Technical Chasing a no spark issue

4 outa 6 firing...I'd drive it! Just sayin'.

 

Exhaust valves on 4 and 5.
Not a rocket arm adjustment issue. Taped on valves, no change.
Those do share an exhaust port. Might unbolt the intake/exhaust amd look.

 

Not sure if you mentioned having a borescope. Got this last year for my phone.

https://www.amazon.ca/dp/B0C4V5LWWL/?tag=atomicindus04-20

 

Well Anthony, sounds like it's time to choose the path from here. A gasket isn't going to fix this one from the sound of it. At least some head/valve work. It might just have a couple bent valves (install mistake?) but it might be easier to pull and drop in the other 250 you have just to get it running.
As @anothercarguy says, if it just needs to yard drive, 4 out of six will beat pushing it.

 

Bigger hammer on E4 and 5?

 

Yep. No change.

 

A gasket might.
I’ve got 4 other straight 6 heads.
If this one just needs exhaust valves then thats what it will get.
A couple from one of those heads. hillbilly valve job with grinding compound and a drill

 

Boroscope in the plug hole, light shining up the exhaust manifold? It's postponing the inevitable. Head has to come off if fixing is the plan.
I'd consider freshening one of the other heads while this is still together, then a day's swap. Less down time, less questions about what's needed to repair.

 

Don't forget to hillbilly "surface" the head by moving in circles on a cement floor for several revolutions both clockwise and counter clockwise.

 

HA! might as well use a belt sander with 80 grit on both head and block! That way they 'match'. Leave the grit in to break in the rings!

Question is, how did the ignition system ID the bad cylinders and cut spark?

 

Some pb blaster and more hammer whacks sealed up.
Fired it up. Still has a miss.
But sounds better.

I’ll get back at it later this evening

 

ID em?
Well we had no spark to begin with. Checked voltage to coil. That was good. Voltage to dizzy was good.
Swapped to known good coil.
Then used point and condenser. No new was available that day.
Got 1 and 3 to hit. 2 was sporadic. No 4-6 fired.
Had a know good dizzy. EZ swap with new points and condenser. Ran better. 4-5 no comp.
Now we have at least all the valves closing.
Seems to be hitting on 4 cyls still

 

I was teasing! That's why the crazy emoji.
Modern PCM/ECM stuff can cut fuel and spark to misfiring cylinders.
This had no spark AND 2 no-compression cylinders. How did the no computer ignition know to cut spark? (it didn't).

As for the lube and percussive adjustment, it could be sticking valves or junk on the valve seat holding the 2 exhaust valves open. Might just keep beating on it with a hammer while letting it warm up. Like you and Mart discussed on page 1.

 

Compression now?
If so, the three things; Compression (fixed?) spark (fixed) and fuel. Look for intake leak at gasket or a vacuum port. Also if carb was filled with junk, intake might have suffered too. You'd expect 6 to be poor, too though if it's still 4 and 5 with no power.

 

Rebuilt the carb
Removed intake and blew it out. Blew out the ports. That’s when I PB blasted the valves and smacked em again.
Don’t have any gauge numbers. Still looking for my plug adapter for the gauge.
Did the finger test. 4-5 didn’t blow the finger off.
I did hook up my homemade cyl pressure tool on all cylinders. All were good after the wacking.

 

There you go, fixed with hammer!
I hate to ask, but the homemade leakdown was done with each cylinder at TDC compression? I'm sure you know, but for those following along after, doing it without that step means it can be anywhere in the 4 cycles.

 

When I have done leak down , air would push piston down 180 BTDC.
**** ring & gas port thoe

 

Yep. Happened today.

 

The spark kind of weird ,
also seen plug dead @ a certain rpm.

I do not know how far you are to find issue / cause , Me donot like not finding.
Wonder if fuel issue on those two cylindes @ idle , like going back maybe lifter @ idle ,
The only way I can think to see if lean
Miss fire @ idle
Is O2 / EGT on those two cyl's
Or maybe a Non ethanol fuel like a race gas that would show with shinny plugs to see porcelain.
with gravity feed tank 1/2 - 1 gal just so you donot need to flush / gas mixed to see on plug .
Or be able to spray fuel in intake runner
after carb individually runner .
Testing all just @ idle to see if miss goes away.
Could drill like # 4 or 6 screw size , then tap after test ..

Just asking wasn't there a issue with
the 250 heads like crack in ports ?
I know 292 intake exhaust made together,,,

 

Kinda get the feeling the guy built the engine:/had it built then had issues and walked away
Engine vibrates bad at idle. Smooths out when ya rev it.
No smoke at all.
done for today.
Honestly just messing with this as time provides.
I tell the kids to not just toss parts at it.
But I’m a points and condenser set invested so far.

 

Oh. Forgot to include the original coil was wired backwards

 

The dirt dobbers (or some other small critters) didn't plug up the exhaust manifold on the cylinders with low compression, did they?

Just for kicks, this wouldn't be the first rebuilt motor that got built with all the ring gaps in line with each other. Much lower compression, poor low rpm performance but better at higher RPM, strange motor noises at idle.

 

It looks like you don't have this problem but I lost a lot of hair on one before finding a shorted rotor ****on in the distributor.

 

I'm slightly disappointed, finding a thread about another juicy electrical problem, and then finding out it's a mechanical issue instead. Oh well, good that you are making progress on solving it!

 

Was/is both

 

had a moment to waste on the truck.
Got all 6 firing.
Had an old plug wire arcing against the coil.
At least one fouled plug.
Still have a valve sticking. Intake.
(missed typed earlier. The 2 stuck were intake valves) Thumped it and it closed. So I guess that’s progress. Left the 2cyls sticking a tad loose on rocker asjustment.
Runs smoother and idles better. It ran long enough to discover a half dozen leaks in the radiator
But was able to get it up to temp. Going to let it cool down and recheck the compression.
Think the electrical part is close now.

 

hey-didn't you win your cl*** year in the chrysler traveling mechanic contests back in high school?

 

dont guess so

I was student government president though

anywho. Number 4 intake stopped sticking.
Number 5 just won’t give it up yet.

 

Spent a last week at the beach.
This week I’m helping write certication test questions.
So I got a moment to mess with it today.

homemade cyl pressureizer with a water/contaminant filter for a spray gun.
Exhaust is good now.
The other intake is as well. Number 5 intake needed help.
Some PB and slow turn with the drill. Repeat.

 

That is genius, how much upwards force do you apply.
Dan