The TPIS ported GM 75mm and 90mm TB were both shown to have several HP over a stock GM TB's in this month's Street Thunder (National Street Machine Club magazine), so why wouldn't the ported stock Truck TB show gains??? We'll find out, as I plan to test the gains as best I can sometime down the road (dyno, flow bench, and/or track).

Here's a before shot, down the throat of the TB. Electronics have already been removed, but all you have to do there is drill off the rivet heads and the black plastic can slide right off.

Click pics to see a HUGE version of you're blind or something...



Similar shot, butterfly open.



Drilling the side dust cover to get a screw driver tip in to pry it out. Not sure why they did this as they also used sealed bearings just like every other TB has (and most don't have the dust cover there)... It's not like it has a vacuum leak or something. :crazy:



Dust cover removed, exposing the throttle shaft.



Removing throttle blade screws.



Use a flat tipped drift punch to drive the shaft out.



I could totally see where someone could bend the shaft reassembling this as tapping the shaft out of and back into the housing/bearings with the drift and a dead blow hammer takes a bit of patience, but it can be done as mine has been out and in several times without bending it (even after removing the front half of the bar. I'm thinking of making a small press to do this easier on a more repeatable basis though.

That's all I have for now until Thursday night when I can complete the actual filling and remachining of the bypass port and TB porting.

 

O.K., finally got a chance to take some more pics as we finished up fast4popper's TB (he's on the silveradoss forums). I didn't get any in action shots of me optimizing the throttle body because I kept breaking tools... the 1/4" die grinder iced up, my 4" angle grinder had internal wiring problems and couldn't be trusted anymore, my 1/8" die grinder kept tossing bits and bending shafts... We just didn't have a very good day as far as fabrication goes, but at least we had enough time to work around all of these delays and get the job done right the first time.

Just FYI, for the major reshaping, I used a 60 grit 2" round sanding mandrel in the 1/4" die grinder. It takes about 10 minutes or so (when everything works right) to get rid of the entrance ridges and knife edge the lip. The idle bypass port is filled with a kneadable two part epoxy that dries in only 20 minutes, then the hole is redrilled from the back side. If there are any more questions, please post them here. For now, on with the few pics we do have. Click on the image to see a huge version if you like.

Side by side, optimized vs. stock.



Optimized TB held open. Almost done here, as the only thing left to do is grind down the backs of the screws. Thread Locker Blue is used to hold the screws in place. Note the reshaped idle port location and the lack of the large ridge on the right side.



To compare, stock TB held open.



I'll get some more in process pics and some install pics when I reoptimize my own TB again (sold my original TB to a someone in a real hurry so I put a stock core back on ).

 

hmmm... wonder how vast of an improvement that will be??? Keep us posted, good info!!

 

Looks good but you are going to throw up if that thing won't idle correctly. This has already been attempted and many failed. But good luck to you. The funny hump in front and behind the throttle plate are there to help transition off idle.

 

Keep us posted this looks good. It could save some people alot of money if it works with no problems.

 

Sorry if I didn't convay this in my earlier post, but... I've had a ported and polished throttle body on my truck for the last few months without any idle issues. I've done 3 total so far for Silverados... none had any problems what so ever. Fast4popper's truck had no idle issues either when we did his truck in my driveway this past weekend. I've been doing throttle bodies like this for over 6 years now, and had a few issues early on in developement, but none recently. That's why I waited to see if my own truck had issues. We used to do the same thing on carbs "back in the day". Just ask any old timer hot rodder...

The only way I've ever experienced idle issues from any optimized throttle body or carb is from A: Trying to knife edge or round the throttle plate itself, B: Trying to port to deep into the bore and removing material from where the throttle plate is supposed to come to rest, C: Getting the throttle plate ****-eyed when you put it back in and it won't close properly, or D: Bending the throttle shaft during reassembly.

I'll take more pics when I port the next core to help the DIY'ers. Hopefully I don't break as many tools this time, LOL! I guess it was just time to replace some of them, just funny how three tools I use all of the time gave it up on the same day and took away our time to take pics...

 

Looks good! Update us with a "before and after" track time, or dyno #'s...

Austin

 

, any dyno before and afters by chance?

 

Nothing yet for dyno numbers. I'll do it later this year when it's warmer out unless one of my cutomers gets a chance to do it before me.

TPIS has dynoed their ported 75mm LS1 TB's with gains of 3-4 HP and TQ everywhere in the RPM band and 8-10 HP/TQ near redline. They also have dynoed their LS2 90mm ported TB's with between 5-10 HP/TQ, especially in the midrange. These were tested along with different intake/TB combinations in the Jan/Feb edition of Street Thunder on a 5.7L LS6 with basically stock internals and ARP harware, with a TPIS ZL15 grind camshaft and stock 243 casting cylinder heads.

Porting TB's does work, there's no doubt about it...

 

I don't doubt you if you say you have. I was going to do to mine what you basically have done and if it didn't work just swap to the 90mm at the time. It always helps to use a little common sense when you have a grinder in hand.