Getting rid of carbon in exhaust ports?

Joined
Jan 23, 2014
Messages
559
Location
Australia
Hi everyone,

I am in the midst of replacing the motor in my Mitsubishi Diamante (3.5L 6G74 to a 3.8L 6G75).

The 6G75 is on an engine stand with no exhaust manifolds on and I can see carbon build up.
I can easily scrape it off and it is quite thin.
There is also what appears like a bit of oil gunk on the valve stems (I will be replacing the valve stem seals).

My question is: should I be bothering to clean all this up, and if so how would I do it?

As my camshafts will be out, the valves will be in their closed position.
 
If it's a thin layer I wouldn't worry about it. It will come back within 1k miles anyway. I'd remove any thick build up that changes the port shape, though.

Same for valve stems.
 
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