[JDM]

I had my cylinder head off my car because i had to change two bent valves that i had. I took it to a machine shop and waited so i could watch him change the valves and check for more bent valves. When he was done with the head he aligned the camshaft and gave me back the head. I turned it over to see how the valve sits when the camshaft was aligned and i noticed that the number 4 cylinder valves weren't closed completely. I was confussed because when you set the car on TDC the number one piston and number 4 piston is up. I had him check for more bent valves and he said that the head was percfect and he guessed thats the way it is because of the firing order. Has anyone else noticed this? Should all the number 4 valves be closed as well as the number 1 valves?

 

[JDM]

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[James92TSi]

1 and 4 are not timed the same. When the camshafts are at 12:00, 1 is at TDC after the compression stroke, and 4 is at TDC after the exhaust stroke. They do not close at exactly the same time. 1 should have all 4 valves closed because it's igniting. 4 should be in overlap at TDC... with exhaust valves almost closed from the exhaust stroke, and intake valves starting to open for the intake stroke.

 

[JDM]

Thanks for the reply i understand now.