hotrodrx7

iTrader: (13)

I've read in a couple of places that exhaust flow in LS1 heads should be around 80 to 85% of intake flow and, if that is the case, the cam used should be balanced i.e. the duration and lift of the intake and exhaust should be nearly the same. However, a lot of cams advertised (like my F11) have greater exhaust lift and duration than the intake side. Is this a bad thing? Would I benefit from swapping to a more balanced cam with my heads? (TEA 1.5 LS6 heads with exhaust flow in the 80 to 86% range)

davered00ss

iTrader: (4)

That is why the intake and exhaust valves are different sizes. Split duration cams can be used to make up for a poor flowing exhaust or forced induction.

hotrodrx7

iTrader: (13)

The exhaust valve is smaller since it is flowing under much higher pressure than the intake and I assume that is taken into account in the 80 - 85% flow bench design numbers. Without checking the dyno results of each cam with several intake and exhaust systems, how would you know if something was a limiting factor? I'm pretty happy with my set-up (406 hp, 399 tq) but I was wondering if a more balanced cam would change the curves any. Also, fwiw, on the dyno, the tuner said it looked like I was running out of air at the top end, based on a known to be strong fuel map, so we leaned it out accordingly. Is this a characteristic of this type of cam split or should I look at cleaning up the intake tract?

hotrodrx7

iTrader: (13)

I'd like to hear some opinions.

GuitsBoy

iTrader: (4)

Running less exhaust duration (on the same LSA) will raise cylinder pressure (raise DCR) which would give you a bit more torque, provided you still flow enough out the exhaust.