Ferocity02

iTrader: (60)

Pulled my valve cover today to investigate a tapping noise that started after a cam/head swap a few weeks ago. I noticed that the exhaust valve on cylinder 7 sits a little lower than the others. As in, the tip of the valve stem doesn't protrude as far out of the head as the other valves. This means that the preload on this lifter is slightly less than the others, about 0.020-0.030" less, and might be the source of my tapping. The valve stem doesn't have any abnormal play in it. Looks normal otherwise.

They are stock 799 heads I got new, now have about 500 miles on them, milled 0.022. Cam is a 212/212 0.561/0.561 114LSA. Brian Tooley dual springs, installed correctly, not broken. LS7 lifters with about 30k miles on them, they were in the engine before the swap. I am using 7.325" pushrods which I measured to give me about 0.075" preload. Oil pressure has been fine, 45psi at idle, close to 60psi at cruise at 1700 rpm.

I also ran it without the valve cover to see how much oil was getting to the rockers, video here: https://ls1tech.com/forums/generatio...eo-inside.html

Anyone had a similar issue?

Thanks!

bww3588

iTrader: (49)

Makes sense. I would back all your rockers off and look carefully at the valve stems then. You may have an exhaust seat working it's way out. If that's the case, you need to get it apart ASAP.

vettenuts

iTrader: (4)

Bent valve would do this. If this wasn't there immediately after the parts swap, any over revs or missed shifts (I assume a stick) that might have let the valve tag the piston? Do you know the PTV?

Ferocity02

iTrader: (60)

That's why I'm thinking, but my rev limiter is stock, 6000rpm I think for a truck, and I've only been there a handful of times. Never missed a shift either. The pushrod wasn't bent. Didn't check PTV because my cam is such low lift, even with the milled heads.

J Glen

I agree that the cam is awful small to worry about PTV, but you should still check it out. Oh and lift doesn't have anything to do with PTV clearance. Duration does.

Ferocity02

iTrader: (60)

Lift has a LOT to do with it. Duration is only 212/212.

96capricemgr

iTrader: (1)

The reason he said lift is not that critical point is because the cam is nowhere near peak lift when the piston is near TDC. Think about it.

bww3588

iTrader: (49)

No, it doesn't....see above.

Ferocity02

iTrader: (60)

Learn something new everyday!

Anyway to see if the valve is bent without pulling the head? Maybe pulling the spring and spinning the valve to see if it feels strange is the best I can do.

96capricemgr

iTrader: (1)

boroscope, leakdown or compression

Ferocity02

iTrader: (60)

I did a compression test and cylinder 7 was about 170psi while the rest were 180-185psi. Is this indicative of a problem?