I took my TBird out for a drive today and got on it pretty good.  It was running great.  On the way back to the house it started missing.  I thought it was running out of gas.  I made it back over 5 miles and the gas gauge is reading 1/4 full. It idles fine, but has an erratic miss when you put a load on it.  I checked the valve lash and everything is perfect and working.  I pulled all the plugs and they are light brown as they should be.  I see nothing wrong with this engine.

My 292 has a stock 1957 distributor and a 4 barrel Holley Carb.  My 57 distributor is the ball bearing type with the straight vacuum advance arm. The vacuum advance is new.  The distributor has a Pertronix One unit in place of points and condenser. I use a Craftsman timing light, the kind with the manual advance dial on the end.  With the distributor vacuum line disconnected and the timing light set at 10 degrees, the TDC mark is right on the pointer.    With the timing light set to 36 degrees and the motor reved to 4,000 RPM the centrifugal advance looks perfect. If I connect the distributor vacuum advance back up, the total advance looks to be off the charts.  Is this right?  If not, can I run the distributor with the vacuum advance disconnected?

I haven't found the issue with the erractic miss yet. I may have bad fuel.

You can run it without the Vacuum Advance. No Idea why the Timing would be so far off with the Vacuum Can Active. Maybe Someone else has an Idea.Does the problem go away with the Vacuum disconnected?

  

I'll try it with the distributor vacuum line disconnected.  The miss did not show up until today. It happened right I ran it up to 5,000 rpm.   I checked all the pushrods (tubular) and they are OK. The valve adjustment if perfect.  The plugs are not fouled.  All the wires are new and connected. The engine idles perfect.  I'll put some new gas in it tomorrow and see what happens.  I think I may have kicked some dirt loose in the tank.

I disconnected the vacuum line to the distributor and the timing is like it should be.  I has 10 degrees on the crank with about 36 degrees total.  The engine idles perfectly. I backed it out of the garage and it still misses starting about 2,000 with a load.   I put a vacuum gauge on it and it has about 14 inches at idle.  The engine has an Isky RPM 300 camshaft.  When you rev the engine the vacuum drops a little then runs up to 22 pounds and hold steady.  I'll try some new gas and see what happens.  I don't think the engine was a mechanical problem.  It sounds like an electrical problem to me. Can a Pertronix unit cause an erratic miss? I would think it would work or it wouldn't.

If you rev up the engine with the vacuum advance connected and check with a light, it will be "off the charts", mostly because there is no load on the engine in neutral. Vacuum advance is strictly load-based. Still, you might be surprised to learn that in stock form most V8 run 45° to 50° BTDC in steady level part throttle cruise conditions on the highway. Not a cause for concern. At least it indicates the vacuum diaphragm doesn't appear to leaking down. This is something to check.

No condenser is used with Ignitor 1

I'm thinking I have a bad Pertronix unit.  It feels like an electrical miss.  I'm going to switch back to points before I get into anything major.  If that doesn't fix it, I'll run a compression test on the motor and go from there.  I have the vacuum advance disconnected for now.

Or cap / rotor, plug wires.


Lawrenceville, GA

Try running the engine at night in a dark garage and check for a light show.

Does your car happen to be equipped with an o/d transmission? I have seen instances where the overdrive kick down circuit would damage the Pertronix when the coil was grounded by the kick down switch. You got the right idea putting the points back in.