From what I've seen the low profile intakes should peak similar to a single plane intake, but carry further past peak
There's one dude with a 388 LS7 with the sniper low pro that made ~680whp and went very fast in a heavy Fbody to back up the power. I've not really seen anyone else with a serious engine combo and one of these intakes.
All I did was stick a tape measure into the plenum after it was already bolted down, but from best I can tell the bell mouth is 3" and my estimation then is the runner entry is 2.5" diameter. The runners are 4.3" long.
A 2.5" circle has a CSA of 4.91 sq inch and I think the port flange CSA is going to be in the range of ~3 sq in. The ports didn't have any significant mismatch and the size is relatively close to a stock ls7 port.. Stock LS7 heads at 259cc runner volume have an MCSA of ~2.8 sq in. This close to the port flange it would actually be better if the runner opening was more in the range of 2.25" which would be a CSA of 3.98 sq in - honestly still too much taper - but if you ported the heads up to 2.9-3.0 MCSA would probably be in the right range.
They very may well be 2.25" my measurement was extremely unreliable and I didn't think to measure it sooner. They are very tapered though - more than any rule of thumb I've seen. I don't expect any benefit from runner length tuning with these super short runners. Harmonic tuning doesn't start to help until ~8500 rpm and are probably not actually in tune until 9k+. They just offer a dead straight shot from the intake to the plenum with super low flow losses.
I've done a lot of time wasting thinking about ITB's, runner diameter and lengths for intake manifolds and 2.5"/63.5mm is right in the right wheelhouse for a 427 to have a consistent taper down to the MCSA at the throat IF the throttle body is at a more typical ~6-7 inches from the port flange. Most kits you'll find are 50mm or about 2" - if you're lucky 55mm. It always gets on my nerves to see intake setups with throttle body diameter less than the valve throat size, but the LS7 2.2" intake valve makes it tough.
In the end, I'm hoping for the right power delivery more than power levels. It has been something I've been chasing for a decade haha. Even at just low 500 whp the car was really outrageously when driven in full anger on a canyon road. The huge cam in the 402 definitely made it pull to 7400rpm which was fun, but I don't want a hog ass cam. I just want the power delivery to match the nature of the car, and have it be rewarding to rev out instead of torque around at 3500 rpm through the twisties. I'm fine with torquey - but think BMW S65 and not your Silverado that got you to the track lol.
I'm also hoping the intake doesn't make any weird noises or cause any tuning problems lol.
