are conventional bbc heads and components more reliable ?
#1
Member
JUNIOR BUILDER
Thread Starter
Join Date: Jan 2004
Posts: 77
are conventional bbc heads and components more reliable ?
When you go to a big chief or other style smaller degree bbc heads, does that make the rocker arms and valve train components less reliable than staying with conventional bbc heads when used in a marine application where there is a lot of run time. I"ve heard of big chief style rocker arms and valve train components being worn out in less than 40 hours of run time even with reasonable lift figures .???????
#2
Senior Member
MASTER BUILDER
Join Date: Mar 2003
Posts: 127
I have heard the same thing. that on the Big Chief style head, lifters were a change out item 40-50 passes..Now I do not know this for a fact just something I had heard about. I think Madcap in CO. builds a convential headed 632 or 637 inch motor and someone posted on a Top Dragster/Sportsman form about the motor not eating valve train pieces up and built good power
#3
Junior Member
APPRENTICE
Join Date: Oct 2007
Posts: 21
big chief heads
Guys its all about the cam shaft profile, big cams, valve trains don't last as long.With respect of spread port heads I don't kwow of anyone using them with less then .750 lift cams I don't beleave they were designed for that application, however there is a big difference in valve train stress from a .750 lift cam and a.900
#4
Junior Member
JOURNEYMAN
Join Date: Aug 2007
Posts: 25
geometry
It's really simple geometry. Look at a small block. Lifter,valve, rocker, pushrod, all in the same plane. No side load (front to back of motor). The design of the big block (canted valves) takes everything out of the same plane and puts a side load on the components. More lift, more spring pressure, more side load. Never seen a Big Chief head, but if it increases the angle of the pushrod, more sideload yet.
#7
Senior Member
RACING JUNKIE
Join Date: Sep 2007
Location: Montvale, VA
Posts: 1,431
Originally Posted by Tod74
I broke out in hives the first time I looked at the valve train on a BBC. :?