I have a 91 305 TBI and wanted to know what kind of horsepower gain I would see switching to TPI. Currently the car has a Crane Compucam 2020, Edelbrock TES, high-flo cat, 3inch cat back, 3:42 posi, rebuilt 700r4 with a 2400 stall converter.

My best time at the track is 15.25 at 89mph. Any guesses at what the TPI would do?

 

My dad switched his 92 RS from 305 TBI to TPI and gained 17 HP and 70 TQ at the rear wheels. The only mods were a stock cat-back from an IROC. The engine had 200,000 miles on it too. He has no track times yet, but we're planning on going this weekend.

I couldnt tell you how much you'd gain, there are too many variables.


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1991 Camaro Z28
5.7L 5-Speed (originally 305)
317 RWHP, 418 RWTQ
13.23 @ 107.62 MPH
Southern California
Member: SoCal 3rd Gen F-Bodies
Member: SoCal F-Bodies
-=ICON Motorsports=-

 

the tbi was hevely modified right? because the difference between a lb9 is 20hp and 40tq so i dont know how it could make that much more just from just a stock engine and when you are that modified you should get a bigger tbi unit anyways. but if you can do it for cheep there is no reason not to switch to tpi unless you are like me but you will more than likely get a noticable amount more tq

 

I have the complete TPI with wiring harness and all. I actually bought a salvage 91 Z28 with an L98 in it. I just don't have the cash to rebuild the L98 yet.

Can I use the 350 injectors?

 

i think so, i think the computer "can" take care of that.

[This message has been edited by firbird (edited October 04, 2001).]

 

How do you get 20 HP and 40 TQ between 170 HP and 205 HP, and 255 TQ and 300 TQ? Thats 35 HP and 45 TQ to me. The TBI engine dynoed at 158 HP and 220 TQ with the exhaust. Maybe GM underrated the 305 TPI's torque? Maybe the peanut cam on a TPI makes more torque than the regular cam? Who knows, but those are the numbers it dynoed.

You can use the 350 injectors on a 305 but it will run rich. You will need a custom prom.

 

Would it also make any sense to use the L98 heads? Would that offer me any gain?

 

The aluminum Corvette L98 heads yes. The iron f-body L98 heads no, not on a 305.

My dad took his car to the track today. We switched cams to one that is 198/210, .450"/.460" lift. With stock exhaust manifolds he went a best of 14.94 @ 92 MPH. A more-heavily modded TBI car there had a best of 15.99 @ 87. Which timeslip do you want?

 

I don't know how heavily modified that 305 TBI was...my best time so far has been 15.25 @ 89mph. I have done a cam, intake, full exhaust, gears and tranny rebuild.

A gain of 35 horsepower and 40ft lbs. of torque....pretty much sounds like a no-brainer to me. Especially since it won't cost me anything except time.

 

It wasn't that modified but it's best is 15.40 @ 87.50mph.
When we raced, I left him everytime at the gate with the same RT and 60 ft times.
From there we stayed even.

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Chronologically challenged. But still kicking!
'92 CAMARO RS
305 TBI 5/spd (now TPI)
B4C Alt.
14.94-92.00 mph
'69 camaro-BB/Lenco,1050 dominators, /Pump Gas/no drugs 8.97-150+/3200lbs.
SoCal Thirdgen F-Bodies

 

Not sure of HP numbers..but consider this..a guy I knew pulled his 305TBI and installed a 10.5:1 compression L98 rollercam,roller rockers, aluminum headed 355 with a crane compucam(big roller cam, foget which one) in his 91 RS but left the TBI on there.He had a automatic and 2.73 gears at the time.

His car ran strong and was an animal.
He could SMOKE the tires into nothing..I went for a ride and really thought this car would blow my car away.it felt that fast.
He had all the goodies like a higher stall,edelbrock headers,trailing arms,2.5 exhaust etc etc...

My stock 86 TPI L98 with aluminum heads,automatic,stock converter,3.07 gears, was rebuilt(engine) the same time as his but had a smaller crane cam.Nothing else was done to the engine then..all stock with a little added compression from the new pistons.
Even had the stock exhaust on it with 90K miles.

We decided to have a little fun and we raced at a light on a deserted road area...when the light turned red, we both took off screaming the tires...I pulled on him and left him behind me almost 5-6 car lengths by the time we got down the end of the road...I was in shock and he was pizzed!His car ran fine he said but he couldnt catch up.

I really expected that car to blow me away because of all the mods he had done to it.

It truly felt fast...I know this wasnt a real time raced but on the street I think the torque of the TPI gave me the edge, not to mention the Vette had slighlty better gears and may have weighed a little less.

His slightly modified TBI was choking his engine, even though he could launch that car hard and do burn outs easily.But it just didnt have the power a TPI had.
His plan was to eventually add a TPI(aftermarket not stock) when extra money came in.

Look how good the stock TPI 305's run..dont always look at specific track times, alot has to do with the driver and tune of the motor and mods...but on the street, Torque from a TPI really makes it fun to pass or get up and go.




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1986 Vette Coupe,auto, 357 L98 w/alum. heads,40 over,crane cam,3.73 Gears,The usual Mods..
Had an 86 Bird before..want to get another F car again!