tpi 305 vs tbi 305 ?
#1
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tpi 305 vs tbi 305 ?
I have a 305 tbi motor but im planning to add a tpi. I noticed that the tpi 305 motor is rated at like 60hp more than the tbi 305. besides the injection was there any internal differences that account for that difference? that's a pretty big hp gain. my motor is a 91 if that makes a difference.
#3
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Re: tpi 305 vs tbi 305 ?
The TPI itself makes up some of that power gain. My 91 Formula (TPI) had the engine replaced with a GM crate engine back on the early 2000's and since you could not buy the LB9 it was an LO3 long block. The original owner I got it from said she couldn't tell the difference. Indeed with the 3.42 LSD and T5 it's still pretty quick. The TPI engines had a lot of torque due to the long, small diameter runners. But they lacked top end. You will see a big gain in torque off the line.
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#4
#5
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Re: tpi 305 vs tbi 305 ?
what are the differences in the heads? now that I think about it I have heard people use the term tpi heads but I never thought about it. the cam grind for the tbi and tpi are different as well?
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Car: 89 Firebird
Engine: 355 TBI
Transmission: 700R4
Axle/Gears: 10 Bolt.Posi-3.73s
Re: tpi 305 vs tbi 305 ?
The main difference besides the fuel injection is the cam. TBI got a very wimpy cam compared to the TPI engines. TPI heads were not the swirl port type like on TBI and thus were better especially on the intake side. 081 305 TPI heads weren't a bad factory casting.
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#8
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Re: tpi 305 vs tbi 305 ?
So yeah - about what you would figure. You're going to lose 20-30 HP with a TBI bottom end, heads, and peanut cam.
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Car: 89 Firebird
Engine: 355 TBI
Transmission: 700R4
Axle/Gears: 10 Bolt.Posi-3.73s
Re: tpi 305 vs tbi 305 ?
Makes me wonder what kind of drop in HP/TQ I will have on my stock L98 running TBI?
#11
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Re: tpi 305 vs tbi 305 ?
mine is a driver. I don't care about peak hp. I want torque. lots and lots of tire squealing throw you back in the seat torque.
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Car: 89 Firebird
Engine: 355 TBI
Transmission: 700R4
Axle/Gears: 10 Bolt.Posi-3.73s
Re: tpi 305 vs tbi 305 ?
I'm not looking for huge power by any means. My L03 is starting to smoke a lil and that's not cool at carshows full of nice cars. Instead of spending any $ at all on a 305 I picked up a good running L98 and freshened it up to drop in along with a modded TBI and intake and chip tune from Brian. Stock #049 cam, probably HO manifolds and magnaflow y. In a few months we will see how much power TBI loses to TPI but at the end of the day I will be fine with a pretty much stock 350 which is light years better than the lil L03. I will give the L03 credit though its been a great running lil engine and I plan to maybe find an older pickup to drop it in with maybe an L98 cam +headers.
#14
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Re: tpi 305 vs tbi 305 ?
I understand the tpi alone will not create the torque im looking for. its just one of the ingredients im also going to do heads and a cam and rear gears. .
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Car: 89 Firebird
Engine: 355 TBI
Transmission: 700R4
Axle/Gears: 10 Bolt.Posi-3.73s
Re: tpi 305 vs tbi 305 ?
Gears, an S10 torque converter, posi, and a shift kit alone will really make it 100x more fun to drive in itself. Even with my weak 170 hp engine I can tear out smoking tires and smoke second gear in mine. I'm running 3.73s but 3.42s would be better suited for these cars really.
#16
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Re: tpi 305 vs tbi 305 ?
something I havent heard mentioned is about the 305 TPI auto and the 305 TPI with 5 speed.. the 5 speed did not have the peanut cam that the standard 305 TPI auto came with. what was the cam in the 5 speed tpi? maybe that would be a good addition?
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Car: 89 Firebird
Engine: 355 TBI
Transmission: 700R4
Axle/Gears: 10 Bolt.Posi-3.73s
Re: tpi 305 vs tbi 305 ?
5 spd cars had the 350 cam.The 91-92 cars even in automatics shared the same cam as the 350 cars. Before that ive heard auto cars had the peanut cam. I can tell you my 91 auto car would flat out move for a 305 car. Pretty much stock except for a chip, 3in exhaust and cat delete it ran 14.7s..
#18
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Re: tpi 305 vs tbi 305 ?
5 spd cars had the 350 cam.The 91-92 cars even in automatics shared the same cam as the 350 cars. Before that ive heard auto cars had the peanut cam. I can tell you my 91 auto car would flat out move for a 305 car. Pretty much stock except for a chip, 3in exhaust and cat delete it ran 14.7s..
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