Poor idle and off-idle performance after distributor swap

[smokinnjokin]

Starting a new thread, as this started in a vacuum advance thread.

Here's the details: I have a freshly rebuilt smog 360 with a XE 262 hyd cam, performer RPM intake, eddy 1403 500cfm electric choke carb. It still has low compression pistons, should be 8.5:1 or less. It had a stock, 318 distributor on it, with a Pertronix Ignitor 1. The car ran fine. Idle was a little rough, but I attributed it to the cam. Car was reliable with pump gas and felt plenty peppy to me. 11.5 MPG, and it would do 6.8 second 0-60 just mashing the gas from a stop, no launch. Timing specs were 12deg initial, 25 mech. 20 vac can.

I noticed a sharp decline in fuel economy and rough running. After investigation, turned out the vacuum can had broke, old diaphragm probably rotted. I started a thread looking for a new can, and during that process I decided to swap distributors. I had a distributor halifaxhops curved for me that was an electronic; this is a points wiring harness car so I swapped the Pertronix into the new distributor and installed.

The new distributor has 20degrees mechanical and 15degrees vac. In order to swap in the Pertronix, I had to take the points breaker plate and swap it into the new distributor. I also had to drill a hole in the breaker plate for the curved-style arm on the vac can. It had the hole for a straight-style vac arm.

So that brings me to the current issue. The idle quality is poor, in order for it to idle right I have to turn the air screws out to like 4-5 turns, and the unburned fuel smell burns the eyes. And the transition off idle is rough, sputters a bit and sometimes even backfires. Mashing the gas, there is a slight hesitation and then it goes very well. The rest of the rev range, everything past initial throttle opening, feels excellent. 0-60 even increased to 6.4, even with the hesitation. The problem is most apparent when climbing my steep driveway with just a tiny bit of gas, runs very rough, surges and backfires. When idling in drive holding with the brake, the idle quality deteriorates the longer I sit there in gear.

I am trying to set idle using mixture screws and timing, I started with the transfer slots exposed a little more than square, and the air screws at 2.0 turns. It absolutely idled like crap, very erratic and timing would jump all over because it was way, way too lean. Now, it idles ok but the mixture screws are crazy rich. Pulling timing back to 12 did not help.

So that's the dilemma. Ran great, swapped distributors, now it runs like crap. My thought process:

1) Is just the swap from a 318 distributor to a custom-curve with less mechanical enough to cause this thing to need radical carburetor adjustments? Again, it ran reliably before.

2) Is the Edelbrock 1403, 500cfm not enough carb for my combo? Am I chasing my tail trying to tune this thing? Again, it worked before... with a different curve.

3) Did I mess up the distributor somehow swapping top plates? I was very careful drilling the new arm hole for the vacuum can, but it is possible I was a degree or two off. This should only affect vac advance though, right? My problem is of course showing up as I tune with can unhooked.

Other details: Plugs are autolite 3926. They were very clean, looked lean on the porcelain and sooty around the thread ring. Fresh fuel from a few days ago. New gas tank, nothing in the fuel filter. Carb recently rebuilt by a specialty carb guy. Ran great before the distributor swap.

 

[dano]

I'd isolate the vacuum advance for now and see if it changes anything. Is it too lean or too rich because you mention both. You also mention air screw, do you mean the one that opens the primary butterfly's? Manual or electric choke, is it hooked up and opening/operating? At idle can you see raw fuel running down the inside of the carb?

 

[smokinnjokin]

I'd isolate the vacuum advance for now and see if it changes anything. Is it too lean or too rich because you mention both. You also mention air screw, do you mean the one that opens the primary butterfly's? Manual or electric choke, is it hooked up and opening/operating? At idle can you see raw fuel running down the inside of the carb?

Electric choke, set properly, warmed up and off choke and the fast-idle cam. And when I say air screws, I am talking about the idle air mixture screws. Idle issues are with vac advance unhooked and hose plugged. Haven't looked down the carb as of yet.

 

[67Dart273]

Most any larger than stock cam needs more than 12BTC, but has that changed between the two distributors?

Are you running manifold vacuum advance or "ported" vacuum? (I run ported, period)

 

[TT5.9mag]

As always with an edlebrock, especially after it’s been rebuilt, check and set the float levels so they are dead nuts. Make sure you have zero vacuum leaks of any kind. As you’ve said, disconnect the vcan and disregard it for initial tuning. Bring it in later and use ported vacuum. The statement “timing was jumping all over the place” worries me. It should be stone cold steady regardless of carb settings. Sounds to me like you have multiple issues that need to be systematically worked through.

 

[smokinnjokin]

Ok, so car is running really good now. Better than ever actually with the new distributor. Here's what I did:

Tq checked intake manifold bolts. Got some movement on a couple of them but I doubt it was enough to cause vac leak.

Took out distributor, removed the curved-arm vac advance can that was using the hole I drilled. Put the standard VC-93 straight arm vac can, that utilized the factory hole on the breaker plate. My theory was that somehow, my cobbled-together distributor was the source of the issue.

Put everything back together, warmed the car up, advanced initial timing until it was happy and turned the air screws way out and with the car idling in D and the brake set (and warmed up) progressively leaned air screws until rpm started to drop, stopped there. Very oddly, I made a mark on the distributor for reference before taking it out to swap cans, afterward I put it in the exact same spot and it was like 10 degrees off. Weird that just swapping vac cans would drastically change the orientation of the distributor. My only thought is that the arm of the vacuum can was somehow interfering with static timing at idle. Not sure how it would do that.

And that was it. Car runs fantastic now. Timing mark still jumps around a bit, vacuum gauge is bouncy at idle too, but I drove the car several times around town and on the freeway and it ran very well through the entire rev range, climbing steep hills at low throttle, sitting at stoplights for a while, cruising on the freeway at 70-80, all conditions.

The new advance can arm is marked 6.5 (13 crank), and I am assuming that my 8.2-8.5 CR 360 probably wants more vacuum advance than that for best performance, but for now I am pretty darn happy with the Frankenstein distributor. My initial is 16 degrees right now, 20 mechanical. I think the engine may be happy with a lot more initial timing, but I am going to wait for a very hot day before I advance it any more. Today was pretty mild.

 

[smokinnjokin]

Most any larger than stock cam needs more than 12BTC, but has that changed between the two distributors?

Are you running manifold vacuum advance or "ported" vacuum? (I run ported, period)

Ported, absolutely. Ran 12btdc on old distributor with 25 mech. New distributor has 20 mech, so I bumped initial up to 16. Will test on hotter day giving it more advance.

As always with an edlebrock, especially after it’s been rebuilt, check and set the float levels so they are dead nuts. Make sure you have zero vacuum leaks of any kind. As you’ve said, disconnect the vcan and disregard it for initial tuning. Bring it in later and use ported vacuum. The statement “timing was jumping all over the place” worries me. It should be stone cold steady regardless of carb settings. Sounds to me like you have multiple issues that need to be systematically worked through.

The bouncing timing mark worried me too, but it the car runs well now and still has the bouncing timing mark. I wonder if it is my inova dial-back timing light, but anything past 12btdc disappears under the water pump/timing cover so I have no other way of verifying. The bounce does appear to get more pronounced the more I advance timing on the light/gun. Before the rebuild, I installed the V-6 timing chain tensioner and my timing was rock solid using a non-dial back light, but it was also at 12. I hope the machine shop that rebuilt the motor used the tensioner, oil dripper tab and hollow bolt, oil slinger, etc. but its not worth tearing down the frontend just to look. Might be a winter project in conjunction with an aluminum water pump housing.

 

[TT5.9mag]

Ported, absolutely. Ran 12btdc on old distributor with 25 mech. New distributor has 20 mech, so I bumped initial up to 16. Will test on hotter day giving it more advance.



The bouncing timing mark worried me too, but it the car runs well now and still has the bouncing timing mark. I wonder if it is my inova dial-back timing light, but anything past 12btdc disappears under the water pump/timing cover so I have no other way of verifying. The bounce does appear to get more pronounced the more I advance timing on the light/gun. Before the rebuild, I installed the V-6 timing chain tensioner and my timing was rock solid using a non-dial back light, but it was also at 12. I hope the machine shop that rebuilt the motor used the tensioner, oil dripper tab and hollow bolt, oil slinger, etc. but its not worth tearing down the frontend just to look. Might be a winter project in conjunction with an aluminum water pump housing.

There is a way to verify. Buy some timing tape, verify tdc accurately, and mark your balancer. You’ll be able to read timing at any advance.

 

[AJ/FormS]

Ima thinking you have several problems.

1) firstly; the arm on the Vcan fixes, that is; sets the position of, the advance plate relative to the signal generator. If your new Vcan arm fixes in a different position, the timing will be off. no big deal at idle, you just reposition the D and away you go.
But, When the Vcan starts to pull in timing, the rotor may get out of sync with the towers, and eventually it may spark to the wrong tower. As the rpm goes up, the centrifugal timing may exacerbate that. To correct this, you have to "phase" the rotor.
2) You didn't say, but there are CCW and CW driven distributors. I hope you knew that, and have the appropriate parts.
3) You have to figure out why, and fix, your jumpy timing .
Do this: Set your timing to about TDC* Crank up your idle rpm as much as you need to but get the idle set to as slow as it will run, in the 500 to 650 range, not a big deal
Aim you light and slowly increase the rpm about 200 to 500. Watch the strobe action.
If the timing jumps all around, or if sparks are dropped, or double sparks occur, then
Then the polarity of your magnetic pick-up is reversed, and it is generating erroneous signals. Your engine will never run right. Reverse the polarity, and retest.
4) once you get that/those fixed, reset your transfer slot exposure under the primary throttle blades, to about but not less than, square, and after this, LEAVE the speed screw alone. Set the idlespeed using idle-timing; Don't even hook up the timing light yet. Just push/pull on the Vcan until you find a sub-800 rpm in P/Neutral, that your engine likes. Set the mixture screws to about in the center of their range. Make sure the secondaries are closed up tight but not sticking. And then, with a fully warmed up engine running ~180*F, lower the rpm to in the range of 550 to 650 in gear, USING TIMING, NOT SPEED SCREW, as low towards 550 as it will idle smoothly and stably.. Do not even look at the timing, let the engine tell you what she wants, rather than forcing your opinion on her.Make sure the Vcan is hooked to the Sparkport. Now, take her for a test drive. Do not go WOT. You are just testing the idle to off-idle transition,just a gentle roll-on, looking for a hesitation.
If you do not find a hesitation, yur done this part. But
5) if you do get one; turn the speed screw in 1 turn, and if the in-gear idle is increased beyond 650, then retard the timing, until it drops back into the 550-650 zone..... and roadtest again.
If you still get a hesitation, twiddle the mixture screws for best lean idle, then add 1/2 turn rich, and roadtest.
If you still get a hesitation, add 1 turn more speed screw, reduce your in-gear idle speed back into the zone, by retarding the timing, and twiddle the mixture screws as before.... then roadtest.
It better be good by now.
But if it is not, gradually increase your idle speed in steps of about 50 rpm atta time, using TIMING, not speed screw, road testing after each change. Do not increase past 650 in gear, for no other reason than, it might clang,bang,or lurch from N/P to in gear..
7) After you get this all dialed in; NOW is the time to check the idle-timing, and to limit your Power-Timing, and to set your Rate-of-advance, specifically for your engine.
8)And finally; to get your cruise-timing up into the range of 42 to 56 degrees, to get rid of that lousy 11.5mpgs. Well, unless you have race-gears, lol.

 

[pishta]

..I hope the machine shop that rebuilt the motor used the tensioner, oil dripper tab and hollow bolt, oil slinger, etc....

you can tell if a tensioner has been used if you can back the crank up 1-2 degrees and the distributor turns too. the tensioner will take out ALL chain slop. Most chains without tensioners no matter how new will have a little slop in them unless they are custom align bored -.010 or something.

 

[67Dart273]

I made a mark on the distributor for reference before taking it out to swap cans, afterward I put it in the exact same spot and it was like 10 degrees off. Weird that just swapping vac cans would drastically change the orientation of the distributor.

Of course they will. There is no guarantee that a vacuum advance is going to be exactly the same as another. The way the vacuum changes timing is the rotation of the breaker plate. So if the arm is a tiny bit off from the original it will change the timing.

Remember dist. degrees are half crank degrees. So if you only change something in the dist. makes a difference of 5 degrees, it will change 10 degrees at the crank.

Don't you have a timing light?

 

[smokinnjokin]

Yes of course I have a timing light, but a small permanent marker mark on the back of the manifold where the v-can is pointing helps put the distributor back in within a few degrees of where it came out.

The comments about the V-can make sense. I didn't make the connection that the can fixes position of the advance plate. I assumed there was a stop that it rode against until vacuum advance was applied. I think the hole I drilled for the new v-can had to much slop, and was rattling back and forth at idle and causing the timing to vary.

 

[67Dart273]

The other issue of course is if you are using a breaker points dist, the point gap changes timing as well. I would assume that on a breakerless Mopar, the reluctor gap would do same thing. It does not take much to change that.

 

[smokinnjokin]

To circle back around after a couple weeks of driving, my erratic timing issue still remains. Car runs very well, idles strong and pulls hard but I am missing power and economy due to this timing issue. Timing appears to wobble by about 5 crank degrees. Idle rpm, vibration and sound all agree with the 2 timing lights I have checked with. I currently have timing retarded below what it wants (set at 10 initial, wants 15-16) for safety until I diagnose this problem.

Balancer does not appear to be slipping.
Have changed caps, rotor, plugs, coil, no change. ignition is very strong and plugs are clean. Fires right up with ease. Don't think it is spark related.

The Pertronix pickup assy is firmly mounted, vac can is fixing its position and there is no wobble in the advance plate.

The only thing I can think of that would cause this is the distributor. It is a factory distributor with a Pertronix Ignitor 1 as the trigger. Did some research, not sure if the Pertronix is known to cause erratic timing.
My theory is that perhaps the advance springs are weak or failed somehow, and allowing advance to bleed in at idle, albeit very erratically. I looked at them today, both advance springs appeared properly seated and in good condition. This jump in timing is consistent through the rev range, but is most noticeable at idle.

What am I missing here? I hate to just throw parts at it. The car runs so well, I can just imagine how much faster and smoother it will be with the timing locked down and not wobbling by 5 degrees. I have contacted Ray about rebuilding a 2nd distributor, would be nice to have a spare.

 

[AJ/FormS]

Sorry if this has been asked but;
have you tried the old distributor, with the previous amp, to isolate the problem to the new system? Then transfer the pertronix into the old distributor to isolate the problem to it?

IDK anything about the Pertronix. Is it polarity sensitive, like the Mopar magnetic pick-ups are? If it has a magnetic pick up, it will be polarity sensitive. And when the pick-up polarity is reversed, it will fire just fine at idle. But as soon as the Rs begin to rise, the timing will go erratic, and the light will see random flashes and missed sparks. Mine was impossible to drive like that. It happened to me that the Mopar pick up died on the hiway. I subbed in a spare set the idle timing and began to motor away. But the engine ran like crap. Then I noticed that the wire colors were different from the one I removed. I happened to have a polarity reversing adapter in my tool kit, so I subbed it in, reset the idle timing, and this time the car motored away as usual. After I got home, I swapped in a Pick-up with correctly colored wires and all was well.
Later I found out that the pick-up I had initially installed, was not for an SBM
Like I said; IDK anything about Pertronix.
Jus trying to help.

 

[smokinnjokin]

Yes, same issue with old distributor. Good point.

Wild theory here, but there is a ton of play in the distributor drive slot. The shaft can turn by what I would estimate to be at least a couple of degrees. I check the drive tip of both distributors, and they were within spec. I wonder if the engine builder either recycled the old distributor drive gear, or put in a new one with excessive tolerance in the slot.

I always assumed that once the engine started spinning, the drive gear would 'load up' under torque and stay tight..

How much play/slop should the rotor and shaft have when installed in a proper, in-spec drive gear?

 

[AJ/FormS]

So if I read this correctly, you are saying the old system had the same problem. Was there any part of the Old system, reused in the new system?
Have you tried putting your timing clamp on #6 plug wire, to see if it is doing the same thing.
And I suppose you have tried turning the clamp both ways?
I assume you have checked the timing-chain slack?

I think that the slot is not the problem. While any variance of distributor degrees translates to double that on the balancer, that is barely perceptible to you in the cockpit. And I challenge you to feel a power difference below 60 mph.
But if all you have is a 5* variance, with no wild strobes, at any particular rpm, then that rules out a polarity issue. And that points to just a mechanical issue.
Starting with the timing chain, the cam end-play, the intermediate shaft, the oil-pump drive hex, and ending at the drive-slot. Of these the chain-slack is the most likely to cause an issue.

Is there the same 5* variance at 3500rpm?
this would rule out the advance springs and the V-can. And should rule out the chain and cam. That kindof leaves just the I-shaft. If it jumps up and down, it will change your timing, by virtue of the angle drive. The oil-pump load should keep it down. But if the pump load varies, and the endplay to the D is excessive, I imagine it could move up and down.
But it is hard for me to imagine the oil-pump load varying with any degree other than constantly increasing with rpm. I suppose if the hex was worn excessively, the I-shaft could be slipping in the pump.
One thing I would check is the wear-pattern on drive-tang,of the old D. This will tell you how deep your D is entering the drive-slot, and that could help to understand if the I-shaft is migrating up and down.

Honestly, I got nothing for you, but just trying to help.

 

[smokinnjokin]

The slot is not the problem

So if I read this correctly, you are saying the old system had the same problem. Was there any part of the Old system, reused in the new system?

I assume you have checked the timing-chain slack?

I didn't notice this issue until I removed the factory distributor to replace a shot vacuum can. I have not been able to restore stable timing through any combination of parts, old or new distributor. It appears to be degrading with time.

You breezed past the distributor drive gear, so are you saying slop in the drive gear is normal and not the cause of erratic timing? I looked in there and it is a bronze drive gear, which is odd because the car has a comp xe262 hydraulic flat-tappet, not a roller cam.

 

[AJ/FormS]

You got ahead of me, while I was editing,lol, Hit refresh.

 

[AJ/FormS]

The problem is most apparent when climbing my steep driveway with just a tiny bit of gas, runs very rough, surges and backfires. When idling in drive holding with the brake, the idle quality deteriorates the longer I sit there in gear.

This points directly to two things;
1) your throttles are not in the right place up on the transfers slots, and
2) your float-level may be high or unstable.

That 262 XE cam is likely about [email protected], am I close. As far as cams go, this is pretty small, but the right idea for an 8/1 nominal Scr 360. I should make gobs and gobs of low-rpm torque.

From your description above;
1) your mixture screws are out too far ..... because
2) your transfer fuel is insufficient ...... because
3) your throttle is too far closed, because .....
4) your timing is too advanced..

So;
You need to set the Transfer-slot exposure, underneath the throttle plate to a tiny bit taller than wide, make it just perceptible. You do this with carb removed, the choke and fast-idle disengaged, the throttle closed, and use the curb-idle screw. Make sure the secondaries are closed up tight but not sticking. Ok flip her right side up, and set the mixture-screws to 2.25 turns out. or about in the center of their working range. From this point on DO NOT ADJUST THE CURB IDLE SCREW.

Ok, flip the top off and lower the wet fuel level back to stock or up to 1/16 inch lower. Be careful not to bend the metering rods on reassembly; I highly recommend to remove them, first.
Alrightee re-install it, pour some gas into the bowls thru the vent , splash a lil down the primaries, tug some timing into her, give her some throttle opening, and fire it up. Let her run on the fast idle until she warms up, then kick her down NOW, pay attention. You will now adjust the idle speed with timing. Just push the Vcan towards the firewall untill the engine wants to stall, then advance it a bit.
Next; make sure your PCV is hooked up to the correct port, and discharging into the primaries just below the throttles.
If you have a power brake booster, PINCH the line off.
Also pinch off or defeat the Vacuum advance. And make sure all other entry points into the intake are capped, including all that may be on the carb.
Next; prove the intake is NOT sucking air anywhere except thru the primaries and the PCV. This includes sucking from the CC. To check this, you put a vacuum/fuel-pressure gauge on the dipstick tube, flip the PCV out of the VC, and plug all other entry points into the engine. Then watch the gauge. At idle speed it should make PRESSURE. Do not let the pressure exceed 3 or so psi, because 4 can blow out your rear camplug, in the bellhouse. I wouldn't be your friend then now would I,lol.
Next; having proved the engine is tight. Set your idle speed, using timing , to 600/650 in gear. Forget about what the timing light says, just do it.
Next; Hook up the Vcan to the SPARKPORT. Rev the engine up to about 1800 to 2000 rpm and put it on a fast-idle step. Exact rpm not important;
Next; screw the mixture screws in/out, equally, to get the highest rpm. then add 1/4 turn out. Finally kick the fast-idle off. Reset the Idle rpm... USING TIMING, as may be required.
Next; if the engine is not ticking over nicely; Take a shop rag and stuff it into the secondary side to see how bad it is leaking. If the rpm changes more than 50 rpm, something is wrong, the blades are not closing all the way. Fix it. After that is done. and you think the engine idle is still too ruff for a 218* cam,lol; Then, take that shoprag and begin to cover the primaries this time. If the rpm goes up, then the engine is idling lean. If the rpm goes down, then she is idling fat.. So the first thing to figure out is where are the mixture screws set to. While counting the turns, close each one, one atta time. Write the turns down. Average them out and put them back . They should have been at around 2.5 turns out, +/- .25 turn. If they are that is perfect.
Now, here comes a lesson.
Your low-speed circuit consists of four parts; the wet fuel level, the transfer slots, the idle trimmers (mixture screws), and the various holes and air bleeds. It is your job to mix these in any proportion to satisfy the three basic conditions that they control, namely; the A/F ratio up to about 2400 rpm no-load, and the idle quality, and throttle tip-in.
We did the first one, ballpark. Next we did the idle ballpark.
Now lets do the tip-in before we move on.
Next; let the idle stabilize for a couple of seconds, then slowly tip the throttle in. You are looking for a sag, a hesitation, or a bog. If you don't have one then I guessed pretty close on the T-slot exposure. When the engine idles, the transfers are spewing fuel together with the mixture screws. A low fuel-level makes the spewing harder, a high fuel level makes it easier. That portion of the Transfer slot above the throttles is bypassing air around the throttles and slamming the fuel being discharged. If your transfer slot is too small, the thing tends to dry up, and the more you have to open the mixture screws to get the fuel. After the slots dry up, there is nothing there to sustain the tip-in, and it takes a few milliseconds to start it up again. In the meantime, the mixture screws were already at their limit, so you get a serious hesitation; sound familiar?
On the otherhand, if you are up too far on the transfers, she will idle rich, and you will shut off the mixture screws. It idles fine like that cuz it has the right amount of combined fuel coming from the two sources. But as soon as you tip in the throttles, she goes lean, and you get a sag in power.
End of lesson
Next, we need to get that tip-in fixed so try it, a few times, always waiting about 10 seconds in between for the idle mixture to stabilize. From the results, determine if you think it is rich or lean. Consult the result from the idle mixture test above, in blue-type
If you need more fuel, and the idle fuel also needs to go up, then if the mixture screws are already at 2.5 or more turns, then;
add 1 turn of the CURB-IDLE screw. If the idle-speed changes, reset it with timing!. Then recheck the tip-in. Continue in this way, counting the changes in the curb idle screw. Because, when you figure out that you might be going the wrong way, you need a reference point to get back to.
What I usually do is after the T-slot exposure was set, I back out the screw until the throttles close and the curb idle screw comes off the adjuster, counting the turns as I go; then write it down. So now, if I get lost, I can get back to the starting point.
Ok, so when you get done all this, you will be targeting a few things;
1) lean-best AFR at 1800rpm plus 1/4 turn @ ~2.5 turns out
2) a nice smooth idle with the mixture screws @ ~2.5 turns out
3) no tip-in hesitation
4) a smooth light-throttle take-off
5) a low enough idle speed in N/P so as not to have it bang going into gear.
6) A high enough idle to still have oil-pressure
7) IDK i'll think of something
10) who cares what the idle-timing is!

Your engine doesn't care about timing until you hit the stall speed and again at about 3400 rpm at full power. Notice that this is the first mention I have made to timing. Do not get excited about idle-timing! it means nothing, let it be what the engine asks for.

Next; you determine what your engine wants for PowerTiming, usually 34* at 3400 is plenty of baseline for a Low-Compression SBM.
Next; you determine your stall, and stall-timing, Which should be as much as possible but not so much as to get into detonation.
Next; you recurve your D to hit those two points, but the advance sghould not start until 200 to 400 after idlespeed, so that you have a stable platform to idle around on. If your advance starts too early and too high, the engine gets to be hard to control at low throttle openings.
Ok now your timing has been worked out for exactly TWO conditions namely. WOT and idle. Under all other conditions, your timing will be dead-wrong.
Next; is your cruise timing. You cannot play with this until your power timing has been fixed. So the first thing you need to determine is what speed you are gonna cruise at. Say you have 3.23s and 65=2700 This is too easy; just rev it to 2700 and put it up on the fast idle cam near that. Then just advance the timing , and keep on advancing it, until the rpm peaks. if this is not 2700, then readjust the speed to 2700 and change the timing again to reach the highest rpm near to 2700. Read the balancer. Obviously you will need a timing tape or a dial-back timing lite. Write it down. return the engine to idle. Put the timing back to where you started from. Now disconnect the Vcan, and rev it up to 2700 again and read the timing again. Write it down, Return the engine to idle and hook the Vcan back up.
Next; subtract the lil number from the big number, and that is ABOUT what your Vcan is gonna have to bring in for best fuel economy. Suppose at 2700 you had 2O* in the D and 7 idle for 27 total. And suppose the engine wanted 48* then 48 less 27= 21 in the Vcan. Well yur in trouble I have never seen a Vcan of that size. But write the number down anyway!.
Next; you will want to optimize your cruise timing at other speed points that you spend a lot of time at. Say for example at 35 mph or 55 mph. So you figure out your rpm at those points and in the gear you will be driving them at, just as before. Then you just rev it up to those rpms, and pull in the timing just as before. Then rev it up without the Vcan as before and again do the math and figure out what timing is missing. You will get some pretty big numbers. You will have to limit the Vcan to the smallest amount. So if that is say 16*, then you need a Vcan to pull in 16*, but if you find the smallest is 21*, BINGO, all you gotta do is modify your current can, by grinding off the stops (Chrysler can), until you get the magic number, BadaBOOM! OK NOW, your engine has half a chance at fuel economy, AND your PT performance will pick-up dramatically.
But you have one more parameter to solidify; If at any time or rpm,you get detonation at PT, you need to eliminate that. On a Mopar can you can stick a tiny allen wrench into the hose-nipple and turn the screw that you find in there. CCW will delay and slow the onset of advancement. You'll still get it all, you'll just have to wait for it.
next; after this is all done; you get to start over, cuz once the timing closes in on perfect, you can lean out the carb some.

Now; occasionally a cam will want more air at idle than what the PCV is able to give. The engine will tell you this by emitting exhaust that burns your eyes. IDK what that is, but when it happens, it sucks. I think your 262 should not do this, But if it does we can talk about that later.

Ok I'm gonna edit some to make it easier to read, but this should cover it
and all-done.
I realize this doesn't address your intermittent flying spark, so back to your main thread.

 

[smokinnjokin]

Sorry if this has been asked but;
have you tried the old distributor, with the previous amp, to isolate the problem to the new system? Then transfer the pertronix into the old distributor to isolate the problem to it?

IDK anything about the Pertronix. Is it polarity sensitive, like the Mopar magnetic pick-ups are? If it has a magnetic pick up, it will be polarity sensitive. And when the pick-up polarity is reversed, it will fire just fine at idle. But as soon as the Rs begin to rise, the timing will go erratic, and the light will see random flashes and missed sparks. Mine was impossible to drive like that. It happened to me that the Mopar pick up died on the hiway. I subbed in a spare set the idle timing and began to motor away. But the engine ran like crap. Then I noticed that the wire colors were different from the one I removed. I happened to have a polarity reversing adapter in my tool kit, so I subbed it in, reset the idle timing, and this time the car motored away as usual. After I got home, I swapped in a Pick-up with correctly colored wires and all was well.
Later I found out that the pick-up I had initially installed, was not for an SBM
Like I said; IDK anything about Pertronix.
Jus trying to help.

This points directly to two things;
1) your throttles are not in the right place up on the transfers slots, and
2) your float-level may be high or unstable.

That 262 XE cam is likely about [email protected], am I close. As far as cams go, this is pretty small, but the right idea for an 8/1 nominal Scr 360. I should make gobs and gobs of low-rpm torque.

From your description above;
1) your mixture screws are out too far ..... because
2) your transfer fuel is insufficient ...... because
3) your throttle is too far closed, because .....
4) your timing is too advanced..

So;
You need to set the Transfer-slot exposure, underneath the throttle plate to a tiny bit taller than wide, make it just perceptible. You do this with carb removed, the choke and fast-idle disengaged, the throttle closed, and use the curb-idle screw. Make sure the secondaries are closed up tight but not sticking. Ok flip her right side up, and set the mixture-screws to 2.25 turns out. or about in the center of their working range. From this point on DO NOT ADJUST THE CURB IDLE SCREW.

more coming

That problem is long gone, carb is tuned to perfection. Just the timing issue now.

 

[smokinnjokin]

On the distributor, there is clearly some peening/wear on the end where it inserts into the drive gear. I never noticed it before. I also compared it to the old distributor, the end was immaculate and had no wear. And on the current distributor (causing issues) the shaft is 0.020" shorter.

Is it possible this is one of those stacking tolerance situations, with a worn distributor shaft and oversized intermediate shaft? I am still curious what the normal amount of slop with new components is. The amount that the rotor is allowed to rotate (appears to be at least 5 degrees) back and forth in the slot in the intermediate shaft seems excessive. Also, wondering if it is ok that a bronze gear was used with a normal hydraulic flat tappet cam.
Should I just replace the I-shaft, they aren't terribly expensive.

 

[smokinnjokin]

Ok so I took the intermediate shaft out, it has significant wear as well where the distributor shaft mates in. They are clearly not seating fully together, looks like just the tip of the distributor shaft is inserting in, and allowing a ton of play. With the 2 parts inserted fully out of the car, they lock up nice and tight. So either the distributor shaft is too short or the intermediate shaft slotted end is sitting too deep inside the gear, not allowing the two to fully mate.

*Edit; I also looked at the old distributor. The shaft was about 0.020" longer, and had nice a nice clean undamaged end. It was inserting just deeply enough into the I-shaft to grab with minimal wobble. The current distributor has more wear on the end and a more pronounced chamfer, so it was barely holding on to the I-shaft.

I ordered a new intermediate shaft from Summit. Hopefully it has a significantly taller/deeper slot and will allow the distributor shaft to seat fully.

 

[AJ/FormS]

OOPs, I guess I shouldda asked.
But it looks like you are on the right track.

A for the short shaft, somebody may have put a washer or a bearing, inside the D under the weight-carrier, and or not punched the bushing down far enough. You might want to take it apart and see what can be done in there. After the shaft comes down, you will need to put some shims above the plastic pinned collar, to take up the slack, so it stays down.

If nothing else, you can shim the I-shaft up.

But I'm still confused; Did you not say that the oldsetup was doing the same thing?
But yes 5* of rotor travel, traceable directly to the I-shaft slot clearance, or the bronze gear on the cam, is a lot.
In my readings, the bronze gear requires it's own I-shaft, different from the regular I-shaft; IDK, as I have never run into that, just remember reading something to that effect.

 

[smokinnjokin]

OOPs, I guess I shouldda asked.
But it looks like you are on the right track.

A for the short shaft, somebody may have put a washer or a bearing, inside the D under the weight-carrier, and or not punched the bushing down far enough. You might want to take it apart and see what can be done in there. After the shaft comes down, you will need to put some shims above the plastic pinned collar, to take up the slack, so it stays down.

If nothing else, you can shim the I-shaft up.

But I'm still confused; Did you not say that the oldsetup was doing the same thing?
But yes 5* of rotor travel, traceable directly to the I-shaft slot clearance, or the bronze gear on the cam, is a lot.
In my readings, the bronze gear requires it's own I-shaft, different from the regular I-shaft; IDK, as I have never run into that, just remember reading something to that effect.

The old setup was doing the same thing, but not as noticeable. The distributor shaft end on the old distributor was a little longer (0.020") and had sharper edges so I think it was engaging a little more, but still not fully.
Judging by the wear pattern on the helical gear on the I-shaft, shimming it up a tenth would not hurt anything, where do I find such a shim?

...And not to dismiss your carb, idle tuning advice, I did follow it when first given and the car idles very well now even with this timing issue. 0-60 is down to 6.2 even with timing pulled back. Car is on the verge of running absolutely awesome. I am going to print that post out and reference in the future. I have a 600 cfm Edelbrock that I will eventually install and tune. I think it may be a little more appropriate choice than the 500 that's on in.