Can I realistically expect any gains in power with the cam and head work without the bigger exhaust? The truck has 140,000 on it and runs and sounds good. But wouldn't mind giving it a little more ooomph.
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>>>*There are a number of sure paths to power gains.
The first thing to remember is all an engine really is, is an air pump. The other point to understand is the engine does not "suck" in the air and fuel when it is running. It simply creates a lower pressure area inside the cylinder than the surrounding atmosphere, therefore the mixture flows towards the lower pressure area.
The exact same situation that causes windstorms and air motion. So any restriction to airflow motion is potential power lost.
All a camshaft does is open up one portion of the system. This works because most stock engines are designed to be smooth and quiet, let's face it, Grandma in her 4Runner isn't going to stand for much racket on the way to her knitting club meeting.
The easiest way to help make an engine quiet is to restrict the exhaust. Plus the factory must deal with ground clearence, too. Customers get crabby if they knock their exhaust pipe off climbing a curb. So we realize the factory aims for quiet, smooth, with adequate power.
The exhaust likes to be loud, it operates not only under pressure, but in pulses as each cylinder fires. So building one a bit small is nice and cheap for keeping things quiet.
Factories like things nice and cheap but adequate.
The exhaust system is number one for power gains, without forcing things, there is nothing I or anyone else can do to beat improving the exhaust.
*Well. 30# of boost will, but..... <img src="/forums/images/graemlins/lol.gif" alt="" />
Once the exhaust is freed up, expect a change in sound. This can be controlled by choice of muffler and pipe sizing, witness our #43 NASCAR stock car, just 81 decibels running 6600 RPM at the old Portland Speedway. Yet no loss of power, in fact we set quick time one day running that sound level.
The factory exhaust manifold is darned hard to top for quiet and efficiency, the header can help more in the middle to upper RPM's. Personal choice there.
Once the exhaust system is well done, this creates opportunity! Now we can add a cam profile that fits our driving style. On cams, the real gains(changes) to powerband come from when the valve opens/closes, how far you hang it open doesn't really gain that much.
*Well, it can, but now you are probably on a dirt track chasing a Pinto, different world.
There are literally hundreds of choices, most will perform similarly if in the mellower street designs. The differences in real life are normally inside of 1-2% and a few hundred other factors involved can make any single one superior to the others in a given situation. Look for around 270? duration or less and under .430" valve lift and you are in the ballpark for a rig you need to drive.
I know. I should insert a comment about the "secret" design here but the fact is, while we do use some lobe shape changes over most, all that does is help keep things quiet.
*Usually...*LOL** (Dang noisy little critters, anyway!)
So power gains go like this: Exhaust first. Cam change 2nd. Reach for your wallet, third..Sure, carb/EFI/intake mods can help, but they are way down the list. The best improvements after the first two basic steps are valves and ports, find and remove the restrictions. Of course, compression ratio is on the list if you don't mind premium fuel.
130 to 140 H/P is fairly easy to reach, after that?...Well, bring the checkbook.... <img src="/forums/images/graemlins/evil.gif" alt="" />......*EB
