Dropped distributor in at TDC. Fired it up, broke in the cam.

Could not get a "baseline" timing setup where it would start and run properly. If I advanced it, it ran fantastic, but wouldn't start properly. If I retarded it, it would start well, but run like garbage.

There is no "sweet spot" where everything starts, runs and idles properly until I can myself to a timing light.

Everything is hooked back up the way I'd had it. I'm lost.

Thank you

 

Looks like your vacuum advance is set up pointed just a little left of pointing straight at the radiator, which is where I'd start.

Maybe a few tweaks to the carb is what you need until you get the timing light?

 

W/O timing light::: Put engine on TDC on compression stroke. Check to see if Harmonic balancer is on TDC. Move engine to timing mark you want to use 10 Degrees???? Take dist. cap off and look at Reluctor wheel, turn dist till the wheel lines up with the pickup center. LINE UP THE TEETH! If my recollection is correct. being off 1/2 tooth on wheel is @ 7 Degrees. Timing should be right on the degree you want unless balancer has slipped.

 

Forget the timing light for now, get it running good then check it. if you can't find a sweet spot something is wrong and a light won't help.

I would start be rechecking your firing order and looking for obvious vacuum leaks. also check the voltage to the coil , weak spark can cause these symptoms.

 

It's always a good idea to verify that the balancer ring hasn't slipped or marks are innaccurate. Use a piston stop tool.

At TDC #1 piston on compression the pointer should align exactly with "0" mark, the piston stop is used to make two marks on the damper after rolling the engine over by hand in both directions. Exactly halfway between those marks is the true TDC, regardless of what the timing marks might indicate. Defective dampers are pretty common and cause all sorts of headscratching. Maybe you know all this stuff already, don't take it the wrong way.

If you know the balancer marks are accurate, it's time for some more diagnostics. Disconnect and plug the vacuum advance port and set the base level ignition timing to 12° BTDC. Then run it up and see that the mechanical advance moves smoothly without sticking to around 34° or 36° BTDC. Also that it moves smoothly back down to base timing. 36° total mechanical advance is right in where you want to be for about every OHV V8 ever made. Rotate the the distributor as required to achieve this, let the initial fall where it may. The initial timing isn't really that critical.

If it has trouble starting at 12° or so, then there is probably an issue with high resistance cables, or a bum starter, especially when hot. The timing numbers suggested are just general guidelines and are dependent on actual compression ratio and fuel quality. But give the engine what it wants, not what somebody says it should want. Verifying the timing marks is important, because everything timing related is based on TDC.

Take it for a test drive and try some full throttle acceleration. Try advancing 1 or 2 degrees at a time. When you get it running good, then re-connect the vacuum advance. These are adjustable. The goal here is different, to prevent ping or engine knock at part throttle, or engine knock at a steady level cruise, though still just as much timing as it will take just short of knock or ping. Make no adjustment at this point to base distributor ignition timing, only to the vacuum canister itself.

If you get really picky you'll maybe want to limit the mechanical advance slot internal to the distributor, install lighter springs etc. What you're doing here overall is basically customizing the timing "curve" to YOUR engine. Pain in the *** but you'll thank yourself every time you drive it.

 

That's fine but if you can't find a place it runs half decent you need to fix that before you do much tuning. you should always be able to find a spot it runs nice no matter what the marks say.

Hopefully it's something easy to correct because there are some not so easy possibilities also. start with the easy.

 

Well tuning is as much verifying proper operation as anything. Maybe the mechanical advance is stuck, or a weight spring broke, or ... who knows. I don't know his skill or experience level. There is a lot more to ignition timing than just setting the initial. Sorry for the novel! Ha ha.

 

Yes there is, but if you can't make it run decent no matter where the distributor is then fine tuning isn't an issue. a spring, vac advance or anything related can be compensated for by moving the distributor. fix the problem then do a tune up.

 

Your Concern Has Been:

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Are there mechanical weights in a Duraspark distributor?

Anyway, what the posts above mine say is all true.

It would be nice to have another truck with the same engine, and then swap your carb and ignition onto it and see how it responds.

Check your vacuum advance servo. Make sure it holds vacuum, and that it moves when vacuum is applied. Make sure it's fastened down to the dizzy nice and tight. That servo is almost certainly adjustable using a small allen wrench through the vacuum port. More fine-tunin' you can do.
And I can see where the advance vacuum line connects on the carb, next to the PCV hose, and it looks like it isn't much lower than the PCV port. You want the lowest vacuum port on the carb to source true ported vacuum - unless you're wanting to use manifold vacuum.

There are at least a couple of tuning strategies you can use with the vacuum advance adjustments, but you need to find out if there is a mechanical advance in that dizzy, and then ensure that it is working up to OEM snuff. You can also fine-tune with different centrifugal advance flyweights.


If I was going to rebuild a still-running engine, I would do the carb and distributor first, before the engine is pulled and disassembled, and then get them dialed in on the engine so that you know they will be really close after the rebuild.
It's like getting everything electrical working on a vehicle before you take it apart for restoration, so that you'll know when the problem arose if something doesn't work upon reassembly.


You're not using platinum spark plugs are you? You can check the coil with an ohm meter, and I would also check to be sure that enough fuel is being delivered, even if it's probably not the problem.

 

Yes, mechanical weights and springs just like previous points distributors. So many of the same tweaking strategies are still valid. As are some of the same diagnosing strategies, looking for stuck or loose weights, worn pins, broken springs, etc.

Paul