440 6-Pack misfire... Driving me crazy!

[440-6pack]

Hi Austa,

All the symptoms would indicate a head gasket but my compression and leak down tests are good...any thoughts?

 

[440-6pack]

And.. I did a coolant pressure test and held 12 psi.

 

[Cudakiller70]

Could it be water pump cavation ?
Could it be detonation?
You did say you changed the distributor did you watch it advance all the way up? And down?
What about vacuum advance, do you have it hooked up? Maybe try it diconnected?
Is your gas good?

 

[440-6pack]

New water pump, less than 50 miles on it. Old one was fine...

I rebuilt the distributor recently after trying one original and one new aftermarket. No change but timing curve is good and I have 12* initial, 36* full mech and 52* with vacuum advance. I have tried disconnecting vacuum advance. No change.

I have 91 octane ethanol free Vpower gas from shell.

 

[Cudakiller70]

Confident mechanical advance is not sticking?
Boiling or detonation? Can you post a video of symptoms?
What was temp when boiling?
If you have headers and a temp gun shoot each pipe for temperature

 

[440-6pack]

Hey Cuda killer,

Thanks for your advice. Yes, I carefully checked all parts and lubed with oil. Very smooth operation.

I believe it is boiling, it only happens when I shut the engine off after it is at full operating temp 185F. If I keep the key in run mode after I shut it down the temp gauge goes above the max. I assume that is normal as there is nothing circulating coolant.

I don’t know what detonation is..?

I don’t have headers but I have a temp gun.

I have a video at idle but not driving at WOT when it cuts in and out. The tach drops a several hundred rpm when it cuts in and out...

 

[AUSTA]

Try starting from cold & put the heat gun at each cylinder exhaust that motor sure is shaking.
How does it sound with a slow rev holding at 2,000 is it still shaking still thinking lifter or valve train it is normal for the temp to rise on shut off (heat Soak) must have a 180 stat

 

[brian6pac]

Is the rad holding pressure ? when it's hot try and squeeze the upper rad hose it should be hard if not the cap is bad and that will let it boil.

 

[DetMatt1]

My god that thing is quieter than my Imperial!
Anyway I’m thinking lifters too. I just had to replace my new lifters after less than 1k miles. I was having performance issues since the complete rebuild and it took me quite some time to figure out. Do you feel like it’s noisy under the hood? If so is it noisier when hot? I ended up pulling the valve covers and plugs and checking half the rockers(don’t ask me which ones right now) with the engine at tdc on #1 and the other half at tdc on #6. I found several were very loose when they shouldn’t have been. My first thought was wiped cam lobes but my oil was pretty clean so I pulled the intake, removed and inspected all the valvetrain parts and put in a new set of lifters(not Comp Cams) and my issues that were similar to yours, not exact but similar, went away and it runs finally like the new engine that it is.

 

[440-6pack]

Hey guys,

Yes, the motor shakes a lot on start up but only after 3-4 seconds. It shakes at all RPM’s.

What will the temperature readings of the exhaust manifold reveal?

I’ll feel the rad hose tonight after it’s warmed up.

 

[AUSTA]

Temp reading should indicate temp balance on each cylinder although may not work as well on cat manifolds
Could also be broken valve spring
are you saying the engine runs smooth at startup then starts to shake after a few seconds
When you rev the engine & it goes back to idle does it shake automatically or run smooth then shake

 

[440-6pack]

It only run smooth for a few seconds on start up. Then rough idle and rough throughout all rpm ranges ... runs rough again when it goes back to idle.

I had the passenger side valve cover off. No broken springs and all rockers moved the correct range of motion. I haven’t checked the driver’s side yet...

 

[Cudakiller70]

Engine running rough all rpms is after burnout and timing chain change?

 

[440-6pack]

Rough idle after burnout. I changed the timing chain after the burn out. It was idling rough before and after timing chain was changed.

 

[Cudakiller70]

Was your old chain stretched and/or could you tell if it jumped a tooth? Lined up timing marks correctly? To check for bent pushrods sometimes you need to pull them and roll on a flat surface.

 

[440-6pack]

The timing chain was a bit loose/stretched. It did not skip. I lined up new chain and sprockets 6&12 o’clock with cylinder 6 at TDC.

I’m thinking I’ll have to pull heads, rods and lifters...sounds like the source of the problem.

 

[DetMatt1]

May not need to pull the heads, one thing at a time.

 

[AUSTA]

Hey guys,

Yes, the motor shakes a lot on start up but only after 3-4 seconds. It shakes at all RPM’s.

What will the temperature readings of the exhaust manifold reveal?

I’ll feel the rad hose tonight after it’s warmed up.

Is the oil pressure coming up with RPM i notice it is at 1/4 but that is probably about right at 1,000 rpm just thinking if the pressure was low it may not be pumping the lifters up

 

[440-6pack]

Oil pressure goes up to 3/4 while cruising, it climbs very slowly...

 

[Cudakiller70]

Distributor pick up coil check.
Connect an ohmmeter to the pigtail leads of the distributor, should be 150-900 ohms.
Also connect one lead from the ohmmeter to ground and the other to either of the pigtail leads. If meter shows a reading the pick-up coil is bad