Hard running condition super stumped

[jaywish]

You can check for spark with the timing light or just ground the end of the wire to the engine and hold it in place gently with some vise grips so you don't get shocked. There should be a nice arc and consistent firing.

To check for spark and check each plug at the same time. Remove the plug, reinstall the wire on the plug, gently clamp the plug to a ground. Turn key, you should see a nice strong spark, once every other revolution. Avoid shocking yourself.

[gadget73]

The mechanical advance you can check just by moving the rotor. It should rock back and forth. If the mechanism jammed, you'd probably see the weights shoved out. If they stuck in, you wouldn't have any problems with idle. Honestly even if they were stuck out, I seriously doubt you'd have any real problems with idle. Kinda does sound like a timing chain jump though why it would go from running fine to running like ass just from pulling and re-installing the distributor doesn't really add up either. I have heard of people jumping chains just by cranking over the engine though so maybe its just a bad timing thing. ROcking the crankshaft back and forth while watching the rotor would give an indication about the amount of slop in the chain. If you can move the crank a fair bit, the chain is pretty bad.

[johnunit]

The mechanical advance you can check just by moving the rotor. It should rock back and forth. If the mechanism jammed, you'd probably see the weights shoved out. If they stuck in, you wouldn't have any problems with idle. Honestly even if they were stuck out, I seriously doubt you'd have any real problems with idle. Kinda does sound like a timing chain jump though why it would go from running fine to running like ass just from pulling and re-installing the distributor doesn't really add up either. I have heard of people jumping chains just by cranking over the engine though so maybe its just a bad timing thing. ROcking the crankshaft back and forth while watching the rotor would give an indication about the amount of slop in the chain. If you can move the crank a fair bit, the chain is pretty bad.

It sorta kicked back reallllllllly hard a few times when I had initially stabbed through distributor in the first time and was trying to start it. I had it a tooth off or 180 off or something. Definitely the most violently the engine has stopped in years.

I think that's the most likely next step for me, putting a bar on the crank pulley and seeing how long it takes for the rotor to notice.

[jaywish]

Gadget it has been so darn long since I have had a manual distributor to think about!

That crank hand check is great and will indicate condition of the chain but not if it did indeed jump. I'd say do a good spark and plug check before opening anything up. Along with a firing order check at both ends of the wires. I know I have messed up the order more then once in my life when I was sure it was correct.

[gadget73]

My thinking with the chain slack is that if you can read a fair bit of it, then its a lot more likely that it jumped. If its tight as banjo strings its a lot less liable to have moved. Violent kicks would make me more prone to thinking it could have hopped though. I know the 85 302 cars got the shitty plastic tooth chain, I don't know about the 351. I would not be surprised if they got that same POC, and those are well prone to jumping. What sucks on the 302 is that when they do, it bends valves. Flat top pistons, so things smash. No idea about the 351 pistons, but I could swear I've seen pics of a Vic 351 with fair sized dishes in the middle of the piston. If it cranks like its got compression, you may have dodged a bullet there. The 302's with smashed valves very obviously spin with no resistance.

[johnunit]

Since it's not running and needs things in the same area (balancer and water pump) I'm probably just going to throw a closes double roller chain at it assuming the firing order isn't wrong.

[gadget73]

No chance someone changed the cam to one out of a 302 is there? I ran into that once.

[johnunit]

Nope, only purposeful change to the engine prior to this starting was the distributor repair.

Prior to that, the exact engine as it sits was a decent runner. Daily driven, cruised at 75mph+ for hours at a time, revved to the moon at autocross, etc.

[gadget73]

What I mean is, has it been a 302 cam since before you got it, and you haven't noticed the odd firing order before? Long shot, its just the only other "derp" type thing that comes to mind thats easy and cheap to fix.

[johnunit]

What I mean is, has it been a 302 cam since before you got it, and you haven't noticed the odd firing order before? Long shot, its just the only other "derp" type thing that comes to mind thats easy and cheap to fix.

Nah I've had to redo the plug wires from scratch a few times and always consciously used the 351w/how firing order. I agree it's behaving sorta like that but I'm 100% it was 351w before. I actually think I initially left the wires on the cap.and just pulled the distributor when I did the original repair work.

[87gtVIC]

I cannot help you out with any ideas but I hope you can get it sorted. I also would recommend checking for slack in the chain before outright replacing it.

[johnunit]

Confirmed firing order, pulled the cap, moved the crank bolt with a 1 foot breaker bar.

Got roughly 1 inch of movement on the end of the bar before the rotor moved. There may be other stuff going on but I think you all have helped me track down a big chunk of the problem.

It'll be getting a high quality balancer, comp cams adjustable double roller timing chain, aluminum water pump, and probably some other junk while I'm in there. Big job but at least the oil leaks will reduce seized fastener issues

[DerekTheGreat]

That may be within tolerance. I think EricTheCarGuy has a video on that with his Fairmont. Seven degrees of slop or less is what he said to shoot for IIRC.

[johnunit]

If I had to guess it was at least 20. Definitely more than I expected

[DerekTheGreat]

Oh. Well in that case maybe it has given up the ghost? How many Km/miles?

I believe the way you check it is to set the marker up at 0* and then begin to turn the crankshaft. When you see movement at the rotor, take note of where the marker is. If that's more than 7* it may be about that time.