MustangWorks.com : Ford Forums - View Single Post - not a 351, but 302 problem i need answered

Jeff Chambers · 02-03-2006, 07:37 AM

Valve stem seals won't show anything in a leak-down or compression check. If the seals are bad, or have worked themselves off the guide, when the valve is open at idle and part throttle the engine vacuum will pull oil down past the valve stem and into cylinder, especially on the intake side. Some racers will actually run without any exhaust valve stem seals since there's no real mechanism to pull the oil into the cylinder from those locations. If the car smokes badly at idle and part throttle, I'd suspect the valve stem seals.

02-03-2006, 07:37 AM	#11
Jeff Chambers Moderator Join Date: Aug 2000 Location: Milan, OH Posts: 2,699	Re: not a 351, but 302 problem i need answered Valve stem seals won't show anything in a leak-down or compression check. If the seals are bad, or have worked themselves off the guide, when the valve is open at idle and part throttle the engine vacuum will pull oil down past the valve stem and into cylinder, especially on the intake side. Some racers will actually run without any exhaust valve stem seals since there's no real mechanism to pull the oil into the cylinder from those locations. If the car smokes badly at idle and part throttle, I'd suspect the valve stem seals. __________________ Jeff Chambers 1990 Mustang GT 10.032 Seconds / 137.5 MPH 14-time Street Warrior World Record Setter CRT Performance 2001 Tropic Green Mustang GT - 12.181 / 113.2 MPH 2002 Ford F-250 Crew Cab 7.3l Power Stroke - 17.41@77.2 "There's nothing boring about a small block automatic shifting gears at 9400 rpm!"