flareside88

I bought a denali with an lq4. Low oil pressure on the dash, but no knocking or taping. Only a misfire on 5 and 7. Found intake valve not closing. I unbolted the rocker and noticed the valve closing. So made sure I was on base circle and still same problem. When tightened down, the valve opens. I tried swapping lifters push rods and rockers. Any thought appreciated

Che70velle

iTrader: (6)

Stuck lifter?

01CamaroSSTx

iTrader: (3)

Are you certain that you're on the base circle of the camshaft? Are you familiar with the EOIC method to determine if you are in fact on the base circle of a particular cam lobe? If the pushrods are too long it can hang a valve open and so I'd also verify that the correct length pushrod has been installed.

Bbknucks

I've had a couple come through my shop with lifters holding valves open.

Check cylinder leakage without rocker installed. If valve is still open then problem in valve/guide or spring broken

flareside88

Stuck pumped up? I swapped lifters with adjacent cylinder that isn't hanging open. Still same cylinder stuck open

flareside88

I took the head off. Valve is closed. Lifter stuck pumped up? I swapped with an adjacent lifter, issue stays with cylinder.

flareside88

No I am not. I bump until the exhaust valve starts to close. Push rods are all same length, and I tried swapping.

Bbknucks

Yes stuck pumped up or internally bound up.. but if you have swapped everything around and valve is definitely closed when all removed then either the lifter isn't going all the way down in its bore or the valve seat has recessed into the head.

If you have the 2 rockers off for that cylinder are the tops of the valve stems level?

Che70velle

iTrader: (6)

Wasn’t referring to lifter internals being stuck, but I suppose that’s possible. I was implying that the lifter wasn’t reaching the bottom of its bore completely and sitting on the cam, because the bore is tapered or hurt. Valve seat could be hammered into head slightly or got cut too deep during a valvejob, or perhaps valves were replaced and the valve height wasn’t cut right from whoever did the valvejob. Being as how you have swapped both lifters and pushrods, as well as rockers, this is all it could be really, if this one valve is the only one giving you trouble.

01CamaroSSTx

iTrader: (3)

You want to bump until the exhaust valve begins to open on a cylinder to adjust the intake valve for that cylinder "EO" and when the intake valve begins to close you adjust the exhaust valve for that cylinder "IC". That is when you will be on the base circle of the cam. Intake when EO and exhaust when IC

If a valve is hanging open perhaps you do have a weak or broken valve spring, insufficient valve to guide clearance or a bent valve stem. If you back all the rocker arms off do the tops of the valves all line up even when you lay a straight edge across them?