I prefer the 70 mm tbodies and matching upper even on lesser than max builds, along with a matching, large up pipe, simply because the air velocity is lower into the manifold for the same air mass, and that allows for better air distributation in the manifold with less "stacking" of the inlet air at the back of the upper doghouse and manifold. The motor runs smoother, and cylinder air/fuel distribution is better.
The Power Plate is a wonderful band aid to the stacking phenomenon, I use them in all builds, even near stock.
Those of you that haven't "lived" on a flowbench for over 40 years can't appreciate this phenomenon.
We also do a lot of 8.1 GM manifold air recircuiting, and PVC mods too, and that is one of, if not THE worst manifold designs we have worked on! Those require cutting the bottom of the manifold off and about 11-12 hours of cutting, grinding, and smoothing to get the air flow balance within 10% or so. Stock they can be as much as 35%+ unbalanced! Since all port fuel injected intakes get nearly the same cylinder to cylinder fuel flow, the mixture AFR is all over the map and at all rpms. GMs "solution" is to incorporate a separate idle/low speed manifold within the large "performance" part lf the manifold. Yeah, it helps at idle, but anything much above the 1500 rpm transition sucks!
On my 8.1 powered 2500 HD 4 x 4, the fuel mileage went from 6.1/ 8.4 to 9.2/12.4 with manifold mods only!
The FIRST thing I noticed, was how much smoother the engine ran at all speeds. Seat of the pants highway speed went from feeling like the normal 68/70 cruise to over 80! I couldnt figure why everyone was driving so slowly! When I knocked it down to what everybody elsse was running, it felt like I was crawling!
RWHP picked up 28 HP+! And those trucks have a 4500 RPM limiter in the computer too. With 3.73 gears and 31" tires my 80 mph cruise rpm was 2100.
The Power Plate makes even stock motors run smoother at all RPMs, and power levels. It also reduces detonation /spark retard due to differing AFRs.
The fast guys change injector pulse width /% duty cycle on each cylinder to keep egts and afrs as close as possible.
Just a bit of knowlege for the interested...
TIMINATOR
and almost bought a 3" up pipe but will probably change intercoolers on the next build. Thanks for sharing your perspective Timinator ! Alot goes into making an engine perform at its best. I think that's why I like Turbo Regals so much. I must enjoy the challenge...
