Whipped383

Well I'd like to find someone to bore my stock throttle body. Any thoughts on if its possible to take it to 85mm?

TIMINATOR

When I get back in the shop Monday I will sonic test a few Throttle bodies and get back to everybody. TIMINATOR

Whipped383

Cool let us know

TIMINATOR

Not happening without major work. There are several thin sections about .090 thick that will break through. The throttlebody is 75 mm, and the bigger step out at the bottom is 76mm. You could safely go to 77 or 77.5mm, but the gains wouldn't justify it unless you could weld it without warping or going thru the thin sections, bore it yourself, and could make your own butterfly. I can, and I just may do it to see what airflow I can get. I always prefer to modify stuff rather than replace it. So far I have ported and smoothed one of mine and picked up a decent seat of pants gain, but I have not slabbed (thinned) the shaft in my mill yet. The porting gain runs between 85 and 100 CFM, depending upon the different variables as it is stock. I'll slab it later and report. Keep in mind that the x-over tube needs to have the Helmholtz resonator removed along with the shroud divot removed also to have the throttle body help as much. Those mods allow the airflow to be more laminar into the bend at the t-body. Then if you believe me, remove the screen and see the gain, if you don't think so then replace it. Mine has been out for several tanks of fuel and no codes or no goofy trims either. Do the airbox and inlet too. Get the headers on and then change the muffs too. TIMINATOR

Whipped383

Well intake is on. Not as much as an improvement as I thought it'd have but the truck is heavy so butt dyno makes it hard to tell. Above 3000 rpm it comes alive tho. Definitely worth it just hoped for more.

TIMINATOR

Did you do the air box, throttle body and crossover mods yet? If not, you will probably get more gains because you will have more available air TO the intake. That's my theory anyway, and its the reason I did the other mods first, so when I do get to the intake, I hope I'll see a truer picture of the gains there.
The headers will help the overall system flow and enhance the intake gains too. The scavenging effect of long tube tuned headers starts intake flow before the piston even starts to move down from TDC. All of these intake and exhaust gains will enhance each other, a lot.
My theory is that what y'all refer to as the "baffle" was not designed as a baffle per se, IE to reduce intake noise, as in the air box, or as a deliberate horsepower limiter.
I believe the design intention was to have the air enter at the center of the manifold BETWEEN all of the runners to allow a better balance of the airflow to ALL cylinders. The effect of better cylinder balance allows the engine to run smoother making more HP, Torque, and better fuel mileage. It also keeps cylinder balance codes from being set.
GM also did something similar with the Grand National turbo manifold, and early crossfire manifold, but with actual baffles to even out the individual cylinder flow.
I am nearly done with my flow bench adaptors that will allow repeatable results between different 8.1 manifolds, with and without throttle bodies, and different sized throttle bodies, and will allow me to measure each individual runner's flow. Then we'll know for sure.
When GM designed the early Corvette Fuel Injection spill valve intake and then their Crossfire intake, they employed a large plenum to enhance top end flow, later, the Tuned port manifold, in use for quite a while, employed a smaller plenum to enhance better low end torque and throttle response while keeping the top end HP. The Grand National turbo manifold had a small plenum for the same reasons. We have experimented with the GN intakes quite a bit, and like others we played follow the leader with plenum spacers in the beginning. Those spacers helped runner balance and slightly enhanced top end HP, but always with a loss of throttle response and fuel mileage. We learned a lot.
Notice that the early Ridge Runner and Tunnel ram intakes of the 60s and 70s all used a large plenum, as did the earlier performance dual plane intakes, where as the later 80s and later, T-rams and dual planes employ a small plenum and still make more upper end HP to boot.
With my 8.1 mods I hope to increase flow, keep the runner flows as balanced as possible, and keep the crisp throttle response of the stock 8.1 manifold. Oh yeah, I am planning to reduce the heat soak conditions too.
I don't ask for much, do I? If anyone cares about plenum size in relation to cylinder filling at different RPMs, and throttle response differences, I may be persuaded to post something, but right now my two typing fingers are bruised and need a rest. TIMINATOR

Whipped383

Everything swapped over.
All done. If you look close by the alternator you can see my new PCV hose. I tried to hide it the best I could. It runs down the bottom of the fuel rail to the back.

Whipped383

Tim I totally agree with you on the intake design. I'll add one more thing to your theory on why it was designed the way it was, the PCV and the EGR come into the bottom of the plenum witch would distribute them more evenly.

I can tell you throttle response is much better. But the overall noise is a lot louder.

TIMINATOR

What year is your T Body? Mine is a 2002 and the stepper motor is much smaller. What I posted about the TB relates to the 2002 and probably earlier only. TIMINATOR

Whipped383

Mines an 03. The year they changed throttle body's. You have an advantage tho they make an adapter harness to run the LS2 90mm TB for about 60 bucks. That adapter needed for mine is 250 bucks. If it wasn't for that I would have modified my intake for a 4 bolt style LS throttle body in a heart beat