What's the worst that could happen?

[moparedtn]

Still trying to diagnose this issue with the GTX, but folks have abandoned my other thread on it, so...
Long story short, new distributor installed fine but no improvement. Car still doesn't want any advance and won't run decently with anything more than TDC timing, vacuum disconnected.
Of course, that's an indicated TDC - could be the marks are that far off?

Was thinking, though - what if it's something simple like the wires being reversed on the coil?
Previous owner did the Mopar electronic ignition kit thing. I did a little preliminary checking of the wiring on it using a diagram I found online, for what that was worth and it seemed ok.

What's the worst that could happen if I try reversing the wires on the coil? Could I wind up doing serious damage to anything?

 

[dieseldazzle]

Nothing. But like in the private message I sent you can check this with a volt meter really easily.

 

[Seventy]

I would start by finding tdc and marking it correctly if it is off.

Next I would make sure there are no vacuum leaks.

As for your coil reversed issue, I have done it, seems not to make a strong spark as when hooked up correctly. Coil is a "step up" converter, wiring it backwards reverses its process and you get very little spark. How does your spark look?

 

[dieseldazzle]

To elaborate in case someone is searching this in the future...... it will still run and fire but the spark will travel from ground up to plug.

Put a voltmeter on the SPAKR PLUG lead, ground it to the block. Set to highest reading and watch the meter when you crank. If it sweeps up you are good to go if it sweeps down then you got the coil leads backwards.....

 

[Beekeeper]

Ed,
You should at least verify TDC sometimes the tab on the timing cover can be off.

 

[moparedtn]

Nothing. But like in the private message I sent you can check this with a volt meter really easily.

I would, DD, but I gots no voltmeter with a needle.
All digital here...

 

[hunt2elk]

I don't remember if you mentioned it before, but could the harmonic balancer have spun?

 

[moparedtn]

Ed,
You should at least verify TDC sometimes the tab on the timing cover can be off.

Suppose so. Guess I'll pull all the plugs and then do the old "finger over the hole" trick on #1.
I DO know the timing dots on the crank and cam sprockets are aligned, did that much myself when swapping the cam out.
I know the distributor drive is indexed to that, as I re-installed the distributor drive/oil pump drive to perfect "front-back" for the slot.
When the timing marks are on TDC as indicated, my distributor rotor is pointing dead at #1 terminal in the cap, too.
Only thing I haven't actually verified myself, I guess, is if the dot on the crank sprocket is accurate versus TDC of #1 piston?

 

[440roadrunner]

What have you done? (Where is the other thread?) I would have checked TDC a LONG time ago!!!

 

[moparedtn]

What have you done? (Where is the other thread?) I would have checked TDC a LONG time ago!!!

There's been a few quite lengthy ones. You'll find 'em pretty easy by clicking on my name. Heck, even got a video or two on youtube under this exact screen name of the cam break-in.

 

[Shorthorse]

Great little tool. You might only use it once but what the heck, car guys love specialty tools.

 

[Seventy]

I think I would have marked tdc, set timing, checked compression, checked for vac leaks, and reset carb, from the start...
I had a small black that someone degreed the cam incorrectly in, the car was restored well and just ran dog slow and timing it made no difference, just worse and worse, needed the idle set way to high to be smooth and was laggy. I ended up just swapping the cam/lifters because I had no card and didn't feel like doing the research for $120 set. Motor was perfect after..

 

[440roadrunner]

I think I would have marked tdc, set timing, checked compression, checked for vac leaks, and reset carb, from the start...
I had a small black that someone degreed the cam incorrectly in, the car was restored well and just ran dog slow and timing it made no difference, just worse and worse, needed the idle set way to high to be smooth and was laggy. I ended up just swapping the cam/lifters because I had no card and didn't feel like doing the research for $120 set. Motor was perfect after..

.............And I intended to mention the cam. You can check the cam degree without tearing much of the engine down, and since an intake is so easy to pull on a B/RB even easier than a SB

 

[moparedtn]

Great little tool. You might only use it once but what the heck, car guys love specialty tools.

View attachment 278933

Pretty slick. I was going to just use a gutted spark plug with a bolt run down through the middle, pretty much same thing?

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I think I would have marked tdc, set timing, checked compression, checked for vac leaks, and reset carb, from the start...
I had a small black that someone degreed the cam incorrectly in, the car was restored well and just ran dog slow and timing it made no difference, just worse and worse, needed the idle set way to high to be smooth and was laggy. I ended up just swapping the cam/lifters because I had no card and didn't feel like doing the research for $120 set. Motor was perfect after..

I've pretty much done all of that already, short of actually finding TDC mechanically.
The car idles well and drives quite normally until you get it up over 4k, then the stuttering and splattering begins, more severely the more load (read:higher gears) you go.
Does not want ANY static advance at all, whether initial or vacuum. The more you retard it towards TDC, the happier it gets - but again, that's an indicated TDC.
Two different (and new/rebuilt) distributors, two different new ECU's, Holley 750vacsec new out of the box jetted up to 75'son the primaries.
Good vacuum at idle, too - around 11hg.

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What's the relationship between the timing mark on the crank sprocket vs. actual TDC? When the timing marks on the crank and cam sprockets are perfectly lined up with each other, should the motor be at actual TDC?

 

[dieseldazzle]

Your cool could very well be wired backwards you can use a lead pencil and split the arch and see which way it travels if you don't have a voltmeter

 

[monaco66coupe]

I would find tdc by putting your finger in the hole and wait for the compression stroke. compare that to the timing mark to check the mark and compare. Then set the rotor on #1. Ignore the timing mark. See if it starts and Idles/Runs better. I also use a vacuum
gauge to see consistency. I put a new comp cam in my 340, designed for the modern fuel. Originally the engine had to be TDC by the book. With the new cam, 15 degrees became the new TDC. It wouldn't run at 0 degrees. Now it purrs like a Kitten. @15 advanced.

 

[moparedtn]

What's the relationship between the timing mark on the crank sprocket vs. actual TDC? When the timing marks on the crank and cam sprockets are perfectly lined up with each other, should the motor be at actual TDC?

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I would find tdc by putting your finger in the hole and wait for the compression stroke. compare that to the timing mark to check the mark and compare. Then set the rotor on #1. Ignore the timing mark. See if it starts and Idles/Runs better. I also use a vacuum
gauge to see consistency. I put a new comp cam in my 340, designed for the modern fuel. Originally the engine had to be TDC by the book. With the new cam, 15 degrees became the new TDC. It wouldn't run at 0 degrees. Now it purrs like a Kitten. @15 advanced.

Again, it starts and idles just fine. Quite nicely, in fact.
I've never seen even a stock 440 that didn't like a little more initial timing than stock 5*BTDC; I usually crank 'em up until I get detonation under load, then ease them back off a few degrees.
This engine has never detonated at ANY setting that I can hear, but it stutters all over the place over 4k under load, moreso with each gear as you go up through them.
Just really weird behavior and it's done this with two different cams, the first of which was a fairly hairy one (509 purpleshaft) and with the current new Comp Cams 270 duration mild one.
Replacing new distributor with another new, orange box ECU with store-bought one, new plug wires, new plugs, carb spotless and using jets from 72-76, new Carter hemi fuel pump, etc. - nothing seems to matter.

 

[sebring+]

For what it's worth... I had a 66 mustang that had the same problem. Run perfect until
Higher rpm under load. This was a while back, 10 yrs. I didn't have any timing troubles.
FINALLY, after checking and replacing several things and removing carb jets for the second time I found that one of the jets had a very small brass flake stuck inside. I could only see it with a loupe. Cleaned it out with a piece of wire. Been running like a champ since.

 

[miller]

What's the relationship between the timing mark on the crank sprocket vs. actual TDC? When the timing marks on the crank and cam sprockets are perfectly lined up with each other, should the motor be at actual TDC?

Yes...but it's just the initial set-up. Dot to dot sets #6 at TDC compression stroke, and #1 at TDC exhaust stroke. Just timing up cam lobes, with crank throws.
For actual timing, crank has to be rotated until timing mark comes back around, to put #1 on TDC compression, where ignition timing itself is set.

Something I came across on mine, using new chain and gears, all done with a degree wheel...I'm pretty sure the three marks on the gear was swapped around. Lined them up, but ignored the particular marks, going off the degree wheel.

Just sounds like you need to re-check things, to make sure you have what you have. Suppose you've checked for spark advance?

 

[moparedtn]

Yes...but it's just the initial set-up. Dot to dot sets #6 at TDC compression stroke, and #1 at TDC exhaust stroke. Just timing up cam lobes, with crank throws.
For actual timing, crank has to be rotated until timing mark comes back around, to put #1 on TDC compression, where ignition timing itself is set.

Something I came across on mine, using new chain and gears, all done with a degree wheel...I'm pretty sure the three marks on the gear was swapped around. Lined them up, but ignored the particular marks, going off the degree wheel.

Just sounds like you need to re-check things, to make sure you have what you have. Suppose you've checked for spark advance?

1. Thanks, that's very helpful. When I installed the cam, I noticed the balancer (keyed, of course) went back on the end of the crank with timing mark dead on TDC (because I hadn't moved anything during reassembly) with the alignment marks on the cam and crank sprockets lined up.
Made sense at the time and was reassuring.

Therefore, when I re-installed the distributor drive gear/oil pump drive, I made sure to have the slot facing front/back along the engine axis - and the distributor went right in pointing directly at #1 terminal as a result.
Again, made sense and was reassuring...

So, if timing marks are right on cam/crank AND balancer timing mark landed right on TDC when installed AND distributor landed right on #1 terminal when installed...
would everything be in the right place, more or less?
Certainly within fine adjustment range?

2. Yes, the timing advances when I goose the throttle.

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Your cool could very well be wired backwards you can use a lead pencil and split the arch and see which way it travels if you don't have a voltmeter

I want to "publicly" thank DD here for all his help, both in the forums and in private. He's going way out of his way to try and help me.

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I don't remember if you mentioned it before, but could the harmonic balancer have spun?

Could be, but it was a pretty snug interference fit on the keyway when I installed it. Key could have snapped, I suppose...