dug

iTrader: (10)

"Head flow:
Contrary to popular belief, when running a plastic intake manifold on an LS1, airflow at .600" is virtually meaningless. There are several reasons why. First, an LS6 intake will start to lop off airflow above 265cfm. A stock FAST 90mm intake seems to lop it off around 275cfm and a ported FAST 90 seems to lop off flow above 280cfm. What all this means is that most all airflow gains above 280cfm will go un-noticed when you bolt a plastic intake up to it. The real trick is to pack in more airflow in the low and mid lifts. If you look at all of the top running heads/cam vehicles, they will all have heads with excellent flow at .300,.400 and .500". "

Dart 205 heads advertised low lift flow numbers are better than AFR. Would they make more power?

Patrick G

iTrader: (14)

If they flowed more in 57cc form at low and mid lifts on a 3.900" bore, then they should make more power. The real trick is getting a head to still flow well once it's been milled so much. I'd be interested to see the flow numbers on a Dart 205 on a 3.900" bore fixture, especially in milled form. The numbers on Dart's website are not as strong as the one's I posted, but perhaps independant third parties have shown higher numbers.

JPH

iTrader: (2)

the dart flow sheet numbers do flow lower than what is advertised by them from what i have found, but respond very well to mild port work. IMO. good results patrick, i'm sure the 402/408 cubed, big heads/cam guys just love reading this thread. nice work.

dug

iTrader: (10)

yeah, most heads low less than advertised. The beehive springs on the Dart heads should work well with XFI lobed cam.

dug

iTrader: (10)

looks like dart is optimistic with flow numbers.

https://ls1tech.com/forums/generation-iii-internal-engine/513445-had-set-dart-205s-bench-morning.html

"Numbers were good for their small runner heads:

Intake, 205 cc port, 2.02i & 1.60e valves;

.050 _34.8
.100 _69.6
.150 101.3
.200 127.1
.250 154.6
.300 181.7
.350 206.2
.400 231.5
.450 250.9
.500 265.5
.550 274.0
.600 279.4
.650 263.8
.700 265.6

These numbers are from a conservative flowbench. To give you a good basis, here is how these numbers rate against other heads

LIFT - 241 -LS6
.050 _33.8 _33.0
.100 _63.6 _65.2
.150 _96.7 100.7
.200 135.2 138.0
.250 166.3 167.7
.300 191.0 192.7
.350 210.4 213.1
.400 223.2 230.0
.450 230.3 243.1
.500 226.5 254.1
.550 226.5 257.0
.600 230.6 238.0
.650 234.6 240.1
.700 237.8 242.3

Exhaust port on the 205s cam in right at 208.5 cfm.

Other interesting bits of information;

PTV clearance will be .015" worse with these heads over stock 241s because of the larger intake valves,(free drop was .150" as opposed to .165") but the chambers are already smaller; thus, there is no need to mill these. Advertised chamber volume is 62cc, so you're going to have better PTV-clearance with these than milled stock castings at 62cc.


This set of heads had a set of Ti retainers on top of its "behive" design springs. A set of .060" shims sat on top of the seat. These springs ran into coil bind at .670" as assembled which with .050" clearance would allow you to run a .620" valve lift safely. Spring pressures were 145#s on the intake and 136#s on the exhaust.

Let me know what you think guys. This is on Thunder Racing's flowbench. Thanks to Thunder and Jason 99TA.

So, if you're contemplating these heads a few things to consider;

Already assembled with big valves
Titanium retainers
A NEW casting
Designed on a wet flowbench
Ports that are nearly the size of LS1 ports, but flow 42 CFM more
62cc chambers (no need to mill)
Better PTV clearance
Springs that are good for .620" lift safely.

I don't have any pictures of it, but before the heads left from Dart they were hand finished with a carbide cutter. You can clearly see where the valve seats were blended into the bowls and that they cleaned up the short side radius. The extra texture could also aide in preventing flow seperation as the wet intake charge will theoretically adhere to it better. You can see these marks below the valve seat and they fade away into the bottom of the runner. They also got at a few of the casting marks on my heads near the short-side turn. Wish I had pictures...

Lastly, keep in mind that flow numbers are not always a direct comparison. It's just easier to flow heads than to bolt them to a motor and plot horsepower curves. Don't put too much emphasis on flow numbers, and remember that this is a port designed outside of the confines of GM starting with a clean slate.

Ben T."

the_merv

iTrader: (88)

Nice thread..alot of research went into that setup..

TAQuickness

iTrader: (28)

Great work Patrick!

Beaflag VonRathburg

iTrader: (176)

This thread is very informative and covers some aspects that most seem to leave out in the quest for power. Such as valvetrain stability and weight. That's such a huge aspect that's often overlooked.

EDIT: Forgot somethings

What sort of flow numbers have you seen out of the ls2 intakes?

With nitrous applications at what point does the cylinder pressure become too great? You mentioned that the nitrous was very hard on your motor with due to the high SCR, DCR, and timing. Even with the high compression can you just continue to pull timing to adapt for larger pills? Or does the optimal timing aspects you mentioned have an affect on this also? I've always wondered this when reading all these high DCR threads.

Louie83

iTrader: (3)

Very thorough and very analytical, as always. This is exactly why I come to you for advice/speccing.

Great results!

Rob M

iTrader: (1)

Congrats Patrick on your achievement!!

The time you and Tony have spent working things out have REALLY paid off. I was heavily considering some TSP heads and having you spec out a cam for me when I get back this time next year from my deployment, but looks as though now im heavily considering "taking the blue pill..."

Again this NEEDS to be a sticky, tons of good info. I know I learned a bit, especially about where the LS6 intake begins to "lop off". From what I gathered to make maximum efficiency of power on stock cubes, one must almost think of themselves as having a TPI car and use all the potential towards the bottom end of the power band( more cfm flow concern should be placed on the lower lift)

Great write up

sciff5

iTrader: (1)

I am just curious how the sinle plane carb style intakes compare like the victor Jr and the GMPP intake.

I am putting an ls1/t56 in a very light car (2400-2500lbs) and I will have traction problems that will be expensive to fix. The ls1 has plenty of torque to get a car this weight moving so I am wondering if in this instance an aggressive high revving H/C combo with focus on high lift flow numbers would be alright, seeing as the car is gonna be hard already to get off the line without hazing the tires. I was hoping the carb style intakes are a little beter than the plastic sytle intakes in the top end but wanted your opinion.

Obviously a shetmetal intake would be the best bet, but just not in my price range.

b005td

iTrader: (9)

damn i couldnt believe i missed this thread

Josh@PremierAutosports

iTrader: (11)

Congrats on hitting your goal. When are you heading to the standing mile again?

Mia

iTrader: (8)

Patrick, what is that Custom PG Ram Air spacer you ? is it made from plexiglass?

99blancoSS

iTrader: (115)

PG = Patrick G

pdd

iTrader: (3)

congrats patrick on a killer setup thanks for sharing

ls2 bait

iTrader: (11)

i was all ready to put my heads on but now this thread has really got me thinking that i should change my entire exhaust set up and get a custom cam to maximize these tfs heads. i almost feel like an idiot slapping these pretty heads on with an off the shelf cam and pacesetter headers...

71CamaroLS1

Hey Patrick, superb results and an excellent writeup. Unlike many other folks, you don't pretend that there is magic and mystery in making power - just attention to the right details.

It looks the the idle clip in your sig is still with your old cam, right? How does it idle with the new one?

eamador11

Love my AFR 205 heads..glad I went with them! I need to save for the mamo FAST 90

hammertime

iTrader: (1)

Excellent - another ringer from Patrick G and Tony Mamo!

A couple of questions based on some of what I've learned from your past posts:

1) Looks like the 112 + 3 cam puts your overlap bias at -2 (if I'm doing the math right in my head). Do you feel that this combo could pull harder up top with a bias of 0 or +1?

2) Does the curtain area of a similar LSK lobe offer any advantages for the the extra .040 lift? Obviously, you've ran them in the past with great success, but just curious what difference you might see.

I'm wondering how a 236/240 .646/.649 111+1 would stack up against your cam. IVC appears to be the same, netting the same DCR out of slightly less duration at the seat and .050, with just a tad more at .200. Overlap bias appears to come in at 0 (again, if I have the math right). It seems that if it were possible to enhance the +.600 lift airflow over what you have already achieved (a tall order) this cam might pull harder up top.

Fantastic results! I can't wait to see what the next shot fired will be...