Engine misfiring att WOT

[Don C]

When you can't adjust the idle mixture you either have plugged passages in your carburetor or you have to have the idle speed screw turned in too far, so the throttle blades are into the transition area and not in the idle area, or both. Try getting the idle set as low as you can and then adjust the idle mixture screws, starting at about 1-1/2 turns out. What's the best vacuum reading you can get? Does the idle speed increase when you advance the timing? If so, get the idle speed up some before you try adjusting the mixture screws and idle speed. I would also disconnect the vacuum advance until you get it running right.

 

[Odmark]

I will try again tomorrow!

The best vacuum reading i have ever gotten is about 16-17 ins/hg at idle.

Man this car is just falling apart, first the problem with the high rpm misfire, and that is gone now, but now it runs like shit when its cold.

And today, the temp gauge stopped working, brake warning light came on, rear diff (That i bought a while back, 3.50 gears open diff) starts to lock and sounds like a rock crusher from time to time etc.

I think i have a real life Christine on my hands, better call of this trade deal and maybe this piece of junk will fix itself (dreams)

 

[Odmark]

I am 90% sure that i have a blown head gasket, the smoke coming from the valve cover turns out to be exhaust fumes. The oil has now started to blacken as well and reeks of exhaust.

Tonight i will start tearing the top end of the engine apart. And pull the rear end.

 

[Odmark]

Today i performed a compression test (turns out my tester is a pop off gauge) and got the following results, Dry and cold engine sadly:

1. 168 PSI

2. 160 PSI

3. 165 PSI

4. 160 PSI

5.165 PSI

6. 160 PSI

7.175 PSI

8. 190 PSI

When testing cylinder number 8 and 9 it sounded really wierd when it cranked.

Anyway intake and valve covers off, everything seems to be moving as it should. Tearing heads off tomorrow.

 

[c9zx]

That 9th cylinder may be a problem . Sorry, I just couldn't stop myself. Chuck

 

[Odmark]

That 9th cylinder may be a problem . Sorry, I just couldn't stop myself. Chuck

Hahahaha damn it!!  :shootself: lollerz

I forgive you, i would have done the same thing 

Of course i mean 7 and 8, i do not have a 9 cylinder cleveland  :whistling:

 

[Odmark]

Small update.

All the lifters/rockers are moving the same amount. I now have the intake off and the number 7 cylinder intake port (the one with 175 PSI) seems to generate a lot more suction then the others, also this one is the one sounding wierd (Also number 8, but not to the same extent).

Its hard to describe the sound, but like filling up a metal tank with compressed air, and then a pop.

Its obvious something is wrong in the top end (Dont know what can cause this in the bottom end except for carbon buildup on the piston, but that feels unlikely), so i will remove at least the drivers side head tonight.

 

[Don C]

Was there any oil in the intake ports or intake manifold?

 

[Odmark]

Was there any oil in the intake ports or intake manifold?

No, not really. Nothing visible at least. I will double check, im going out to remove the head now.

 

[Odmark]

So, no oil in the intake ports what so ever.

Pulled the drivers side head now. No blown head gasket, cylinders and pistons look good, combustion chambers look good etc.

The only thing is that the valves have almost 1MM of play in the guides  :whistling: Dont know how this really can affect the compression though, that is very very odd.

And can valve guide affect performance so much that it could have caused my problems?

Anyways the heads are probably junk...

 

[Odmark]

So i have reassembled the engine. Compression checks out this time, about 165PSI on all 8.

Engine fires right up, idles beautifully, vacuum higher and much more stable then before.

But i still have pressure in the crankcase. Not a lot but still enough to blow the smoke out in small "puffs".

And also if i floor the gas pedal the car just instantly dies... I Believe its somehow running super rich because there is black smoke coming from the exhausts and it smells terrible.

Also i replaced my old cork valve cover gaskets with rubber ones, wich i hate because they always leak for me. And guess what, they leak and drenched my drivers side header in oil  :shootself:

 

[Don C]

Did you have the heads rebuilt and new guides installed?

I agree the carburetor may be the problem.

Did you use an adhesive gasket sealer to stick the gaskets to the valve covers, to keep them from moving around during installation and tightening? Did you torque them to specs, and not over-tighten?

 

[Odmark]

Did you have the heads rebuilt and new guides installed?

I agree the carburetor may be the problem.

Did you use an adhesive gasket sealer to stick the gaskets to the valve covers, to keep them from moving around during installation and tightening? Did you torque them to specs, and not over-tighten?

No i didnt have the money right now, i bought a set of used heads in better condition so i can rebuild my old ones when i have the $$.

No adhesive, but maybe its a good idea to tighten all the valve cover bolts  :angel:  :shootself:  no more leak, haha!

 

[Don C]

They probably have the umbrella style valve seals and you're still getting some blow-by on the exhaust valve stems.

 

[Odmark]

They probably have the umbrella style valve seals and you're still getting some blow-by on the exhaust valve stems.

It also puffs from the dipstick tube if i remove the stick. Could the blow by from valve stems really be so great that it causes pressure down in the crankcase to blow up the tube?

 

[73pony]

They probably have the umbrella style valve seals and you're still getting some blow-by on the exhaust valve stems.

It also puffs from the dipstick tube if i remove the stick. Could the blow by from valve stems really be so great that it causes pressure down in the crankcase to blow up the tube?

It could be. Did you give a close inspection of the valve seals on the new/used heads you picked up? Would have been something I prob would have replaced on them prior to install as it isn't a tough job and not expensive for parts. 

Also is your PCV system operating properly? Correct PCV valve? Hooked up correctly? From what you are describing you may have a few issues going on.

 

[Odmark]

They probably have the umbrella style valve seals and you're still getting some blow-by on the exhaust valve stems.

It also puffs from the dipstick tube if i remove the stick. Could the blow by from valve stems really be so great that it causes pressure down in the crankcase to blow up the tube?

It could be. Did you give a close inspection of the valve seals on the new/used heads you picked up? Would have been something I prob would have replaced on them prior to install as it isn't a tough job and not expensive for parts. 

Also is your PCV system operating properly? Correct PCV valve? Hooked up correctly? From what you are describing you may have a few issues going on.

Oh i forgot to mention i replaced all the valve seals with new ones.

I have this exact valve : 

And its installed on the passenger side valve cover, and connected to the PCV port on the front of my edelbrock carb.

The drivers side valve cover has a breather cap.

When i remove the pcv valve with the engine running it seems to have good vacuum.

 

[Don C]

Are the valve stem seals the umbrella style? If so, they aren't really a seal, they are just a splash shield. It doesn't take much valve guide wear for the exhaust gases to blow into the heads and then the crankcase. With your compression readings you shouldn't be getting much ring blow-by. What does your spark plugs look like now?

 

[Odmark]

Are the valve stem seals the umbrella style? If so, they aren't really a seal, they are just a splash shield. It doesn't take much valve guide wear for the exhaust gases to blow into the heads and then the crankcase. With your compression readings you shouldn't be getting much ring blow-by. What does your spark plugs look like now?

Yes they are the standard umbrella type seals.

I pulled some plugs today, sadly i just got three of them out before my kid woke up and i had to go inside the house. But the three i removed were soaked in fuel.

 

[Odmark]

Could this be "ring wash"?

A friend of mine from work has a 1961 Volvo 544 and he had similar issues just a couple of days ago, his carb drenched the engine in fuel, he got a lot of crankcase pressure. Replaced the carb with another unit and all problems were gone.