Anyone have numbers on what an intake manifold swap does for tbi engines?

[Supercharged111]

That sounds pretty good, I'll do some digging to see if a 92 has one.



The Pro-flo has a TPS, I'm not sure if we can tap into it or not. I've never had the TCC control explained to me before and I've never really messed with anything with an automatic before, and really nothing GM either. This is my first GM in about 15 years.

As long as it has the same voltage sweep you should be able to tap into it easy peasy. If not, you can set up a remote TPS. I would personally make this my first course of action. A TPS sensor should be 0-5V regardless of manufacturer, I'm not aware of anything else out there.

 

[Frank Enstein]

Not a fan of the Pro-Flow. Edelbrock doesn't offer repair parts after the system goes obsolete and Edelbrock was just purchased by the COMP group that also owns FAST.

 

[Erik the Awful]

I'm fine with something that does it automatically, but I don't want to have to flip a switch all the time.

Currently my stock TBI computer is still in the truck, controlling TCC lockup and it's working fine without the TBI.

I rebuilt my original 700R4, and it's sitting in the shop until the current junkyard transmission finally kicks the bucket. I bought a TCI vacuum switch so that I can ditch the TBI computer at some point. As far as I understand it, I can run power through the vacuum switch directly to the TCC wire on the transmission. Inside the transmission, the factory 3-4 pressure switch will limit the TCC to only 3rd and 4th gears, while the vacuum switch will only supply power to the wire in high-vacuum conditions, i.e. cruising. www.summitracing.com/parts/tci-cmp3766b

 

[Schurkey]

I bought a TCI vacuum switch so that I can ditch the TBI computer at some point. As far as I understand it, I can run power through the vacuum switch directly to the TCC wire on the transmission. Inside the transmission, the factory 3-4 pressure switch will limit the TCC to only 3rd and 4th gears, while the vacuum switch will only supply power to the wire in high-vacuum conditions, i.e. cruising. www.summitracing.com/parts/tci-cmp3766b

Twenty-five-or-so years ago I bought the TCI "Kit" for torque converter lockup, using a similar vacuum switch. I'd put a 700 into a 75 Nova, using it as a "work beater".

You're gonna hate that vacuum switch, if it's the same as what I bought. The switch has no hysteresis, it engages and disengages at the same vacuum level. You can adjust the vacuum level higher or lower, but wherever it's set, it's engaged above that level and it's disengaged below.

The GM switches would engage at a certain vacuum level, but they disengaged at a somewhat lower vacuum level. That's the way it should be done.

Functionally, the problem with the TCI switch is that you're driving along, the engine develops enough vacuum at cruise to engage the switch, and therefore the converter clutch. The converter clutch engages, which of course drops the engine RPM. The engine now develops less vacuum because the RPM dropped, so the switch disengages, and the converter clutch releases. RPM goes back up, vacuum goes up, clutch engages, vacuum drops, clutch disengages. Repeat until you stab the friggin' throttle in frustration. That switch is why folks put a toggle under the dash to override the vacuum switch.

 

[L31MaxExpress]

Twenty-five-or-so years ago I bought the TCI "Kit" for torque converter lockup, using a similar vacuum switch. I'd put a 700 into a 75 Nova, using it as a "work beater".

You're gonna hate that vacuum switch, if it's the same as what I bought. The switch has no hysteresis, it engages and disengages at the same vacuum level. You can adjust the vacuum level higher or lower, but wherever it's set, it's engaged above that level and it's disengaged below.

The GM switches would engage at a certain vacuum level, but they disengaged at a somewhat lower vacuum level. That's the way it should be done.

Functionally, the problem with the TCI switch is that you're driving along, the engine develops enough vacuum at cruise to engage the switch, and therefore the converter clutch. The converter clutch engages, which of course drops the engine RPM. The engine now develops less vacuum because the RPM dropped, so the switch disengages, and the converter clutch releases. RPM goes back up, vacuum goes up, clutch engages, vacuum drops, clutch disengages. Repeat until you stab the friggin' throttle in frustration. That switch is why folks put a toggle under the dash to override the vacuum switch.

GM used a vacuum delay in the vacuum line, ported vacuum and a thermal vacuum switch in that line. Even still the TCC lockup hunted in and out on my 83 G20 on the slightest grade or even headwind. Usually coming up to a grade, I stabbed it into the secondaries and let it eat.

After my TBI swap, used the factory lockup wiring and ECM control. The TBI ECM did a much better job controlling the lockup.

 

[Schurkey]

GM used a vacuum delay in the vacuum line, ported vacuum and a thermal vacuum switch in that line.

Ported vacuum assures that the converter disengages on deceleration. TVS keeps the converter from locking up when the engine is cold--I don't know what the big advantage is, there.

The vacuum delay might have been useful to me. I wish I'd thought of that. It would have been worth a try.

 

[Ryannn]

I don't know about resident expert, ha ha.

What I can tell you, if you don't already know, the TBI is set up to fire the injectors synchronously, meaning one fires then the other one does. If you look at the intake manifold and the ignition firing order, each injector fires when the cylinder's intake valve it's feeding opens. Maybe a useless tidbit but, kinda interesting to me.

I have the Edelbrock 3704 performer TBI intake manifold with a 46mm TB (they say flows 650 CFM) 20 PSI spring, Summit Racing 162108 heads (2.02/1.60 valves), Lunati bump stick with 1.6 full roller rockers (yada yada yada), where I do see that my MAP is only ~90 Kpa (plus it's running pig rich according to my WBO2) with WOT @ 5200 RPM (I do see 100 Kpa at lower revs) which may indicate lack of flow. I still need to tune it some more to see.

A bigger 4 BBL manifold would probably flow better but, may not get enough fuel to the corner cylinders. I saw on Engine Masters (I think) where they had to re-jet the front and rear bowls on a dual quad tunnel ram manifold to get enough fuel to the corners using a WBO2 sensor on each cylinder. We don't have that option with TBI, obviously. If I were to go with a 4 BBL manifold, I'd use a good adapter that will help with flow like this one instead of a simple plate adapter. Does any of this make sense?

www.ebay.com/itm/233652976731?hash=item3666cd7c5b:g:eUQAAMXQfj9SMzuY

Hey would you know where I could get that manifold?

 

[TylerZ281500]

Hey would you know where I could get that manifold?

bruh type it into google they are everywhere summit jegs ebay amazon marketplace etc. but ages ago before this post was even made that manifold was proven to improve nothing. generic performer for a carb with an adapter was a way better candidate and the heads suck more than the intake. The downside of the internet is stuff gets buried after 10+ years so finding it all again becomes difficult

 

[PlayingWithTBI]

but ages ago before this post was even made that manifold was proven to improve nothing.

Really? Who proved that? Edelbrock seems to think otherwise. Here's a question from a couple years ago...

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[L31MaxExpress]

bruh type it into google they are everywhere summit jegs ebay amazon marketplace etc. but ages ago before this post was even made that manifold was proven to improve nothing. generic performer for a carb with an adapter was a way better candidate and the heads suck more than the intake. The downside of the internet is stuff gets buried after 10+ years so finding it all again becomes difficult

ALL FALSE information. The 3704 manifold improves torque, horsepower and fuel economy while staying emissions legal. I found a further power gain installing a 2" bore TBI unit on a factory marine TBI to square bore adapter on a performer rpm square bore manifold but that requires adaption and an EGR delete. The stock heads are far down the list on power improvements. It is easy to get close to 300 hp at the crank with the stock heads and over 250 hp with the stock heads and cam. I had better than stock vortec power from a 1-ton TBI engine with its low 8.75:1 compression ratio, stock heads and stock 194/203 @ .050 flat tappet cam.