Left side idle misfire

[Chrispy]

Evening everybody
I could use some fresh ears on a misfire issue I'm having. I've got a 78 pretty much stock except for a 2 into 1 exhaust someone put on. Still running points and original alternator. It's just on the left side, and when I've got the timing light going (which is often) I've noticed that the light doesn't flash when the side misfires so I've been hunting electric problems to no avail. Let me know if this sounds familiar or if you have follow up on questions. I've had one too many old guys walk up and tell me my engine has a misfire.

 

[motormike]

We'll azoom the points are clean and adjusted... and since it's just the left side.. we can azoom the advance unit is spinning happily.... so, switch plugs side to side... if no change.. switch coils side to side.... if no change this will eliminate those two components. Doesn't sound like a condenser problem.. but they are strange and mysteriously evil buggers.

 

[Jan_P]

Not that easy
I remember the advice I got from a first class shop many yeas ago. 20 years
Points Points Points and then Points.
( clean out and replace so not grounding and that is done even if they look good and of course new spark plugs )

Now the strobe light if that is a good one .and it blinks ..then there is something to work on
But I have seen mine not giving accurate info all the time.
Once I had a cracked hose from intake to petcock sucking in air making a misfire on the left.
A leaking exhaust can make a misfire

But again Points Points Points and then Points.
If this was me I would replace spark plugs ..Remove Points clean up perfectly with solvent and rags
Install new points setup perfectly -- gap and timing
Mostly that will do it --- after that next step
Checking the exhaust bolts is a quick must do ..

 

[Chrispy]

alright update to this. I think I have a death by 1000 cuts situation. I think there are air leaks all over the left side. The exhaust bolting looks different and worse than the right, maybe added to by a carbeuration problem on the left side. maybe added to by weak sparks from old coils. The whole left side is super sooty but the plug is white on the tip so lean idle? Carb boot is definitely leaking on the left, i can see oily residue where its blowing out and it fails the carb cleaner test. And when i pulled the boots off, the valve i can see in there is just coated in soot and carbon. So i think there are leaks from intake to exhaust and i think the valve is probably not sealing right now because of the fuel condition created. which is both a bummer and sort of a relief. But who knows it could be something else entirely.
oh also it isnt ignition because i switched the leads and flipped the cam rod and it was still the left misfiring

 

[Jan_P]

Given the strobe light not blinking all the time
A shift of plugs from right to left could be a simple test
even if Intake leaks are there
I am thinking a leaner mixture with more air --- less soot if leaking intake
but i am no Carburetor expert

 

[Chrispy]

Salutations all,
I fixed the problem. Turns out that a part of the gasket on the enricher circuit on the left carb blew out. Lord knows when. So I made a new gasket and cleaned and synced the carbs and now its running really smooth and strong