Jimmyz28

I did MANY searches and can't find this info.

Does anyone know the #'s:

Lift------Intake (cfm)-----Exhaust (cfm)
0.100
0.200
0.300
0.400
0.500
0.600
0.700

0Brian@RPT

I would like to see those numbers as well

0Louis @ LG Motorsports

I will get the entire flow data on the stock heads tomorrow, but they flow 323 @ .600 here. Every bench will be a little different

Uncle Sam

I have both the intake and exhaust flow charts from GM, but I don't know how to attach them. However, I got them off of this forum so maybe a search will bring them up.

I am not allowed to post attachments, sorry!

Michrider

These are the published numbers for an L76/L92 on a 4" bore, which should be real close to an LS3. Maybe a hair more flow on the LS3 with the larger bore unshrouding the valves a bit.

Lift---Intake (cfm)---Exhaust (cfm)
0.100
0.200 151 111
0.300 208 152
0.400 256 174
0.500 294 183
0.600 316 189
0.700

Jimmyz28

Lingenfelter has this for STOCK #'s on their website:

Valve Lift .200 .300 .400 .450 .500 .550 .600 .650 .700
Intake:--- 156 226 276 294 310 324 332 332 308
Exhaust:-- 120 158 183 190 194 199 202 204 205

SpinMonster

Those numbers are for a 4.125" bore.

Smaller bores yeild smaller numbers.

Jimmyz28

Their website says they're for a 4.065 bore. Anyway, you're right. Wonder why GM put such low number on the exhaust side...hmmm.

Michrider

Emissions would be my guess. Big exhaust port flow probably not the greatest for low rpm complete combustion. I remember the gigantic ports of the old 426 hemi engines, get behind one of those cars and they pump out the black smoke when they get on it.

Wallacefl

the LPE site shows a good improvement in exhaust flow on their ported LS3 heads...would like to see if ported only exhaust translates into + rwhp.

Jimmyz28

^^^ Yup, I thought the same thing Wallacefl.

andreas g.

My LS3/L92 heads CNC ported flowed @ .600 lift 360 CFM intake , 280 CFM exhaust. Charlie @ RPM motors did the work. He refered to it as a medium street port. It works well.

Jimmyz28

What cam and what kinda power did you see with this setup?

LS3 Machine

Yeah... what he said!

I can't wait to see the LS3 with some head work, the Wieland mani, aggressive cam, LT headers, and pulley will all add up to. Add some gears (and better tires) and Im guessing it will be quite the beast.

andreas g.

The motor was a stroked L92/LS3 block with a 4.100 crank 427 ci. All forged. The cam was small for big inch motor, 232/234/595/598/112. Because of the great head work it made good power. 525rwhp/500rwtq.
It's my daily driver. It had to idle good and get decent milage. @70mph it gets 27.5 mpg. Best of both worlds. I'm now waiting for the release of the FAST 92 for LS3 heads. They say it's worth 20 on a stock LS3, so maybe more on mine. Charlie told me the L76 intake manifold falls over at 5800 rpms. so this new maniflod should help.

Jimmyz28

Ahhhhh...

Yeah, been down the stroker path with my Camaro. So these numbers are from a CNC'd LS3 head. My LS6 stage 3 ported heads did 310/225 cfm @ 0.600. 360/280 cfm is just nutty!!

WOW! I know flow #'s aren't everything but DAMN!

SpinMonster

Not what I said. Yes, they work on a 4.065" bore. What I said was that the flow numbers listed above are what they flow on a 4.125" bore. On a 4.065" and a 4" bore the flow numbers are lower due to more shrouded valves. I hope that is clearer.

SpinMonster

One tuner who doesnt want to be named got an 8HP improvement from ported LS3's (probably just from the compression) that yielded 355cfm on the intake side and 240cfm on the exhaust side. Quoting what killer flow numbers will do for performance doesnt always add up to the expectations. Its why a Cartek head flowing 306 at .600 lift puts down 485+rwhp with a 228 cam and runs 10's while countless other name brands did 500+ with 23x cams and run 11.2's. By the way, this last example was using the same driver on the same day as a joke. The results were unexpected. Another note, who runs more than .600 lift on a cam anyway? Midlift flow numbers are much more important. The LS3's do that unexpectedly well and porting more often than not improves peak lift flow at the expense of mid-lift. So you get a silly flow number at .600 or .650 lift and you run a .588 lift cam....yeah babay.

You cant race flow benches and porting a head with 260cc runners to get 355 cfm increases runner size and slows air down. The theory on the exhaust side is to use a different lobe to build up the air speed. The unported heads on the LS3 are making 485 RWTQ cam only. Dont go by flow numbers. The LS7 heads have pretty bad exhaust side flow but the speed is clearly the winner there as it is here. Velocity may be why the flow number isnt high on the exhaust side.

Charie from RPM motors used to go back and forth with me on this. I was looking at countless cams in 4" bore (non-stroker motors) making a dip in the low end TQ and he was insisting they were good. One guy was constantly telling me I didnt know what I was talking about ad showing me stroker motor results to show I'm wrong. I wasnt impressed with the TQ....it was a stroker. Then Charlie puts a 238 cam in a 6 liter, tunes the magic and gets 508rwhp and 480rwtq. The point was it set the bench mark for TQ. A 6 liter motor made 480rwtq.

I changed my mind about the heads and can tell you with my 3rd cam on the LS3's that they dont work with every combo. Unfortunately, no one is sharing info and you just have to trust tuners to deliver what they say they got with their LS3 cam. Until the poor guys get the 6 liter motors, there wont be any public DIY info. I am privy to some trade secrets and as such they will remain secrets but the heads are sensitive to exhaust side changes (LG headers made a big difference and maybe more than most would see) and the intake side doesnt work like it does on a cathedral port head. A smaller (and sometimes lazy) lobe makes more TQ. Some bigger lobes work well too but the aggressiveness of its opening is key. Compression is a good thing but the heads done give you much room without flycutting.

I think what is needed for these first few years is milling, flycuttin, no porting and a cam swap. With the new Ls3 FAST you will see 535rwhp and 500rwtq......jeeeez....those are stroker numbers. To date the best is 517rwhp and 484 rwtq...Louis at LG setting that mark without a FAST because they didnt market it yet.

Ragtop 99

What style of lobe builds air speed? I've liked the Xer on the exhaust since it stays shut a couple degrees longer for a given duration at .05 and then opens very fast.

The agressiveness is key as in it should be aggressive or that lazier big lobe seems to work better?

I guess I should also ask (while you are typing away ) whether asymentrical lobes have any advantages here.

SpinMonster

Two ways to flow more: duration, faster ramp rate. In a small runner, both work well together, on a big runner it will stall with too much of either.

Yes different lobes are both better and in the case of the LS3 they are required.

If you open a valve too long and too fast the combustion chamber is filled too fast and the air stalls....it runs out of steam. The intake runner is huge and building airspeed is better served with a not so aggressive lobe if the duration is short to moderate. If you open the nozzle on a garden hose 1/4 the water shoots out fast and far. If you take off the nozzle it droops out and doesnt go far due to less speed.

The exhaust side is small in comparison so the longer duration makes up for it. Again here faster ramp rates dont serve it well if both are used. If you open it for less time then you want it open faster. If the exhaust isnt so free flowing, opening it too long or too fast can result in reversion. The intake side would and does work well with shorter duration lobes as proven by DTE and Synergy. Rick has said that he uses a non XER, LSK, XFI lobe and its a 224 on the intek side resulting in a 490rwhp and 480rwtq with a 224/228 on a 112. More einteresting is the non-fast ramp rate lobes. You can only guess but Rick is famous for cam motion lobes and their version of XE's probably work best.

LG on the other hand uses some other aspects such as really long duration on the exhaust side and it inst an LSK. The intake side is a secret and doesnt fit the normal intake runner thinking. My guess is close LSA and effieciency of the exhaust side gets the air out better allowing more aggressive intake lobes.

Rock posted his results on a 6 liter in the dyno section of LS1tech to see the sick results of such a small cam. If he increased the ramp rate and used LSK lobes, my gues is he would stall the runner and lose power. More duration costs you TQ. Find the balance.

Ignore the silly size splits the theorists have like 232 intake and 248 exhaust. The exhaust isnt poor flowing. Its fast flowing. Better headers will equal better results with normal cams.

When GM came up with a cam for the LS3 and these heads all they did was make the intake lift higher on the intake 5%. Another variable.

Where is glass slipper when you need him.
This stuff is his bag.

Keep in mind AFR heads make 500rwhp with a 23x cam and they only flow 305 or so at .600 on the intake side.