KnightmareCS

iTrader: (7)

Engine Details:
Manual Quadrajet 4bbl Carb w/ Electric Choke
Centrifugal/Vacuum Advance HEI Dist
Chevy 350
4-Speed Manual
3.23 Posi Rear
Vortec 062 Heads
Edelbrock Performer RPM Intake
EGR/Air Delete
Crower Cam - INT/EXH - Dur @ .050” Lift: 220°/226° RR: 1.5/1.5 Gross Lift: .462”/.470” LSA: 112° RPM: to 6200 Redline: 6500
https://www.crower.com/chevy-262-400...lic-cam-6.html
ACDelco Plugs - Gapped .045"
Accel 8mm Wires
Stock spec Coil
1 3/4" Shorty Headers, true duals no cats welded to stock over the axle pipes to stock dual mufflers

Sup guys,

NEED HELP!

Just getting back to putting the '82 back on the road, but this time with a little more oomph.
I took off the stock computer controlled E4ME and CC-distributor, and swapped on a manual Quadrajet from an 80s? Vette along with a centrifugal/vacuum advance dist.
The carb was recondition/jetted/set by a carb shop. It's supposed to be a bolt-on set up.

I've researched the internets and the youtubes, but can't get a straight answer. My point of reference: https://www.thirdgen.org/hei/


How exactly do I set timing and idle RPM speed?

From my understanding:

1. Plug all vac ports on carb.
2. Figure out TDC of Cyl 1.
3. Set base timing for dizzy to 4*BTDC, 4 degrees advance, as a starting point.
4. Turn on and warm up engine. *I need help figuring out how to tell if the Choke is on or off. I have the choke wire disconnected for now.*
5. Set idle speed screw way down. (the screw that butts up against the throttle lever right)
6. Once warm, hold throttle at 3000RPM.
7. Advance dizzy to 34 degrees total timing (base + centrifugal).
8. Return throttle to idle.
   1. *What should my idle RPM be?*
9. Remeasure initial timing, should be 14 degrees.
   1. *At this point, how do you set idle if it's too high?? If centrifugal advance comes on at 800RPM, and you're now at 1100RPM idle, what do you do?*
10. After all above is done, connect vacuum line from ported vac from carb to vacuum advance can on dizzy.

Do I have this right and what do I do about the bold?

sofakingdom

iTrader: (1)

If you make 2 assumptions, neither of which should be made, then that's somewhat reasonable, with certain notable exceptions.

The 2 assumptions are:

1. The timing mark system is ACCURATE; and
2. YOU already know what timing the engine wants, better than IT does.

Personally, I never feel very warm about either one, let alone fuzzy.

But for the moment, let's play along with them. Your mark is already known verified checked dead-on-***** ACCURATE, because you used a piston stop or dial indicator or similar method of locating #1 and/or #6 TDC before you put the heads on; and, … well, I'm not real sure how the other one could possibly work, but we'll do the thought experiment anyway.

First thing you need to do is to put the entire cab & vacuum system BACK like it belongs, except for the line that hooks to the distributor. Disconnect that one and plug the hole in the carb.

Next, DO NOT rely on any kind of a "dial-back" feature of the "light". They are NOTORIOUSLY WRONG. They CANNOT POSSIBLY be right, because the light has no idea how fast the engine is turning, which it would need to know in order to turn the TIME between sparks into DEGREES (fraction of a rotation). Some do a better job of this than others, but they are NEVER right. Instead, add marks to your crank damper at 10° intervals BTDC: wrap a measuring tape around it, divide the number you get by 36, (10° ÷ 360°), and make 3 or maybe even 4 or 5 marks in a row spaced exactly that far counter-clockwise from the main timing mark. I'd suggest getting some random white or yellow or light blue touch-up paint at the parts store, filling in the "mark" with it, and putting a dot at the above spots at the front edge. NOW, instead of using the timing light's "dial-back" feature, you have "marks" at 10°, 20°, and 30° BTDC, which you can then read directly off of the "tab", while leaving "light" at 0 (it blinks EXACTLY when triggered by the spark). For example, if the damper circumference reads 21¼" (a 6¾" damper), then 10° of circumference is 0.589", which is right around 19/32"... you'll make marks at 19/32", 1-3/16", 1-25/32" etc. CCW from the main mark. Make your own measurement, do your own arithmetic (it's not even math).

Next, the choke has a thermostatic (bi-metal) spring inside it, which when cold, closes the blade and otherwise set it into cold-temp operation; the electric part is a heater, which once the car is running, by some slight electrical sleight-of-hand, gets power applied to it, which heats it up, which after a time, causes it to cease to be in cold mode. Normal starting procedure for a carbed car is to pump the gas to the floor ONCE when the engine is cold and the temp is above 60°F or so, then take your foot COMPLETELY OFF the gas, then turn the key; the engine should start, run kind of funny for a second or 2, then begin to smooth out and idle faster than normal. If the temp is below that, add ONE more pump to the floor for every 15° below 60°; so, pump twice if it's 45°, 3 times if it's 30°, and so on. The act of pumping the gas releases the linkage and allows the choke spring to do its thing, then as the engine runs, the heater does ITS thing, and at some point the choke no longer calls for cold mode. At that point, if you lightly touch the gas to rev the motor, the linkage will drop out of the choke setting, and everything will be back to normal. When the choke is closed (cold), the blade on top of the primaries closes, and the fast idle cam on the pass side down at the bottom props the throttle open a bit.

So... to "set" the "timing", put the vac lines back like they belong, hook ALL the wires back up, and drive the car for awhile, until FULLY warmed up. Leave it running. Verify that the choke is fully open and the fast idle cam is totally disengaged. If not, you have some troubleshooting to do. Then, disconnect the vac line that goes to the dist at the carb end, and cap the fitting on the carb. Hook up the "light" and observe the "mark".

Next, assuming that YOU know what THE ENGINE wants better than THE ENGINE does, open the throttle while observing the "mark" with the "light" until the RPMS are around 3500 or so; or, until it stops advancing. That then is your "total" timing. Vortec heads are well and widely know to typically want slightly less timing than older heads, so you probably will want to set the dist body at this point for a timing of 32 - 33°. 34° is probably too much. (See why the stress earlier on about ACCURATE is a big deal?) Then when you let the RPMs back down slowly, you should see the timing decrease starting as the RPMs pass through some point, then gradually lose advance as it approaches idle.

Chances are, with an unmodified factory crappy-curve distributor, you will see the idle timing drop to about 8°. Oh well, it is what it is, as long as you have a crap distributor in there, you're stuck with it. A "good" curve for a motor at the level of yours is more likely to be something like 16° at idle, centrifugal advance starting just off idle (say, 1200 RPM or so), with the full advance "all in" at around 2800. That means that instead of your dist giving 24° of advance, it only needs to give 16°. But that's not easy to change in any kind of a reliable, accurate way. Chances are, with your stock emissions-crippled crappy stock timing curve you're likely to have, the centrifugal will start at 1500 - 1800 or so (converter stall speed ish), and will not reach full advance until at least 3500, maybe 4000 or more. Stock curves are TERRIBLE for performance but that's what you're stuck with.

Set the idle speed using the screw on the driver's side of the carb to around 750 - 800 out of gear, or 600 - 650 in gear.

Once you get that set, hook the vac adv back up. Since you're using a terrible emissions-crippled stock emissions carb, the port for vac adv will have no vac on it at idle. As you open the throttle the blades will reach, and pass, the port in the bore for that, and at some amount of opening, you will begin to see vacuum. Engines usually run ALOT better with full (non-ported) vacuum, i.e. such that vac adv is active at idle; you can try both places and see. You'll have to reset the idle speed as you go between those 2 hookups. Full vac adv will be around 10 - 12°, which is not really "enough", but it helps: its purpose is to begin combustion earlier in the cycle when the mixture is rarefied (high vacuum), high speed, and lean; IOW, cruising. Most engines, probably including yours, will want closer to 15° of vac adv, with the adv starting at around 3 - 4" below cruise vacuum and "all-in" by about 2" below cruise vacuum. Of course the timing affects vacuum, just like the vacuum affects the timing due to the vac adv, so it's "interactive"; requires some playing around to get it dialed in just right. But again, with a crappy stock emissions-crippled dist, there's nothing you can do about it.

KnightmareCS

iTrader: (7)

Thanks for the thorough reply! You've helped in the past when I was setting up the CC-Carb, so appreciate your help again!

Have a few Q's based off this:

I will confirm timing accuracy in the manner you suggested. I'd like to get timing tape to back up the tape measure and mark method.

Only vac lines to carb are power brake, PCV, and vent to canister. All other ports are capped. I've disconnected the choke wire from the choke for now as well.

I'll attempt marking my balancer as you suggested. Not to sidetrack, but wouldn't the timing light know how fast the engine is turning similar to how any tachometer pick-up works?

So it is correct to assume the basics: choke wire disconnected, car cold, flick the throttle - this is the cold mode of the carb linkages and coil? The flappy blade at the top of the primaries is closed.

I think this is one of the problems where I was doing wrong. I was playing with everything cold assuming it was warmed up. I did some settings without ever driving around thinking I had the engine out of choke (temp gauge was up and everything was hot). When I came back from going around the block, my idle changed. It probably came out of cold mode when driving around.

Given the above, what should idle RPM be at this point?

I'm fairly certain the is the dist I have (came with a motor I bought). https://www.speedwaymotors.com/HEI-D...ed,293930.html
It looks just like this. The weights are adjustable. And apparently the vac can. Do you recommend changing the dist or playing with this one? If changing, can you recommend one or what to look for?

So 750-800 would be for a stick shift car? What if the RPMs don't come down even after the screw is no longer pushing on the linkage?

Say I switch from port to full, the full vac on the vacuum advance will max it's advance timing at idle (highest vacuum). This advance timing will raise idle RPM. What if I have the same problem above, where I can't back the idle speed screw out any more to lower RPM?

By full vac adv of 10-12 degrees, this is additional to the base and centrifugal advance at idle? I have my vac gauge connected to the top of the manifold in the rear. This is probably where I need to mount it in some way to see it when I get to adjusting cruise.

sofakingdom

iTrader: (1)

Put it back. As described above, without that wire, the choke will NEVER pull off, and will be in effect at all temperatures. Gotta have that wire and the system that it works, hooked up and operating.

Idle speed. Every time you change the advance at idle, the idle speed will change. Reset it every time to the target; 800ish out of gear, 650ish in gear.

Probably more flexible than a junkyard stock one, but beyond that, I have no details. Adj vac adv is a plus. No idea what its max centrifugal advance is, or whether that's adjustable. You can play around with springs & weights on any distributor; but if the basic design of it creates 24° between none and full centrifugal advance, then … there's only so much you can do, if you get the total right, but the idle advance is WWWWWAAAAAAAAAAAAAAYYYYYYYYY low. The dist fundamentally sets that difference.

Find other paths by which air enters the intake, and reduce them. PCV, any leeeeks, busted brake booster, etc. Sometimes loosening the screws on the throttle blades and settling them more accurately centered in their bores can help. Secondaries are particularly prone to needing that. Obviously you have to find and deal with whatever the causes of excessive idle speed might be, when you get to that point. Every engine is different, not only in terms of parts that were used, but the details in how they are installed and how they operate.

Yes. But not so much at idle; but, at the RPMs and other conditions where it's needed. Specifically, cruising. "Total" timing is BEFORE vac adv. Vac adv is ON TOP of that. Many motors like MORE THAN 50° advance at cruise.

Have I used the word "ACCURATE" enough times in talking about all this?

NoEmissions84TA

iTrader: (1)

I think you are not understanding this. If the choke wire is disconnected, that DOES NOT mean that it is OFF. Disconnected means ON here. It takes 12v to warm the thermostatic coil and turn the choke OFF. Flappy blade thingy CLOSED = choke is ON. Flappy blade thingy OPEN = choke is OFF.

KnightmareCS

iTrader: (7)

Thanks again for the insights sofakingdom!
I'll be back at it when it's warmer out. I know what to look for now.

NoEmissions84TA,
Understood. The choke wire is the voltage source for heating the therm coil. I have a suspicion my alternator is bad as well, related to the choke light coming on when running. Part of my steps will be to look over the alternator wires, specifically the single one on the rear. It is pretty corroded. Past that, I now have a replacement on order.


Question to all, is the choke wire 12v constant? Or is it controlled by the computer? I will probe it with my multimeter.
The only electrical things I have which are disconnected are: anything emissions related, the flat-4 dist wire, carb wires (will connect choke), and oxygen sensor. The temp sensor on the thermostat housing is still hooked up.

OrangeBird

iTrader: (1)

Here is the choke/alternator wiring diagram for your 1982 . Looking at how the choke relay works in tandem with the alternator you can see how if the relay's coil does not get power , the brown wire to the alternator won't be getting powered properly , resulting in a no charge condition . If the choke relay does not energize and close it's switched contacts the choke light will be on since the choke heater will not have +12V on it and will instead provide (through itself) a path to ground to light the choke light . Checking the 10 amp fuse labeled "C-H" should be your first step after hooking the choke heater back up if there is no +12V power on the relay's coil with the key on , and yes of course clean the cruddy connection you mentioned on the alternator , that alone could be the reason for both the no charging and the choke light being on (with everything hooked back up properly , of course) .....

KnightmareCS

iTrader: (7)

Thanks OrangeBird! That clears it up nicely. Fuse check added to the list.
Have to start reacquiring the relevant docs from the forum, as everything I had was on an external hard drive ages ago. I'm forgetting more than I've learned!

sofakingdom

iTrader: (1)

Here is another, equally error-filled schematic, for 83. The cars themselves are largely the same in this area, therefore work essentially the same way.



The indicator shown as "Volts" is actually labelled "Choke" on the dash, and AFAIK exists regardless of whether a car has gauges or not. It certainly does in my car with gauges.

The "convenience center" is a little tray sort of thing right above the driver's right knee, with the OBD1 connector on it.

When the key is off, the relay is not operated (i.e. is in the position shown on the schematic. Nothing in the circuit is powered.

When the key is turned on and the engine is NOT running, power is applied to both the brown wire (250) and the pink/black (39). With the alt not charging, the brown wire (25) is essentially shorted to ground inside the alt. The "Choke" light is lit because it has 12V on one side and ground on the other; and the relay operates, for the same reason. When the relay is operated, the source of power to the choke heater, the brown wire (250), is DISCONNECTED from the choke heater's light blue wire (78). The choke heater is not powered. The brown wire (25) carries a small current into the alt, through the light bulb and relay coil, and through the Field winding and regulator to ground.

When the engine begins running and spinning the alt, the current from the brown wire (25) provides a small amount of magnetism in the alt's Field winding, the rotor, causing the alt to begin generating slightly. Without this current, the alt will usually never "start up", therefore the bulb burning out can disable the charging system. The more the alt generates, the higher the voltage on the brown wire goes toward 12V and away from ground; the higher the voltage there, the more the alt can charge. It forms a sort of "positive feedback" loop which brings the alt up to full efficiency quickly (small fraction of a second), at which point the regulator can begin to control its excess current-delivery capacity to maintain the proper voltage at its "sense" terminal, via the small red wire (2) in the same plug with the brown wire. When the alt reaches its full charging efficiency, there is 12V coming out of the alt on the brown wire, produced by the diode trio inside the alt; then since the bulb and the relay coil each have 12V at both of their ends, the bulb goes out and the relay drops out. With 12V on the brown (250) and the relay not operated, power passes through the relay contacts to the lt blue (78). This causes the choke heater to begin heating, which gradually reduces the tension holding the blade closed, and eventually allows the blade to open.

Therefore, if the alt is not working, the choke will stay on (closed) FOREVER. In this state the engine will run STOOOOPID rich, probably blow out black smoke and stink, the throttle will be up on the fast idle cam thereby preventing the normal curb idle screw from doing anything at all, and fuel consumption will be in gallons per mile instead of miles per gallon. All efforts at "tuning" a carb when in this state are FUTILE. The same thing will happen if the lt blue wire (78) is disconnected from the choke: the carb CANNOT work right in either case because the choke will remain closed.

Besides a simply defective alt, things that can prevent it from working include the "Choke" bulb being burnt out, corrosion or dirt on the connectors anywhere in the system, bad relay, the Choke Heater (C/H) or Gages (sic) fuse blown (or possibly the ECM Ign fuse although I don't think that's right), or even simply the alt connector being unplugged. Start with the simple stuff: is it plugged in? Then check the light bulb; does it come on with the key on and engine not running? Then the fuses; then some of the other things. Unless of course if you already know you have corrosion on connector terminals, go ahead and clean those up. A solution of baking soda in warm water works wonders.

Fix the alt problem first, and verify that the choke pulls off after a few minutes of the engine running, like it's supposed to; and then you can return to attempting to tune it.

KnightmareCS

iTrader: (7)

Thanks for the in-depth explanation of the alternator relation to the choke operation. This definitely points me in the direction of a bad alternator. It likely has an intermittent faulty regulator. Details below.

I think I've got it!

Here's what I did:

Electrical

• Looked through all fuses under dash and didn't find any blown, everything checked out
• Confirmed choke light turns on with key on, engine off
• Found that the alternator was barely tensioned, tightened it up
• The wire that I thought was bad on the alt was actually the black/red BAT wire on the rear stud, and it wasn't even as bad as I thought. I cleaned it up and reinsulated it
• The two wire brown and red connector I didn't touch
• I cleaned up the wiring for my dual e-fans while I was at it

Timing Mark

• Spun crank to TDC, used borescope from Autozone (loan a tool!) to verify cyl#1 position through sparkplug hole
• TDC slot on balancer lined up with 0 degree tang on timing tab, as expected, all good
• Measured circumference of balancer and divided by Pi to get diameter
• Cleaned up balancer and put on Mr. Gasket 1588 timing tape for 6 3/4" balancer
• I'm no longer going to use the timing light's advance or the timing tab numbers, strictly using the tape

Choke

• Car was ice cold in the morning, manually actuated throttle with engine off, the top flappy blade closed, pass side linkages actuated, cold choke seems functional
• Reconnected choke heater wire

Timing

• After everything above was done, I plugged the vac advance line, backed off the idle speed screw to barely touching the throttle, and set the dist to 0 degrees by eye as a base to start off
• Reseated the carb
• With the engine on, checked base of carb and other lines for air leaks, nothing found to be bad
• The engine turned on without needing any throttle and idled ok
• I checked timing and it was right around 0 degrees as expected
• The choke light was lit
• Voltage across the battery was 14.95V
• I disconnected the choke wire and saw it was getting 11.96V
• Reconnected choke wire, probed it while plugged in to the coil, and it was reading ~1.94V
• I noticed at this point, the top flappy blade was cracked open, definitely not closed, choke light still on
• I said screw it and let it warm up at idle, which at this point was ~1000rpm
• I revved up the motor and saw it peak out centrifugal advance at 2400rpm at ~24 degrees of timing
• Now I understand the physical centrifugal advance limit sofakingdom was talking about
• At this point it became a two-man job
• I held the revs up at 3000rpm just to keep it fast spinning. Specific hold RPM doesn't matter much because it's centrifugal advance and will peak when it is 'all in' and will not go any higher
• I had my brother advance the distributor body while I watched it reach 33 degrees advance and tightened it down
• I let it come back down to idle, at this point was ~1090rpm, at ~16 degree advance
• Got back in the car and saw that the choke light went out
• Said screw it and took it around the block to see what's up
• It seemed to be driving around fairly well, so I floored it
• She took right off, the secondaries opened, but something happened where it felt like the accelerator stuck and it kept pulling even though I let off
• I slowed the car down in gear to the point the revs dropped, and tapped the throttle. Whatever it was disengaged, and throttle was back to normal. Idle also felt like it dropped some
• Drove back home, rechecked timing, still at 33* deg advance at 3000rpm.
• Idle was now at ~900rpm, didn't check timing
• Turned idle speed screw out. Found it actually wasn't fully backed off, so there was some room to set idle. Adjusted down to 650rpm, then raised back up to ~750rpm.
• Connected vacuum advance to PORT advance since idle seemed to be good
• Put timing light on and saw ~56* timing at 3000rpm
• Took it out for a drive and the thing BOOGIES, throttle is very responsive
• I did get some choke light flashes under hard acceleration, but I believe that is the alternator belt slipping or just the alternator acting up. The volt gage had a tendency to swing during the drive
• Turning the car off and on, had no problems with dieseling or hard starting

The new alternator is expected to arrive tomorrow. I will install that tomorrow to hopefully resolve any choke/light issues. I will also experiment with full vacuum advance now that I have had a reasonable idle experience.
Will update with findings.

Thanks again for everything dudes!!

KnightmareCS

iTrader: (7)

Idling videos for reference.

Set at 650-700rpm. Right before I reread sofakingdom's 800rpm out of gear number.

Set at 750rpm. Ignore the timing light cutting out, I quickly hooked it up just to shoot the video quick, mainly wanted to show the vacuum gauge connected to the manifold.

sofakingdom

iTrader: (1)

Progress is a good thing.

Sort out the electrical problem and the sticky throttle (check things like, hanging up on the air cleaner), and enjoy.

sofakingdom

iTrader: (1)

I should note also:

One of the more serious errors in the 82 schematic up there is the choke heater relay contact arrangement that it shows. Observe that the contact is shown supplying power to the choke heater when the relay is OPERATED, i.e. it's a normally open contact. This is WRONG. It supplies power to the choke heater when the relay is in the NON-OPERATED position, like the 83 schematic shows.

If they'd put the pin #s on there - for whyever, on virtually EVERY automotive relay they have bizarre inscrutable numbers like 35, 86, 87, 87A - it would be obvious how they porked the pooch on that one.

Ya just can't trust ANYBODY, can ya.

NoEmissions84TA

iTrader: (1)

Guys, verify this for me. His first video - at 30 seconds, shows the choke linkage rod going to the choke plate. It looks backwards to me, and is most likely his sticking throttle problem.

And I see 12" on the vacuum gauge.

sofakingdom

iTrader: (1)

I think you might be right; the one link does look it might be upside-down. That'll make it hang up on the outer edge of the hole in the air horn it passes through.

Callout # 356 on this somewhat fuzzy diagram.

It REALLY needs more advance at idle, but the amount of centrifugal advance that the distributor gives, won't allow it. It REALLY needs the advance limited to 16° or so. Using hard vac for the vac adv would probably just make it worse... it would want to die every time the vac went below the can's setting, and it would have to be set so low to avoid that, that it would ping like a beotch on throttle tip-in at higher speeds and loads like going up hills.

NoEmissions84TA

iTrader: (1)

Remove the screw (don't drop it or the lever) and disengage the other end of the rod from the arm down inside that hole. Flip it over, work into the hole in the arm below, and reconnect the top arm.

EDIT: I was wrong about this. See #23.

sofakingdom

iTrader: (1)

Zackly: that's what makes it hang up that way. Maybe I should have called it inside out, instead of upside down. In fact, it's hung up in that photo.

KnightmareCS

iTrader: (7)

The alternator is in. I'll be back at it after my WFH meeting.

Looks like they have the LT BLUE wire out of the Choke Heater Relay off one junction. It should be one to the right.

Is the 12" of vac low for idle? I'm reading around that 18-19" is more of the target at sea level.

Does this sound proper?:
If I can get the centrifugal advance total to be 16* (instead of what it currently appears to have ~20*), then when I set it to 33* total advance, it will equal to 17* idle timing (33-16=17). From there I would leave the vac advance at port.
This timing change, and readjustment if idle speed, will subsequently help with increasing idle vacuum.
***If I were to connect the vac advance to manifold vac, it'll advance that 17* idle timing even further and would require readjusting idle speed to lower it. I'm afraid this will lead to very high idle advance and cause dieseling.

I will have to check if my dizz has, and is capable of changing out, the Advance Stop Bushing. This would allow limiting centrifugal advance.
Referencing the following:
https://www.cpperformance.com/instructions/121-3606.pdf

You guys are awesome!
To clarify, do I flip it around in direction A (red) or direction B (green)?

sofakingdom

iTrader: (1)

The "A" direction. At the bottom, there's no "Z" bend like at the top; only a "L".

"Vacuum" is the difference between atmospheric pressure and the pressure inside the intake. It results from the engine emptying the cylinders at the end of the exh stroke, then enlarging them during the int stroke so that the pressure in THOSE becomes very very low, and the molecules in the intake trying to rush in to fill the cyls; and then, the atmosphere not being able to push enough molecules back into the intake to replace the ones that escaped into the cyls, because the throttles are in the way and all the atmosphere can do is push a few at a time through that little crack. So, it really doesn't make all that much difference what the ambient pressure is, within reason; at really high altitudes though, like above 12,000 feet or so, the air starts to get so thin that the mixture goes very rich, because carbs work off of air volume and not the # of molecules. That's one of the biggest strengths of a MAF based EFI system; it quite literally counts the # of air molecules going by, since that is, in effect, what "mass" is. I don't know if you realize it, but that big round tower thing at the front of that carb, was to accommodate a provision for that; certain carbs in that series (only a very few actually) came with a part they called an "aneroid", that was a sort of chamber that could expand and contract based on ambient pressure, and raise or lower a rod to adjust the mixture when the pressure changed. But it was very fiddly and hard to get really dialed in, and the aneroid itself was fragile and often cracked, so it never really did work as well in the real world as it seemed like it could. Anyway...

Your vacuum seems somewhat low for what it could be, with the cam you have. I doubt it will ever be 18 - 19" but it probably could be 16", which your carb (M4ME) needs, in order to really work right. Q-Jets really don't work well AT ALL if the idle vac is too low, without some serious modification. I think it's because you don't have enough timing at idle.

One "cure" for this is to use full manifold vacuum instead of ported vacuum; the thinking being that then, you will have vac adv helping out at idle as well.

The PROBLEM with this is, that if the idle vacuum EVER goes below the vac can's setting, the engine will SUDDENLY lose 12° or whatever, of advance; the idle speed will slow WWWWAAAAAYYYYYYY down; the vac will stay low; and the idle speed may be SO low that the engine will die. Quite unpleasant. The only cure for this is to set the vac can's setting SO LOW that the idle vacuum NEVER drops below it. The problem with that then is, that under light to moderate loads at high engine speeds, as you open the throttles, the vac will stay high enough to hold the vac adv in effect, when it REALLY needs to drop out. Hooking up to manifold vacuum to improve idle quality is therefore a REALLY blunt instrument with lots of potential for unforeseen consequences. When it works, it works; but when it doesn't, it's … a mess.

The only realistic tuning option to get all this right, is to limit the centrifugal advance. That way when you set the "total" timing to ITS optimum (which is REALLY the first and most primary setting of the dist anyway, even though physically, you don't set it in that order), when the centrifugal drops out (at idle), you'll have the right idle timing.

BUTT... if your dist doesn't have swappable bushings or some such, then to do this, it's necessary to shorten the slots in the little cam plate right under the rotor, that the pins that hold the springs, go through. No idea whether that dist has that or not. I've heard of all manner of bizarre things people have tried to do, to put this into effect, but the only truly effective way I know to do it, is to weld them up maybe a bit too far, then file them out with a round file to the length you need. Problem then is of course, if you go too far with the filing, you have to weld them back. It's really an awkward thing to tune. The "easy" way would be to make several cams with a variety of lengths of slots in them, or of course, use a cam with REAL BIG slots, and bushings with the holes at different spots.

But then... observe carefully the interaction of the shape of the curve of the weights, against the OUTSIDE of that cam. THAT controls how fast the advance comes in, and is YET ANOTHER tuning aid. This is IN ADDITION TO the simple beginning and ending RPM points that the advance occurs. Instead, think of the difference between a curve that gave, say, 16° of advance, starting at 1200 and ending at 2800 RPMs; and one that gave the advance faster or slower at the lower end of this range, and then the opposite toward the upper end. You could for example, create a cam shape that gave a consistent even 1° per 100 RPM curve. Would this be optimum? Iunno, probably not. So maybe instead you'd want a curve that gave 1½° per 100 between 1200 and 1300, steadily decreasing to 1° at 2000, and continuing to decrease to ½° between 2700 and 2800. Again, is that optimum? Iunno; might make the thing have the peppiest throttle response EVAH, but it might ping off-idle. Iunno. It's called "tuning": you try stuff and see what THE ENGINE likes. There are SO MANY variables you can play with, it's FUN!!! And we haven't even TOUCHED the carb yet. If you are starting to think that there's LOTS of "handles" and "*****" you can grab and twist in the ignition, JUST WAIT til you start digging into what's available, or not, in the carb.

Things like this are the difference between Edelbrock getting 435 HP out of their Performer RPM "kit", and your neighbor getting 275 HP out of THE SAME parts as far as what came out of the box. It all adds up.

KnightmareCS

iTrader: (7)

Roger that.
Here is a clearer pic of what it looks like. Seems to be correct?



EDIT 1.

After flipping it, it is binding up on the edge toward the center of the carb.



I will switch it back to original position.
EDIT 2.
Can confirm no bind in original position throughout linkage travel.

sofakingdom

iTrader: (1)

You may have mismatched parts.

Try putting it back the way it was, and flip the little short link at the top over. But if it doesn't bind, it … doesn't bind, and that's what matters.

KnightmareCS

iTrader: (7)

I put it back. If I flip it over, it'll rub that inside wall on the horn again. That bind appears to be a one time thing. I took it around the block with varying throttle positions and had no hang ups. We'll call it gucci.

I thoroughly enjoyed reading the theory behind vacuum generation, especially the realization of the bolded. Makes the term "toilet bowl" fitting. Volume versus mass.
I'll google more into that "aneroid" feature. Interesting to see what the engineer's tried back in the day.

I will have to confirm my vac gauge is accurate with a second gauge. This one is of questionable background borrowed from work.

Point of reference: I'm at 16* advance at idle of 750rpm.
So I tried manifold advance out. I hooked it up, had idle speed increase, adjusted it down to ~800rpm (lowest I can go with the idle speed screw). This resulted in 46* at idle!!! Cracking the throttle open increased it to nearly 60*!! Too sketchy for me to fathom. Unless that is expected? I didn't drive it around like this as I was worried about detonation. Also for reference, I run 93 octane. I switched it back to port for now.

I think I'd be capable of following the above methods to try and fine tune the centrifugal advance. I'll look into the bushing swap first to see what I can work with (minimal time investment). Given that I'm still going to work, I can't tackle fine tuning with the cam plate just yet. But if I end up fulltime WFH like the rest of the company, then it's welder investment time! lol

I've left off at having the car running better than it has (knock on wood). Though at the end of the day, I screwed up and blew what I think is a fusible link somewhere in the alternator change (all electronics are completely dead: lights, ignition, etc). But I can save from troubleshooting that here, I can figure it out.
When I did have it out for test runs earlier, I was able to chirp first and second hard. Third pulled as well. Secondaries opened smoothly. I didn't experience any dead spots in throttle. Choke light stayed off. Turning off the engine didn't result in any dieseling. In summation, pretty gnarly.
I'll continue shaking it down in more conditions (highway, backroads, etc.) going to work.
Appreciate all the help!

NoEmissions84TA

iTrader: (1)

I looked at a bunch of Quadrajet choke linkage images on the internet, and I was wrong. His carb had the rod correct.

KnightmareCS

iTrader: (7)

Lit. Thanks for confirming!