1989 T/A 305's were rated at about 170hp
Then in 1990 they were rated at about 225hp

Why the sudden change?

EDIT:

And gas mileage

Also why does the V6 2.8L get 17 city, 27 hywy
But the 305 gets almost the same, 16 city, 25 hywy

Why would anyone go for the V6???

 

One thing for sure that effected it
was insurance reasons and smog laws

correct me if im wrong guys
theyve always been kinda weird when rating HP

 

because your comparing a tbi 305 to a tpi 305

 

ahh fuel injection... I've heard the tpi is farely easy to work on.. is this true?

 

No matter what the garbage is going to be said in the up
comming posts .. Im stickng with TPI for my own reasons.

Tuned Port Injection is easy to assemble and disassemble

But to maintain and run properly is another ..
Its computer (ECU) controlled ..

Not so easy to adjust and tune with
wrenches ..

I recommend visiting the TPI boards for this topic ..

because thats what its designed for

 

tbi is easier to work on that tpi, carbs easier than both. stock for stock tpi makes more power than tbi, not because of the induction but because its a different long block. Both are reliable, ive had tbi work flawless for close to 400k miles (combined vehicles). Ive only had 1 tpi and besides a leaking intake gasket no problems in 50k miles.

 

The TPI motor Im currently working on
is gunna be nothing but a "rubber roaster"

TPI, known for torque, but also known to choke at
high RPMs because of the long runner design
and other induction flaws

Is a nice setup, for the time it came out .. think
of it as a early LT-1 (I like too hehe )

However, youll find it easier and cheaper in the long run to grab a LT1 or LS1 if ya got the $$$

TPI is gorgeous looken ..make a motor stand out!!

they do it at GoodGuys car shows and such,

throwin a TPI setup in a ole 36 Hotrod w/ flames ..

very good looken indeed:hail:

 

TBI is still controlled by a computer. TPI is as well. Both rely heavily on a computer and neither would function without it.

TPI makes more torque. Period. The heads hurt TBI cars quite a bit because they put the swirlport heads on them..but given an identical longblock, the TPI setup will still make more torque down low. TPI also has a revving limitation as mentioned above. It starves for air up top. TBI is known for lasting a long time with no service required but scheduled maintenence.

Also, as mentioned the '89 power rating you listed was for the TBI. The TPI models of the same year produced around 190HP and 295FT-LB torque. TBI made 255FT-LB torque in that year. These are the specs with the "peanut cam" that all TBI cars received and all the automatic 305 TPI cars received. Note also that in '89, the 5spd version of the 305 TPI put out 220HP and 290TQ (add 10 to each value in the GTA models). This is because the 5spd cars got a more aggressive cam (which happens to be the one in the L98, which is fairly similar to the LT1 cam).

In the later years both auto and manual 305 TPIs came with the same cam. Power was reduced from the '89 5spd rating and raised from the '89 auto rating. The G92 cars got the power upped to 230HP.

That's why the power is different between the two years. Different motors and transmission combinations were given differing amounts of power.

 

I wouldn't say its cheaper OR easier. Its a cool mod and makes good power, but is very costly and VERY time consuming.. *especially* the LS1 swap.

 

Also, 85-89 were the MAF cars, whereas 90-92 were SD.

 

The question is like comparing Apples (TBI) & Oranges (TPI) it just can not be done.

 

Actually Dean, any 305TPI auto car between 1986 and 1992 will have the peanut cam. The Larger, L98 cam only came on the 5spd equipped 305TPI's and 350TPI's.

In 1985, all TPI cars recieved the L69 camshaft, which is pretty close the L98 cam.

 

What I mean by my above statement was

you are going to need a lot more money to
get a TPI inducted motor to achieve as much HP and Torque
as LT1 or LS1 if invested equally ..

the LT1 and LS1 would dash on ya all day

I just speak the truth, I dont like the truth either

I wouldnt have name Myself "TPI" on TGO
if I didnt love the design and low end performance it delivers

all I know is my motor is gunna have one on it

 

Hey ThirdGen,

I looked at your lil link on your car ..

I wanna know .. did you TIG weld those runners on your TPI??

Or they come like that with the welds visible??


CUZ THAT IS QUITE A PEICE OF WORK ..

I wanna do it to mine now
:hail:

 

n/m

 

But in '90-92, the autos and manuals made the same amount of power unless it was a G92 car. Then it got the boosted amount of power. They still used the same cam but picked up a bit of power with the speed-density system. The G92 cars got the stronger cam.

And yes, in '85 the TPIs got the good cam as well, though the '85 MAF computer sucked. :shrug:

 

It would be hard to prove the statement that SD was a reason for any power increase ..... in fact, in contradiction, most guys notice no power gain when doing a simple Maf -> Map swap, and do it for tuning reasons or future plans of forced induction in which the Maf tables tend to max out.

Having said that, I wish I would have gone for a S/D car.... Maf Sensors can get expensive if they break.

 

I have been browsing through the forums to find info on this and this thread seems to be close so I thought I would post here.

According to the horsepower technical data on this website, in 1991 the 5.0 TPI LB9 engines produced either 205HP/285TQ or 230HP/300TQ with the same compression ratio. I noticed the higher power engine is only available with a manual tranny, and I am guessing no T-Tops. Can anyone verify this?

Did they purposely make the T-Top cars with less horsepower and torque do to chassis flexing?

Is the main difference between the LB9 engines the cam, or is there anything else they fooled with to lower the power?

It sucks that my engine has around 25 HP and 15 ft/lbs of torque less than what it possibly could in stock form (which my car is).

Any info would be appreciated! Thanks.

 

Let me throw in the dual cat option that was introduced in 1989. This was good for a 10 horsepower gain over the previous years.

Regarding T-Tops. They were available in 1989 for even the high horsepower 350 cars. Not sure when GM started phasing the T-Tops away from the high output cars again. Probably sometime in 1990.

In my opinion 1989 was the best year because all the goodguy options were available from the factory like the nine bolt rearend and so forth. Even something as mundane as the adjustable TPS switch was also used. 1990 and up the TPS switch is fixed.

IMHO the 1989 car is the easiest to switch over from MAF to Speed Density if one wanted to do so.