhere near 2000rpm. And you slam it to 80%. And the engine gets to work no problem. You hold it there for a bit, but as the shift-rpm approaches, you back off the throttle to 1%, and this is when the stumble shows up?
I mean this is what I'm thinking as I read your words.

If yes,
then pressure test your exhaust system.
If no,
Please clarify
Click to expand...

It happens in drive around 2000 rpm’s. In second gear I mash the pedal %80 to the floor and it’s accelerating nice and quick. I go to %100 foot to the floor I get the stumble like it’s out of gas (rough idle and ping then engine shuts off unless I lift off the gas) and it will go no faster or move other then the momentum it has already picked up. I then lift my foot off the gas back to %80 or lower and as I am lifting (decelerating) it picks up speed as if it was to the floor. It doesn’t matter how long I have my foot to the floor or how much I push the pedal down it does this. In each gear as well as idle.
 
Your fuel system is not producing the necessary volume of fuel to maintain that speed. I would suspect a bad fuel pump or clogged fuel lines.
 
or filter on pick up tube is clogged in tank
 
Have you physically looked into the carburetor throat and witnessed a good, string stream of fuel when the throttle is opened?
 
Dogdish95 said:
It doesn’t matter how long I have my foot to the floor or how much I push the pedal down it does this. In each gear as well as idle.
Click to expand...
I would normally agree that this is a lean condition.
But if it happens in every gear the same way; with fresh non-alcoholized fuel, then I am inclined to believe there is another factor at work here; and I think the pinging is the clue. Therefore I recommend;
1) to make sure the mechanical advance system is not frozen, then
2) I would recommend the exhaust back-pressure test; because this costs almost nothing. If that doesn't find it, then
3) a fuel volume test, cuz that's easy. But if inconclusive, or new parts do not solve the issue, then;
4) cam timing, excessively tight lash, or lobe failure.

numbers 2 and 3 can be flipped
 
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Its spark scatter or lack of fuel is my 1st thought, like most.

Also sounds like you might want to check the hose at the sending unit coming off the tank for any cracks...very well could be sucking air ..and would maybe leak too.
Had a friend with a 440 satellite that wouldn't rev over a certain rpm, 3000 or something...that's what it was.
 
Air leak tiny pin hole in hose at tank,on a slant six.Ok till fuel level dropped in bowl.Which should be checked.
 
1920 fuel -43.jpg
 
1920 is air bleed carb.27/32 puts fuel at correct level for main system air bleed holes.Above that level main system richer. Below that level main system leaner.In picture you can see first air hole just above fuel level.
 
Some times power lever breaks or push down rod misses it, no power valve activation. One more thing air bleed hole in venturi feeds main system very small, make sure it is open.
 
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