The Stovebolt Site Forums The Shop Area Engine Shop 216 Stuck valves and a bonus?

I hope you are all enjoying getting outside and smelling like old truck again. I sure am.

Here are the latest symptoms.

Engine starts and has a lumpy bumpy idle.
I ran a compression test.

1-5 at or near 95psi
6 perhaps 10psi. Hard to read that low.

Tried adding oil through the sparkplug hole.
No change to #6 compression.

Stuck / burnt valve(s) right?

Next test.

Engine at Idle. Just for grins I pulled the plug wire off of #6. No real change. No surprises there.

Plug wire off of #5 - Motor lags
#4 engine lags
#3 NO CHANGE?
#2 NO CHANGE?
#1 engine lags

Checked plugs

#6 black/sooty (rich)
#5 rich
#4 rich
#3 clean as a whistle
#2 clean like #3
#1 rich

What the heck is going on? Why does this thing run at all?

What should be my next step?


-Joel

Remove the valve cover and look at the valve train with engine running.

I don't know if a valve stuck wide open would strike the piston or not. I can tell you that a valve stuck closed will bend a pushrod (don't ask me how I found that out ). The head is actually pretty easy to remove. You will need to get some help to lift the boat anchor off of the block. From there you can check the valves, pistons and cylinders.

As for certain cylinders running rich I would suspect the plug wires, cap, rotor, or plugs themselves. Unless there is a blockage in the intake manifold, the gas distribution between the cylinders should be relatively equal. Good luck.

you state 1-5 have comp of around 100lbs,,6,at 10 lbs,,then state 3 cyl,s working and 3 not so here we go,1 check intake manifold bolts 2 check plugs and wires and cap also point cam in dist 3 remove VC and see if cam is flat,push rods off or bent,broken valve springs,rocker *** condition,,4 if nothing found remove rocker *** and inject shop air in each cyl note where air escapes...doc

Since you have two adjacent cylinders that have good compression and aren't working the most obvious problem may be wires crossed. That could also account for the clean plugs, they get washed with gas but never get lit!

As for the low comp on 6, it could be a burned or stuck valve or a badly damaged piston/ring assembly. My money is on a valve. As someone else pointed out , air in the spark plug hole with both valves closed will tell you quickly. Air leak heard from the carb= intake valve, From the tailpipe=exhaust. With the valve cover removed you can see if the valve is seating.

Two crossed wires!?!

Wouldn't THAT be the coolest fix. I'll give it a shot. Can't hurt.

As always, you guys are the best.

-Joel

Don't you love it when the simple fix is the right one?

Swapped the two plug wires and it smoothed right out. Thanks!

I was thinking that the old 216 was REALLY underpowered for something this big. I guess I shouldn't judge the poor old thing based on 3 functioning cyls. *grin*

Amazing it ran at all.

Thanks again 'bolters.

-Joel