TBI Throttle body 88-95 ridge removal

[Pinger]

Nope, just a 1/4 mile time. I've been looking for an apples to apples comparison for a long time, all I see is people claiming benefits but no real data. It does stand to reason, if you have a modified engine and are running higher revs than the 4400 these 5.7s normally go, you need better air flow. This TCI calculator (go to the bottom) shows somewhere ~650CFM for a 5.7L @ 6000RPM. Will you get 650CFM just by shaving the horns and throttle bar? NO but, it'll help along with other mods like, boring and opening up the flow around the injectors. Stuff like the pod spacer, the "salad bowl" intake spacer, the air box, etc.

https://www.tciauto.com/racing-calculators

The limitation though is in the stuff you mention - not valve size, valve lift, duration, inlet port dimensions or flow.

 

[PlayingWithTBI]

The limitation though is in the stuff you mention - not valve size, valve lift, duration, inlet port dimensions or flow.

That's a different story. Once you get the ability to flow through to throttle body, you need to get it into the combustion chamber which means better heads and cam. The TBI "Swirl Port" heads and peanut cam need to go. This is where the L31 Vortec shines obtaining ~250 HP when the L05 TBI gets only ~200HP (most people say closer to 190). Then you need to get it to exhale better with headers and low restriction pipes, cat(s), and muffler(s).

I think we were just talking about getting the TBI throttle body to flow for better performance, which IMHO, can and has been done.

 

[MSCustoms]

I added the injector spacer and removed the ridge rings around the two bores and I don't like it imo. I noticed the engine required a little less effort to maintain speed but I dont notice it now. The reason I don't like it is because the injectors seem to be too far away from the tbi base. I noticed that the top of the throttle body is sticky with fuel and I see that as a waste that isnt worth it.

 

[90halfton]

Going to need a wheelie bar

 

[CrustyJunker]

I added the injector spacer and removed the ridge rings around the two bores and I don't like it imo. I noticed the engine required a little less effort to maintain speed but I dont notice it now. The reason I don't like it is because the injectors seem to be too far away from the tbi base. I noticed that the top of the throttle body is sticky with fuel and I see that as a waste that isnt worth it.

Nail on the head. The "ridge," above the top of the bores is to help steer the fuel spray down where it needs to go.

I'm not saying these mods are a bad thing, but I do believe they can make a difference when used in the correct application. Stock applications would see some, but probably minimal gain.

Increasing the area around the fuel injector can allow more airflow in at higher RPM's, but more of a mess at lower RPM's for turbulence and other weird reasons.

By both raising the injectors and buzzing away the ridge, that pretty fuel injector fan pattern becomes more vulnerable to changes in direction...Especially when we're just cruising and those throttle blades are mostly closed. Thus - that varnishy fuel mess.

Another big contributor is the stock air cleaner design. Most of the air going down the intake rushes in from one side. Then has to fight with that restrictive ring/shroud around the injectors where the PCV comes in. That's why the Hypertech Power Charger/"salad bowl," mod alleviates some of that aggressive air direction-change and helps unshroud the injectors. Again - a modification with higher RPM gains in mind.

So in your flow path, you have your one-sided air cleaner inlet, a stud or two in the way, wiring/connectors, a restrictive injector shroud, and large non-aerodynamic injectors directly in the way. Compare GM's Rochester injector tops vs. the older Holley 670 upgrade/Dodge style design!

Our OE

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Holley/Dodge

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There's some extra performance to be had - at a cost. No huge gains will be had from the "ultimate mods," alone. GM got really creative in the smog era with early fuel injection, super mild cam grinds, and their swirl port cylinder head design - performance not in mind. Although it was far from the best, TBI gave some power, some fuel economy, all while trying to keep emissions compliant.

All TBI's are officially antiques now.

 

[Horntoad]

Thanks for the info and discussion. From both my own calcs and those I’ve seen online, I also don’t believe, given its rev limit, the motor should be starving for more airflow than the stock GM TBI can provide, which seems to be somewhere in the 490-520 cfm range (though I've seen as high as 550 and as low as 475 quoted), and wouldn't really start to be unless it were spinning closer to 5500 or above. That’s why I wasn’t in a rush to grind that ridge. And now, considering that some of the commentary provided here supports my suspicions about the purpose of and potential tradeoffs from removing that ridge/ramp, I don't think I'll mess with it. It could be a more suited modification for some, but I don’t feel it’s right for my use, which is mostly cruising and trails.


I do know about the “salad bowl” (Jegs makes one also), and if I came across one for the right price would go for it.


I'm not making any plans to buy one, but I do appreciate the pic of that Holley. I was thinking to myself just the other day while cleaning the 220 how bulky, obstructive, and unstreamlined the injector pod/regulator design seemed. And, while not something that needs routine tweaking, I envy that the adjustment screw for the fuel pressure regulator is on the top and accessible!


Thanks again!

 

[Schurkey]

Folks need to remember that Holley dumped those "streamlined" "Dodge" injectors because they were a high-failure item.

Despite Holley and others using old photos, what you'd get now looks like this:

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[Frank Enstein]

Nope, just a 1/4 mile time. I've been looking for an apples to apples comparison for a long time, all I see is people claiming benefits but no real data. It does stand to reason, if you have a modified engine and are running higher revs than the 4400 these 5.7s normally go, you need better air flow. This TCI calculator (go to the bottom) shows somewhere ~650CFM for a 5.7L @ 6000RPM. Will you get 650CFM just by shaving the horns and throttle bar? NO but, it'll help along with other mods like, boring and opening up the flow around the injectors. Stuff like the pod spacer, the "salad bowl" intake spacer, the air box, etc.

https://www.tciauto.com/racing-calculators

 

[Frank Enstein]

Didn't mean to quote that. One thing that may help a bunch or not at all is an adjustable fuel regulator (JET-61510 @ Summit) The computer ignores the O2 sensor above around 80% throttle opening. By adjusting the fuel pressure for best performance at full throttle it usually puts you near the middle of the fuel trims under 80% throttle opening. I usually recommend the throttle body spacer and the regulator and perhaps the fuel line extensions (TRD-2458 @Summit). I consider this 1st stage mods. If you want more then the Cereal bowl, K&N (or similar) Air filter and second snorkel. If you don't mind the intake noise removing the restrictor in the airbox (10 HP supposedly) can help. An open element air cleaner is a poor choice as it feeds the engine hot underhood air. For every 10 degrees the inlet temp drops the power increase is 1+%.

 

[alpinecrick]

GM got really creative in the smog era with early fuel injection, super mild cam grinds, and their swirl port cylinder head design - performance not in mind. Although it was far from the best, TBI gave some power, some fuel economy, all while trying to keep emissions compliant.

All TBI's are officially antiques now.

But.......with apologies to the Mopar 318 and the FoMoCo 1st gen 302, the TBI's may be the most long lived cast iron V-8's ever designed by humankind. Precisely because they are low rpm motors that make decent hp and torque.