1970 Bus - Engine Issues

[hambone]

Hello,
this is a '70 Bus with a brand new 1600 d/p installed.
Here's the symptoms: it runs absolutely great for about 4 mins and then starts missing and coughing. #3 is suddenly dead.

Adjusted the valves, set timing, adjusted carb, replaced cap and rotor and coil. Ran like a top with tons of smooth compression, then starts suddenly missing/running rough.

It is running an 009 with Pertronix. For kicks I checked dwell, and it's pegged at 70 deg. "Bad Pertronix" I think. I installed a good vacuum only distributor, but when I tried to set the timing statically, the timing light doesn't act right. It stays lit for 1/4 revolution of the crank pulley (normally, when the points open and close the light goes on and off). This also happens with the electronic ignition 009. The engine would not run at all with the vacuum distributor.

I am thinking something is wired incorrectly. There is a homeboy rig starter switch on the dash - and it does start the engine. I have never encountered this issue before and could use some advice! I had to leave the poor guy hanging.

[Amskeptic]

Hello,
this is a '70 Bus with a brand new 1600 d/p installed.
Here's the symptoms: it runs absolutely great for about 4 mins and then starts missing and coughing. #3 is suddenly dead.

Adjusted the valves, set timing, adjusted carb, replaced cap and rotor and coil. Ran like a top with tons of smooth compression, then starts suddenly missing/running rough.

It is running an 009 with Pertronix. For kicks I checked dwell, and it's pegged at 70 deg. "Bad Pertronix" I think. I installed a good vacuum only distributor, but when I tried to set the timing statically, the timing light doesn't act right. It stays lit for 1/4 revolution of the crank pulley (normally, when the points open and close the light goes on and off). This also happens with the electronic ignition 009. The engine would not run at all with the vacuum distributor.

I am thinking something is wired incorrectly. There is a homeboy rig starter switch on the dash - and it does start the engine. I have never encountered this issue before and could use some advice! I had to leave the poor guy hanging.

Bobbobbob,

Do not use a vacuum-only distributor on a dual port!
Any carburetor that fits on a dual port manifold does NOT have the correct vacuum signal for a vacuum-only distributor!

You did not tell us what carburetor is supplied on this engine!
Please go back to the Pertronix (make sure that the pick-up is gapped away from the trigger)
and do a spark test during cranking and let us know if you have a spark!

Bobbobbob . . .
Colin!

[SlowLane]

I checked dwell, and it's pegged at 70 deg. "Bad Pertronix" I think.

Not necessarily. I recently learned that my Crane XR-700, which has worked flawlessly for the last 14 years, sets the dwell at 71 degrees. The stock coil has never complained about it.

It stays lit for 1/4 revolution of the crank pulley

90 degrees of crank rotation equals 45 degrees of distributor rotation. I don't think there's a problem there.

This also happens with the electronic ignition 009.

That's inconsistent with the 70 degrees dwell it was giving you. Can you or he just install points and condenser in the 009 and take the Pertronix out of the equation?

The fact that it runs like a champ for a short time and then dies suggests a fuel issue to me, but ignition gremlins need to be sorted out and eliminated first.

[hambone]

Carb is a 30/31 pict Brosol with that offset plate, so the vacuum only dist. should get the right signature, no?

We pulled off a working 009 from his Bug, that wouldn't work on the Bus. When I time statically, after turning the pulley CW (awaiting that little light bulb), I then back off on the crank pulley CCW to adjust the distributor, and the light goes off. With today's funky engine, the light stays on for a much greater degree of pulley turning. I was unable to statically time correctly and I've done it a million times. It was not behaving normally.

Why would #3 suddenly lose power? Fuel wouldn't account for that. Why would it run like a top then suddenly take a dump?
This one has me stumped. The bus is not with me, I helped the guy for a couple of hours but that was it. Way out in Skamania! 45 mins from Portland in the Columbia River Gorge.

The carb could be having issues too. Lawd.

[SlowLane]

When I time statically, after turning the pulley CW (awaiting that little light bulb), I then back off on the crank pulley CCW to adjust the distributor, and the light goes off. With today's funky engine, the light stays on for a much greater degree of pulley turning. I was unable to statically time correctly and I've done it a million times. It was not behaving normally.

Let me see if I got this straight:
You start the static timing with the light off. Points are closed (or Pertronix is between magnets).
You rotate the crank CW until the light goes on, then you stop.
You then rotate the crank CCW, and it takes a full quarter-turn of the crank for the light to go out again?

That sounds like a mechanical issue in the crank-to-distributor drive-line. Like way too much backlash in the mesh between the crank gear and distributor drive gear. Did he have the spring between the distributor and drive gear? Distributor fully seated in the case? Were you able to observe the action of the distributor shaft as you rotated the crank back and forth?

Puzzling.

[bus71]

Pertronix needs to be timed while running with a timing light. There is no "dwell" in the conventional sense. There is a pulse to the coil which determines the spark. Set it at 28degrees at about 3k rpm or 7.5 btdc at idle. Check for a bad plug on #3, and remove wire ends and look for corrosion between resister and wire. I have been fooled by bad brand new plugs, yes they were Bosch. Hope this helps. Good luck!
p.s listen for pinging and retard timing if needed.

[hambone]

I just talked with the guy: #3 plug had a broken ceramic nib. And apparently the coil/distributor connection wasn't good. He replaced all the wires, and last I heard it's running. I'll bet something was wired to the coil incorrectly.
All I can say is "WHAT-evah". Hurried troubleshooting SUCKS.