turbo6man

iTrader: (5)

I was wondering with all these big power SBE turbo builds on the stock 317 heads where do the ports stall out on a flow bench. If you were to change the cam at which point does the lift to flow gain not be worth the spring pressure and geometry issues.

Forcefed86

iTrader: (4)

ablakez28

iTrader: (9)

Casting Number 317, 035
Head: 2001+ LQ4 and LQ9 6.0 Liter Truck
Material: Aluminimum
Part Number:
12562317 -LQ4
12572317 -LQ9
12572035 -LQ9
Combustion Chamber Volume: 71.06cc
Compression Ratio: 10:1 LQ9 Flat top pistons
Compression Ratio: 9.6:1 LQ4 Dish piston
Intake Port Volume: 210cc
Exhaust Port Volume: 75cc
Intake Valve Diameter: 2.00 inches
Exhaust Valve Diameter: 1.55 inches

Stock Head Flow Numbers
Chamber 71.06cc----0.100---0.200--0.300--0.400--0.500--0.550--0.600
Intake 210cc-----------66-----142-----196---228----236---238-----240
Exhaust 75cc----------59-----104-----137---155----167---173-----177

From WCCH
Here's the stock 317 port:
Lift......Int...........Exh
.100" ..64.8........53.3
.200"..142.1.......111.6
.300"..204.3.......146.8
.400"..233.5.......164.9
.500"..250.0.......174.2
.550"..251.2.......181.2
.600"..253.0.......184.4

Test bore = 4.030"
Exhaust tested without pipe.

turbo6man

iTrader: (5)

Thanks, I have searched and seen the flow numbers are redily available up to .600". when I look at those numbers I see the head drastically began to loose any significant flow after .500" and that is what got me wondering what they were up to like .700"

Using this as an example
.400"..233.5.......164.9
.500"..250.0.......174.2
.550"..251.2.......181.2
.600"..253.0.......184.4

I could see the benefit of running a .500 lift cam based on above flow data, just wondering how much is gained by going bigger than that? Also I know a flow number does not tell the whole story so I was wondering If I was missing somthing and hoping some one could give there thought on the big picture of flow vs lift to = more power

JoeNova

You have to remember that a .600 lift cam doesn't spend all of its time at .600 lift. The higher the max lift, the more duration that is spent in areas closer to max lift.

According to the flow numbers, a .550 lift cam won't make much power over a .500 lift cam. But a .550 lift cam will spend a lot more time with the valve open further than .400 than a .500 lift cam will, and therefore take more advantage of that .400-.500 flow differential. A cam with only .500 max lift will spend more time at lower lift values than a larger cam. This is something that shouldn't be overlooked.

Also, boost scews flow numbers. A head will typically flow more when subjected to boost, because the pressure differential on the front and backside of the valve will be greater, increasing flow velocity.

stock48

iTrader: (17)

I have seen them stall around .550" and 799's stall at .500" and then backflow after .525". Just like said above tho extra lift will not hurt as long as profile is not too aggressive. I like to run a mild lobe with heads that flow well in the lower lifts when using hyd rollers.

turbo6man

iTrader: (5)

Interesting!!! I am in the process of changing heads and cam now. I had stock 317 heads with a hyd roller dur@ .050 was 235 247 and lift was .647" and .657" installed @ 114 degrees I/C. Car ran 9.2@148 but it really would severely drop in power after 5500. that's what got me thinking about the flow of stock heads(and spring pressure and the 5/16 .120" wall pushrods). I also feel that that cam could have been increasing the back pressure which would also effect exhaust port flow right?

turbo6man

iTrader: (5)

Thats exactly what I'm doing now. Chris Frank set me up with a killer set of cathedral tfs heads that have amazing mid lift flow numbers. I had tick hook me up with a much milder custom ground cam which has way less overlap.
I want this motor to make some steam all the way to 6500

2000RATA

Care to pm me those TFS frank numbers? Also what size valves and runner volume?

stock48

iTrader: (17)

It's most likely you were losing control of valves or crashing lifters. That is typical of a high lift or aggressive profile on a hyd roller turbo engine. Many times I have seen the mild low lift lobes pay dividends over those combo's. I have a old mild hyd roller I use in my NA BBC's. It's a 90's erra mild lobe. I have tested it against many later design and more aggressive lobes and they are all down on power unless you use high end short travel lifters, and light weight valve train. Seen same things with the aggressive hyd flat tappet's.

Tjabo

Yeah, I was going to say this is the forced induction forum, I don't think port stalling is really relevant, maybe not even possible, is it? Maybe something like port velocity at different pressure differentials or something? But that's probably way too theoretical, I guess first hand experience is king here!

In turbo setups, relative flow of the two sides of the turbo have a lot to do with what happens in the ports and combustion chamber too... So complicated! Lol

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turbo6man

iTrader: (5)

I did not get alot of flow numbers from Chris, we talked more about what I wanted the car to do and perform like. We talked about the cam that Martin had speced for it (smaller than original cam) and also that it was street driven. We talked about the new turbo (s484 with 96 ex wheel and 1.32 A/R t6). We spoke about how the car had gone 9.2@148 and that I would like it to run solid 8.5's in the mid to high 150's but have good street power as well. Based on that he recommended a 65cc (317's were 70cc) chamber which with my piston yielded a static compression of 9.7:1 (Im on E85). He chose to do his 242cc intake runner program and his power adder exhaust port. They have 2.080 intake valves and 1.600 exhaust valves. He said that this port would have way better low and mid lift flow but also run up to .750" without any flow issues.

turbo6man

iTrader: (5)

I am really excited to see the difference especially from 5500 to 6500. I got to say though that old school Lope from a cam really appeals to me... I know it robs some power for my turbo application, but hopefully this new 230's duration @.050 will have alittle chop to it....
I am also curious as to what the stall to mid range into boost will be like because I gained static compression from lower cc heads as well as dynamic compression from the cam change.

stock48

iTrader: (17)

I used to run a Pt88 T4 on my truck and on a mild ported 317 9.0:1 370 with my 215/114/.566 cam it charged to 6800 rpm and trapped mid 140's on mph at 4800+ lbs. That was with shimmed single springs too lol

turbo6man

iTrader: (5)

See that is what I have been telling my friends. The car runs good but at 3180lbs and over 23lbs boost should be faster. It is laying over above 5500 when it should be charging much harder all the way to 6800.

Here is another interesting thing. When I bolted on the s484 (I have not ran it with new heads or cam yet) and went to the track it ran the same times but on the Holley learn table it only asked for more fuel in the mid range area. It did not need any more fuel above 5200 or so. So that made me believe something was not letting it flow more air which means it did not need any more fuel. That is why I am trying a cam with much less overlap(backpressure) and heads that flow more air (pretty sure it was not this cause you can attest to going fast at a much higher weight) or valvefloat(I upped spring pressure, went to 3/8 pushrods, and short travel lifters).

oscs

iTrader: (19)

Good info here