Warm engine misses

[Bo Dillingham]

After years of trouble-free driving, my '65 has suddenly started to "miss" terribly. When I start it up, it seems fine, but as I get about a mile down the road, it starts to miss, and if I come to a stop it will die if I don't keep giving it some gas. I just put in a new set of plugs and drove it around the block, and got the same results (I thought that the problem had gone away when I started it up with the new plugs, so I went around the block and bingo, same problem.) Before I change the points, rotor, cap, wires,or anything else for that matter, I thought I should seek advice here, as it's been years since I have been under the hood of a car.

When driving along, it seems to "miss" frequently, and when I have to stop (for a light, a stop sign, etc) it almost stalls unless I give it some gas. On one occasion, it died, but fortunately it started up again.

Could this possibly be a fuel problem?

Oh! Also, when I put a timing light on it, it seems to be set for one tooth above the hole in the timing "Reference pointer".

Thanks in advance,

BoDill

 

[Mac]

I was going to suggest rotor cap and/or points but I see you're already thinking about that. If thing else, visual inspection for scorching...

Perhaps before removing the rotor cap, lift the hood and leave the engine running on a dark night to see if there's any escaping spark.

What makes you think of fuel? Does it act like it's running lean? When was the last time you changed the fuel filters?

Mac

 

[Tom Bryant]

Check that the choke is opening fully after it's warm. Is it putting out any black smoke when it misses?

Tom

 

[Vettehead Mikey]

Oh! Also, when I put a timing light on it, it seems to be set for one tooth above the hole in the timing "Reference pointer".

Thanks in advance,

BoDill

Check the points. The above indicates that the dwell is off.

 

[Bo Dillingham]

Tom, Mac, and all,

I haven't had a chance to do the "Dark of night" test yet, but I just pulled the distributor cap to check the points. Much my surprise, I found that the points had been replaced by a PERTRONIX module! Sincerely, I had never heard of this (as I said, its been years since I was under a hood!). I just wrote to the PerTronix company (with pertinent part numbers) and asked them for the correct troubleshooting sheets, which they have on-line. I have no idea when I might hear back from them.

Now, there is no black smoke that I can see, and there is no backfire. The spark plugs that I just replaced all looked good, and a new fuel filter didn't help either. The choke, which is manual, functions well, as it has for all these 15 years that I have had the car.

Within the last half hour (around 11:30 EST), I started the car, and if I let the RPM drop below about 1000, it will slow way down and stall. Please keep in mind that I have been driving this car in the summers for 15 years with absolutely no problems, and there had been no diminished performance before it suddenly started "Missing". Quite honestly, I don't think it was missing at all the last time I had it out; it just started missing suddenly a couple days ago, and it started shortly after I started the car.

Any advice is welcome......

BoDill

 

[Vettehead Mikey]

Tom, Mac, and all,

I haven't had a chance to do the "Dark of night" test yet, but I just pulled the distributor cap to check the points. Much my surprise, I found that the points had been replaced by a PERTRONIX module! Sincerely, I had never heard of this (as I said, its been years since I was under a hood!). I just wrote to the PerTronix company (with pertinent part numbers) and asked them for the correct troubleshooting sheets, which they have on-line. I have no idea when I might hear back from them.

Look no further then. What you describe sounds like classic module failure. Google pertronix and failure and you'll hundreds of examples.

 

[Bo Dillingham]

To Vettehead Mikey and all,

Thanks. Now, since I have a set of points with the attached condenser sitting in the garage, do you know if it would be OK to just replace the PerTronix with the points? The coil label says, "Flame Thrower, carb E.O. # D-57-10"; is there any known reason why that coil will not work with points?

By the way, an auto parts store near me has coils for my Corvette for about $30. If there is any doubt about the "Flame Thrower", I'd just as soon buy a new coil. Please advise.....

Again, thanks,

BoDill

 

[c5vetter]

Thought - you said you replaced the sparkplugs and then this started, correct? Have you made sure all the plug wires are properly attached, etc.? Just trying to help you recreate where you were before this all started, and then work forward, or in this case backwards......

 

[Bo Dillingham]

To c5vettter,

I apologize if I wasn't clear. The first thing I did when the missing started was replace the plugs, but it didn't solve anything. It is now around 6 PM my time, and I am going to start replacing the PerTronix stuff with standard points, condenser, coil, and lead wire.

When I am finished, I will post my results, though it might not be tonight.
BoDill

 

[Vettehead Mikey]

To Vettehead Mikey and all,

Thanks. Now, since I have a set of points with the attached condenser sitting in the garage, do you know if it would be OK to just replace the PerTronix with the points? The coil label says, "Flame Thrower, carb E.O. # D-57-10"; is there any known reason why that coil will not work with points?

By the way, an auto parts store near me has coils for my Corvette for about $30. If there is any doubt about the "Flame Thrower", I'd just as soon buy a new coil. Please advise.....

Again, thanks,

BoDill

I can't find any details of the coil to know if the primary resistance is similar to a stock coil or not. Since the Flame Thrower coil doesn't really offer much advantage over the stock GM unit, I'd get rid of it.

 

[Tom Bryant]

I assume that the PerTronix requires a direct 12 volt feed like other electronic ignitions. You will need to use a ballast resistor with the points ignition. Yours may still be there. Some guys just move the distributor wire to the hot side of the resistor to bypass it (hot feed and distributor wire on the same post) when converting to electronic instead of splicing wires.

Tom

 

[Vettehead Mikey]

I assume that the PerTronix requires a direct 12 volt feed like other electronic ignitions.

Some do, some don't. Definitely the stock points, condenser and coil need one.

 

[Bo Dillingham]

Replace PerTronix

To all,

So far (three days later) I have not received an answer from PerTronix regarding replacement parts, and with the advice in this forum, I think I'll skip it.

Now, though I'm pretty sure that I am capable of converting the system back to points and plugs, I see several distributors, both stock and with HEI ignition, available on e-bay. Since I'm not going to get the time to work on this for a couple of days, I thought I would ask you about it. Though price is not a major consideration, a stock distributor runs around $400 to $500 while an HEI distributor (from CRT Performance and others) costs less than $200.

Can anyone give me some advice regarding replacing the PerTronix with an HEI as opposed to a stock set-up?

As usual, thanks in advance.

BoDill

 

[Tom Bryant]

One concern would be clearance with the air filter. Your low profile air filter housing may want to occupy the same space as the distributor cap. I had this problem with my stepside when I installed a Mallory HEI. I had a low profile standard 14" aftermarket open element air filter and it just wouldn't clear. I installed a raised base and now have 1/2 inch clearance. But, of course, you don't have that option under a Corvette's low hood. You will need a minimum 2 3/4" measurement from the center of the distributor cap forward to the air cleaner for clearance. Also your stock ignition shielding top will not fit over a HEI cap.

The last used HEI I was going to use was from a friend but had a loose shaft. You never know what you are buying in a used distributor until you have it in your hands. My parts list included housing bushings, shim kit, cap, rotor, coil, module(just to be safe), and a vacuum advance that was right for my engine. The parts list alone exceeded the cost of that new Mallory HEI I bought from Summit.

But even then you can't have your cake and eat it too. Chevrolet HEI distributors don't have tach drive. Zip Products shows a custom HEI with tach drive in their catalog for $199.95 plus another $9.95 for a wiring harness pigtail to plug it in.

My opinion is if your stock distributor is correct for your car except for the Pertronix conversion, why not just restore it to points? Zip also has every part you will need to convert back to points. I'm sure Corvette Central does too.

 

[Tom Bryant]

BTW It looks like Summit has all of the PerTronix parts in stock.

PerTronix Replacement Parts

 

[Vettehead Mikey]

Can anyone give me some advice regarding replacing the PerTronix with an HEI as opposed to a stock set-up?

Either is a heck of a lot more work and money than going back to points using your existing distributor.

 

[Bo Dillingham]

To Tom Bryant,

Thanks for responding.

Now, first, I have a high-rise manifold (if that makes a difference), and a stock hood.

Next, I went to the Summit site with the PerTronix part numbers that I have, and wrote to them asking if they had them or an equivalent (as I didn't see them listed), because I STILL haven't heard from PerTronix.

So, if Summit doesn't have the parts I need, and I become convinced that an HEI distributor won't fit, I will VERY LIKELY look at rebuilt stock distributors on E-bay and elsewhere.

Again, thanks, and any additional wisdom will be appreciated and heeded.

To Vettehead Mikey,

Unfortunately, the breaker plate (the plate that the points mount on) is different, as I bought points before I found out that I had a PerTronix set-up, and they would not fit on the plate. With that said, I have no idea what is going on, and would not mind paying for a good distributor and getting back to basics. I was bit of a "Gearhead" in my youth, and would be happy to wrestle with stuff that I understand.

WAIT A MINUTE!!! I just took another look at the beaker plate, and there are TWO sets of holes that might be used to mount "Points"; The pair of holes that I measured when the regular points wouldn't fit, the ones that the PerTronix module fit, are 2 1/4 inches apart. It appears that there is another hole that the points might mount to which would make the span 2 3/8 inches apart (or so). I am working at home so I won't be able to do much more until tomorrow, but this may be a problem of my own creation. If so, standard points it is, but I'll report back when I have had a chance to confirm. Also, I returned the points to my auto parts store, so I'll have to pick up another set to try for fit, etc.

BoDill

 

[Vettehead Mikey]

WAIT A MINUTE!!! I just took another look at the beaker plate, and there are TWO sets of holes that might be used to mount "Points"; The pair of holes that I measured when the regular points wouldn't fit, the ones that the PerTronix module fit, are 2 1/4 inches apart. It appears that there is another hole that the points might mount to which would make the span 2 3/8 inches apart (or so). I am working at home so I won't be able to do much more until tomorrow, but this may be a problem of my own creation. If so, standard points it is, but I'll report back when I have had a chance to confirm. Also, I returned the points to my auto parts store, so I'll have to pick up another set to try for fit, etc.

BoDill

This would make sense as no alteration to the breaker plate is required when converting to pertronix. If you do find that the stock points don't fit, just buy another petronix unit similar to the one you've got. All three generations I,II, and III are still in production. Yours might be gen I.

 

[Bo Dillingham]

Thanks for your patience,

I have replaced all the PerTronix with stock points, condenser, and coil. For the last couple of days and nights I have been rearranging wires, and repositioning the distributor, because whoever installed the PerTronix unit had the distributor wires arranged with the number one wire where the number four wire belongs, and he had the coil mounted in front of the window that is used for point adjustment. At any rate, now I can't get any of the plugs to fire (I have spent a lot of time trying different things, and got no reaction with a timing light). I have repositioned the distributor rotor a couple of times (because I didn't want to pull a rocker cover to watch the lifter) and done some other useless things. I thought that maybe my timing light didn't work, so I tried a simple circuit tester between a plug wire and the block and got no "Spark" when turning the engine over, so I assume that I am not getting a flow of electricity.

Right now I am completely drained of enthusiasm, and at 70 years old my body aches all over from bending over fenders. I thought I should ask you if there is something I should check, like the solenoid, or should I work my way through the system starting with the distributor wire and working backwards thought the coil, etc, etc.

Maybe you could put me touch with an article about dealing with this sort of problem.

The engine turns over very well, and I have tried changing the gap in the points a few times, but the timing light doesn't get a signal except at the last instant when I release the starter button (yes, I am using a remote start switch).

I can't think of anything else to report, but I am too worn out to try anything else for a day or so. Also, I am trying to find a local guy who knows enough about this stuff to help me.

In the immortal words of Arnold Schwarzenegger, "I'll be back".

Bo Dill

 

[Vettehead Mikey]

There's no reason the engine should not have run with the plug wires in the 'wrong' holes. It might not be factory correct but that doesn't stop it from running, assuming that rotor was moved over accordingly. I guess at this point you have no idea where the rotor is oriented with respect to the rest of the engine.

I'd start back at square one and put the engine on TDC on the compression stroke then orient the rotor to the correct position. Contrary to most GM cars, the C2 Corvette did not have the rotor, #1 cap tower and wire pointing at #1 cyl. See pic, courtesy of John Hinckley.



Check to see if you have 12 VDC at the upstream side of the ballast resistor with the key 'on'.
Check VDC at the downstream side of the resistor with the key 'on'. Might be 8-10 VDC or so.
Check VDC at the + side of the coil both the key 'on' and key at 'start'