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I'm really excited to see what a Peak Speed ported tbss intake will do as I had my old tbss intake ported by somebody else with no gains (no runner work just cut a section of the "tube" out).
The Fast 90 was first up for testing. It sounded decent with fairly clean air flow. The cfm tampered off around ,.600 lift. We decide to push the intake all the way to .850 lift to see if it would go turbulent or the intake port crash. The Fast managed to hang. My impression is the intake would benefit from some basic clean up inside and flow better. Brett remarked the interal structure of the Fast 92 was slightly different and a better. Hopefully, we will be able to test a Fast 92 next time thanks to the WS6 Store and see what difference we can find in airflow.
The Peak Performance Radical Ported TBSS was up next. My first impression was this is a very nicely cleaned up intake. I expected to see a few cfm better than the stock TBSS. By .300 lift even I noticed how clean and smoothly the TBSS flowed. I realized Bret had noticed immediately. He committed the TBSS sounded very good on the bench with the clean crisp flow. We pushed the TBSS just as hard to .850 lift and on the top end at very high lift, it out flowed the Fast 90. It sounded clener than the Fast intake through out the test. The ~88 mm snout opening of the TBSS could possibly be opened up to a little more to maybe 90-92 mm. There appears to be enough material. The porting definitely improved airflow.
We didn't collect .450 lift data and I didn't realize this until after the test. We used preprinted sheet to record the results and it didn't list .450 lift.
Brett at Land Speed was outstanding to work with through the testing. I very much appreciated his willingness to do the testing and dedication to getting accurate data.
I decided to compile a new chart with all of the test data. It also includes a sneak peak at what's coming in the future thanks to WS6 Store stepping up and providing several popular intakes for testing!
Brett mentioned that one way to think about the flow numbers is what happens during the intake valve event. The valve is on the seat, initial lift occurs along with a bit of reversion, the valve continues to open, reaching peak lift briefly and then begins to close.
For instant for a .650 lift cam the event looks like this.
.000 on the seat
.100 valve is cracked open, some air flow and reversion
.200 airflow pattern established filling the cylinder
.300 to .600 air flows into the cylinder as cam approaches peak lift
.650 peak lift, airflow at peak, then the valve starts to close
.600 to .300 air flows into the cylinder
.200 airflow pattern begins to falter
.100 valve is cracked open, some air flow and reversion
Basically in the cycle we have airflow at each lift value twice in the cycle except for the peak lift which only occurs once.
Definitely just looking at peak flow numbers can be misleading. This makes a good argument that the mid-life numbers are most critical.
So here is sort of how I think about out intakes that have been tested based on the above concept. We should add up all the flow numbers between .200 and .600 and count them twice due to the valve opening and closing. The peak valve should only count once. Given that momentum and velocity are important the .550 number should be included since our range is .200 to .650 lift. I decided to toss out the .100 lift number due to reversion occurring, airflow momentum being low and velocity not being well established.
There are other ways to think of the data, however applying the above idea in layman's/novice terms leads to this chart.
After adding up airflow, diving by the 13 lift points gives a rough idea of airflow for the .200 to .650 lift for a given intake.
Note the Mamo MSD, Super Vic & LSXRT standout with over all airflow.
The Ported TBSS, 90mm LS6 & Fast 90 stand out as the next group of intakes.
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Last edited by 99 Black Bird T/A; 11-05-2018 at 09:05 AM.
A simple extra back cut on the valve will increase low and midlift numbers by quite a bit. Gm started that on some of their 243 heads and it helped flow alot surprisingly. Nothing to do with the intake but will also make the intake flow more also on the head.
I wonder the the TBSS's slightly shorter intake runners are what allowed it to pull head of the Fast 90 in the very high lift range?
Originally Posted by tech@WS6store
A simple extra back cut on the valve will increase low and midlift numbers by quite a bit. Gm started that on some of their 243 heads and it helped flow alot surprisingly. Nothing to do with the intake but will also make the intake flow more also on the head.
That's an excellent point. Both Brett & Jim mentioned the valve job that's on these old GMPP's could be improved in the middle lift numbers by doing that. Before bolting these GMPP's on an engine one of those back cut valve jobs would definitely be worth looking into.
I know it's extra work, but a before- and after-backcut flow test would be beneficial. That might be the reason GMPP CNC heads usually fare just a bit worse than the better ones from TSP, S-D, and others.
Yes, a before and after "back cut" revised valve job would be interesting.
The heads have 2.00 stock sized intake valve & 1.550 stock sized exhaust valves.
Brett has mentioned the heads have a solid 10-20cfm left in them with the stock sized valves with a revised valve job. Brett had extensive experience at Katech tweaking GMPP/LPE heads for optimal results. Some of the Katech prepped race cars used the GMPP/LPE head as part of sponsorship.
BTW - The GMPP 250 cc intake ports makes them tricky to cam on a 5.7 LS1 but possibly a nice budget cathedral for a LS2 or 402 LS2 stroker with new valves and valve job
Maybe Land Speed Cylinder Heads will chime in
Last edited by 99 Black Bird T/A; 11-06-2018 at 08:11 AM.
My take is that between the Fast 90 and TBSS ported, they both should make near the same hp. The TBSS might peak a little higher since the runners are a bit shorter. Too bad the TBSS looks like azz and is too tall for 4th gen fbodies.
I've seen different runner volume for the Wegner 799 heads. Some say 229 and others closer to 250.
Last edited by wannafbody; 11-06-2018 at 09:30 PM.
I will be quite interested to see the results of the Fast 92 v 102. Although I've always been curious about the "under the curve" differences between these two manifolds and an LS6.
The Fast 92 should produce more under the curve power than the 102 based on runner length. The 102 should produce a bit more power at the top. Flow testing won't give you that info but a dyno would.
Yes, a before and after "back cut" revised valve job would be interesting.
The heads have 2.00 stock sized intake valve & 1.550 stock sized exhaust valves.
Brett has mentioned the heads have a solid 10-20cfm left in them with the stock sized valves with a revised valve job. Brett had extensive experience at Katech tweaking GMPP/LPE heads for optimal results. Some of the Katech prepped race cars used the GMPP/LPE head as part of sponsorship.
BTW - The GMPP 250 cc intake ports makes them tricky to cam on a 5.7 LS1 but possibly a nice budget cathedral for a LS2 or 402 LS2 stroker with new valves and valve job
Maybe Land Speed Cylinder Heads will chime in
the GMPP ls6 heads are pretty badass and capable of big hp. They’ll support a lot of rpm.
11-05-2018, 08:27 AM
