When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I use the Holley and BBK without issues, prof. products is a lower cost copy I have NO experience with but for the price I would be game... in fact there are a few on eBay under 200.00
I bought my BBK used years ago, and it's given me no trouble at all. It did not require drilling the IAC hole or any other modification, and holds an idle very well with my cam.
Notice how the IAC passages are on this Holley vs BBK. The BBK IAC is connected directly to the plenum while the Holley is sealed off like stock. The BBK style is more likely to give you split BLMs.
Downside of the Holley is that there is no stopper and pushing the gas pedal all the way down will put the TPS voltage out of bounds. I have one and had to make a stopper to prevent it from opening beyond 100%.
It's odd Holley doesn't have a stop...it's actually quite stupid if you can potentially damage your TPS with no mechanical hard stop.
Is that shared passage with the plenum the reason I read people inserting a brass tube to seal that area off? And or enlarging the hole by small increments after looking at IAC counts?
Yeah, it was pretty annoying too because it would send the TPS to 5v+ and throw a code at WOT. And yes, that's why people insert a brass tube or make inserts to separate the IAC passages from the plenum. Some throttle bodies can also be used for L98s which don't have dedicated IAC ports like the LT1.
I had to drill up to the next size with my Holley to get enough idle air with my h/c 383. You can crack the throttle blades open rather doing this but it will only make idle splits worse. I managed to get the Holley to close/open without sticking by doing some light filing to the butterfly edges and careful assembly. It was a lot more work than I anticipated for something that costs over $400 but it did reduce my idle split down to about 8-10 units although there's still room for improvement.
It's surprising that something costing $400 still needs some modification to work...
I'd be curious to know why BBK and Holley have such (what seems to be ) fairly important feature differences. One connects IAC port to plenum and one does not.
The Holley is made specifically for the LT1 and the issues I had with it were from poor design/manufacturing. Not surprised that an aftermarket part needed some massaging. Thankfully I got it fairly cheap as a scratch and dent on their ebay page. My combo needed a larger TB because the stock one seemed to hit a wall beyond 330 g/sec. I guess it was worth the hassle in my case.
I think the BBK's fit the older TPI vehicles as well. I would have purchased the Holley for my 97 Z if I had known about the split blm's on the BBK unit. I did the "mod" on the BBK and now it whistles a little off idle. Almost sounds like a suercharger whine... so it's ok I guess lol!
Notice how the IAC passages are on this Holley vs BBK. The BBK IAC is connected directly to the plenum while the Holley is sealed off like stock. The BBK style is more likely to give you split BLMs.
My BBK has a sealed IAC passage, but I've had it for a number of years. In any case, regardless of brand, it's an undesirable design feature.
Yes, you will have to drill a (stock sized) hole through it if it's sealed. If you don't your PCM will have to adjust which can take massive amounts of start cycles. I didn't realize my Accell billet was sealed for nearly 17 years and hated resetting the PCM because the engine would stall all the time when coming to a stop until the PCM learned. Drilled the hole and the problem went away.
It was my understanding that you want a sealed IAC passage design (like the Holley) and simply drill the hole to correct any issue since the stock TB is sealed with a hole.
I don't think I was clear. There should be an IAC passage for sure, but there should also be a hole in the indention on the bottom center of the TB that goes through the TB front to back. i just don't remember the diameter. It is critical you do not oversize that hole or it could lead to idle issues.
Understood. I agree with the small hole inside the passage. My clarification is with the need for the additional milling joining the IAC hole with both TB holes:
Sealed passage (preferred?? drilling hole may be required)
Additional milling (not preferred and needs brass tube insert?? drilling hole may be required)
Gas Monkey Built a 6-Wheel Ferrari Testarossa With a Corvette LT4 Engine
Slideshow: The controversial Ferrari F6 swaps its original flat-12 for a Corvette Z06-derived LT4 V8 and sends power to four rear wheels through a custom-built drivetrain.
7 Most Reliable High-Performance Engines GM Has Ever Built
Slideshow:These GM engines didn't just make huge power, they survived abuse, boost, track days, and six-digit mileage with a reputation for refusing to quit.
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Slideshow: From wobbling harmonic balancers to failed EBCMs, these are the issues that define long-term C5 ownership and what repairs typically involve.
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Slideshow: A modern Camaro transformed into a retro icon, this limited-run "Bandit" build blends nostalgia with brute force in a way few revivals manage.
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Slideshow: Cadillac didn't just crash the high-performance luxury vehicle party, it showed up loud, supercharged, and occasionally a little unhinged...
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Slideshow: A one-off sports car that looks like a vintage Italian exotic-but hides a C6 Corvette underneath-just sold for the price of a new mid-engine Corvette.
How do you justify one TB over another 
