You are correct. The TB IAC passage goes into a passage at the front of the intake then runs downward into the belly of the intake then dumps into small holes at the base of each runner. I have a spare TB and intake in the garage to look at.

My point is that the factory TB looks more like the Holley and your Accel and NOT the BBK version. therefore I assumed that "sealed passage" version was more desirable from a design standpoint.

 

Summit brand TB ordered. We will see how much effort it takes to work right.

 

Holley here. Slotted the TPS and adjusted it with a scan tool. 5 minutes of extra work when I installed and I have had perfect start/idle since.

 

I have a BBK. Came with the motor when I bought it. I've had to slot the TPS, drill the IAC hole, insert the brass tube, the linkage came loose and had to be welded, and the blades would stick until it was ported.

 

I bought a TPIS 58mm, its a machined piece of art

 

I can confirm the Summit TB does not have the small hole at the bottom (the hole people are drilling out to fix IAC counts). Also, I do not see how you can use the airfoil on this new TB. There is a threaded piece that falls into the stock TB from the top so you can use a long bolt to hold it in place....the new TB does not have top plate access.

No, this stock TB did NOT come off my car. It is a spare that I mess around with...

 

Why aren't all of these mono blades? Always thought those two holes were kinda small to feed a motor.

 

Cost I would guess. I expect to see gains going to this 58mm not only from more air flow but in reduction in intake restriction.

I'm hoping that with my custom 4" intake tube, my stock TB is where most of the drop in MAP kPA is coming from. Less restriction = better air flow and better efficiency.

Goal is to port my stock intake out to dual 58mm holes (not touching ports) and dyno the car as is. Then swap the TB, adjust as needed to get it to operate correctly and dyno again to see back to back runs.

 

Can't see cost being much different.

 

Tell that to AS&M...

My goal is to spend enough to make the most difference. Given my goals and purpose for the car, spending an additional $300 over what I spent on a dual 58MM TB to get a monoblade AS&M regardless if it's a fully CNC billet piece does not matter to me. Cast the body and machine the important stuff is the same as a CNC piece at a lot less cost.

If I gain 10hp (a wild guess) with a Summit dual 58mm unit at $160 and I would gain 15hp from a AS&M for $400...it's not worth it.

Some like pretty things. Not my style
Some like to get every last bit out of their setup and will PAY for it. My pockets aren't deep enough.
Some find a happy medium making worthwhile improvements within their financial means. Count me in.

Come to think of it for the cost of a AS&M, I bought a bigger TB, rear rod ended LCA's to replace the stock units, and a AC delete pulley to dump some weight off the nose. 3 for the price of 1 lol.

 

So AnotherWS6 you got me thinking...

A 350 CI motor at 6000rpm will need 607 CFM at 100% efficiency. A guess at a LT1 being what...80% efficient?? So that's 485.6 CFM.

AS&M states their 58mm flows 1050 CFM and the monoblade flows 1300 CFM.

 

Getting a stock TB bored tp 52mm is way more "plug & play" vs buying a aftermarket TB and then modifying it to get it to idle right IMHO.

If one is intent on a 58mm TB than they will have to do what many have done (drill mod, etc) to get it to work right, especially with larger than stock cams

IDK what the difference would be in HP gain from a 52mm vs 58 mm....depends on the motor build. I suspect single digit gain if much at all .....YMMV

 

HCI with more compression and E85 is the goal so I am adding parts to help support that.

I'm not worried about the work it takes to make a 58mm word correctly.

 

i have a 97 z28, bone stock other than a CIA, would jumping up to a 58mm tb be wise, or should that maybe not be the first bolt on i do?

Thanks,

 

no, or the 2nd bolt on you do.

When you get into a head/cam build is when a larger TB comes into play

If you bolt on a 58 mm now you will first need to pull the intake manifold and have it machined for a 58mm opening...then get a new PCM tune so your line pressure is corrected..or automatic trans failure will not be far behind

you can bolt on a 52mm TB but you would still need to get PCM re-programmed if a automatic car.

either way on a stock motor you won't lose any HP...but not gain much, if any, for a stock motor. Considering the cost not a worthwhile $ to HP gain for your current motor.

 

okay, exactly the information i needed to know. Thank you for your insight ******.

 

Dyno time scheduled for this Saturday to get the Summit TB on the car. I'll report back with my findings.

 

Summit and Professional Products are the exact same unit, I have ran them both along with the AS&M. Not perfect, but great price. All three needed the drill mod and isolation to idle properly on my H/C build, but with Speed Density my 93 is a bit more finicky than a MAF car so of course YMMV. One thing to note, I had to rotate the return spring one extra time on my PP TB to get a proper crisp throttle return. There have been stories of them getting stuck open at WOT due to a weak return spring. All will make the exact same power btw. A 58mm will flow above what all but the most extreme stock cube LT1s will need, even with heads and a cam.

Nice to see the new Holley units have the IAC isolated. For a while NONE of the units had proper functioning IAC passages since they were all re-purposed TPI parts.

 

Well, got it all sorted Saturday. No modifications were needed. It was a bolt on and go. It will idle correctly SOMETIMES. Here is the kicker though...

I'm now running the TorqHead 24x conversion AND E85 on Speed Density. The car can and will idle normal about 850-900 rpm but sometimes it will stay at 1500 rpm. This could be something physical with the TB (drill mod, adding brass tube etc) OR it could be PCM/operating system related. The 02 Tahoe OS that I'm using was correct for this 411 PCM AND has E85 capability BUT it was originally a drive by wire setup. My tuner has come across this issue once before with the car sometimes not wanting to idle with this modified OS. He mentioned for whatever reason the PCM is not recognizing that the car should be idling.

I just drove it around today, so it's not 100% but it's getting there. We will revisit this soon to figure it out.

It's quite possible I'm the first TorqHead 24x LT1 car running E85 Paul from TH and I have been in constant communication getting this squared away so next generation PCM's can handle flex fuel. Keeping the LT1's alive and kicking.

 

Does anyone hear actually run the holley throttle body?
i have a 350 with a cam similar to the gm847. 230s/ 240s.
i run a 58mm throttle body holley, would it be necessary to drill out the IAC to create a hole similar to the stock set up or should it be fine.
im 24x btw also. I think with the larger throttle body im just gonna have to modify the IAC tables.