are conventional bbc heads and components more reliable ?

[badbug3]

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 .???????

[dak697]

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

[promodjohn]

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

[burgessdg]

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.

[olds48]

Exactly!!!

[Tod74]

I broke out in hives the first time I looked at the valve train on a BBC. :?

[olds48]

I broke out in hives the first time I looked at the valve train on a BBC. :?
:lol: :lol: The first(and only) motor I ever built/tore down was a BBC.I was 16 and had never even changed plugs before.The first time I ever installed spark plugs in my life was when I got my "built" 396 back from the machine shop.Before that my extent of mechanical work was adjusting one set of points with the help of my Grandpa,he was the only one I knew that still owned a dwell meter.I wanted to assemble it myself,and I did.Had no problems,but thought they had sent me someone elses pushrods.They were reeeaaalll short.HAHA!Didn't ealize the length difference when I pulled them out.Wanna see something real weird look at the exhaust ports on a smog Ford 460 :shock: :?