Help me find good numbers for a cam. Take power and streetability into account. My car is driven very hard, but still sees around 1,200 miles a month.

I am having a 383 roller with forged internals built. I have slp cold air, 58mm tb, ported superram and mainifold, nice afr 195 heads, 1.6 rr's, eldelbrock long tube headers, 3" exhaust.

From my general reading and research, I've come to find out that:

-duration is the rpm peak hp will occur (on a 350) 220 = 5500; +/- 10 = +/- 500rpm.

-Lift is more important than duration because it has a direct effect on torque at any given rpm.

-superrams are good up until 6k rpm

-for every 25 additional ci, add 5 to the duration to make power at the same peak. SO in a 383, to peak at 5500 would require about a 226 duration.

-lower lobe seperation = more power, but worse idle.

QUESTIONS:

-I can understand how cam lift and head flow work together, but how does rpm come into the equation? What makes the difference at what rpm the peak power is at? Is rpm related to lift at all?

-Single pattern or dual pattern? Which one is better for this setup.

-I already have a lpe 219/219 .560/.560 112; I see lots of cams with better durations, but the lift (important) is always lower. So should I just stick with this cam?

-What's the intake/exhaust ratio mean? I remember hearing about something to take into consideration if the ratio is at 80% or better (which mine is), but I can't remember what.

Here is my head flow. Notice that from .550 - .600 it flat lines, but doesn't lose power. Would having a lift of greater than .550 be a waste? Or would it be better because it gets to see a constant high flow for longer?

Thanks!

 

Running that 219 cam with a 383 and with those heads will really be a crutch on those heads and their abilities. I know that it has about the highest lift for the smallest amount of dur. for a hydraulic roller, but that little bit of lift does not equate to having between 10-16degs more dur. when talking hp. The superram should be ported immensely also to get it somewhere near those head flow numbers. Only ported SRams make peak power at around 6k.

I'd recommend calling Comp and having them grind you a custom cam on a 112 LS at either 230/230 dur or 236/236 dur. The lift on the XE lobes is as good as you'll get for a HR cam. If it's not enough go with a SRoller. If your head flow is above 80% you should run a single pattern cam like the ones mentioned.

One more thing, where did you get those heads ported? And were the exhaust #'s attained with a pipe?

 

Everybody will tell you to get a bigger cam, but those that have used the 219, 383, superram combo will tell you that it is the best compromise of power, torque, driveability, gas mileage and emissions.

Other cams will make more power, but at a sacrifice. My combo peaked around 55-5700. You must remember that you are limited in airflow to the heads by that intake, so you must take advantage of the ramming effect and the short duration, high lift of that cam and intake combo. I ran several cams on engine analyzer, and the 219 made the most avg hp and tq with good vacuum. That's why I picked it. It doesn't really lope either.

The only real way to know is to run the 219, then swap to another cam and see the difference.

 

This can get really complicated really quick, and this is a gross oversimplification. But the easiest way to understand it is to realize that at higher rpms, the valves need to be held open longer to allow the engine to breathe. Consquently, the valves are also open longer in the lower rpm range, but here the effects are negative. The cam is allowing the cylinders to bleed off pressure because the engine isnt turning enough rpms to take advantage of the duration. This is what shapes your power curve. This is also why cam manufacturers recommend a higher static compression when using aggressive cams, the engine needs a higher static ratio to try to maintain the dynamic compression at lower rpms when the cam is bleeding off cylinder pressure. The bottom line is that a cam is a compromise, you can have high or you can have low, but until we get SBC solenoid-actuated valves you cant have both.

The I/E ratio of your heads looks pretty good, if you have a good exhaust system and your going to run a fairly mild cam, you could get away with a single pattern.

People seem to have good luck with the 219 in SR applications, but all combinations are different.

The ratio of the intake flow to the exhaust flow at a givin lift. Of course a more efficient exhaust port is always desirable.

Dont get too wrapped up in peak lift flow numbers, the valve spends most of its time at mid-lift, those are the main numbers to be concerned with. But to answer your question, there really is no point to lifting the valve past peak flow.

 

camarojoe

The heads were ported by TEA. Stage 1 port. Not sure how the exhaust flow test was done.

The user Johnnyiroc was the one who had these heads ported and tested. I pretty much bought his entire setup off him a few months ago, cam, intake, superram, heads, afpr, injectors, rr's, etc...

He ran a 11.9xx with his 383 and this setup. So, I know that this cam can get me into the 11's...but if I can beat my friend's 11.8 '99 Camaro SS, that would be bad as hell.

What I ment by the superram and 6k is that 6k is pretty much the limit on the superram. Even though mine is ported, I should be peaking a fair bit below that, especially with the lpe 219 cam.


89gta383

Have you ran your setup at the track before? You said your combo peaked at 55-5700. How did you determine that? Have you had your's on the dyno. Johnnyiroc peaked at 4950.


formularpm

So are you saying that even if I got a custom grind, that I would either have to choose big duration or big lift, but not both?

You said not to worry to much about peak lift because the valve spends most of it's time at mid-lift. If I had a lift of something close to .600 though, wouldn't my mid-lift then be raised and I would get better flow?

 

4mul8r, I figured your heads were ported at TEA as they get better #'s than most porting companies. I know, cause that's where the heads I run got ported. I posted my flow #'s a while back, they were similar on the exhaust as yours.

There's nothing wrong with the 219 if you want brutal low end tq. But you could go with a little bit bigger cam to pull your power band up. Heck you could just retard the 219 cam 2 degs. like Todd85 does with his SR/383/219 setup on his vette. I think his hp peaks at 5600 this way and he's running 11.60's at 117 in his 85 auto vette.

 

No, you can have lots of lift and long duration in the same cam. What you cant have is both great top end power and great low end power when it comes to the cam itself, its a comprimise. Thats not to say you cant bandaid the lack of low end with low gears or a high-rpm stall, though.

While raising max lift to .600" would seem to move up the 'mid-lift' figure as well, there are other factors that play in, making that number pretty obscure. I would expect that cam ramp rates have some effect on it. FYI, the valve only spends more time at mid-lift because it passes it twice, on the way to peak lift and back to the seat. Anyway, what I was really refering to is how people seem to pay too much attention to peak head flow numbers and little if any to the midrange/low lift numbers.