430 build Part II...this time a 455!

Apparently not so bent as he thought.

 

It's not unusual, but as per my previous post, when i tapped on the valves with a rubber mallet (with the rocker arms on) the valves kept going down without rebounding to their original position. That's why i thought the valves were possibly bent. What would cause them to do that?

 

Knocking the oil out of the lifters with the hammer taps would cause that. Depending on the lifter, the check valve and it's pumped up state you could get something like .2" of change from fully pumped up to bottom of lifter (on the high end).

 

He's not saying the pushrods were going downward with hammer taps, but rather the VALVES, and the valve springs were not able to close them (raise them)...they were "stuck".

Afterwards is where I got more confused, when the valves on the entire bank closed normally once the rocker shafts were removed.

o No:

Was the engine hot when the hammer test was done? Was the engine cool when the valves closed once the shafts were removed?

Devon

 

Ah yes, I had that backwards. Hmm.

 

You had WHAT backwards?

 

I was thinking he was tapping it with a rubber mallet and the valve was going up and the lifter collapsing, when he was actually describing the issue being tapping the valve and the valve went down and did not rebound back up.

 

The engine was cold both times.

 

Put the head back on with 72 rocker arms and still no joy with compression. Validated that the valves are operating properly so I'm completely baffled. I'll try the other head tomorrow with a stock head gasket and see if i get the same results and if so I can only assume the rings aren't sealing for some reason.

 

If you have one head on, perform a leakdown test to see where the leakage is. Noise out the carb--or the intake port--is the intake valve. Noise out the exhaust is the exhaust valve. Noise out the crankcase is rings.

 

Don't I need compression to have leakdown? There is no pressure being made period in #6 cylinder.

 

Pressure is supplied by an air compressor. You follow the trail of where the compressed air leaks out.

NO compression in #6? Not likely to be (just) a problem with rings. Even broken rings should build some amount of pressure. First Guess: Bent valve(s).

 

Pour some oil into the cylinder and try the compression test again. If the pressure goes up a fair margin then it's your rings. If not, then you have a big leak somewhere.

 

Unless I have missed it. Have the heads been to the machine shop for a valve check and if neede, reworked ? Has anyone thought about applying compressed air into #6 with both valves closed to hear for air leaking into the intake, exhaust or lower end ?

 

Ok, I'll try the compressed air idea and see where the air is leaking from.

 

Alrighty...here are the results:

#6 cylinder the air was pouring out of the exhaust port so valve. So for comparisons sake i decided to try another "good" cylinder and all the air was escaping into the crankcase. I assume that is NOT a good thing but that particular cylinder developed good pressure so what does that mean? Excessive blowby?

 

Was the test done with the rocker shaft assemblies off?

Devon

 

Or at least with each cylinder at TDC Compression, and using an actual leak-down tester?

ANY leakage past the valves is unacceptable. ANY leakage into the cooling system is unacceptable. SOME leakage into the crankcase past the rings is acceptable, but unless it's measured and compared to known-good cylinders, or a master orifice, it's impossible to judge what's acceptable and what isn't. Thus the requirement for a leak-down tester using a standard-size main orifice and an appropriate gauge or two. The best leakdown testers have a "Master" orifice, for testing the tester, almost none sold to the general public do.

The one I bought a few months ago, to supplement a Snap-On single-gauge leakdown tester
http://www.amazon.com/Aircraft-Tool...&sr=8-2-spell&keywords=Leakdonw+tester+master



Another from the same vendor, this one is the "genuine" unit approved by Continental aircraft engine company:
http://www.amazon.com/Aircraft-Tool...UTF8&colid=2VLYZKC3HBBDO&coliid=ILXFPWWQVNH79

 

The test was done with the rockers off but i don't have a leak down tester. I guess that's next on the list. Theyre awfully pricey though...can they be rented anywhere?