Head Selection on L33
Holdener said that in his testing, the 706s always performed better than the 317s due to the added compression. So, if you have the fuel to support it, it'll make more power even if you turn it up to 25psi.
Of course, real world says octane limits how much boost you can reliably use on a higher compression motor. For most, dropping compression and upping boost does the same thing.
But what's interesting about the TFS 205 vs 706 comparison is... that's the same compression. The added flow adds power. Again, more boost takes care of it.
But it's still interesting to see more flow is worth 50HP on a very mild setup. And more compression on a slightly more aggressive setup is only worth about 30HP.
Of course, real world says octane limits how much boost you can reliably use on a higher compression motor. For most, dropping compression and upping boost does the same thing.
But what's interesting about the TFS 205 vs 706 comparison is... that's the same compression. The added flow adds power. Again, more boost takes care of it.
But it's still interesting to see more flow is worth 50HP on a very mild setup. And more compression on a slightly more aggressive setup is only worth about 30HP.
9 Second Club
Joined: Nov 2003
Posts: 13,616
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From: Norn Iron
What would make for an interesting test...is the 205TFS....vs the 215TFS
And likewise the 220 vs the 225
Just to see if the extra CNC work is really worth anything in the real world vs as cast
And likewise the 220 vs the 225
Just to see if the extra CNC work is really worth anything in the real world vs as cast
Staging Lane
Joined: Dec 2016
Posts: 82
Likes: 3
The coefficient of discharge is one of the most important part in determing the power potential of cylinder heads. More than cfm flow. Thats why those small stock 706 heads work better than those other ls heads on a 5.3l. Airflow versus valve sizing.
TECH Fanatic
Joined: Feb 2015
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How do you translate coefficient of discharge to velocity?
Staging Lane
Joined: Dec 2016
Posts: 82
Likes: 3
At the correct bore size ur using
average airspeed is 246-268 fps.
Peak velocity 285-310 fps.
pinch point should not exceed 300 fps
Should be pretty safe numbers.
average airspeed is 246-268 fps.
Peak velocity 285-310 fps.
pinch point should not exceed 300 fps
Should be pretty safe numbers.
Last edited by Stonerracing; Aug 17, 2018 at 07:56 PM.
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Joined: Mar 2014
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From: Ohio
I made 712whp and 802 ft-lbs on a Sea-Land dyno at 17 PSI with it a couple of years ago through a 4L80e. I don't think the converter was locked the entire pull, we never verified.
I'm thinking somewhere in the ~875whp/950wtq range at 24 PSI on pump gas.
No solid E.T. at the track, I couldn't reliably keep boost down on the launch well enough to stick it. I switched to using timing-by-gear and ended up grenading the transmission.
Trap speeds back up the horsepower figures.
I'm thinking somewhere in the ~875whp/950wtq range at 24 PSI on pump gas.
No solid E.T. at the track, I couldn't reliably keep boost down on the launch well enough to stick it. I switched to using timing-by-gear and ended up grenading the transmission.
Trap speeds back up the horsepower figures.
I made 712whp and 802 ft-lbs on a Sea-Land dyno at 17 PSI with it a couple of years ago through a 4L80e. I don't think the converter was locked the entire pull, we never verified.
I'm thinking somewhere in the ~875whp/950wtq range at 24 PSI on pump gas.
No solid E.T. at the track, I couldn't reliably keep boost down on the launch well enough to stick it. I switched to using timing-by-gear and ended up grenading the transmission.
Trap speeds back up the horsepower figures.
I'm thinking somewhere in the ~875whp/950wtq range at 24 PSI on pump gas.
No solid E.T. at the track, I couldn't reliably keep boost down on the launch well enough to stick it. I switched to using timing-by-gear and ended up grenading the transmission.
Trap speeds back up the horsepower figures.
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