Valve Problem - need help as to next steps

[roverdave]

I started to troubleshoot a bad miss on my 67 IIa 2.25 petrol today. The number 1 cylinder (closest to radiator?) was not firing. When I did a compression check on this cylinder I got a zero reading . I popped off the valve cover and noticed right off that a pushrod (2nd valve in from front) had come disconnected from the rocker. The pushrod still was straight so I compressed the valve and reinserted. After setting the gap I checked the compression again and this time got 30 lbs. All other cylinders read at or near 130.

I know this engine was rebuilt less than 5K ago. At that time the head was redone to support unleaded gas. I believe the prior owner did the lower half also. Any ideas as to next steps? Pull the head? Are there other tests to narrow the problem to the valve? Thanks!
Dave

[Moose]

If you have a air compressor on hand here is something you can try. Turn the engine so that both the exhaust and intake valves are both closed on the number 1 cylinder, then remove the spark plug from number one. Blow air into the the spark plug hole. A rag will help seal the hole up around the air nozzle. If air comes out the exhaust pipe, you have a problem with the exhaust valve. Air up the carb and it is the intake valve. And air up the oil filler tube and you have a ring problem.

Another test is to put a bit of oil into the #1 cyl through the spark plug hole, and repeat the compression test on that cyl. The oil is supposed to help seal up the rings. If the compression is still low, then most likely it is a valve problem

Hope this helps.

Brett

[thixon]

Don't rule out a problem with the rocker assembly. Plenty of heads get "rebuilt" and no attention is paid to the ra. You did say a push rod had made its way past the rocker right?

[daveb]

does the valve open and close like the others as you turn the engine over?

I started to troubleshoot a bad miss on my 67 IIa 2.25 petrol today. The number 1 cylinder (closest to radiator?) was not firing. When I did a compression check on this cylinder I got a zero reading . I popped off the valve cover and noticed right off that a pushrod (2nd valve in from front) had come disconnected from the rocker. The pushrod still was straight so I compressed the valve and reinserted. After setting the gap I checked the compression again and this time got 30 lbs. All other cylinders read at or near 130.

I know this engine was rebuilt less than 5K ago. At that time the head was redone to support unleaded gas. I believe the prior owner did the lower half also. Any ideas as to next steps? Pull the head? Are there other tests to narrow the problem to the valve? Thanks!
Dave

[roverdave]

The valve does move up and down when I turned the engine over by hand. And yes, the pushrod did make it out past the rocker. I did try to move the rocker around side to side to check play. It seemed pretty tight. I do have a compressor, so I can try some of the other suggestions tomorrow.

Another question - from the front of the engine (radiator), this is the 2nd valve spring of the 8. Does anyone know if this is the intake or exhaust valve? If a valve is not opening, what other damage could running the engine cause? For instance, if the intake opens and the exhaust doesn't, where does the exhaust go?

Dave

[daveb]

intake. 1,4,5,and 8 are exhaust. just look @ the manifolds.

yes you could be causeing additional damage if there is something in the cylinder. but if the engine does not jam then your chances are good.

was the screw backed off of the rocker? are the rockers on in the correct places? there should be a helpful diagram in the factory service manual.

The valve does move up and down when I turned the engine over by hand. And yes, the pushrod did make it out past the rocker. I did try to move the rocker around side to side to check play. It seemed pretty tight. I do have a compressor, so I can try some of the other suggestions tomorrow.

Another question - from the front of the engine (radiator), this is the 2nd valve spring of the 8. Does anyone know if this is the intake or exhaust valve? If a valve is not opening, what other damage could running the engine cause? For instance, if the intake opens and the exhaust doesn't, where does the exhaust go?

Dave

[Tim Smith]

I guessing that a valve problem could be the issue. Could a weak valve spring cause sluggish reaction (leading to the pushrod disconnect) or maybe something as simple carbon build up jamming the valve for a few revolutions. Oh hang on, it was rebuilt so there shouldn't be much carbon.

Are you getting any oil in the coolant or coolant in the oil? Thinking a bad head gasket could be giving you poor readings.

[Eric W S]

Get a vacuum gauge and hook it up to the engine. It will save you some time and provide a load of useful info.

http://www.gregsengine.com/vacuum.htm

Try that link first then google using a vacuum gauge. Other good sites out there.

Good tool to have as you can time the enine and carb very accurately using the gauge.

EwS

[roverdave]

I did try putting a some oil into the cylinder and still got zero compression. This time I had my wife hit the starter and the compression does spike up but goes right back down to zero. Also, to answer an earlier question, the adjustment screw for the pushrod had not come up. I'll trying blowing some air in later today.

[I Leak Oil]

What's the highest it spiked at? What do you mean it went right back to zero? The gauge went back to zero or it read zero on a second test? Most gauges I've seen will leave the indicator at the highest reading.
Jason T.