1972 Suburban (Plymouth Fury III Wagon) TUNE UP HELP

Engine, Transmission & Driveline

  1. MBar

    MBar Active Member

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    My car has the stinckys!!
    I have the 400 engine with electronic ignition. Since I got it I have struggled with smelly exhaust. I did read the posts and pretty sure my tailpipe is stock angle and my windows are closed. I did changed the valve on the air pump and it seemed to run smoother and helped the smell go away a little.
    I got some good advice here about my 68 Newport 383 that included the use of a vacuum gauge but I didn't get one. Well, I got a gauge and want to do the best I can to tune this car.

    Yesterday, ,I finally spent a little time adjusting the timing to about 7 degrees but had to use a 1/4 inch socket with a u-joint and at some point it interferes with the vacuum advance when I turn it...bought a set of claw wrenches and gonna give it another shot today...
    Do I disconnect the vacuum advance and when?
    I am a bit confused: it seems there are 3 things that affect the idle speed - the idle screw, the mixture screws and the timing...
    Soooo....in what order do I adjust these settings? I have read that when setting timing, I should connect my vacuum gauge to manifold vacuum and advance the timing until the vacuum doesn't rise. Is this the same for the other adjustments?
    I did buy a dwell and tach meter but the RPM readings don't seem to make sense.
    I love driving the wagon and it get's a lot of attention (I am not an attention hound..lol) but it is a bit embarrassing to be so stinky.
     
  2. Davea Lux

    Davea Lux Senior Member FCBO Gold Member

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    By "smelly" exhaust are you talking about black exhaust (too rich) or something else? There are a lot of things that can cause a too rich condition. Check to see that your choke is opening up with the engine warm. Check to see that the heat riser is free and functioning. If the heat riser is stuck open, the choke will not function properly. After the car has warmed up, turn it off and remove the top of the air cleaner and look down the carb bores with a flashlight. Do you see any fuel dripping? If so the carb needs a rebuild and that is likely what is causing your exhaust smell.

    Disconnect the vacuum advance prior to setting the timing and plug the line. As you noted, connect a vacuum gauge to manifold vacuum and keep advancing the timing until the vacuum pressure stops increasing and note the degree reading. Reconnect the vacuum advance and test drive the car, if it "pings" excessively, back off the timing in 2 degree increments until the pinging is acceptable. Record the degrees of advance and keep that as a reference for future tune ups.

    If the carb is ok, set the base idle at 650-700rpms or whatever the emission sticker says to set it at, usually it will be in the 650-700 range. Find a competent helper, have them set the park brake and start the car. Next have them place the car in gear with one foot on the brakes. (Note be darn sure the helper does not touch the throttle as he/she could cause the car to move while you are under the hood, and do not touch the throttle linkage your self either!) Now pick one of the idle mixture screws and start turning inward until the engine just starts to misfire and back the screw out 1/4 turn. Do the same with the other mixture screw. Have the helper take the car out of gear and recheck the idle speed as changing the mixture settings may have altered the idle speed. Test drive the car, if it performs ok you are done.

    Dave
     
  3. MBar

    MBar Active Member

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    Thanks Dave!! smelly but no visible smoke....I will try your directions today...always a big help bud!!
     
  4. Davea Lux

    Davea Lux Senior Member FCBO Gold Member

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    If it still has issues after checking all of those things, you may have a bad EGR valve. If this car has a smog pump with California emissions, most likely it will have an EGR valve. These were troublesome when the cars were new and have only gotten worse with the advent of ethanol blended fuels. The passage the EGR is attached to carbons up and the plunger for the EGR gets stuck open causing poor performance and significant fuel mixture issues. I would suggest you invest in a block off plate for the EGR and remove it to save problems down the road. If it is not currently leaking, you can disconnect the vacuum hose to the EGR and block the line.

    Dave
     
  5. CBODY67

    CBODY67 Senior Member

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    Non-CA spec 400 2bbls didn't have an external EGR valve in '72. The '73s started with "floor jets" on EGR-equipped engines. Then full external EGR valves in '74 . . . as I recall. My '72 Newport Royal 400 2bbl is "federal" and has no external EGR, nor floor jets. BUT it does have the carbon cannister!

    Hot base idle speed should be in the 650rpm range in "N" or "P". Base timing, as I recall, is 7.5 degrees BTDC, + or - 2.5 degrees.

    You'll have better luck with the distributor hold-down bolt with a shorter wrench, possibly a 12 point, from my experiences. Don't need to "nail it down", just get it snug enough that it doesn't move easily. Might need the ratchet/extension/u-joint to initially get things loosened, then the wrench to tighten things when done.

    Do the hot base timing FIRST. Remove and plug the vac advance line, THEN do the timing setting/adjustment. Clean the balancer so you're looking at what you thing you're looking at (the timing mark on the balancer).

    With the timing set, then move to the hot base idle speed. For good measure, with the engine stopped, get a screwdriver and check the existing adjustment of the idle mixture screws, seating them GENTLY, counting the number of turns clockwise it takes to get to that point. Then gack then out the same amount on each side. This way, you know where things are.

    Then start the engine and let it idle in "P". Set the hot base idle to the noted specs (which I recall to be about 650rpm). Check to see that the trans goes into "D" with no big lurches, but smoothly engages as the engine rpm decreases to about 550rpm in "D". Then return the gear selector to "P".

    Now, with all of that done, turn one idle mixture screw clockwise about 1/4 turn and see how the rpm reacts. If it decreases, then put it back where it was. Do the same with the other side.

    Then move one mixture screw counter-clockwise 1/4 turn to see what the idle speed does. If it increases, then reset the speed back to where you started. Then do the other screw. Cycle repeat. Let the speed stabilize after each adjustment.

    IF the idle mixture is too rich, then turning the screws clockwise should lean it a bit and also result in an idle speed increase, on each side. It can take a bit to get these tweaks done, mixture and base idle speed, but when you're done, then ANY clockwise/leaner turns of the mixture screws should result in a hot base idle speed decrease.

    When done, move the gear selector lever from "P" to "N" and then to "D". The trans should engage smoothly as the engine rpm similarly decreases. Any throttle movement should be responsive with just a light pat of the accel pedal.

    With the shift lever in "P", turn off the engine and see if the engine just stops, not trying to keep running. It should restart quickly and easily, too.

    In setting the idle speed, you might add an extra 10-20rpm to the hot base speed adjustment, with the air cleaner removed. With the air cleaner replaced, sometimes the hot base idle speed will drop below specs, so doing the idle speed adjustment to compensate for this might be a good idea. But not completely necessary. Key thing is that the engine starts and stops as it should, with the ignition key.

    NOW, if all of this does not really decrease the smells out the back pipe, then get a new carbon cannister. The valve on top of it has probably gone bad. Reason I mention this is that on many '85 Buicks, they'd "fog mosquitoes" out the exhaust pipe. Carb rebuilds and other things did nothing to change that. The "purge valve" for the carbon cannister had failed and was the cause of that situation. On those cars, it was an inline valve with a bunch of vacuum lines going to it. On the '72 Chryslers, it's a part of the cannister itself, on top of the housing, with a few vacuum lines going to it.

    The "shadetree method" I used to use back when those cars were newer, was to get the idle speed (parking brake firmly applied!!!!) in "D" to just where the exhaust pulses at the single exhaust tail pipe just smoothed out from separate pulses into one smooth flow. In "D", with the a/c operating. That was the base hot idle speed I base-lined things at. Then I set the carb idle mixture to where a 1/4 turn inward would result in a 20rpm drop in idle rpm (in "P") from the base idle rpm. Then I'd put it in "P" and see how high that rpm was AND if the engine would stop smoothly when I turned the key off.

    The other check I did was with the parking brake firmly applied, gear shift in "D" (as I generally did this solo), was to check the exhaust flow smoothness out of the back, but to ALSO put the palm of my hand in the flow and then smell it to check for minimal hydrocarbon smells. Ensuring that the mixture adjustments were "right on". With the lower compression ratio of '72, the exhaust output temp was a good bit hotter than on the 9.2CR '66 383 we had at the same time.

    Hopefully, everything should operate "as designed" when done.

    Kind of the same thing as Dave mentioned, just a different way of getting there. Which worled well for me. Personally, I never did have any real luck with vacuum gauges, preferring dwell tachs instead. A vacuum gauge can be a good diagnostic tool to check for burnt valves and a too-rich fuel mixture, due to how the gauge acts, but I just liked the accuracy of tachs better.

    Please keep us posted.

    Enjoy!
    CBODY67