The other day, like a fool, I over revved my engine. I gave it about 6500rpm on parts that aren't much better than OEM.
Now there's a bub bub bub bub bub sound to the exhaust that wasn't there before.... I think that a valve is bent, since I looked at the pushrods and they seem ok.
The next thing I'll do is a comp test. But I have to fix the bendix gear on the starter first. Meanwhile I just thought I'd ask, What happens when lifters pump up?
Is it valve float, and then the lifter over fills with oil, and then the valves are held open by the pumped up lifters?

Edit:
Did a compression test and all the cyls were 190 +or- 5psi.
I guess it isn't a bent valve.
Maybe I should take the pushrods out and give them a closer look.
Any ideas on what the problem might be?


Thanks

 

Valve float is when the valve doesn't close completely when it should. It can be inadequate valve spring force to move everything out of the way so the valve can close, or harmonics that have the same effect of reducing effective valve closing force.

Lifter pump-up is the plunger within the lifter not moving that slight bit as the lifter first starts to move up. Therefore, it doesn't release all the way when it is coming down, keeping the valve open a slight bit. Typically occurs at high RPMs as well.

How did the plugs look when you pulled them for the compression test?

 

None of the plugs had an appearance that would have set any one of them apart from the others, or at least that I noticed.
Is there anything in particular that I should have been looking for?

A test with a vac ga showed steady vaccum.
A compression test was good.
Still, it's running as if a plug wire had come off or something like that, it's just a steady bub bub bub to the exh note.
I haven't removed the pushrods yet, I just looked under the valve covers and they all looked normal at a glance.

If it ends up being a bent pushrod, that's easy to fix. I hope that's it.
It's pouring rain now, I'm not up for dealing with it.

 

When the lifters "pump up" due to valve float (which is what happened when you zinged it) they will bleed back down again over a period of a few seconds. Idle may be rough for a while but should smooth back out again shortly. It's not a permanent type of condition.

Odd that your compression readings are all 190- that would indicate that the valvetrain, valves, pistons and rings are all still in good shape and doing their job.

 

Yeah. It's really odd.
I was thinking that it may be an exh pushrod that was bent, thus allowing the compression to be good but not allowing the spent gasses out of the cyl. I checked the pushrods by rolling them on a glass plate and they're all fine
I think I'll recheck the ign system.
I have a feeling that I'll put it back together and it'll run fine, and I'll never really know what was wrong. Or at least that's what I'm hoping.
The off idle is a bit rich on the carb, blackening the plugs, so it makes it difficult to tell much by taking a plug reading.

 

Checked the pushrods one more time after noticing an odd wear pattern on some of them where they go through the holes in the head.
I cleaned everything surgically clean this time and sure enough, about half of them are bent. It's only about .005 on the worst of them, but I guess that must be enough to cause some binding or some other valve timing abnormalities.
I'll replace them and see how it goes.

 

If you have an engine that has had an otherwise docile life, your temporary high RPM excursion may have liberated carbon and fuel deposits that had attached to the backs of valves, chambers, etc. You may actually have some cylinders that are flowing better than others. A power balance test under load at the middle RPMs (dyno type test) may reveal the weaker cylinders.

Is oil pressure normal? Is the distributor rotor normal? Are there any other mechanical noises that accompany the "blub-blub" notes in the exhaust?

 

I found a set of pushrods that will suffice til a new set shows up.
I'm going to put those in tonight and fire it up.
I'm also going to test my plug wires. It seems unlikely that the wires would suddenly choose to go at the time I revved it.
No mechanical noise that i noticed. if the problem continues, I'll definitely be looking very carefully for mechanical noises tho.
Oil press normal.
Haven't looked at the cap and rotor but I hooked a timing light up to each wire and they were all 90deg apart.

Thanks

 

well...
have you checked your header gaskets?

 

Did you check your rocker arm studs? One of them may have pulled loose. They really take a big hit when the valve hits the top of the piston!

 

The studs are pinned, so I'm guessing they haven't moved. I'll check them and all other valvetrain parts tomorrow.
I tried to get it together tonite, but my hands froze.

Header gaskets?? That ain't it, the sound is coming out the tailpipe.