What size nuts hold down the rotor on a 454

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i don't think you will find an oxy sensor on an '85 ..............how about the vacuum advance??........or a huge vaccum leak......... bad batch of gas..........to cold  sparks plug will glaze over in time and give all different kinds of symptoms ..........can you hear a knock when pulling hard or does it "diesel" when shut down??...........

still scratching my head>>>
 
digiacomo said:
i don't think you will find an oxy sensor on an '85 ..............how about the vacuum advance??........or a huge vaccum leak......... bad batch of gas..........to cold  sparks plug will glaze over in time and give all different kinds of symptoms ..........can you hear a knock when pulling hard or does it "diesel" when shut down??...........

still scratching my head>>>
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There is no knocking and it doesn't diesel when I shut it down. Whatever the problem is, it only occurs when the engine is warm.
 
hmmmmmm.........now i'm really grasping straws........can you hear any timing chain noise??........could it be vapor lock......do you get any backfire down hill.......plugged exhaust [bent pipe]........ heat riser frozen [stuck shut]    .........i would get a some either or carb cleaner and spray around the q jet and intake while running to check for vaccum leaks..........they could get worse as the engine warms...........

this is a good one.......you might have to go try the chevy forum    http://www.chevytalk.org/fusionbb/portal/index.php?  there are a lot of old motor heads in there.........
 
  If you have a check engine light or service engine soon light you have an O2 sensor. I doubt you do unless that was a CA emmision control vehicle as opposed to Fed. E.C. Is that an unleaded fuel engine?
  P-30s were regular gas/ no Cat until 85/86 or so. You can check your year if you can find the VIN for chassis. In the middle of the serial no. you will find a letter that designates the factory, the number before it designates chassis year, i.e. xxxxxxxx4Jxxxxxxxx= 1984 manufactured in Janesville, WI.
  Not to dispute your troubleshooting but I'm still leaning towards fuel delivery problem.
  Did you replace wires, cap and rotor?
  The main causes of a missing/hesitating GM with HEI and quadrajet are: Plug wires, cap or rotor; 30-50K volts off the rotor looking for a ground. A hi ohm wire or bad plug and that voltage will find the path of least resistance.....like a carbon arc to another plug wire going to a cylinder with an open valve. Did you replace wires, cap etc?
  Quadrajets are famous for hard seals on the accelerator pump.
  I must argue with your can't be accelerator pump/runs good cold theory........wouldn't the closed choke affect that?
 
It's too old for all that stuf, it's just a good ol' American engine. My dear ol' '85 Pace had a faintly similar issue where it ran fine when cold but at times after warmup would literally do nothing more than barely idol when I hit the gas. Did the carb, plugs, wires, vacuum lines, etc. What it turned out to be was a microscopic crack along the rigid fuel line along the frame rail at the rear that when heated would suck air. Took almost 2 years to track that one down. later, another hesitation type issue turned out to be timing, and the cam was wrong, consequently so was the timing marks.
 
bigskymt said:
  If you have a check engine light or service engine soon light you have an O2 sensor. I doubt you do unless that was a CA emmision control vehicle as opposed to Fed. E.C. Is that an unleaded fuel engine?
  P-30s were regular gas/ no Cat until 85/86 or so. You can check your year if you can find the VIN for chassis. In the middle of the serial no. you will find a letter that designates the factory, the number before it designates chassis year, i.e. xxxxxxxx4Jxxxxxxxx= 1984 manufactured in Janesville, WI.
  Not to dispute your troubleshooting but I'm still leaning towards fuel delivery problem.
  Did you replace wires, cap and rotor?
  The main causes of a missing/hesitating GM with HEI and quadrajet are: Plug wires, cap or rotor; 30-50K volts off the rotor looking for a ground. A hi ohm wire or bad plug and that voltage will find the path of least resistance.....like a carbon arc to another plug wire going to a cylinder with an open valve. Did you replace wires, cap etc?
  Quadrajets are famous for hard seals on the accelerator pump.
  I must argue with your can't be accelerator pump/runs good cold theory........wouldn't the closed choke affect that?
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I do not have an engine light so there must not be an oxygen sensor.

I used to rebuild carbs. I know exactly what it feels like when the accelerator pump is bad. First off, if your acc pump is bad then starting the vehicle becomes a bitch. You don't have any fuel to prime the pump so you have to crank and crank and crank to get the engine to start. This thing fires right up no problem. The second thing that happens is that at a stop light when you push on the gas to accelerate there is a momentary hesitation until gas starts flowing through the venturi. That doesn't happen. I push on the gas and it accelerates perfectly. However, as I am accelerating, at about 20 or 25 mph I will get a pop or hesitation that lasts just a fraction of a second.

Now that I have been driving it like this for a while I have noticed that after it warms up it is no longer running smoothly while accelerating. It is just a bit rough, like too rich a mixture. I don't feel like this problem is a gas shortage, it feels like too much gas, like the timing is off.

No I have not replaced the cap, rotor, wires and plugs yet. I was going to do that first but in another thread on this forum several people told me they had the exact same symptoms as I did and it was the module that was bad.
 
i was thinking that you had already gone thru it, [plugs, wires, cap rotor and timing]..........make sure you check the vac advance or just replace it with along with plugs and wires.......when i got my old bounder in the driveway, it had a fan that was about to go thru the radiator and plug wires burnt to the plugs........the distributor was retarded as far as it would turn........i have always set the timing by sound and performance, i live at over 5000 ft and have to climb in three directions when i leave town so i can't really go by what a timing light tells me...........i just listen for "knock' going up and back fire coming down.........adjust somewhere in between and let the vac advance take up the slack  .........

i have also found in the last couple of years that it's better to buy just regular gas, [because it's fresher] and treat it with octane booster, ........if i could buy av gas, that would be my choice...

the crack in the fuel line is another very good thing to consider.......... thanks for the tip jeff......i'll try to store it in my "hard drive" for future troubleshooting.... ;D
 
I was going to do the cap, wires, rotor, plugs first but got talked out of it. I will be doing them soon as I can afford to go to the auto parts store. I haven't checked the vacuum advance yet, but I will when I replace the cap and rotor. I have never used anything but regular unleaded in my vehicles. Maybe I need a higher grade of fuel?
 
regular unleaded will give you the fresh fuel [i hear gas breaks down faster now than it used to???] i use lucas upper cylinder lube  and on occasion octane booster......gas makes a big difference in our altitude and we get 85 octane for reg. with ethanol added for good measure  :mad:............[.ethanol should be used for other purposes if you ask me].......  i would imagine when made, those engines [big blocks]  were engineered for 92 plus octane.........i know that the book on my 72 monte carlo 402 big block recommends at least 92 and leaded or unleaded.........

if i keep my old bounder, i'll probably go ahead and buy what i need to fuel inject it in the future........the computers seems to regulate things better than we can manually.................i never thought that i would admit that  ;D
 
  Unless it pings you don't need a higher octane fuel. The reg gas P-30/454 required min. 89 octane, lower at higher elevations. Octane or lack of will not cause the problem you describe.
  I agree with your accelerator pump diagnosis based on your latest info.
  The 'rich' mixture you describe is a new issue.
Quadrajets use a brass seat with a neoprene impregnated needle. Over time the needle develops a ridge and doesn't seat properly. Another problem is the float absorbs fuel and loses buoyancy, both allow extra fuel into the bowl that has to go somewhere. The fact that the problem manifests itself when warm (and running leaner) would support that theory.
  You might examine the exhaust tips for soot/unburned fuel.
  The 'pop' or backfire through the carb would be caused by either a lean condition or bad wire.
Maybe you can ohm out the wires.
  The life expectancy of plug wires on your model P-30/454 is about 5 years.
 
My problem is I was a Ford man most of my life. I can rebuild a Holley with my eyes closed, but I have very limited experience with a quadrajet. The last time I had this problem it was two bad plug wires. The time before that it was a clogged fuel filter. I will ohm the wires when I replace them.
 
Pull the air cleaner lid and look and see what kind of fuel shots you are getting. Strong or small squirts.
J
 
Sounds like all kinds of "nuts" hold down the rotor on a 454.  I suspect many of them are about 6 ft tall....  ;D ;D ;D ;D
 
I replaced the rotor and the dist cap today and that did not solve the problem, but then again I wasn't expecting them to. I am doing this one step at a time so I can see what actually was the problem. Tomorrow I will replace the plugs and then the next day I will replace the wires. I tested the vacuum advance and it is advancing correctly. I did find that the vacuum line that feeds the vac adv had a small slit at the end, which I repaired, but that didn't solve the problem.
 
34footer said:
Pull the air cleaner lid and look and see what kind of fuel shots you are getting. Strong or small squirts.
J
Click to expand...
Why should I do that?
 
No, I haven't left on my trip yet. I am parked at a friend's house in Las Vegas. No problem.
 
seilerbird said:
Why should I do that?
Click to expand...

To be sure that your accelerator pump is working good. I went back and read the whole thread over again so I guess it's not starving for fuel. And you know an overly rich mix would show signs at the tail pipe. If you have dual exhaust compare the exit point of the two pipes. Misfiring might show up there. Then you can narrow down to one bank of cylinders.
J
 
I know the acc pump is working properly. A bad acc pump presents a totally different set of problems.
 
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