leakdown test shows exhaust valve leak

I have been having a code of P0303 which is a cylinder #3 misfire.
I just had a leak down test done.
The mechanic indicated that I had leakage of 10% on #1 cylinder, 35% on #2, 40% on #3 and 20% on #4.
He indicated that the combustion chamber leak-down is exiting through exhaust valves.

Will a new cylinder head fix my troubles?

 

How did he know it was specifically the exhaust valves? A rate of decay test is only qualitative.

 

If it truly is the exhaust valve(s) its because they're burnt most likely, I'd thoroughly check the head for cracks/warp/etc: before shit canning it for a new one & no a new head won't change anything unless its been rebuilt

(if i'm understanding you right)

 

What I'm trying to determine is if a new (or most likely rebuilt) cylinder head would fix my problems based on the data that I have or is more data needed.

 

From what I have read, when performing a leak down test, if you hear air hissing out of the tailpipe or exhaust manifold this means an exhaust valve leak. I would assume that is what the mechanic did.

 

This would be correct.

You could try sourcing a new head but then unless it's rebuilt you still don't know for certain what you're gonna get, why not pull yours and have it checked out and see what can be done.

 

Pull yours and send to machine shop they can also replace the valve for you too. Most wont set your valve clearance though

 

Cool.

I would most definitely rebuild what you have rather than buying some Chinese Advance Auto Parts special that won't last 24 months.