I have looked at several flow charts for 862/706 heads and the exhaust to intake port flow is in the mid 70's percentage. Everything I have read states if your exhaust port flows 75% of your intake, that calls for a single pattern.
Why do we see mainly 4-8 degree splits on camshafts made specifically for trucks running these heads? It seems to me this extra exhaust duration is blowing torque out the pipe where its needed most in a truck.
Thoughts?

 

The most common cam out there (IMO) is a single pattern. The 212/212. Several ppl make em

i think they supply what we want and we keep asking for and buying cams with duration splits

 

Isky triple 12? I don't know about it being the most common. I would say just reading the forums that the 212/218 pops up more than it. Anyway, would you agree the single pattern would be a better choice for a truck application running these heads?

 

I'm thinking with cathedrals headers and maybe dual exhaust yes.

 

I think all but one of those Gen III motors had dual pattern camshafts. The L33 being the exception. The Gen IV 5.3s also used the same grind until 2009 when the following year VVT was introduced and the split pattern with a grind very similar to the LM7 became standard. I would say VVT is the reason for split patterns for the later engines but not sure why on the earlier ones. I like the single pattern in my truck, but then again I'm used to it now.

 

While that may be true for head flow,That is only part of the equation. Your intake flow and exhaust flow also factor in. It doesn’t matter what your intake ports flow or what your exhaust ports flow if there is a restriction before the intake or after the exhaust.

 

Very good point!

 

On cathedral port heads it really depends on the setup, on Rect port heads they naturally favor the intake port so increased exhaust duration is common and expected. You want a balance. It’s pretty easy to have a low restriction intake, having a zero restriction exhaust is more of a challenge. This is where the exhaust bias comes into play.