Helping my son with his car, its a civic with a type R motor, just had the bearings replaced. It now has a rattle which sounds like around the head somewhere. Gave a code of mis fire #3, and has hesitation when driving. did a compression test 210 all cylinders except #3 180, and the cylinder looked a little wet. So looking for some ideas as where to look.

 

The noise could be a valve tap, have them checked/adjusted accordingly. Could very well be the cause of the misfire as well. Listen for the tap at the valve cover directly under the 3rd cylinder.

Also, is a '91 Type R like super rare?

 

A valve adjustment may help slightly but I don't think its going to solve all of your problems. You may, worse case scenario have a bent valve. Instead of guessing and fooling around you can get a better idea of what's going on by doing a leak down test on #3 cylinder. If you don't already have the gauge you can buy one for ~$150 or so here

http://www.autozone.com/autozone/acc...er=347237_0_0_

or

make your own for ~$15. Go to an auto parts store and buy a valve with a gauge on it here for $7.99

http://www.autozone.com/autozone/acc...er=978090_0_0_

and your fittings needed here for $4.99

http://www.autozone.com/autozone/acc...er=977885_0_0_

and use your hose from your compression gauge with some plumbers tape

Simply put the cylinder that is in question on top dead center. The screw in the hose just like you would when you did your compression test. Apply compressed air to the cylinder. Open up your oil cap and listen for air escaping from it. Then check the intake by taking of the intake piping and listening threw the throttle body with the butterfly open. Then take off the radiator cap and watch for bubbles. Then walk around to the back of the car and listen by the exhaust. If you hear air escaping from any of the areas other than the radiator cap. Typically means you have a bad valve on either side of the intake or the exhaust depending on where you can hear the air escaping. If you have bubbles in your radiator then you have ether a bad head gasket, cracked block or cracked head. Now if you have air coming out of the valve cover. You either have bad rings or bad valve seals. To isolate(sometimes it works sometimes it doesn't) pour some fresh oil down into the cylinder then re-attach the hose and listen for air again. The oil will settle on the piston(hopefully stopping possible air escaping pass the rings) and will isolate the valve stem seals.

Sorry long winded was just bored lol. Good luck on what ever you decide to do!

Mike