clearances problem after new valves seats on a M20B25

[Mordan]

Hey,

It is annoying. It is the 3rd time I open the valve cover after 500 miles and the clearances for exhaust rocker/valve is 0!!!

I did a head cylinder job and replaced the exhaust valve seats by a machine shop.

i changed the eccentrics, studs and bolts. Same old rocker arms.

The clearances on intake valves are ok.

What the hell. That's about 3* 0.25mm gone! that's about 1mm!

Is it the seats or the eccentrics?

[Bill R.]

The machine shop didn't get the valve seats all the way down when they pressed them in and now they are slowly moving inward , as the seat moves further into the head the valve stem moves upward which decreased your clearance....I'd check them frequently to make sure that you don't burn a valve. After enough time goes by the seats should be all the way in, but i don't like the idea of driving around until they seat, your valve grind may also change depending on whether the seat was pressed squarely into the head or if its going to change when it reaches the bottom.








Hey,

It is annoying. It is the 3rd time I open the valve cover after 500 miles and the clearances for exhaust rocker/valve is 0!!!

I did a head cylinder job and replaced the exhaust valve seats by a machine shop.

i changed the eccentrics, studs and bolts. Same old rocker arms.

The clearances on intake valves are ok.

What the hell. That's about 3* 0.25mm gone! that's about 1mm!

Is it the seats or the eccentrics?

[Mordan]

The machine shop didn't get the valve seats all the way down when they pressed them in and now they are slowly moving inward , as the seat moves further into the head the valve stem moves upward which decreased your clearance....I'd check them frequently to make sure that you don't burn a valve. After enough time goes by the seats should be all the way in, .

tough news but thx anyways. how do you know if one of the valve is burnt? (a burnt valve is because the explosion in the combustion chamber burns the seat and the valve, which eventually break ? right?)
Because at first I did drive a long time before opening a 2nd time and the rockers were glued to the camshaft. the engine wouldn't even start when cold.


but i don't like the idea of driving around until they seat, your valve grind may also change depending on whether the seat was pressed squarely into the head or if its going to change when it reaches the bottom

what else can I do lol? short of removing the cylinder head?

[Bill R.]

You can do a compression test or a leakdown test after you set the valve to determine if it has a burnt valve... I would talk to the machine shop and let them know about this.



tough news but thx anyways. how do you know if one of the valve is burnt? (a burnt valve is because the explosion in the combustion chamber burns the seat and the valve, which eventually break ? right?)
Because at first I did drive a long time before opening a 2nd time and the rockers were glued to the camshaft. the engine wouldn't even start when cold.



what else can I do lol? short of removing the cylinder head?