340 Chugging instead of Reving

[TT5.9mag]

@MOPAROFFICIAL compression test results are in post 143

 

[Bewy]

[1] The centri curve is going to move the rotor position as it fires. Same with the vac adv. The dist will be made so that these movements are centered around the matching terminal in the cap.
[2] The firing point of the p/up is just as the trailing edge of the reluctor tip passes the pole piece.
[3] The thick reluctor is junk, looks to be stamped not machined, the thick tips gives imprecise timing. Don't know why fools buy this junk.

 

[AJ/FormS]

The carb responds to the pressure differentials it sees from atmospheric pressure above it, to the reduced pressure (commonly called vacuum) below it. It doesn't care about rpm.
So if you have a lot of Idle-vacuum, the engine will pull hard on the Transfer Slots and Idle Discharge ports which are under the throttle-valves, which should be nearly-closed.
But if your throttle is too far open because of retarded timing, then the transfers will be dumping because the fuel flow is directly governed by the amount of slot exposure; you can't be using the Idle Mixture screws to band-aid too-far closed throttle valves. If the engine won't idle right with the mixture screws at or near the center of their adjustment range, something is wrong, and my bet is that it has to do with the T-Slot exposure..
But if you have a bit of a cam, then the vacuum will be lower to very low, easing the tug on the Transfers.
But
The worst thing is that the boosters don't care which way the air is going thru them, in order to respond. So if your intake valves are not closing 100% while the boosters are on line(*1), and the plenum pressure gets to pulsing, that pressure-differential pulsing may be read by the boosters, to which the carb will respond. If the pulses actually reach the boosters, then there's gonna be even more trouble.

(*1) or there is any change of air-pressure in the intake plenum; like a mini explosion/"backfire"; or as when the overlap cycle gets to pulling hard.
(*2) some air-filter housings wreak havoc with bowl-venting
==============
As to rotor phasing; this is easy to prove. Just put a timing light on it and rev it up while watching the timing mark;
If nothing crazy happens then you don't have a rotor-phasing problem.
If the strobe starts missing when the rpm gets into the chugging range, but the timing marks do not otherwise change, probably the spark is being shorted by excessive fuel; Put a vacuum gauge on it and see what the manifold pressure is doing. Or, possibly, the coil is failing. Between the vacuum gauge, and the strobe-action, something should give you an idea of what's going on.
If nothing is talking to you, check the valve timing.
===============
I don't see a vacuum advance. For a streeter this is as good as crazy; Your timing will be retarded almost all the time, and the engine will be very fuel-thirsty while on the low-speed circuits..

 

[1969GTS340]

What does the timing do, not just the number on the balancer, but what does the strobe look like when the engine starts to break up?

It now runs steady at 32* prior to havng the ignition box worked on, the timing was irratic and retarding by 12 to 14*

 

[1969GTS340]

Ok try this, with the distributor advance locked at 32, MAKE the pole on the reluctor line up with the pickup dead nuts on center AND the rotor line up dead nuts on center on the number one terminal in the cap. You might have to remove the distributor to do this. Do NOT line them up at TDC put your balancer at 32 degrees btdc

TT5. Not sure if I answered your question correctly. With the timing mark at 32* and the distributor locked, the pictures show that both rotor and pickup are not lined up perfectly with their mating contacts. When I turn the distributor I can aline them both to the coil and #1 button on the cap.

 

[AJ/FormS]

Where the rotor points to, matters not a bit; but at the appropriate time, it better be under a tower who's wire goes to the appropriate cylinder. We use number One cylinder (the driver's side frontmost cylinder), because the balancer is already marked for it; but we could just as easily use any cylinder, just by finding and marking it's TDC on the balancer.
During operation, the flyweight mechanism, moves the rotor into rotation. Because of that, the rotor has to start on one side of a tower, and sweep past it, yet not get very far from it, else the spark will jump to a cylinder that is under less cylinder pressure. The coil is lazy like that, always looking for an easier spark-path.
But again, where the rotor actually points to, whether the left front intake bolt or the right or the passenger side apron or anywhere else , matters NOT one tiny bit, except that; custom wires fit best when you use the position that the factory chose..... plus it makes it easier for the newbe mechanic to diagnose problems.

Your engine's power timing usually falls in the range of 36* plus/minus 2*.
Therefore if your centrifical system is bringing in 20*, you would set your base-Idle timing to 16 +/-2*. So then in a perfect world, your rotor would start at 10* before the chosen tower, and sweep to 10* after it. So then, you can see this with the engine off, by setting your balancer to 16* +/-2*, and manually jockeying the rotor between it's limits. However, at this same time, the reluctor better be in the firing position. If it is not; something has to be changed. Either the reluctor has to be rephased, or the rotor tip has to be. The rotor is usually easier.

 

[TT5.9mag]

TT5. Not sure if I answered your question correctly. With the timing mark at 32* and the distributor locked, the pictures show that both rotor and pickup are not lined up perfectly with their mating contacts. When I turn the distributor I can aline them both to the coil and #1 button on the cap.

But by turning the distributor you are changing the timing. Like I said earlier you might need to pull the distributor up and move it a tooth and set it back in.

 

[408 swinger]

But by turning the distributor you are changing the timing. Like I said earlier you might need to pull the distributor up and move it a tooth and set it back in.

Good point. Some of these aftermarket distributors don't "phase" in like a stock one does. Like, after you set the tower shaft in, the slot should face first intake bolt on driver's side.

 

[1969GTS340]

Where the rotor points to, matters not a bit; but at the appropriate time, it better be under a tower who's wire goes to the appropriate cylinder. We use number One cylinder (the driver's side frontmost cylinder), because the balancer is already marked for it; but we could just as easily use any cylinder, just by finding and marking it's TDC on the balancer.
During operation, the flyweight mechanism, moves the rotor into rotation. Because of that, the rotor has to start on one side of a tower, and sweep past it, yet not get very far from it, else the spark will jump to a cylinder that is under less cylinder pressure. The coil is lazy like that, always looking for an easier spark-path.
But again, where the rotor actually points to, whether the left front intake bolt or the right or the passenger side apron or anywhere else , matters NOT one tiny bit, except that; custom wires fit best when you use the position that the factory chose..... plus it makes it easier for the newbe mechanic to diagnose problems.

Your engine's power timing usually falls in the range of 36* plus/minus 2*.
Therefore if your centrifical system is bringing in 20*, you would set your base-Idle timing to 16 +/-2*. So then in a perfect world, your rotor would start at 10* before the chosen tower, and sweep to 10* after it. So then, you can see this with the engine off, by setting your balancer to 16* +/-2*, and manually jockeying the rotor between it's limits. However, at this same time, the reluctor better be in the firing position. If it is not; something has to be changed. Either the reluctor has to be rephased, or the rotor tip has to be. The rotor is usually easier.

To aid in diagnosing the issue with the ignition box, I locked the distributor at 32*. Now that the box issue is resolved and if i understand you clearly, I will unlock the distributor, reinstall the springs and set the mechanical to be all in at 34*.
After timing the engine ~12* I can remove the dist cap, rotate to TDC and inspect the position of the rotor. I expect to see the rotor close to the #1 tower and be able to swing the rotor by hand to see it pass evenly across the tower, indicating the advance swing. In conjunction the reluctor post should be on the pickup at this point. I may need a day or two before I can get enough time in my shop, so bare with me on the results.

 

[1969GTS340]

But by turning the distributor you are changing the timing. Like I said earlier you might need to pull the distributor up and move it a tooth and set it back in.

But by turning the distributor you are changing the timing. Like I said earlier you might need to pull the distributor up and move it a tooth and set it back in.

I'm wondering if I should try this before

But by turning the distributor you are changing the timing. Like I said earlier you might need to pull the distributor up and move it a tooth and set it back in.

I wonder if I should try jogging over
a tooth before trying AJs instruction? It would be a quicker test, and if it corrects the phase, I can still revert back to setting up initial and advance in the distributor later.

 

[TT5.9mag]

I would not change anything until you can get the phasing correct. Keep the timing locked, it eliminates variables and makes diagnostics easier.

 

[TT5.9mag]

With the distributor locked out, you should be able to get the engine running, set the timing to 32 deg on the balancer with a timing light. Shut it off, rotate the balancer by hand to 32 degrees btdc on number 1 compression, pull the cap, and the rotor better be damn close to the number one terminal on the cap and the pole on the reluctor be damn close to the center of the pick up.

 

[TT5.9mag]

I should continue my post above ^^

…….If theyre not lined up you need to pull the distributor and move it a tooth so they do. MAKE it line up.

 

[fishmens67]

Does the reluctor have a couple different ways to install on the shaft like the factory distributor has.
The factory reluctor has two different roll pin areas and 2 arrows, one for counter clockwise and one for clockwise.
If you don't get the roll pin in the right hole the reluctor would be off in relation to firing the rotor

 

[1969GTS340]

Does the reluctor have a couple different ways to install on the shaft like the factory distributor has.
The factory reluctor has two different roll pin areas and 2 arrows, one for counter clockwise and one for clockwise.
If you don't get the roll pin in the right hole the reluctor would be off in relation to firing the rotor

Great question. There are two spots for the roll pin and only one pin. I've had it apart a couple times and marked the location so it went back the same way. The shaft has one location for the pin. I'll definitely look into this. It may have the same result as skipping over a tooth.

 

[AJ/FormS]

In my opinion;
here is the quickest and best way to do this.
With the distributor working normally;
1) Set you balancer to TDC-#1-Compression.
2) Then back the balancer up to the advanced position of; 1/2 of your centrifical timing Plus your Idle-timing.,
3) Then, with a Sharpie, and on the side of the cap make an index mark to indicate the center of the #1tower. Transfer that mark to the outside of the Distributor body, then remove the cap.
4) loosen the distributor clamp, AND with the ignition in run, AND the coil wire near-grounded, rotate the magnetic trigger past the nearest reluctor vane, in the normal direction of rotation, until you see the spark from the coil wire. If you have to back up a bit first, just do it. Repeat several times to ensure consistency.
5) when you find the exact point that triggers the coil, lock the D down.
6) now; compare where the leading edge of the rotor tip is, to the mark you previously made. It should be,
as TT5.9 says " the rotor better be damn close to the number one terminal on the cap".

<Now, if it it is not, something has to be re-aligned.
You have three choices;
1) If your rotor-tip is adjustable, just move it to where it needs to be.
2) almost as easy is; to remove the cap, rotate it a couple of towers, set it down with tower in the right spot. Then go find the metal tab that indexes the cap to the distributor, and mark the cap as to where it is, then cut a new notch in the cap, to fit the tab.
3) I suppose you could move the reluctor to where it needs to be, but if you miss, you gotta start over.>

7) Finally, install the #1 wire in the tower that is above the rotor tip, and follow that by the rest, in the proper firing order.
8) done.

 

[Bewy]

Post #157.
Moving the dist one tooth does NOT change the phasing of the rotor to the segments inside the cap. What it does do is changes which cyl the rotor is pointing at.

 

[AJ/FormS]

I once chased that idea round and round and no matter which tooth I set it to, the result was exactly what @Bewy says. And might I add; I total and complete waste of my time. Well not quite a waste; I did learn something. And I was very young so had lots of time ..... That was about 47 years ago, lol.
Ok so, don't go wasting your time, lol.

 

[TT5.9mag]

Post #157.
Moving the dist one tooth does NOT change the phasing of the rotor to the segments inside the cap. What it does do is changes which cyl the rotor is pointing at.

True. But If you look at his pictures it appears that the rotor and the reluctor are off an equal amount. I’m trying to get him to set it up at 32 degrees locked and get the rotor, the reluctor and the pickup all happy without twisting the distributor. Maybe then we can get a pic of the alignment and know how the phasing is.

 

[TT5.9mag]

Or he needs to drill a cap and shoot it with a light.

 

[Inertia]

My kids put an injection kit on theirs, they ruined a cap, the final line of the instructions said - "set the total timing to 32* - 34*"
jmo .

 

[12many]

When I turned the engine over to do the compression test, gas was spaying out the remaining open plug holes onto the tops of the fenders.

That’s extreme. I don’t care how bad an ignition might be: scattered, misfiring, not firing, timing off etc etc. That amount of fuel into the chambers means it being drowned with fuel, sounds like a Fuel “delivery” issue.

 

[Carnut68]

Recheck the floats. Set to bottom of sight glass. Then remove carb and check the gasket under the pv. Make sure it's properly installed and not damaged.

 

[1969GTS340]

Update 10/01. Good news / Bad news

Good news - Moved the interrminate shaft counter clockwise wise one tooth. At 32* locked the reluctor and pickup are dead nuts. The rotor was just prior to reaching the #1 tower. Per plan, this is exactly what I wanted to see.

Bad news - No change.

I slowly adjust the timing from 20* to 40* while testing the throttle and she popped at the same ~ 2500 3000 range.

I did look at the reluctor roll pin notches and they where exactly 180* across from each other and inline with one of the reluctor spokes. So I did not re-index the reluctor.

I reversed the ignotion/distributor wires again to see if that had any effect now that the phase was corrected - but none....

With the timing light at idle it appeared to bounce a few degrees but with a little throttle it held steady at 32* when it reaches the popping point the timing drops ~3* I would expect to see a more stability but I don't think this minor movement would cause this particular problem.

I see recommendations in the post suggesting the carburetor may be contributing. Once I'm satisfied that the ignition is off the table I'll go back to the carb.

 

[1969GTS340]

I’ll repeat: Get it running, turn off the fuel pump so that you are running on what’s in the bowls and see if it runs smooth or as you say, still chugs at those rpm’s. Super quick easy thing to check.

Just tried this. Shut the fuel pump off while at the trouble rpm range. It continued to pop for 10 seconds and stalled