racer02GTstang

ok... well getting close to the end of the valve spring swap and cam swap... on cylinder number 4, when i put the pressure hose on the connection to the spark plug hole... air blows out the intake port... the car felt like it has lost 20 hp and sometimes has a weird idle. it holds compression in the cylinder, but not as good as the other cylinders. the valve is fully closed. what would be the cause of this?

GodAmGT00

Can you absolutely confirm the valve is closed?? Normally, if it were valve seals, it wouldn't necessarily come through the valve train into the intake.. That does sound odd.. What kind of compression are you getting??



JT

oxfordgt

Hmmm you might have a bad ring.

contentsunderpressur

A ring would not cause air to come out of the intake port, it would cause it to get into the crankcase.

Could be that the valve isn't seated, bent or cracked valve or cracked head.

racer02GTstang

can i reseat the valve by pushing it down and bringing it back up by chance??

contentsunderpressur

I don't know of any tricks to reseat a valve with the head still on. Maybe someone else knows a trick. I've always done it with a seating tool with the heads off the car.

FDNYBullitt

You can try tapping it with a hammer a few timesbut make sure the piston is down and away from the top. Lay a straight edge across the top of the valves and see if that one is sitting lower as it could be bent, or have some serious carbon on theseatcausing the leak. I have run into this a few times over years and was able to get the spring off and get the valve to close by using 2 different methods, one was to block off the intake port with a quickly made plate that bolted over it and the other is to feed some very flexible 1/4" rope into the cylinder and then bring the piston up and the rope holds the valve in place while you change the spring. Also, if you have a small enough drill you can chuck it onto the valve stem and spin it slowly while pulling up on it to knock off the carbon and get the valve to seat. Hope this helps and good luck.