Stock heads flow rate
07-15-2006, 05:18 PM
#1
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Stock heads flow rate Does anyone have the intake flow rate on stock ls1 heads? The flow on the stock LS6 heads?
I want to know where I'm starting at when looking for a set of aftermarket heads or stock Ls6.
I want to know where I'm starting at when looking for a set of aftermarket heads or stock Ls6.
07-15-2006, 11:52 PM
#3
Phil,
Those numbers seem a tad high...
My bench (and others I trust) show a stock LS1 in the 230-235 range and they almost always peak at .500 lift....the 243 LS6 casting go in the 255-260 range and they normally peak at .550. Both heads normally "back up" after they peak.
Exhaust flow is very similar on both....around 190-195 CFM or so (@.600 lift) with a 1.75" flow tube. The exhaust doesnt back up but only climbs a few CFM if you check it over .600
LS1 Int. volume usually 200-202 cc's
LS6 Int. volume 210-212 cc's
Hope this helps...
Tony
Those numbers seem a tad high...
My bench (and others I trust) show a stock LS1 in the 230-235 range and they almost always peak at .500 lift....the 243 LS6 casting go in the 255-260 range and they normally peak at .550. Both heads normally "back up" after they peak.
Exhaust flow is very similar on both....around 190-195 CFM or so (@.600 lift) with a 1.75" flow tube. The exhaust doesnt back up but only climbs a few CFM if you check it over .600
LS1 Int. volume usually 200-202 cc's
LS6 Int. volume 210-212 cc's
Hope this helps...
Tony
07-16-2006, 06:58 AM
#4
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Have never seen anyone's stock LS1 flow sheet in which the heads peaked stalled at .500. Can you post the flow sheet you are referring to? Have noticed the heads gain marginally above .550 to .600 but have not noticed a reversion effect.
Reviewed a number of flow tables posted over the years here at LS1tech.com and other LS1 sites. None have indicated the LS1 head ceases intake flow gain above .500" lift. If correct, your post indicates cams with lift in the .570/580/590" range on stock heads are essentially of no use. Strange in that reputable cam manufacturers, both mass market and custom designers, do indicate lift in the .550 to .600 range for stock LS1 heads.
Reviewed a number of flow tables posted over the years here at LS1tech.com and other LS1 sites. None have indicated the LS1 head ceases intake flow gain above .500" lift. If correct, your post indicates cams with lift in the .570/580/590" range on stock heads are essentially of no use. Strange in that reputable cam manufacturers, both mass market and custom designers, do indicate lift in the .550 to .600 range for stock LS1 heads.
Last edited by Felix C; 07-16-2006 at 08:32 AM. Reason: additional info
07-16-2006, 09:18 AM
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I have seen stock heads on the bench and did stall but they didnt drop either. Cam places make the .500+ lift cams so that the ramp rate is easier to make aggressive that way.
07-16-2006, 11:47 AM
#6
Originally Posted by Felix C
Reviewed a number of flow tables posted over the years here at LS1tech.com and other LS1 sites. None have indicated the LS1 head ceases intake flow gain above .500" lift. If correct, your post indicates cams with lift in the .570/580/590" range on stock heads are essentially of no use. Strange in that reputable cam manufacturers, both mass market and custom designers, do indicate lift in the .550 to .600 range for stock LS1 heads.
Put a manifold in front of the heads and watch alot of things change. Also, a running engine acts much differently in regards to airflow because things are happening so fast the heads spend tiny increments of a second at or near peak lift. Even if the heads do back up a little on an actual running engine, getting to the big airflow numbers sooner (with a more aggressive cam) still makes sense. The head on my 383 backs up a little around .600 lift because I was forced to mill them more than I was hoping due to my pistons coming in with a larger dish than expected (long story) and I refused to build it with less than 11.0 to 1 CR. My solid roller is around .660 lift and still seems to be very effective with a head that backs up a little some .070 sooner....the dyno numbers and performance results are testament to that. Once again....a running engine is a completely different animal than a flowbench, but a flowbench is certainly an excellent tool (one of them) when it comes to cylinder head devleopment work.
I will dig around for my stock LS flow data this week if I have some time. The numbers I quoted are from memory and I know my peak numbers and where they occured are right on....cant recall how much they pull back (or just possibly flatten out), but Im thinking the LS6 head backed up more.
Tony
