Expert: Vern Bullock - 9/9/2010

Question
Hello sir.
I have a 62 falcon 170 six cyl, that I have been restoring.
After doing total basic tune up and carb rebuild,
vac advance, etc, It has been starting and running
super for a year now.  But, 80% of the time lately.
The problem is not the starting aspect. After sitting all night, or for a while,  (not me, the car) It starts instantly and keeps running, but most times it runs very rough for 30 seconds no matter what the combination of  gas or choke, But then it will run excellent all day.
When it is rough, it also has a very noticeable tapping
up high maybe in the valve cover area.  Sounding like tappets or whatever. This settles down at the same time, and also does not come back.  The oil light goes off right away as normal, so it seems to have the proper oil pressure.  Im not a great mechanic, but I have general knowledge and understanding.
Any help would be very much appreciated.
Thanks so much for being available.


Answer
Hi Dana:
The tapping noise is most likely the valve lifters. Until oil gets to them and the oil pressure is raised after warm up, most lifters will tap for a while. You can use a heavier weight oil to help keep them quiet. In summer a 20/50 and in winter a 30 should help.

Regarding the rough running when cold, it sounds like you may have a small air leak in the intake manifold. Once the air is warm, the air/fuel mixing is OK. But while the air is cold, the mixture is off. Which means, not enough air, so it should run a bit rich at first.