1974 Valiant Scamp, timing retarding when revved

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The 1406 should be set up for the 16"vacuum that your engine is making.
But to answer your question, yes. But to expand on this it is easy to prove. With the engine running, loosen one M-rod cover and turn it far enough to the side so that you can see the piston down there. Cover the screw so it can't fall out, and have a helper put the tranny in gear.The piston should stay down during the engagement.
Now, getting back to the real issue. What causes the engine to stall? This is usually a sign of a bad T-port sync,which is often caused by late ignition timing,but not always.
If the throttle is too far open, in an attempt to get enough fuel into the engine to cover a vacuum leak, that is another cause.
If the idle speed is set too high,in an attempt to make the engine idle smoother, possibly in response to insufficient timing, that is another.
If the TC is too tight, and putting it in gear drags the idle-speed down too fast and too low,that is another.
But the principle and common denominator is that the engine is stalling due to either A)flooding because the metering rod pistons popped up, or B) airspeed through the venturies dropped too far,too fast to sustain fuel flow from the low-speed circuit.
Remember that the low-speed circuit is actually the Transfer system, augmented at idle, by the mixture screws, and modified by the fuel level.This is why it is so important to get the fuel level exactly right and the T-ports synced.
The T-port sync will demand an idle timing, to get the idle speed up/down to where it needs to be. I am one of the few guys here,that does not set the idle timing to satisfy the highest vacuum philosophy. I set the idle timing to what the engine tells me it wants,not to what I think it might need.You can,or may get to the same end point following either philosophy.But the T-port sync may be correct over just a very small range, so it has to be set first, in my opinion.
 
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I'll give it another go tomorrow if the rain lets up. I'll try lowering the idle speed screw a bit more, I tried earlier and it lowers the idle, but I can never get it back to the 750RPM spec, regardless of how I change the idle mixture screws - light still shows right at 10* initial timing all the way down at 500RPM. Obviously at that point it is barely idling and with stall instantly if I put it in gear.

Maybe I'm not understanding the T-Port sync, but it seems the gist of it is to get the throttle blades closed as much as possible and prevent the timed vacuum port from getting vacuum at idle correct?
 
Did you check out my thread ?
I believe you are correct in that you do not understand the T-port sync. The point of the sync IS NOT to close the primaries, as far as possible. The point IS to give the engine the correct amount of fuel through the low speed circuit so it doesn't do strange things. Things that include stalling when put into gear,hesitations or flat-spots at throttle tip-in,rough idle,and unresponsive idle mixture screws.
AJ's guide to Transfer Port Synchronization

Once the sync is established, you will not touch the curb idle screw again. You will use timing and idle-air bypass to set the idle speed. With a stock cam, it is doubtful that your teener will want any bypass air at all so make sure the secondaries are and stay fully closed but not sticking.Then set the idle speed by timing, to in the neighborhood of 600 to 650 in gear, 750 tops in Neutral. Then fine tune the mixture screws. From this point on; if the idle mixture screws both work and the engine idle is smooth with those screws turned out to between 1.5 and 2.5 turns, and the idle timing is somewhere between say10* and 18*, you are in the ballpark. This assumes the engine is otherwise mechanically sound.
If the engine still stalls, NOW you have a problem.
If the idle is not smooth, Now you have a problem.
Do not be tempted to change the curb-idle screw adjustment more than a half turn in either direction, and memorize your starting position, so that you do not have to pull the carb off again to reset it.
It is very doubtful that the curb-idle screw can fix any rough running or stalling issue, so try to leave it alone after the sync.
 
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Yessir, I read over it. What I'm having trouble translating over the the edelbrock between your directions and the manual are these two steps "2)With the Curb-idle screw,set the t-port exposure under the butterflies,to about square to rectangular,or .025/.030 high. 3)Set the idle-speed with bypass-air,and idle-timing."

2) I read this, and your response to another member with a similar issue. This sounds like I want to close the butterflies with the idle screw JUST to the point where vacuum to the timed port dies off? I'm not sure how the .025/.030 measurement is used in relation to the t-port exposure. Should I pull the carb off the intake and set it using a feeler gauge?

3) This sounds like once the t-port is set in step two, I would get my idle speed set at the 750RPM spec using only the air the butterflys allow past them, adjusting the idle mix screws, and timing to get it in spec and smoothed out?

Sorry if I seem dense or stubborn, this is only the 3rd REAL carb'd vehicle I've had, and second Edelbrock. Never had such strange issues on the Pontiac 400, but this particular car has had a lot of very shady work done to it while the previous owner had it. Just trying to understand it and reverse engineer it all.
 
elementaltoad said:
Yessir, I read over it. What I'm having trouble translating over the the edelbrock between your directions and the manual are these two steps "2)With the Curb-idle screw,set the t-port exposure under the butterflies,to about square to rectangular,or .025/.030 high. 3)Set the idle-speed with bypass-air,and idle-timing."
Click to expand
2) I read this, and your response to another member with a similar issue. This sounds like I want to close the butterflies with the idle screw JUST to the point where vacuum to the timed port dies off?Forget about the timed port. You have to open the butterflies quite far to involve that guy. I'm not sure how the .025/.030 measurement is used in relation to the t-port exposure. Should I pull the carb off the intake and set it using a feeler gauge? YES! You will need a wire gauge feeler. Or just eyeball it. Every engine is different so I cannot say that exactly .025 or exactly .030 will be correct. It is just a starting point and it looks like a little square to a little taller than wide. Eyeballing is fine for now. I also puts you and me on the same page, so I can tell you what to do later if it doesn't work out 100%.

3) This sounds like once the t-port is set in step two, I would get my idle speed set at the 750RPM spec using only the air the butterflys allow past them, adjusting the idle mix screws, and timing to get it in spec and smoothed out? Well sort of; the air flowing past the butterflies is now fixed by the speed-screw, so don't touch it again.The idle mixture screws will not or should not affect the idle-speed, only the idle quality.And they should achieve the best idle quality when set between 1.5 and 2.5 turns out.If not, then the sync will need a minor adjustment.The timing is the principal player in setting the idle speed now.
Oh yeah, forget about factory specs; they were designed to meet the regulatory agencies restrictions of the day and on the fuel available also at that time.

Sorry if I seem dense or stubborn, this is only the 3rd REAL carb'd vehicle I've had, and second Edelbrock. Never had such strange issues on the Pontiac 400, but this particular car has had a lot of very shady work done to it while the previous owner had it. Just trying to understand it and reverse engineer it all.
Click to expand...

We all started out pretty much like you, so don't lose any sleep over multiple questions. Bring 'em on!
 
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We are on the same page now, I get ya! The transfer slot, or how much of it is exposed on the underside of the blades.

I pulled the carb when I got a break from the rain and set it at .030 using a feeler gauge. This is the timed vacuum port side, as you said it's not exposed at all when the transfer port is spec'd to about .030.
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Manifold vacuum port side for reference.
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And here is the shot of the distributor, #1 is the wire under the brown wiper wire. Basically pointing to #1 cylinder.
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I realize I am coming in later here and admit I haven't read through the entire thread - elementaltoad.. just something to consider - the distributor will go in correctly or 180* off - have you gone through the process to make sure it is in correctly? #1 piston at TDC and rotor pointing essentially at #1?
 
The engine currently runs,and the timing is set to 10*BTC, at last post; so he is well in the ballpark.

Bur ET, since you posted that last picture, I sense that you are concerned with your distributor orientation. So, I'll tell you a secret; 1) if it runs and revs out,without any crossfires or dropped ignition events, then it is in the ballpark, no matter where the rotor is pointing. 2)The factory orientation just makes it easier to set the timing because the Vcan falls into a generous swing range. 3) if your Vcan is currently oriented to allow timing changes from about 5* advance to 25* advance, then it is perfect. 4)if you want to change the orientation, take note of where the Vcan is now and which way you would like to move it and how far. Pull the dizzy out. Look down the hole and find the drive slot. Reorient that slot to the previously determined location, by lifting up the driveshaft, turning it, and dropping it back in. During this process two things are gonna happen;1) the drive gear may not not drop all the way back down, as the hex at the bottom may not line up with the oilpump drive socket. and 2) the gear that you see down there has helical cut teeth, which means that as it drops back down it corkscrews into place.So you cannot orient the slot to where you want it and expect it drop right into that position. No you have to compensate for the corkscrewing. Sometimes it takes several tries and sometimes you have to rotate the cam,via the crank to get the hex-drive to simultaneously engage the oilpump; and then return the timing to the previous 10* advance to continue.So it may not sound easy, but after you have done it a few times, it is. For a first-timer it may sound a bit daunting.
To make this a painless as possible, I start with the #1 cylinder at TDC compression. Then I advance the timing mark on the balancer to the top of it's timing tab to 10*Advance. Pop the cap, and the factory would specify that the rotor should be pointing to the left front intake bolt(left being the driver's side). This again, puts the Vcan in a good place and usually puts the rotor under the tower that is marked @1, making it simple for anyone to install the wires. But to repeat; it does not have to be so. And to repeat; if it runs and revs with no crossfires or dropped ignition events,and you can vary the initial to in the range of 5* to 25* fugedabowdit;for now.

Ok this triggered a memory. If your dizzy driveshaft has excessive end play, it would be possible for the oilpump driveshaft to climb up the helical gears,with rpm. As it rises it would corkscrew, and since it is simultaneously driving the dizzy driveshaft,it too would be corkscrewing. The result of that is the reluctor would also be rotating, and when that happens, the timing takes a dump. So now I don't recall if this rotation would drive the timing into advance or into retard; but I do know that if I had designed this micky-mouse system, I would have designed it to drive it to retard so that at least the engine wouldn't detonate itself to death.
Now don't be yanking up on the rotor in an attempt to check the endplay;on account of that top part is not directly attached to the bottom. The only way to check the dizzy endplay is to pull it out and manually push pull it's driveshaft up and down. I don't recall the spec except that the factory was pretty generous. I like to run it pretty tight maybe .008tops. Chrysler used to sell a bag of hardened shims to tighten that up. If you go after this, be advised that the little nylon collar that is used to limit the travel has usually gone brittle, and often breaks during the removal/reinstall process. Also the little hole for the roll-pin that retains it,is seldom drilled dead-center; so make sure it goes back on EXACTLY the same way it came off, cuz if it breaks you will be parked until you fabricate a new one. No that's not true;metal ones are available aftermarket.
In any case I would at least check it IF IN FACT, your timing is retarding with rpm.

sidenote; I have purchased those select-fit endplay washers in a kit from Ford too. They are just .500ID hardened very thin washers
 
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AJ, it runs great after setting the transfer slot as you said. I get a fairly smooth idle at 850rpm just adjusting the idle mixture I can put it in drive and it idles at about 750rpm with 12" of vacuum, on 10* of spark advance.

I think it could use more fine tuning but the baseline is set, I need to check vacuum and mechanical spark as it was a California car with it starting at 5* ATDC there is no telling how they have the spark curve set up.

Thanks again for the help with this, without the transfer slot spec I'd have been scratching my head for days!
 
Here is a video of it while I was testing a few throttle stabs and seeing if it would idle in gear. I messed with the idle mixture adjustment to get it sounds right at idle, but I think that threw it off in gear. I think I'll just have to reset and start over with the mixture screws, and then adjust the timing. This is Houston, Texas, I didn't think it would like a lot of initial timing, but I guess that's what it's asking for - trying to lower timing closer to TDC just makes it sluggish again.

Yes, it is ugly, and has leaking wiper seals and there is water in the floorboard...that is next to address.

 
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MOPAROFFICIAL said:
Rob, It would retard it 8-10 degrees , can't remember that it would advance backwards though....
Click to expand...

Thanks. That's one mistake I have never made......not because I am smart, but because I was just lucky, so I was not sure how it would react.
 
Well, the vac advance pot looks to be oriented correctly, here's what I'm looking for.......... B engine distributor bodies are 'dentical to A engines in dimension, 'cept the pot pulls
clockwise so the cut & placement for the vac is different. HOWEVER, the shaft would appear identical except the weights would rotate the rotor the opposite(counter-clockwise)
direction to the A(clock-wise). Pull the cap, which way will it let you turn the rotor against the adv. springs,...should be clock-wise. I actually considered doing this on purpose on
my 383 when I had the spray on it, using the A housing w/B guts, and solenoid pulling the plate to retard the timing when I hit the button.
 
Way-to-go, ET
See you're learning already.....The engine is telling you it wants more initial, and you are hearing it.
Forget the specs. They were established to limit certain pollutants, and do nothing but make your engine sluggish. When they were brand new it was tollerable, now decades later, not so much.
But if you advance it more, the idle will go up, and at 850rpm already,you don't want this. So your reflex will be to slow it down with the curb idle screw; DON'T DO IT! That will mess up the T-port sync! If you have to slow it down, your only option left is to reduce the air intake somewhere else.
To reduce air intake somewhere else,your options are:
1)Making sure the secondary plates are fully closed, but not sticking; BOTH of them EQUALLY. It can happen that the secondary plates were delivered to you with the plates not synced. On a big cam engine this is mostly no big deal.But on a stocker this is a very big deal. If one plate closes and the other hangs open a bit, then two things happen; A) the idle speed may be higher than desired on account of the extra air, but worse is B) this lopsided air delivery has no fuel in it. This causes a bit of an idle-tuning issue on account of the mixture screws have to also be lopsided to compensate. But it it's not even that simple;the two back cylinders on that plate are gonna get the majority of the dry air, and will run lean. While the two closer to the front plate will be a lil fat. There is no tuning this out. So if you find this you gotta fix it.This is mostly an idle issue, but can also affect the low-speed tip-in.
2) the PCV can be swapped out for one with a lesser flow rating. Of course you are gonna have to buy about ten different ones to maybe find one that sorta works. Or you can take yours apart and modify it. But before you get tangled up in that,simply clamp that PCV line off and see how much change it will actually make and if the headache will actually bring a good result.
3) while you are clamping things, you might as well clamp everything in sight to make sure no vacuum devices are faulty, especially a brake booster
4) the intake gasket needs to be proven to be NOT sucking air, as well as the carb base gasket, and the throttle shafts. This last one cannot be sealed up 100% tight, and some leakage here is inevitable, so don't pull your hair out trying to figure out how to overcome it. As long as the primary shaft is not flopping around and causing problems with the T-port sync, forget about it.

So if you can't find any air leaks, and the idle gets higher than 850 in N/P, while dialing in a few more degrees, then I really cannot see a good way to increase the idle-timing beyond the 10* that you currently you have.
Now having advanced the idle-timing, this has also advanced the power-timing. This is something you have to prove acceptable, or change it to be so. Max power-timing on a stock,open-chamber headed low-compression teener is probably 36*. Some won't even take that much. And I guarantee you won't feel the difference of 2 to 4 degrees, on the street. So play it safe and modify your dizzy as may be required to limit that power-timing to say 34* plus/minus 2*.
AFTER that is done; you can experiment with weights and springs to bring the mechanical advance in as fast as she will take it without detonating.
AFTER that is done; you can start experimenting with the Vcan.

But right now, limiting the power-timing is job#1.
 
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Right,... has it stopped retarding the timing as the RPM's increase or no?
 
Timing is no longer retarding, correct. AJ, thanks again, and that will be the first order of business here in the next day or so. I pulled out the harnesses from the bulkhead connectors and I'm working on rewiring and looming them all. While working in the bay on the distributor and wiring, the pickup coil harness tore in two!

I really should just go ahead and start a project thread. At this point I pulled the voltage regulator, pickup coil, harnesses, battery cables, coil, ECU, etc. Perhaps I've just had too much caffeine, but I already went through half the harness and cleaned it up. I'm going through it with a brass brush now to knock the corrosion off the terminals. Once the harness is back in I'll replace the pickup and focus on getting it running better in gear. Some of the wiring on this car really concerns me. I also decided to rip off the vinyl top and trim, good thing too:

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I probably just imagined it honestly, it ran horrible when I got it and all I had was a cheap HF light. I think I just caught it going ATDC since idle was set at -5* and it stumbled, choked and stalled off idle. so every time I caught the mark with the light it looked like it was going the wrong way. The pickup wiring tore loose the other night after I got it running halfway decent though so I pulled the whole harness to go through. I also have a couple new ECU to try as well since my current one is fubared.

Only way I could figure it was actually retarding though would be voltage or bad electronics which I suspected with the guts all over my inner fenders haha
 
If it runs, the box is still good.I've seen them die, but never while running. It's just one day you will go out to start it and doh, no sparky. I've had one like yours run for years still, but I always carried a known-to-be-good,spare. I've also seen quite a few like yours and worse, still running. I figured that junk must just be a water proofer.If you replace it with a new one, throw this one in the gbox for a spare; it might last longer than the new junk.
 
That's good to know, I was afraid it was beginning to overheat. I bought two new ones, a Mopar Orange/blue box and some off brand box. The Mopar box has the same sticky gel like packing in the back of it while the off brand has an epoxy fill. I wonder if it would be ok to fill the old one with epoxy? I'm just trying to bullet proof this thing a bit while waiting on parts to come in.

I did get some of the wiring harness cleaned up and redone, I also found a cable with a thick enough gauge and length for the alternator to battery connection. I am doing the fleet bypass on the car with a junction distribution block for future additions and fused supply leads to the stock black/red wires under the dash through a grommet in the firewall. It should work well enough to serve the car well into the future I hope.

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I took breaks in between wiring, crimping, looming to hose down the top and get it cleaned up. It came out better than I thought. My only concern is patching the rear window channel.
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BTW, just in case I missed it, what is the timing chain play in that puppy?
 
Hopefully minimal, it was rebuilt before I got the car about 17k miles ago. When I had it running, shortly before I ripped the pickup wire in half - timing was steady and I didn't get any erratic readings. Once I finish up the harness, fleet bypass, and feel safe driving it, it will be getting a whiplash cam anyway, along with a new timing set just in case.
 
Kudos to you on the progress. Ive been reading thru hoping to learn bits here and there. The roof looks brand new compared to the "before" pics. Nice work!
 
Well the car is back up and running. I finished rewrapping and looming the engine bay portion of the wiring harness. I also did a fleet bypass. 2AWG wire from alternator stud to the battery directly, 2AWG from battery to starter directly, then a 4AWG to the relay, and a 4AWG to a distribution block I added in and fused which connects to the ammeter bypass. Voltage is a lot more consistent, and the headlights are 10 times brighter than they were. I ordered a completely new distributor as it has been one thing after another with this current one. The pickup coil connector ripped in half...from an old splice that was apparently done. I cut it out and respliced, but I imagine that the splice is adding resistance that shouldn't be there and the vacuum pot looks ancient, though it works.

Once the new distributor gets here I'll drop it in and retime the car, however at the moment I have no turn signals. They were working fine after putting in the new harness when I first ran the car but after fuse #7 popped (20amp) I lost brake lights, turn signals, and the dash "Test" lights that come on before you start the car. I'm guessing something in the column is not happy.

I replaced the fuse and brake lights as well as the dome light work again, but I have no hazards or flashers. Likely turn signal switch damage from dropping the column and removing the cluster?

I also noticed the stock wiring is routed extremely poorly. It's hard to believe this is factory wiring , so much bare wire and nearby sharp edges.

ON THE PLUS SIDE, my AC/Heater blower is working now. There was a two wire grommet above the brake booster with one brown and one tan wire, neither of which matched any FSM for AC wiring, but that was it. Brown to green on the blower, and tan to dark blue on the engine disconnect harness. However the compressor is not kicking on so I'll need to check the fill level on the R12.
 
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