Need advice with 350 four bolt main
#14
Originally Posted by dalematney
I was told to have the valves grinded to allow better air flow. Is this true?
I am unsure what valve jobs are legal, but a five angle, three angle or radius job are all options to consider.
Dave
#16
Member
JUNIOR BUILDER
Join Date: Feb 2008
Location: Childers Australia
Posts: 98
a backcut is a different angle (in your case 30*) cut from the normal seat angle ( IYC prob 45*) It goes from very near the edge of the seat inwards till it goes into nothing into the head of the valve( hope this is clear) It is done on a valve refacer. It will allow more airflow as will paying very careful attention to the valveseat area specifically as Dave has stated.I would also add since valves are "free" in these specifications you may consider thin stem valves also.
#18
I also do a 25 degree top cut on the head of the valves. But do not compromise the thickness of the valve (leave margin at .030 to .060).
A top cut will create a tighter cone shaped air flow areound the circumference of the valve head, especially important on the exhaust valve.
Dave
A top cut will create a tighter cone shaped air flow areound the circumference of the valve head, especially important on the exhaust valve.
Dave