Still trying to diagnose #5 dead cylinder and a weak #2 when pulling the wires one by one ('61 283/315). Everything else seems to check ok. I found that the distributor shaft had .049 end play when I put couple feeler gauges in the gap (see photo). Could this be causing the above problem?

 

That won't cause your issues but is typical for a stock distributor. I always shim them to .015 when I rebuild one.

Jim

 

I had the same provlem with
my 61 ended up with a bad wire on #5 did not show up at first.

 

That point cam looks rougher than a night in a county jail. How is the dwell when measure with a meter? Steady?

 

With this Pertronix version it doesn't use the cam.

The instructions state a certain end play for using this version too. If you don't have them I can dig mine up.

 

Pertronix?

 

I forget from your other thread - have you replace the cap and rotor? Sometimes defective plug wires are hard to identify by testing. I had a new set of BB shielded wires that had a bad plug terminal connection that would intermittently short and kill the cylinder. It came down to about the only thing that could be killing the cylinder was the plug wire and after a lot of testing I finally caught it in the shorted out position. New plug wires (again) and everything was fine.

 

If the trigger plate wobbles excessively up/down as it rotates, then that can account for a misfire (wobble causes the trigger plate to "miss" on firing the sensor - in other words, the sensor can not see the trigger plate if it goes past it's range).

The end play of .049 is not excessive for "normal" application, but can be tightened up somewhat. But the real fix is to determine if the trigger plate is wobbling, and then fix that wobble.

As far as end play reduction, depends on if you have an aluminum vs. cast iron dist. housing, and since I assume you have a cast iron housing, it can be reduced to as low as .010" (.015" is fine as 1snake mentioned). But note that end play reduction will not help stabilize the spark (as past rumored). When the engine is running, the dist. gear is always loaded by the oil pump, so the dist. shaft is always forced upward, due to the helix of the gears. When you are aligning the trigger to the sensor, always push the dist. shaft up for adjusting optimum alignment to the sensor.

Adding various thickness thin washers between the trigger plate at the mounting points (at the rotor screws / studs) can sometimes be used to reduce the wobble, and shift the trigger plate for better alignment of the trigger plate to the sensor.

I see from your picture that you have some thin washers there already, but check for wobble and alignment to eliminate that as being a possibility.

Plasticman

 

Dwell is steady. Wires were swapped out on the effected cylinders with no change.

John, I did not install this Pertronix. I know there is a ring with magnets (trigger Plate) a sensor (mounted to the base plate) on the pertronix. I am not sure how or what to align since I have no past experience with Pertronix. Do you have an illustration or more detail how to align the trigger plate and sensor or what it should look like?

 

Best to remove the dist. from the engine, and then with the dist. cap off, rotate the shaft by hand (biasing the shaft upward). Observe the trigger plate's up / down motion in ref. to the sensor. If it wobbles too much, try adding a washer or 2 to lessen the wobble.

While looking at the wobble, also look for alignment of the trigger plate to the sensor (again, when the shaft is pushed upward). If it is too high or low, adjust with the spacer washers.

Your first picture shows the trigger plate with some spacer washers.

See this video for air gap and alignment spacing / adjustment.

http://www.pertronix.com/support/vid...y/default.aspx

Note that the wobble issue (that I have seen) is not mentioned.

Plasticman

 

So, you think when you let off the gas, the oil pump suddenly quits pumping?

 

No. The oil pump pushing oil through the oiling system is always loading the dist. gear (unless you are low on oil). It is always loaded, and therefore the gear will not back off while running. Timing will not change due to end play on the dist. shaft..........

Plasticman

 

If it's always the same cylinder and the plug, cap and plug wire check out OK, the only possible contribution from the Pertronix unit would be a dead magnet in the magnet ring. Re-position the magnet ring 180* and see if it's still the same cylinder.

 

John Z, I did the 180 flip and there was no change. The #5 is still dead.

 

Thanks JB..great video

 

After reading all the above, I'd say that the misfiring has to be caused by one of the following: cap, #5 wire, or spark plug.

Even though a spark plug may fire ok in air, it is possible for it to misfire due to higher voltage requirements at the gap when under compression.

The cap and wire may also leak when stressed to the higher voltage required by a plug under compression.

 

That is likely because you shoved maybe .010 of the distributor shaft up into the top bushing where it wasn't worn and is stabilizing the dwell. Wait'll that little bit wears off and you'll be back where you started from.

 

Sounds very likely to me!

 

My Pertronix is currently hooked up with the red wire going to the hot side of the side of the resister and the black to the negative coil. I have a separate green wire that goes from the positive coil to the low voltage side of the resister. Is this set up for the Pertronix to get a full 12 volts? What is the wire for that goes from the positive coil to the low voltage side of the resister?

How do I wire this back up to put the points back?

 

'Hi you may find this post , with a problem like yours, helpful, the forum helped me, read through all the replies and the fixes

Jack

http://forums.corvetteforum.com/c1-a...my-l-79-a.html