We are rebuilding a 2002 R/T that had a broken timing belt and bent valves. The head has been redone with a complete new set of valves lapped in. Currently the rocker arms have not been installed so all valves are closed and the spark plugs are installed. This being said the cylinders should be airtight.

Now, when the crankshaft is turned slowly by hand a small amount of air seems to be breathing in/out of the exhaust and intake ports on the head.

Is this normal?

 

I don't know the answer to your exact question, but if the valves are the only thing that aren't "airtight," where else would you expect the built up pressure to go?

 

lapping is soo old school no one does it anymore, that being said if they were lapped they would be sealing

did you grind the valves and seats?
or just slap new set of out of the box valves into a head you didnt clean the seats up on?

machineshop may have cut some corners, instead of your valves and seats

 

It's all back together and running great.

 

-My Dad STILL uses his old valve lapping tool and valve grinding compound. I'll be using it too when I rebuild my old Tecumseh lawnmower engine. Cleaning the seats and lapping the valve is an essential part of a good running engine. The valves need a perfectly matching seat to seal against any kind of leaking. Otherwise, even though it may run, it won't generate the compression it needs to run correctly. But glad it's running great, Neisg1!

L8R,
Matt

L8R,
Matt