Hard running condition super stumped

[johnunit]

The car:
Stock internals and heads 351w with a duraspark, catted exhaust, and holley 4160.

What I've done so far:
Car was running pretty well until a wire broke in the distributor. Pulled distributor to put in a new magnetic pickup and pigtail. Upon putting distributor back in these symptoms started.

Checked firing order.

Checked plug condition

Replaced reluctor, magnetic pickup, duraspark ignition box, and coil (aftermarket pertronix with no resistor wire but it's exactly what I was running before. Also replaced battery and have had to recharge it twice during this process.

Checked all wiring between coil, distributor, and ignition box.

Checked that distributor is not 180 out.

Pulled front fuel bowl and metering block, cleaned, and replaced power valve.

Repeatedly moved around base timing, from way too advanced (idle rpm dropping from too advanced) to clearly too retarded.

Inspected for obvious vacuum leaks


Current symptoms:

I can eventually get it started with the timing waaaaaaaay retarded. Visually the distributor vacuum advance port is pointing dead straight or slightly to the drivers side instead of noticeable to the passengers, where it was at my previous tune before this all started.

Once started it runs like poo. How bad depends on how retarded the timing but if it's retarded enough to start it's retarded enough to idle noticeably poorly and at 500-650 in park.

I can get the idle up to where it was (1050-1100 in park) by adjusting idle while running. I do not know what this is in terms of base/initial timing as the engine dies immediately if you pull the vacuum cannister line. Even if you pinch it first (so it's not the vacuum leak killing it). The engine needs that much advance to run at all. Somewhere between 25 and 40 above base timing.

It will feel fairly smooth at idle even in gear once I get the timing just right, but will not rev up quickly and will pop back and died given load by footbraking/Brake torquing with significant throttle.

Once it dies, it will not restart at the ignition advance where it ran best. It will seem to fight the distributor hard like I have the timing way too advanced, fight it hard enough to almost completely stop the engine turning over. I.have to retard the timing by an obviously extreme degree to get it to start again.


Possible thoughts:
Clogged cat
Massive vacuum leak
Skipped timing chain
Burnt valve?
Demonic possession?
Cat stuck in Flux capacitor?

[jaywish]

Start with the basics.
Bring the mark on the crank to zero and see if the #1 wire is in the correct place. (180 out is ok too.)

If it was a common 302 distributor I would suggest a JY replacement.

Is it easy to pull a RS Valve Cover on that engine? You could check the cam position. But if it is only off a tooth you may not be able to see it anyway.

[Tiggie]

This sounds fun. Definitely sounds timing/spark related.

Do you have a timing light to see where you are and/or what it's doing while running?

Once you've got TDC on 1 compression cycle (I usually just feel for it), check the balancer and mark if needed; then check the distributor to get you in the ballpark. Sounds like you have probably already done this.

Couple random questions. You haven't rotated the distributor cap/wires 180 out have you? Also, is your advance to ported or manifold vacuum? And this is a single advance distributor, not a dual advance/retard, correct?

It's always nice to have a picture too:

[johnunit]

The ring has slipped on the balancer. I previously used a piston stop to mark the correct tdc and added new timing tape but with all this backfiring an stuff I'll have to redo that and check for where the rotor is at tdc. I haven't really used the timing light much since it's so obvious when it's getting better, and I can't pull the vacuum line to check base timing without it dying anyway.

That said, wouldn't it have probably found the correct setting in my experimenting by now? I've gone from way too advanced to way too retarded (backfiring through carb badly and showing less than zero advance with vacuum advance included) in fairly small increments and nowhere did it run right.

[johnunit]

Distributor cap is correct with 1. Wire closer to the back of the engine and slightly to the drivers side.

Distributor has both mechanical advance and vacuum advance, set to manifold vacuum. I believe it is what came in a 76 torino with nothing but advance spring and slot modifications.

[Tiggie]

Your vacuum advance diaphragm isn't blown out is it?

[johnunit]

Your vacuum advance diaphragm isn't blown out is it?

Just went out and confirmed it holds vacuum

[Tiggie]

I am wondering if you switched the vacuum advance to ported vacuum instead. I usually hook my old carb'd stuff up that way. Try to find a happy medium where it will start and idle okay (which I understand might not happen with it right now), then run decent with the ported vacuum advance. Although if you were hooked to manifold vacuum before and it worked well, then this shouldn't be the problem

I am wondering if the advance (mechanical or vacuum) is jammed somehow when you replaced the pickup.

[johnunit]

Just checked and can get the movement I expected by applying vacuum to it. Not sure how often confirm mechanical advance.

[DerekTheGreat]

You said you changed/worked on the distributor... Do you have a buddy with a good one or a known good one in your stash to swap out & test? Sometimes even new replacement items are junk right from the start.

[johnunit]

You said you changed/worked on the distributor... Do you have a buddy with a good one or a known good one in your stash to swap out & test? Sometimes even new replacement items are junk right from the start.

I do not have any access to a spare. I changed the reluctor and magnetic pickup but not the whole distributor.

[jaywish]

Hi,
If the fuel situation is good and you are rotating the distributor that far or even close to that far I am thinking timing chain has skipped. You said it is backfiring, is it also popping back through the carb?

Probably in order of less work, get another distributor first then verify the cam timing.

Like I said pull RS valve cover to see rocker position when you rotate the engine to tdc. Intake & Exhaust should be completely closed well before TDC is reached. Maybe someone knows how many degrees before TDC the intake should be closed? IIRC number 3 valves should also be completely close at #1tdc as they should also be in compression stroke at this point?

[johnunit]

It is backfiring and popping through the carb as well.

[jaywish]

Let me also ask this.

Did you verify consistent and strong spark?

Did you check the firing order at least 3 times at both ends of the wires?

These would be the big two for your symptoms.

[johnunit]

Besides checking plugs (fouled, since cleaned, but consistent cylinder to cylinder) and the timing light I have not checked spark quality. The duraspark module, plug wires, coil, and wiring are all new though so not sure what to check.


I'll check again just because it takes 30 seconds but I've checked firing order repeatedly