Don Terrill’s Speed-Talk

Dead stock 2003 4.3l owned by a buddy who is leaning towards a future full engine build. 101k miles. I convinced him to let me loose on it for a few quicky ft/lbs. Idea was throttle body porting rough surface texture. Improve air cleaner plastic conduits. Install K&N filter later this week. Butt dyno from buddy in near future. With my luck it will run with a big enough kick to cancel the engine build.

4.3l come with a large thottle body stock. I decided to do some flowbench work the experts can abuse me on. With a 2.82" exit bore on the tb it flowed 725 cfm at 15" which was the best depression my bench could muster. Way more than I would have expected. That was bone stock.

Tb hat knocked flow down to 580cfm at 20.7" which was the best the bench could do. I should included stock tb had a horrible sound. The flow with the hat puzzles me. The hat is designed like a very low profile 90 degree intake port with a square ssr.

The easy part of the project. Rough surface tb treatment with radius edge. Just this changed the tb flow to 760cfm at 13.7" depression. That is a 39 cfm increase losing 1.4" depression. Interesting. Unported hat on ported tb 605cfm at 19.5" depression. Ported hat 610cfm at 19" depression.

Upper aircleaner housing radius mod. Time limited project so I was not able to flow full conduit. Which would have been fun.

With my own car I hooked up a Scangauge and had it watch intake manifold pressure and temperature as I drove around. Pedal to the metal the intake manifold pressure is 99% of barometric and the temperature (after the engine has been running for a few minutes) is within a couple degrees of ambient. That was enough to put off all thoughts of installing an aftermarket cold-air intake and filter; the stock setup is already a cold-air intake!

The only issue with mine is that the air intake duct passes over top of the engine, so if you stop the engine for a few minutes, it heat-soaks, and it takes a few minutes of driving to recover ... which is not worth pursuing.

The little tweaks should help a little ... but only a little!

Intake filter bottom venturi mod. Diameter of venturi is necked down to 2". Why would Chevy do this? I believe increasing the airspeed at the air inlet reduces inlet noise. Diameter increased.040" and finished with fine surface by hand.

Brian P wrote: ↑Sun Apr 08, 2018 3:01 pm With my own car I hooked up a Scangauge and had it watch intake manifold pressure and temperature as I drove around. Pedal to the metal the intake manifold pressure is 99% of barometric and the temperature (after the engine has been running for a few minutes) is within a couple degrees of ambient. That was enough to put off all thoughts of installing an aftermarket cold-air intake and filter; the stock setup is already a cold-air intake!

The only issue with mine is that the air intake duct passes over top of the engine, so if you stop the engine for a few minutes, it heat-soaks, and it takes a few minutes of driving to recover ... which is not worth pursuing.

The little tweaks should help a little ... but only a little!

I need that 1%!

We will see if my buddy feels a difference.

LOL I know the feeling. What about that wonky 45-degree bend and flex hose just ahead of the "hat"?

Brian P wrote: ↑Sun Apr 08, 2018 3:11 pm LOL I know the feeling. What about that wonky 45-degree bend and flex hose just ahead of the "hat"?

I know, I wanted to flow the whole mess but was afraid of ruining the mass air meter. I had enough work rigging a decent tb setup that I could operate the butterfly.

I did extensive induction and exhaust work to both my 4.3 vortecs in my company work vans and have many parts leftover after hanging up my contractors hat. Would be will to practically give some of them away if you pay the ride. To list a few...

Granatelli tb
Ported slabbed oem tb with screen removed
Modified/raised/epoxy tb hat
Taylor vmax plenum spacer
Improved efi spider
Cold air intake setup
Modified oem upper and lower plenum
Msd coil

Probably have a few others i can't think of right now and could work on digging them out for pics if needed

^^^^ beat me on the epoxy raised hat

Most oem air setup are designed for packaging and noise. I plan to use my stock airbox on a sim project but replace the zig-zag n shape changing tubing between it and the TB. Also I'd cut the filter box lid to open it more and open up/remove more metal from the core support.

Very interesting TB mouth results I had wondered what burr would do there.

LOL I'm gonna have to pull the hat on my 09 Silverado to see if it has all those plastic lips someday.

Can you get a spacer to raise the hat any? idk the diameter but if you can't get a premade spacer might be able to find some plastic tube about that size and epoxy it to the hat. I'd prob not want to do it on a daily but a carb hat is one of the places I'd prob try n help the flow with some epoxy here n there for a cruiser/race project anyways.

I drove the truck down to the plant and my buddy drove me home. I didn't know s10's had an axle hop issue. My buddy is thrilled, he said it feels totally different, snappy and has never burned the tires like that before. I will take it as a win.

The hop can be pretty bad, you can fix it with springs clamps or helper springs. I prefer to use helper springs and you install them on the forward instead of rear like they are supposed to be used. Then either the top or under side will change ride height bout 1/2", I did top and it lowered the rear.

edit: I remembered how it went so I corrected it.