chief455

iTrader: (21)

Which is choice:
1. lower cfm numbers with over 80 percent int/exh ratio
2. high flowing intake port, slighty less exhaust flow with 72 percent ratio
SEE #4 POST BELOW!

Will the better flowing intake head allow a bigger lift/dur cam on the intake = more power, and with a split pattern exhaust lobe even things up?
Or will the lower but closer to equal flowing head simply be more efficient and make better power? Would the even flowing head be best with a straight pattern cam?

Have pairs of heads like this and wonder which pair to use and in turn best way to pick the cam.

Beast96Z

iTrader: (21)

From the discussions I have seen, A better flowing head will require less cam to make the same givin power. So in turn, a poorer flowing head will require more cam to make the same power. To answer the question, it looks as if a better head with a smaller cam will be more efficent and probablly drive better and be easier to tune.

Bo White

iTrader: (59)

Another way of putting it is a motor with a kick *** set of heads but has a crappy cam will almost always make more power than a motor with an awesome cam but mediocre heads. There is a such a thing as a cam taylored to a set of heads to bring out the best they can produce but that has already been discussed. I will always like a cylinder head that flows 75 to 80% I/E so main thing is to find a set of heads that have those traits and also flow well. But if you have a set of heads that flow more than 80% then I would look into a reverse split cam- but only then.

chief455

iTrader: (21)

head # 1: $1000.00 cost
int: 200/152 300/223 400/256 500/272 550/290 600/296
exh: 200/113 300/149 400/186 500/200 550/213 600/218
head # 2 $2100.00 cost
int: 200/140 300/200 400/251 500/261 550/292 600/298
exh: 200/112 300/170 400/203 500/221 550/226 600/230

This is what I'm talking about. Can I make a cam work with the less expensive heads?

Bo White

iTrader: (59)

Run the 1000 buck heads and have the exhaust touched up and you will still come out ahead money wise. I would probably not even do that, just buy em and run em the way they are.

LSonederfull

N/A exhaust to intake ratio is not that important, i would take better flowing intake every time. Compensating for this is acceptable with more exhaust duration. Pro Stocks use this method and there is excellent power/efficiency from them.

BrentB@TEA

I would use head 1 also.

Tony Mamo @ AFR

iTrader: (13)

If your comparing "advertised" numbers or numbers off of two different flowbench's your only kidding yourself thinking you have actual data to compare. Also, assuming the data was good (same testing equipment hypothetically), if one head was 210 cc's and the other was 235 cc's, its a completely different ballgame as well and this information must also be factored into the equation.

chief455

iTrader: (21)

Agreed Tony. But as consumers that IS all we have to go by when deciding. Every porter gives the flow numbers that they recorded with the variables at that session.
We as buyers can oly overlay the flow charts, consider the consistency of the porters work, the "other" variables like runner volume, hardware used and finally - price!

Assume the 2 specs I had given to me were at 28" water, and the same bore because I was told they were. They have the same hardware installed. They were both ported from similar castings and commonly used LS1 porters so I can't imagine the runner volumes being vastly different. As a buyer - my concern is that lesser flowing exhaust on head #2.
That was my question, and it seems that the slightly higher intake flow, even if skewed by different bench flowing, is still a reasonable choise with a proper exhaust lobe to componsate. I was not sure about that.
thanks everyone!

Slowhawk

iTrader: (12)

Tony has it right.CC's of the runner's make a huge difference on how they will perform.
Chief,you would be happy if you just put it in my hands to pick your setup.Probly save you $$ because you keep wanting to switch it

chief455

iTrader: (21)

I was wondering when you'd catch me doing homework in here
I am planning on doing just that - but watching all the advertised numbers from websites and such made me ask about this. Plus the obvious for you: my current heads are milled too far to alow a .600 lift cam. Head #1 is a stock chamber 2000 LS1 head that has srings for up to .650
It is tempting but before I just read your post I decided to pass, wait and drive up with my 12 bolt and locking PT4000 already in
I just want consistent mid 11's .. is that so wrong
See you soon Slowhawk!

Slowhawk

iTrader: (12)

Your better off not coming by anytime soon.We have alot of stroker motor's laying around and you might get tempted