What could cause this?
Thread Starter
Registered User
Joined: Jul 2004
Posts: 3,034
From: Raleigh, NC
What could cause this?
Went to the track with my brand new setup a couple weeks ago. It ran real strong even though I couldn't hook. Anyway, to make a long story short, a valve got stuck and/or bent on #3 cylinder. The rocker was still very very tight, so that didn't come loose. What could cause just one valve to stick?
I tried tapping it lightly and prying as gently as I could but it wouldn't come up, so I'm pretty sure it's bent. The valves are brand new Manley 2.0 pieces and I'm not sure about the guides. I do know that whoever ported the heads but they did remove all of the guide that was exposed in the runner. Oil looked good although I haven't run a magnet through it yet.
Any ideas?
I tried tapping it lightly and prying as gently as I could but it wouldn't come up, so I'm pretty sure it's bent. The valves are brand new Manley 2.0 pieces and I'm not sure about the guides. I do know that whoever ported the heads but they did remove all of the guide that was exposed in the runner. Oil looked good although I haven't run a magnet through it yet.
Any ideas?
Registered User
Joined: Jul 2003
Posts: 553
From: Southern California
A little more information would be helpful.
What was the valve-to-guide clearance? The valve may have galled in the guide and hung open long enough to smack the piston.
How much valve-to-piston clearance did you have?
Is it an intake or exhaust?
c
What was the valve-to-guide clearance? The valve may have galled in the guide and hung open long enough to smack the piston.
How much valve-to-piston clearance did you have?
Is it an intake or exhaust?
c
Thread Starter
Registered User
Joined: Jul 2004
Posts: 3,034
From: Raleigh, NC
I know it's an intake valve, but I didn't get any paperwork from the machine shop that did the valve job with those other numbers.
The problem isn't that it won't open, the problem is that it is stuck open.
I'll try and talk to my friend who built the motor and see what he had for PTV clearance. I know the pistons were in the hole 0.010" and I used a .039" head gasket. The max lift on the cam is around .604" and the heads had 55cc chambers.
The problem isn't that it won't open, the problem is that it is stuck open.
I'll try and talk to my friend who built the motor and see what he had for PTV clearance. I know the pistons were in the hole 0.010" and I used a .039" head gasket. The max lift on the cam is around .604" and the heads had 55cc chambers.
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Joined: Jul 2003
Posts: 553
From: Southern California
The two most likely scenarios in my world would be either a galled guide or a bent valve. Either way, the head will need to come off to isolate the problem. The duration numbers on the camshaft at .050" lift would be helpful. The fact that the valve is stuck in an open position would lead me to believe that it is bent. The guide may or may not be involved in the cause/effect scenario. Intakes don't usually cause as much problem as exhausts.
Does it appear that the spring and the retainer are intact? What was the spring pressure on the seat and at full lift? How tight did you wind the motor?
c
Does it appear that the spring and the retainer are intact? What was the spring pressure on the seat and at full lift? How tight did you wind the motor?
c
Thread Starter
Registered User
Joined: Jul 2004
Posts: 3,034
From: Raleigh, NC
The duration at .050" was 230*. The spring, retainer and locks are intact. The spring pressure was around 145 on the seat and 375 open, but it's been a while since I had that measured. I didn't spin the motor past 6800rpm. The rev limiter was set for 7k and it didn't even touch it.
I thinking the valve guide was the cause.
I thinking the valve guide was the cause.