valves leak after valve job

[cruisintalonawd]

Should the valves leak air after a valve job is performed?

 

[Eclipsethis90]

Are you at top dead center before testing leakdown? If you are not the cams may have the valves open slightly, causing the "leak" you are describing.

 

[TOONAH]

I should think not. Back where I come from (England) the last thing we would do on a valve job is hand 'lap' the valves. Before installing the valves, springs and all, we would apply a little light rubbing compound to the valve seat.
Then after inserting just the valve and a drill to the valve end we would spin the valve around, making light contact at the angle cuts on the seat and the valve.
Then after the valves are all installed (but not the cams) and the spark plugs we would bolt a rubber gasket and plate to the deck and pump up the combustion chamber to at least 50 psi and check for leak down.
Have you done a compression leak down test? If you have and it is no good I would take the head back to the machinist.

 

[cruisintalonawd]

No cams in the motor yet, Is there a way I can do I compression test with out the motor in the car?

 

[BogusSVO]

how do you know they leak? is the head on or off the engine?

 

[cruisintalonawd]

how do you know they leak? is the head on or off the engine?

By doing a leak down test, Do you not know how to do one?

 

[96mitsugsx]

Send the head back to the machine shop.

 

[TOONAH]

Take the head off and have the machinists double check it. But I stand by my original statement, there should be minimal leak down through the seal of the valve to the seat. In an ideal world there should be no leak down, but then we all know this world is not real or ideal. It is just a figment of Vishnu's imagination!

 

[BogusSVO]

By doing a leak down test, Do you not know how to do one?

yes I do know how to do one....

the machine shop should have done a vacuume test of the seats before letting you pick it up. It should also be over 27in for a proper seal

if the valve tip height is off,too tall, then that can also cause the valves to be cracked off the seats once the hlas/rollers and cams are installed
what equipment did the shop use when they did the valve job?

 

[97ebaygst]

By doing a leak down test, Do you not know how to do one?

sorry to bring this back from the dead but I read this and laughed. I've come across enough of BogusSVO's post to know that he knows what he's talking about so when i read this comment I just thought to myself "you dun goofed up"

 

[boosted97gst]

I believe there should be no leaks. I took my cylinder head for a valve job recently. When I got it back, sprayed some carburetor cleaner in the runner (with the cams off so the valves are shut), the carburetor fluid leaked right out in 2 intake valves. One of the intake valves if I put a flash light on the valve (combustion side), looking inside the intake runner, I can see the light through the valve and valve seat. I can't trust any machine shops these days. There goes my $200 buxs.

 

[cruisintalonawd]

I would take it back to the.... I found out a year later and used a $100 head gasket. They said they couldn't do anything because it had been so long.

Good for you 97!!!