Phil99vette

iTrader: (11)

Anyone have hard data supporting the idea that a smaller CC runner will make more power than larger runner. Engine dyno or chassis dyno would work....
Phillip

GrannySShifting

iTrader: (10)

i dont think it woudl show up in power, ie high end hp, but more of a low end midrange things. Once you get he rpm up velocity is goign to be there, as a function of rpm the air has to move with some speed. At low-mid rpm though, I could see how a large runner woudl have a larger volume of air and be more "stagnent" right after the vave opens and carry into the chamber with less "momentum"

think the scavenging effect would be weaker as a result. just ideas nothing based on fact. Would be hard ot have a 200 cc runner, and a 220 cc runenr that flows the same at all lift points to test

Brian Tooley Racing

iTrader: (13)

Sorry, all the data I have supports the bigger runner making more power.

TTT for ya brother

Tony Mamo @ AFR

iTrader: (13)

Hello...

For a street or street/strip car which most of are driving, I'll take a more efficient, high flowing "smaller runner" cylinder head any day of the week and twice on Sunday. The key is to try to have both to make it an extremely effective engine package (meaning ports that have a small cross-sectional area and high flow). You can certainly make big power with a large high flowing port, but it becomes more narrow in its focus and is better suited to an application that spends most of its time in the upper part of your tachometer....that is really the only area it will be extremely effective. Show me a smaller head that flows the same or better and it would still be my choice even in that narrow focused racing type environment.

Once again, every engine builder will have his or her way to approach making power....speak to 10 and you will probably get 9 different answers, but the generalization I just laid out for you would probably be accepted by most....

Stay tuned for some hard facts (dyno numbers) on the new AFR "small runner" 205's....The results I have seen this week have been anything but small!!

I will be starting a thread this weekend with some preliminary information pertaining to that.

Regards to all,
Tony Mamo

Brian Tooley Racing

iTrader: (13)

Tony, I think what Phillip was looking for was some data, I know our LS6 heads that are bigger ports and valves whoops the dog $hit out of our LS1 style heads, that have the smaller ports and valves. I will attach a file, a 5.3 LS1 head with 225 cc and 2.02 valve, and a 230cc 2.05 valve, on stock shortblocks, with basically the same combo of parts. The curve labeled Ryan is a 5.3 head with the smaller ports and valves and the curve labeled Andy is a LS6 head with the bigger ports and valves. Hope this helps.

BTW, Tony, can you guys send me a set of bare LS castings, or two, I have a customer that wants to make 1200 hp and he needs your deck thickness. I will try to call.

99 Black Bird T/A

iTrader: (4)

Of course this is just me speculating based on what little we data we have seen on the board.

I think about veloctiy vs port size vs flow vs power like this. The flowing data is ~for all cases but fairly typical of what we've seen on the board or heard about AFR's new heads. The intake runner length is assumed constant in the below examples. Since all these heads bolt up to the same short blocks and use the same intakes the intake lenghts should be similar. For a true comparison it would be criticle to know the EXACT intake runner lengths in each case.

The velocity index was calulated by CFM/port size with the runner length being held equal for all cases below. The following is of illustration and discussion only.

Examples:

Stock head
220 cfm, 205 cc, the index is 1.07

Generic ported LS1 head
290 cfm, 225 cc, the index is 1.27

GMPP ported LS6 head
305 cfm, 230 cc, the index is 1.33
305 cfm, 235 cc, the index is 1.29

Top notch 5.3 ported head
315 cfm, 217cc, 1.45

Top notch ported LS6 heads or 6.0's
325 cfm, 225 cc, the index is 1.45
340 cfm, 228 cc, the index is 1.49

Super High Velocity - Small runner type 205 type/style head
305 cfm, 205 cc, the index 1.49

Super High Velocity II- Small runner type type/style head - speculated
350cfm, 225 cc, the index 1.55 - this will rock!!!!

Of course with an intake in place the flow numbers will change and go down. This could have a very dramatic impact on the flow numbers. Not every head will lose the same flow thru the intake. Some will shine and only lose ~10 to 20 cfm. Some will suck and lose 50+cfm thru the intake. Knowing the exact flow thru the intake (LS6/LSX) would might allow a better calculation of the velocity index

Here is what I think based on what little data I've seen. The velocity issue in this example is a wash for the better LS6 heads (with bigger runners & high flow) vs the newer AFR 205 (small runner) based on we've been told to date which isn't much.

Will the AFR 205 dominate a stock or ported LS1 head or mediorce ported LS6 casting? Yes, without a doubt.

Will the AFR 205 dominate top notch ported LS6 casting on the flow bench? I don't think so unless AFR gets similar flow to the best LS6 with a smaller runner or shorter runner.

In power production I don't know because chamber design is currently the wild card IMO. I would expect AFR to have a good chamber and have an edge if they use a double quench/racing style chamber.

What will TEA, Absolute, MTI shooting for with a bare AFR? I think opening up the tiny cross section and give the port a little more volume. I'll bet the flow increase enough to make the extra 10 cc's worth it.

the 205 when the aftermarket gets its...
350 cfm, 220 cc, the index is 1.59 - you got something special IMO.

to

and the 225 when the aftermarket gets it...
400 cfm, 250 cc, the index is 1.6 - you got something special IMO.