TBI perfomance options???

[slb1985]

I have an 87 tbi 350 and was wondering what i could do for performance, i would like to get around 400-450ish, and not have every sensor start going crazy. I've read somewhere after after some things are done i need to switch to 454 style injectors but would it be more of a headache to convert everything to more fuel or a carb with some regulators in place?

[RandyP]

http://67-72chevytrucks.com/vboard/s...d.php?t=317519

Some extremely smart cookies in that thread when it comes to TBI information. That's where I'd start. It's where I wish I would have started.

[BLE 'BURBAN]

Check out www.tbichips.com

[68 TT]

Originally Posted by slb1985

I have an 87 tbi 350 and was wondering what i could do for performance, i would like to get around 400-450ish, and not have every sensor start going crazy. I've read somewhere after after some things are done i need to switch to 454 style injectors but would it be more of a headache to convert everything to more fuel or a carb with some regulators in place?

I've seen different numbers all over the place for cfm ratings on the stock small block TBI unit from 390 cfm to 500 cfm. The butterfly's are the same size as those in a 750 holley carb so it makes sense that it is only half that flow plus a little for the lack of taper and booster interference that the carb has so the low end 390 cfm number sound right to me.

You can get close to 300 hp out of it with a bit of work and a cam but to go much more than that it will take a bunch of money & parts. Even at 300 hp you will need to custom tune the ECM to make it run right.

You can get the small block TBI unit bored out to flow enough air to make 340 hp then you have to step up to a big block unit. The stock TBI heads are a major restriction to making more power even fully ported. Due to their swirl ramp under the intake valve you just can't make them flow enough air to make 450 hp unless you are running forced induction.

To make 450 hp without a blower or turbo on a TBI 350 you will need to put on different cylinder heads, install a much larger cam, replace the intake, install a bored out big block TBI unit, install 1-5/8" tube headers & dual 2-1/2" exhaust and custom tune the ECM to make it run right.

[slb1985]

I am looking at vortec heads fully ported with an edelbrock air gap intake gonna do a cam just not sure which one yet, also read around about lifter clearance on the heads but I can get my shop to fix that if I need it. I already have 2 1/2 exhaust on it but all this is gonna take time I'm young enough I want a toy but just old enough that I can't really afford it
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[RandyP]

Be careful with the cam choice, too much cam is bad for a TBI system. My cam is .450 Intake /.460 Exhaust and sucks badly for the TBI. Basically it is not creating enough vacuum at lower RPM.

[68 TT]

Originally Posted by slb1985

I am looking at vortec heads fully ported with an edelbrock air gap intake gonna do a cam just not sure which one yet, also read around about lifter clearance on the heads but I can get my shop to fix that if I need it. I already have 2 1/2 exhaust on it but all this is gonna take time I'm young enough I want a toy but just old enough that I can't really afford it
Posted via Mobile Device

I'm assuming you have no emissions testing to go through.

Not having a computer to have to re-tune will make things much easier for you and keep the low budget intact.

I would run the vortec heads, air gap intake and a carburetor if you really want 400 to 450 hp. You will spend a bunch of money trying to make a TBI system function at that power level.

Have the vortec heads machined for retainer clearance at .550" lift.

With ported vortec heads the LT4 hot cam, 1.6 roller rockers and some Comp beehive springs will get you to the 400 hp level at the crank.

[slb1985]

thanks TT you have gave me great advice now its time to get this tranny in order so i can keep goin to work then start buyin parts piece by piece ill look through the forum and find everything i need like proper fuel pumps right carb and how to remove computer without tearing stuff up. when this every gets started ill let u guys know

[rfmaster]

Originally Posted by RandyP

Be careful with the cam choice, too much cam is bad for a TBI system. My cam is .450 Intake /.460 Exhaust and sucks badly for the TBI. Basically it is not creating enough vacuum at lower RPM.

I would have to partially disagree with that statement. Valve lift is not an issue it is the cam duration and overlap that affect idle vacuum. In my latest project (HOT 383) I have used 0.500/0.510 lift cam with 212/220 duration at 0.050 with LSA 114 deg. 383 is TBI injected and it idles at about 725-750 with 16-18 in-Hg.

Back to discussion
400+ HP from any SBC (carb or FI) will require careful parts selection and engine work. At these power levels little things begin to matter and the money drain increases exponentially. FWIW, if I may ask why do you need 400HP in a street truck?? Your current TBI engine LO5 is about 180 to 190 HP on a good day. As it was mentioned Vortec heads, correctly selected cam, matching intake, dual exhaust, and with custom tuned BBC TBI can bring your engine close to about 300 HP with a reasonable investment. The next 100 HP will take a lot more money....

//RF

[68 TT]

Originally Posted by rfmaster

...400+ HP from any SBC (carb or FI) will require careful parts selection and engine work. At these power levels little things begin to matter and the money drain increases exponentially. FWIW, if I may ask why do you need 400HP in a street truck?? Your current TBI engine LO5 is about 180 to 190 HP on a good day. As it was mentioned Vortec heads, correctly selected cam, matching intake, dual exhaust, and with custom tuned BBC TBI can bring your engine close to about 300 HP with a reasonable investment. The next 100 HP will take a lot more money....

//RF

I was going to suggest the same thing but with a small budget friendly slow build up approach.

I would start with some data logging and basic tune work on the truck to optimize it for what he has already. If he has 2-1/2" dual exhaust he most likely also has headers so the engine is probably running pretty lean right now and is down on power. I know my 90 Z71 was way off after just simple exhaust system mods.

After getting the truck running right as it sits now then I would get a better cam in there with specs like the hydraulic roller TPI cam that the 9C1 cop cars used in the TBI motor. With good exhaust it is good for 210+ hp with stock TBI heads. Converting to run a roller cam is an option but not really budget or time friendly in a daily driven vehicle. I would try to find one for this stage of the build that has similar specs to the TPI cam but is a flat tappet hydraulic instead.

While you are changing out the valve springs put in a full set of umbrella style silicone valve stem seals on all the valves. Some cylinder head shops only put them on the exhaust valves but they are so cheap it is worth it to put them on all the valves for a little added protection.

You might as well add a better dual plane carburetor style intake at the same time as the cam swap since you will have the intake off to do the cam swap already. Don't waste your money on the Performer TBI intake. Go with a standard Performer RPM intake and run a TBI adapter plate.

After the cam & intake swap you will have your hands full re-tuning it but the end result will surprise you.

You can use the ANLU bin as a good tune starting point for a cam upgrade in the TBI 350. It is the program for the 9C1 cop car 350 TBI with the factory installed TPI roller cam. It will get you close but came in the car version of the TBI ECM so you will have to do a comparison in TPRT to get the VE info and the other modified tables into the truck 747 ECM and your truck bin.

I would look for another engine to build for the next step in power so you can run the LT4 hot cam and vortec heads. If you can find a vortec engine to start with it will already have the heads you want, already be a hydraulic roller engine and will have a better crank & block that will be more up to the task of handling 400 hp. This way you can also sell the entire old TBI engine to cover some of your costs after you swap out the engines.

[rfmaster]

a good summary from my friend TT.

I also would like to add that Vortec heads can handle about 32 to 34 deg of timing at WOT whereas swirl heads commonly used on LO5 make peak power with about 20 deg at WOT - that's a huge difference! So just swapping from swirls to vortec heads timing tables must be up updated to take advantage of vortec flow capability. Vortec head chamber design stems from famed LT1 development minus reverse cooling.



//RF