Ive been reading and researching far to much on cam selection lately. But this might be of some importance to my build..(marine and reversion)

http://www.popularhotrodding.com/eng...ine/index.html

Notice build 17

Test 17-COMP 1.6/1.5 rockers:
Max 442 tq, 414 hp
Avg 419 tq, 335 hp
We wrestled rocker arm ratios around for quite a while and found that 1.6:1 ratio intake and 1.5:1 ratio exhaust were the best combination of all rockers tested until that point. They gave a torque improvement with no hp loss. Looking back now, Test 17 may have been the best overall combination of power and torque. Especially considering that these parts are all still low on the cost scale.


I am not even going to try to go into event timing and flow rates @ lift...However with this combo of 1.6 I and 1.5 E could that be related to or as simple as the ex valve closing eailer and miminzing exhast reversion....Im thourghly confused.. I was under the impression the Ex was the weaker part of the vortec head

Or could the 110 lsa have something to do with this

 

An engine is just a big air pump. As the piston moves down the cylinder, it has to pull air into the cylinder. Bigger valves or higher lifts allow more air to be pulled through the valve opening.

On the exhaust stroke, it's all about velocity. The piston pushes the exhaust gasses out of the cylinder no matter if it's a 1" hole or a 2" hole, the gasses will get pushed out. A smaller opening with a smaller vale or less lift means the velocity of the gasses is quicker. It the exhaust velocity is enough with a regular sized valve and 1.5 rockers, you'll gain very little by installing 1.6 rockers on the exhaust. There's a lot more engineering involved in what actually goes on inside the cylinder between the exhaust going out and the fresh air coming in but that's the basics.

 

Thank you for the reply, Question is this high velocity aided by cams with longer durations than the intake duration aka dual ramp cams?

Another question if i may, I have read that Vortech heads need a piston that has a quench area and without that most of the benefit of the vortech design is lost. The 4.3 2000 model year does not have this design..They have a flat top....Can this be true or just speculation

Lastly i am begining to believe there would be very little benefit to porting or polishing a exhaust port since it is being (gases) released under pressure...Does intake porting aid high pressure turbo's or super chargers..I know there would be some benefit but any real practical benefit?