Bryan2380

iTrader: (11)

So my friend and I were doing a valve spring swap on my recently purchased 33K mile LS2 longblock. The longblock is factory assembled and on an engine stand without an intake manifold. We removed the valve covers, rockers, stands, pushrods, and spark plugs. We thread the air hose into the spark plug port and pressurize the cylinder to 80psi via a small pancake compressor. The regulator maxed out at 80psi. We were able to get all 16 springs swapped, but 12 of the 16 valves leaked, badly. It is what I would call gross leakage mainly out the intake ports, but a couple were out the exhaust. My friend has done 3 different spring swaps, all with the engine in the vehicle and he said that none of them exhibited this behavior.

What, if anything, were we doing wrong? I find it very hard to believe that 12 valves are bent and/or bad valve seals. All the rocker arms looked great, none of the original valve springs were cracked or broken, and none of the pushrods were bent.

I am thinking that my little pancake compressor was not supplying enough volume of pressurized air to hold the valve shut. As the valves are much more prone to leaking at low pressure than they are at high pressure.

I am very interested to hear your thoughts on this.

Thanks,
Bryan

midevil1

iTrader: (17)

They are leaking with the rocker arms completely off the heads. NO pressure what so ever on the retainers or valve stems???

BigRich954RR

iTrader: (1)

it wounldnt be the vavle seals. its the seats, the seats are a little rough not much other to say about it

G Engines

Sounds like its time for a valve job

Pwebbz28

iTrader: (31)

Compressor isn't big enough. Mine did the same thing. Run it.

CamaroZ28_LS1

iTrader: (5)

yea you have no seated spring pressure on the valves... don't think it's an issue...

Bryan2380

iTrader: (11)

yes, the rockers were completely off the heads.

If 2 or 3 valves were leaking, my first thought would have been that it was time for a valve job, but 12 leakers was making me think another vaiable was at play.

Thanks guys for confirming my thoughts. I think I will borrow a friends 30gal compressor and check them just to be on the safe side.

Johnny-LT1-runner

iTrader: (15)

If they weren't leaking before the swap I'd look for another cause.

BigRich954RR

iTrader: (1)

there no way to know if there leaking before the job cause i bet he never filled up the gas tank then pressured the valves,

Ive had valves not drop or leak with 60 psi in the cylinder. If is a very little bit or air no biggie but all 16 should leak about the same,

Are you losing hp from it yes no doubt how much who knows most likly not worth worrying about it

Bryan2380

iTrader: (11)

Valves had carboned up. A good smack with a rubber mallett while the cylinder was filled with compressed air fixed the problem. Thanks!

Oh4GTO

iTrader: (46)

Before tension is applied to the valves via springs there will be gaps. These gaps are actually visable is you shine a flashlight on the other side. But the minute pressure is applied they seal up. My 70,000 heads did this and there were no issues when ran on the car.