Dumb Corvair Engine Trouble

I've started having a problem with my 1964 Corvair convertible.  It's a pretty stock engine, flat 6, twin carb.  4 speed manual.  The engine starts up fine and drives OK when cold, but as it warms up it gradually runs worse.  The "worse" here means, it starts bucking and popping, hesitating badly at anything off-idle, but at WOT as the revs go up it sort-of smooths out.  The  longer it runs the worse it gets.  Last night I came home and even at idle, it seemed to be misfiring or something.  It sort of sounds like the ignition is breaking up, maybe.  Stuff I've done:

I had both carbs off last week, cleaned them out, adjusted the floats, etc.  Fuel filters (those little sintered metal things in the carbs) were clean, no debris.  Put everything back together, carbs are reasonably well-synched- made zero change in the problem. 

The ignition is a Perktronics that's been in the car as long as I've had it (13 years now) and has a perktronics flame thrower coil.  I changed the coil out to a used Bosche coil I had- no change in the problem. 

Put new plugs (gapped properly), wires, cap, rotor.  No change to the problem.

Las night when I got home I checked the voltage to the coil- it was around 10-11 volts at idle, but when I revved the engine in neutral it dropped to like 7.  Not sure if this is normal.  With the engine off and the key on it reads 13.5V. 

When I pull the vacuum line off the distributor at ide, the RPMs drop a bit.  I can see the vacuum dealy on the distributor working when I connect/ disconnect the hose.  It also pulls more at high vacuum - like, a steady state rev with the car in neutral.  So the vacuum advance is working.

I'm stumped.  I feel like it's a misfire or ignition breaking up or something.  Could the Perktronics be slowly dying?  I hate to drop $$$ on a new Perktronics and I don't have any points to try out.  The car was running fine when I put it away last winter, it's started doing this just this year when I started driving it. 

Thinking out loud... 

I don't think the voltage should drop with RPM. That would indicate increasing resistance, a failing wire.  If it drops on all circuits, then the alternator or main wiring to the alternator and battery is suspect. If it only drops on a specific circuit, in this case ignition, then the wiring to the specific device is suspect. Do the headlights dim when you increase RPM? That will be a pretty good indicator that the ignition components are not to blame as you are having a system wide voltage drop. I would check other circuits and see if the voltage is dropping over the system. 

In reply to tester (Forum Supporter) :

Generator, but yes, I think you may be on to something.  Generator was recently (past 2-3 years) rebuilt, by a local shop, and seems to be charging.  I was thinking maybe jump a wire from the battery to the coil and see if the situation improves. 

Just put a voltage tester from the big wire on the alternator to negative and rev the engine to test it.  Even if the generator is bad, the battery should certainly hold the voltage up for a while though.  If not, it would be dead when you stopped.

Pertronics have been known to fail, so that is a possibility.  They used to be very reliable, but at some point they changed something, and that affected reliability (I don't know exactly when that was)

Certainly try a re-wire for the Pertronics.  I would also check grounds.  Do you have the large ground strap that goes to the motor?  Corvair drivetrains are pretty well isolated and need to be grounded to the body (late cars use four smaller ground straps).

If you are looking for a nice upgrade, and you don't mind a less than stock look (especially if your distributor is worn) I just put a Stinger ignition distributor in my car.  It's a bit pricey, but everything is in the distributor, and it's very adjustable (it does include a vacuum advance).

In reply to aircooled :

Gen seems to be fine, battery has been getting charged and the amp light on the dash stays off.  Turn signals, brake lights, radio, horn, headlights, and starter all work as they should.  Engine cranks nice and fast.  If it is electrical, it's probably somewhere isolated in the ignition circuit.  Engine is well-grounded.

I figured if the Pertronics failed, it would be an all or nothing deal, but perhaps its breaking up slowly as it gets hot.  I know coils sometimes fail that way. 

The stinger dizzy looks neat, but seems to require an additioal external box (MSD or something).  I think I'll troubleshoot what's there and see where it leads me.  I'll keep y'all updated.  

Las night when I got home I checked the voltage to the coil- it was around 10-11 volts at idle, but when I revved the engine in neutral it dropped to like 7.  Not sure if this is normal. 

That can't be normal....  7 volts at the positive side of the coil with the engine revving.  That can't be good.  

Since I wrote that I realize that there is a resistance wire to the coil, but 7 volts while revving engine does not sound good.

The coil isn't hooked to the resistance wire, he said he was getting 12v at idle.  I have never run a Pertronics so I don't know their failure modes, but it seems to be at least a good candidate.  Searching on Pertronics failures might bring up some useful info.

The stinger does not require an external box, its all internal.  It can run a box if you want and has the hookup for that.  With a 2 carb motor, you just drop it in and time it (a 140 requires changing the advance curve).  The only minor issue is clearing secondary linkage (which you don't have) and making sure it clears the shroud (it's very tight, but mine didn't require anything).

I ran Seth's (the guy who developed the Stinger distributor) HEI system for many years, so I trust his work (he actually worked with a vendor to convert an existing one).  He also makes some excellent ignition wire sets.

If the voltage at the coil is dropping with increased electrical demand, what does this tell us?  

Not enough amperage.  

What powers the coil?

Shall we run a jumper from B + to coil + and see whether the problem goes away?  

I like how this discussion is heading.  I didn't get out tot he garage today (doing a bunch of other stuff, none of it car-related) but I'll try jumping the wire from the B+ and see what that gets us. 

aircooled said:

The coil isn't hooked to the resistance wire, he said he was getting 12v at idle.  I have never run a Pertronics so I don't know their failure modes, but it seems to be at least a good candidate.  Searching on Pertronics failures might bring up some useful info.

The stinger does not require an external box, its all internal.  It can run a box if you want and has the hookup for that.  With a 2 carb motor, you just drop it in and time it (a 140 requires changing the advance curve).  The only minor issue is clearing secondary linkage (which you don't have) and making sure it clears the shroud (it's very tight, but mine didn't require anything).

I ran Seth's (the guy who developed the Stinger distributor) HEI system for many years, so I trust his work (he actually worked with a vendor to convert an existing one).  He also makes some excellent ignition wire sets.

Correction, I was getting 10-11 volts at idle.  13.5V with the engine off.  Something's wonky. 

If there is no load on the circuit, as in when the points are open, the coil will have battery voltage at both terminals.  Points closed, it will be lower.  

Yesterday it was fairly warm, so I did some further testing. 

• Confirmed that at idle, volts at the battery was 14.1, and did not change when revving. 
• Voltage at generator was 15.5 at idle (who says generators don't charge at idle!)
• Voltage at coil was 12.5 or so at idle, dropped to 9.5 when revving (approximately 2500 RPM)
• Connected jumper wire from battery to coil, got 14V at coil, did not drop when revving.
• Disconnected wire to coil, leaving jumper (so engine kept running), measured 12.5V at the supply wire, which did not change when revving (since there was now no load on it)

I shut the car off and disconnected the ignition switch plug, and ohmed out the line from the switch to the coil.  It was about 4 ohms, so there's resistance there somewhere.  From the switch to the plug in the engine compartment in back was about 0.5 ohms, but from the plug tot he coil was 3.5 ohms.  There's no ballast resistor in this circuit.  So the problem is from the connector back.  Last night I cut the wire at the connector and added a new connnection to the coil.  Te switch is still disconnected, so I need to put all that back together, but hopefully this fixes that issue. 

OK, silly question:  You aren't using the stock ignition (coil) power wire right? 

As you are likely aware, the Corvair does not use a ballast resistor, the power wire to the coil is a resistor wire.  I have no idea if it behaves as you describe (I would think the high voltage at idle would fry points).  Anyway, like I say, probably a silly question.

Another thing to check is the main harness connector to the engine compartment (left front of engine where the throttle linkage comes in).  Those are WELL known for getting corroded and causing electron flow issues.  I think the main power supply wire (thick red wire?) is the one that normally has issues (a common fix is to bypass the connector, you should just be able clean up the pins though), but I am sure others could to.

In reply to aircooled :

Not silly, because that's exactly how it was set up.  The previous owner had installed this Pertronics unit, and just used the stock ignition power wire.  But, it did work for 13+ years.  Odd that just now it would be causing a problem...

Yes, that main harness connector looks plenty tired.  I cleaned it once a few years back, but it could stand it again, probably, and a light coating of dielectric grease.

volvoclearinghouse said:

In reply to aircooled :

...I figured if the Pertronics failed, it would be an all or nothing deal, but perhaps its breaking up slowly as it gets hot...

In my experience they mostly fail with weird drivability issues.  Just like you're experiencing. 

I haven't ever measured it but I suspect your voltage drop when the engine is revved is normal.  You're measuring voltage between two resistors.  The resistor wire and the coil.  The module pulls the - side of the coil to ground to allow current to flow through the coil building the magnetic field in the coil and then releases the - side causing current to stop flowing, the magnetic field to collapse and the coil to fire.  When there's no current flowing the voltage measured anywhere along the circuit is going to be supply voltage.  When current is flowing the voltage will be dependent on whatever the resistance of the primary side of the coil is and the resistance wire.  With a typical 1 ohm primary the voltage will be 4/5 of the supply voltage. So, with a 12v supply 9.6 volts.

Here's where it gets interesting, or frustrating.  You're measuring the voltage with a DC voltmeter.  Great tool for steady voltages but you're not looking at a steady voltage.  You're looking at one that's constantly changing and you're going to get whatever voltage the meter integrates the value to and that value is going to change with the frequency of the voltage change which is dictated by RPM and the higher the frequency the lower the value the meter is going to read.  The only way to really see what's going on is to use an oscilloscope. 

Alternatively you could just replace the Pertronix which is what I suspect the problem is.

In reply to APEowner :

I understand what you're writing (V=IR, right?  ), the odd thing is that running a direct line to the battery from the coil fixed the sagging voltage issue.  Perhaps because I reduced one 'R' (the one in the resistor wire).  The Pertronics coil the car has is a 1.5 ohm primary.  I checked it, off the car, and it does read 1.5 ohms. 

I do have a 'scope...and I love looking at pretty waves.  It might give clues as to the health of the Pertronics, too...but since the wire likely always had that resistance, the problem likely isn't fixed, though that needed to be done anyway, it sounds like.  I'll try a new Pertronics unit next. 

volvoclearinghouse said:

In reply to APEowner :

I understand what you're writing (V=IR, right?  ), the odd thing is that running a direct line to the battery from the coil fixed the sagging voltage issue.  Perhaps because I reduced one 'R' (the one in the resistor wire).  The Pertronics coil the car has is a 1.5 ohm primary.  I checked it, off the car, and it does read 1.5 ohms. 

I do have a 'scope...and I love looking at pretty waves.  It might give clues as to the health of the Pertronics, too...but since the wire likely always had that resistance, the problem likely isn't fixed, though that needed to be done anyway, it sounds like.  I'll try a new Pertronics unit next. 

You are correct.  Removing the resistance wire reduces one of the R values to near zero so for all practical purposes there's no longer a voltage divider and the voltage at the coil will no longer measurably change.  At least not when measured with a DC volt meter.

Some Pertronics coils (and I think some modules) are designed to be used with a resistor and some are designed to be used without.  You need to check on what setup you have.

Sadly, I've had terrible luck with Pertronics in the last 10 years or so.  So bad that I've actually got an old set of points in my Formula Ford right now because the module I put in acted up after 20 minutes of running and the backup was bad right out of the box.  My recommendation is to carry a known good spare.

A 1964 Corvair still has a generator, right?  The reduced voltage when the engine is revved makes me wonder if it needs to be polarized:  https://starautoelectric.com/instruction-for-polarizing-generator/

Sounds like it had a generator swapped in.  My 64 had a generator in it for a few years.  It had a little oil hole in it to lube the bearing. Kind of weird since it was the only thing in the car that needed oiling (I guess you could oil the hinges).  I think you were supposed to oil it ever oil change.

The generator makes plenty of voltage.  I'd polarized it when I installed it.  This is a '64, so it had a generator originally.  The one in it now is the original; I'd had it overhauled a few years ago.  As I said, the battery voltage is 14.1, and it's charging.  And, as aircooled said, it does have the little oil holes in it- one at each bearing.  I give it a few drops of 10W-30 every few months. 

I think APEowner is probably on the correct track here with the Pertronics issue.  I've had good luck with them, I run one in my Volvo 122 as well.  And if the one in the Corvair lasted 13+ years...well, I'd say that's pretty decent service.

The Stinger dizzy is intriguing to me, I may research that more.  The website did confuse me, it sounded like it required a separate box (MSD, etc) but aircooled says it does not.  My distributor does have some play to it, not wobble, but the shaft will spin a degree or so either way before the drive gear engages.  The mechanical advance seems good, though, and vacuum does work.  At ~2500 RPM it's "all in" with about 34 degrees of total advance. 

I checked Pertronix website, and they do state to use the stock resistor wire with the Ignitor unit.  So, that was fine.  The Ignitor II states it can be used either with or without, so since I've already modified the circuit, I ordered an Ignitor II replacement.  Should be here in a few days, will update once installed.  I'm also thinking I may relocate the coil to the rear vertical support, to get it off the engine and away from the heat.  The coil is already a 1.5 ohm Pertronix coil, which is fine for the Ignitor II, it seems. 

Here is a shot of my installation. I replaced my distributor because it was pretty worn and the timing would wander a bit. You can see the supplied connector below the distributor, and the wires running to the coil.  The unconnected gray wire is the signal wire you can use with an external ignition box.  You can also see how tight it is with the secondary linkage (yes, it moves freely after I offset the mount and bent the arm a bit).

The only part I was concerned with with the installation was initial timing.  I had no way of knowing where the timing would be, but got super luck and had it right around 10 deg when it dropped in!  There is very little room to rotate the distributor, so there is not lot of range in how it will fit in anyway.

The one weird, but highly appreciated, affect it had was to drop my idle.  Because I run four primary carbs, and it idles on all four, getting the idle low enough is very tough.  Not sure why it did that.  Maybe a more steady spark?