Projects Mild custom '51 Pontiac Chieftain

Was just a thought!

 

And a most valid thought, too. Gen-yoo-wine Eye-talian tune up!

I gave the car a run today at speed but all that did was seemingly loosen up my points because it's now got a misfire. I'll pop the lid on it tomorrow, clean and reset them.

 

102 miles so far today. Getting an intermittent misfire which is ignition related because the tach jumps. Disconnected tach, problem persists.

Funny really. It's driving better now, before I was being too gentle on it during shakedown.

Next on the to-do is diff oil seals...

 

Well, woud'cha know it.

Recall I've been occasionally moaning about intermittent ignition problems?

I found the problem.




Ignition switch.

 

Yup. That's the way it goes.

Devin

 

So did you switch the switch?

 

No, but I did repair it.


The terminals were burned and dirty.

The slider was not great either.

Zealous application of cleaning and polishing compounds led to a suitable contact surface again.

A little bit of dielectric grease to help prevent it going bad again.

Now, no matter where in the arc that is "on", the switch provides good contact.

Hopefully that'll make it run better for a while yet.

Phil

 

Just went on a test run to the store and back.

Better. Now to readjust the timing and dwell because I was messing about with that to try see what was what.

 

Sixteen thou', check.
Check again.


I think the distributor might need to come apart again. Something isn't quite right.

Phil

 

Just think about how many thousands of times that thing must have been turned in its lifetime!

 

If you average a trip to 20 miles, close to 6000 times.
Sadly that's not the original key switch, but it's got a fair bit of wear to it, you can see the groove.

 

Just thinking, probably could do with checking the timing chain and gears.

Might be that causing the timing to suck.

 

A lot of ignition switch wear is caused by keyrings that contain every key the driver owns! Those switches were not designed to resist the gravity of 2.5 pounds of keys!

 

Yeah, I have a pleather keyfob and 3 keys on it. About design spec.

 

I have a separate fob with the keys for each car I own for this very reason.

 

I have gone in the direction opposite to HAMB's general thesis.

I have added a second muffler. A second 24" cherry bomb in series.

Makes a fair bit of difference- reason being was the single one was headache-inducing drone at 55. So, now the bass note remains but it's less like a low flying aircraft.

I can deal with that.

 

That much added restriction will probably add about 1.5 seconds to your 0-60 time.... from 26 seconds to 27.5 seconds....LOL! Actually makes sense.... some of the BOP's of that era had a drone that would either put you to sleep or turn you into a raving maniac.

 

They're both straight through mufflers (the $27 off the shelf one at AutoZone), so not a real amount of restriction. The exhaust is larger diameter than stock so that should make up for it.

 

Doesn't sound too bad, admittedly. Still got that flathead note.

 

Now you can hear the radio!

 

Had a near breakdown today, the car started to spit and buck and cut out.
It's been acting weird for a while but not bad enough to worry about. My gut feeling was something flashing over inside the distributor cap.
The tach was flicking, which is usually indicative of a low tension issue, but overall that didn't really follow the stutter.
Coupled with that, if I bypassed the coil ballast resistor, the symptoms got a lot worse (the HV is increased so more likely to find a fault).
So, to check, I dragged my scope outside.

Connected up a 10:1 probe to the CB side of the coil and started to eyeball the traces.

Quite a lot look like this- the trigger is not on a specific cylinder so which one is good and which is a fault- unknown. But, that's a reasonable spark trace, a HV spike, a slight oscillation then a nice spark discharge curve then it mostly blows out cleanly and then the coil rings as it extinguishes. Wire/plug resistance is a touch high on that one but it fired ok.

This one, however, shows the spark starts then tracks out partway through and ends in a spike then the wiggly line of the coil ringing.

A useful online resource has this.

Yup, rotor cap insulation is breaking down. New cap time.

Phil

 

Looks like you have a few more devices to use than most
Nice work figuring it out

 

It's just an old 1970's HP oscilloscope. You can pick them up fairly cheaply. Same idea as one function of the tv screen in one of the old SUN testers.

 

It sure sounded GR8 going out fo & into the driveway. !st upshift sounded good too. I sure like that car

 

That was 1-3, gearbox was getting hung up again.
When the new cap comes in and its running right I'll film it working properly because we've got some cold weather right now and in the cold it shifts smooth as butter.

 

Now you only have to learn finnish..
Good luck, you are on right track.i have a specially automotive oscilloscope and like you see, very good instructions how to find fault in points ignition.

 

Very useful to understand!


Today, I replaced the distributor cap and rotor arm. That got rid of the stuttering. I replaced the plugs also and the smooth has returned.

 

Phil
What plugs are you using now?
Greg

 

Autolite 291