<VV> 140 Cam timing

[James Davis]

Well I was totally agreeing with your answer until the 304 cam came 
up.  At 0.050 lift the 891 has 218 degrees duration on both sides but 
the 304 only has 213.degrees duration at the same lift both 
sides.  Neither cam has any overlap at at 0.050 lift.  The problem 
with the 891 cam is in the 3,700 rpm and above range the valve spring 
harmonics and lift profile of the cam cause the lifter not to follow 
the cam lobe, especially when the exhaust valve is closing.  While it 
is not the dreaded valve float, it does effect the power output of 
the engine. In the 3,700 rpm and above range the 304 shows its 
superiority by better controlling the valve action even though it has 
less duration at 0.050 lift.
Jim Davis


At 06:08 PM 8/20/2006, Brent Covey wrote:
>e 140 PG crank gear does not improve low end, it improved higher RPM
>performance- the original plan with the RN 140/PG 3839889 engine was the 95
>cam tamed it and gave it better low rpm power and the special crank gear was
>to restore some of the mid to upper range performance lost by using the dud
>95 HP short timing cam. The special crank gives longer legs to the weak and
>buzzy 95 cam with the better breathing 140 heads.
>
>3872304 is a pretty zoomy cam and with the RN engine crank gear would be
>very weak (much worse than stock) at low rpm. A 140 Powerglide with this
>arrangement would be very disappointing at low rpm. Use a straight up crank
>with 3872304.
>
>for those wondering which is which-in descending order of 'hotness'
>
>3872304 is the 1965-'66 turbo cam
>3839891 is the 110 HP (all passenger cars) cam and 140 MT, and early 1965
>140 Powerglide
>3839889 is the 95 HP, 110 FC, and late 1965-on 140 Powerglide cam
>
>Only 140 Powerglide using the 3839889 cam had a special crank gear to alter
>cam timing 4 degrees for improved 3000+ rpm power with the 3839889 (doggy,
>but torquey) cam.
>
>Hope thats some help,
>Brent Covey