The Stovebolt Site Forums The Shop Area Engine Shop firing on 5 cylinders

I am looking for help on what to check on my 235 1960 6. I noticed it hasn't been running as strong and didn't sound smooth. So set the timing and points.running better but not normal. Starting pulling spark plug wires of to hear the difference started in the back firewall and came forward got to the second one engine didn;t sound different. Pulled the plug it was black and crusty, so I put a new plug still no difference the plug wire has strong spark. the first plug was burning normal. Any help would be appreciated.

Maybe it’s not the spark plug
The cam shaft may have worn its lobe too flat to open the valve
Or maybe it’s a rocker issue under the valve cover
Given what you tried already I would suggest looking at the valves next to see if they are opening
Could also be one is stuck open too
-s

Thank you I had a feeling that is where I would be heading next. I will check those out tomorrow.

Good morning I took the valve cover of and all the lifters are working perfectly. They are all very quiet, with engine turned off I felt them and none of them had any play in them at all, is it possible that on that cylinder the valve are to tight. The spark plug wire has spark to the plug yet when pulled of still no change in idle engine sounds the same. would lossening the valves on that cylinder make a difference. Thanks

I would do a compression check. That will give you the information you need to diagnose the problem. A leak down test is also very useful after the compression check.

Hi Mike,
Possibly...with a 1960 235 you could have hydraulic or solid lifters. Do you know which you have? This sounds valve related. You could rotate the distributor until the rotor tip points to the wire connection spot for the cylinder in question (number 5? it sounds like) and check to see what your valves are doing there. If you're seeing the lifters push up the rocker arms and seeing the valves open/close, that's worth knowing. Once around 1980 I had a valve spring break down low...just messed the spring up enough that it no longer was doing its job but the engine was still running (except for that cylinder). Grab the valve springs for that cylinder and try to move them by hand. If one wobbles, then there's the problem. Also if you have a way to send compressed air into that cylinder, get the piston at top dead center (look for the spot where the rotor will point to the place where that wire connects to the distributor), push air into it and listen at the exhaust pipe and carburetor throat. You can tell which valve isn't doing right by that approach. Please let us know.

Sorry 55 first series...I was typing as you were posting...

Before I even did the compression test or messed with valve adjustment, I think I would try to eliminate the possibility of a spark issue.

If you have one of those little inline spark testers, they work great. Inspect the inside of the cap and make sure that contact looks exactly like the others. If that checks out Ok, see about the plug wire. Visually inspect it. You could also they swapping the wire from the misfiring cylinder to a different cylinder. See if the misfire follows the wire.

You probably want to start with some low hanging fruit. Install a new wire for that plug and a new cap and rotor. See what that does. And yes, I am with the others, do a compression test.

Just got out my guages and tried to adjust the valves I started with intake .006 and at low idle tried all of them, I couldn't even slide it in to adjust any of them. I had a 1954 235 blue flame and would adjust it this way worked perfect. I even tried the exhaust and couldn't get it to slide in. ? does that mean they are hydraulic lifters. I will check compression and the springs on that cylinder. thank yo for the insight. I will also switch out wire. I did pull the end cover back and had a good spark all the way to the plug just put new points roter and cap a couple months ago.

A quick way to identify a hydraulic lifter is to stop the engine with the valves fully closed on any cylinder- - - - -doesn't matter which one- - - -and apply a firm pressure on the pushrod side of either rocker arm with a big screwdriver or a pry bar- - - -like you're trying to force the pushrod back into the lifter. A couple of minutes of firm (but not excessive) pressure will cause the lifter to collapse and a gap of 1/8" or so will appear at the valve stem side of the rocker arm. It will disappear as the engine fires up again- - - - -with maybe a minute or so of rattle as the lifter re-establishes its normal preload.
Jerry

In a previous thread I think your engine was determined to come from a car with AT, so it has hydraulic lifters.
Engine ID Thread

Compression check idea sounds like a good plan.

okay thank you Jerry.

Any wisdom of why I couldn't get my .006 guage in any of the lifters even the exhaust?

mike -- Hydraulic lifters run at zero clearance all the time. They don't force the valve open unless they're on the raised area of the cam lobe as the shaft turns. At 2500 RPM each valve is lifting and closing 21 times a second- - - -no time for the slight leakage built into the hydraulic lifter to have any effect on the operation of the engine!
Jerry

I definitlely have hydraulic lifters. 110-112 psi on all the cylinders except the one not fifing it has 0 ugh and it runs so good on 5 it is a amazing engine. now what?

Find out why. Hole in the piston, rings completely worn out or broken, or valves not closing all the way.

A borescope would be useful to see the top of the piston.

Blow compressed air into the cylinder. If you hear air coming out the exhaust pipe you have a exhaust valve stuck open. Air out the carburetor is a stuck open intake valve. Pressure build up in the radiator means a blown head gasket.

Thanks Otto I will round up a borescope and take a look. I don't have any water in my oil as to have a blown head gasket. If one of my valves is stuck open what's the fix?
Pull rocker assembly off and pound on them lightly lol

One could be bent. Do the air test on the compression stroke when both valves should be closed completely.

If a hydraulic lifter is adjusted too tight, it will prevent a valve from closing, causing a dead cylinder.
You need to adjust all of your valves now anyway. Might as well start with that. It may solve your problem.

The cylinder leak down test only works properly with both valves closed (distributor rotor pointing at the plug wire for the cylinder youre testing, brakes set and/or wheels chocked both directions), and air pressure introduced into the cylinder with an air line quick connect fitting made from an old spark plug shell. Air out of the carburetor- - - -bent, stuck, or burned intake valve. Air from the tailpipe- - - -bent, stuck or burned exhaust valve. Bubbles in the radiator- - - -cracked head, cracked cylinder wall, or blown head gasket. Air from the oil filler cap- - - -hole in a piston and/or broken piston rings. Very low or zero pressure means a valve job, or an engine overhaul is coming soon. Sticky valves seldom cause a total compression loss, just lower compression on the affected cylinder(s). Good call on the tight valve adjustment!- - - -that's a definite possibility. Good luck!
Jerry

You can have a blown head gasket without getting water in the oil. It can be blown to an outside edge or an oil drain. Bringing the dead cylinder up to TDC on the compression stroke. Then fill the cylinder with compressed air. As stated earlier, listen for air flow from the tail pipe, carburetor, valve cover and radiator with the cap removed. You should hear air escaping from one or more of the areas. At the tail pipe is an exhaust valve. At the carburetor it is an intake valve. At the valve cover it is a head gasket leaking into an oil drain. At the radiator it is a head gasket leaking into a water jacket. If it is leaking to an outside edge you should hear it on either side of the block. Good luck on your diagnosing.

You could have an exhaust valve that looks like this.

Good afternoon Well did as directed and I have air at the carburetor and exhaust none at radiator or head gasket. I backed off on intake and exhaust valves to free them up still the same, changed out spark plug wire still the both wires are new and good.

I am going to run the valves lose for awhile and see what happens have to pull lawnmower trailer today to cut grass maybe it will free up it runs good on the 5 cylinders. thanks for any suggestions

1) While applying the air, the engine was at a position where both of that cylinder’s valves SHOULD have been closed, correct?

2) I don’t know if you ever shared. Which cylinder # we talking about?

3) If rotating the engine by hand, do the valves on the offending cylinder SEEM to move up and down the same distance as the other cylinders? (That’s not a great test, by any means. But it might tell us something if there’s a really obvious difference)

Was the distributor rotor pointing toward the low cylinder's spark plug wire during the air pressure test? If so, and you were getting air from both intake and exhaust, something's WAY wrong- - - -bite the bullet and pull the cylinder head. Back both rocker arm adjustments off so there's a BIG gap between the rocker tip and the valve stem- - - -like 1/4" or more, and repeat the air test. If you get intake or exhaust leaks that way, pull the cylinder head and do a visual inspection.
Jerry

Yes the valves were closed springs were all the way up and the cylinder is number 2 and they look the same as the others when moving I'm 70 but still se half way decent lol
I took the valve cover off and i backed off the adjustment screw so there was about 1/8 inch clearence

The answer on the rotor button is no it was pointing at number 1 on rotor cap. eg the rotor is pointing to 5" O"clock where number 1 plug is on distributor cap instead of 7" O"clock where number 2 is on distributor cap. When I bring number 1 up to TDC the rotor is pointing to number 1 at front of engine.

If the “bad” cylinder is #2, but the rotor was pointed at #1 when you did the air test….something is wrong.

Need to back up, put #1 TDC on compression stroke, and perhaps redo your firing order as 153624 clockwise around the cap.

Repeat the air test with #2 pointing at #2 and both valves closed.

Sorry for my misunderstanding I just did a new post that explains what I meant

Thank you bill and yes i could but I get air in both the intake and exhaust Getting a borescope next

I'm still confused. Was the rotor button pointing at #2 plug wire when #2 piston was at TDC compression stroke and you detected air coming out all over the place?

Number 1 plug wire on the distributor

But #2 is the one that has zero compression, right?

Are you going to do the test again with #2 at TDC compression stroke when the valves are supposed to be closed?

As moderator of this forum, I’m going to clear up the confusion in the last few posts and get this thread back on track.

If you backed off both rockers to get a 1/8” gap, you can assume that both intake/exhaust valves are closed. It’s time to remove the head and do a visual inspection as Jerry suggested several posts ago.

Mike- - - -"you've got mail"- - - -click on the flashing envelope at the top right of the page and read the private message I just sent you.
Jerry

Any update on this issue?
Todd

Leaky exhaust valve - - - -Mike confirmed it during our phone call. Time for a valve job!
Jerry

Thank you so much Jerry. And yes it is time to rebuild the head