Besides ones TPI and one is TBI, Internally and anything else:

91 RS 305 TBI
89 GTA 305 TPI

Ive got a possibility of picking up one and wanted to knwo the difference.

thanks..
-steve

 

tpi heads aren't swirl port. depending upon the tpi's transmission, the camshaft is different. Which is a difference of 60hp. The tpi makes more torque, and is a better car to modify. The tpi may also have 3.45 posi gears. I dont know compression ratio

 

thanks for the reply.. ive got the TBI car, with the TBI motor in it.. but its got "issues" (rod I belive) I may have the chance to get a 305 TPI motor out of an 89 GTA. To put into this TBI car... Of course its only the long block, so I'd have to use the TBI on the TPI motor.... which is why I was asking about the differences in the motors..
thanks.
steve

 

I'd grab the TPI. The heads are much better like McDamit stated.

The part about the transmission and camshafts is BS though. There's no "manual transmission camshaft" or "automatic transmission camshaft".

The 305 TPIs all made the same amount from the motor, it's in the drivetrain where some of the HP and TQ get lost, and obviously a manual transmission takes less power away from the motor than an automatic, obviously not 60 hp difference.


TBIs can be made for a great performance application. The TPI has good low end and mid range, and good gas mileage, but is far from a performance application without MAJOR modifications.

TBI or TPI, I'd take the TPI motor, and swap whatever intake you wanted on there... atleast you'll be gaining a set of good heads

 

sellmanb then please explain the LB9... the one with the peanut cam and the one with the L98 cam. If the GTA is manual it has a larger cam. The tbi i believe makes 170hp for that year. my car which minus the airbox is the same thing as the GTA it produces 230hp with the stock L98 cam and 081 heads. An automatic car of that year made 190hp,

 

The LB9 is a 305, the L98 is a 350 motor.


More cubes. Yes, the L98 used a different cam. He wants to know about 305 TPI and 305 TBI , not a L98 (350 TPI). The 305 TPI uses a different motor code. a LB9 motor w/ a manual transmission will only make 5 - 10 hp more than a LB9 with a automatic. Same for the L98 motors. You're comparing apples to oranges. I dont mean to offend you, just help you get the facts straight... I know all the motor codes and such confused me at first too (and still do sometimes!)

 

The 305's that got paired with manual transmissions recieved the same camshaft as the L98's.

But, aside from that, yes, TPI heads are the way to go.

 

sellmanb go do some more research the manual cars were door banging the 350's, i can run a race with an L98 and take it. I have never track tested but some of the guys on here with stock 305's pull low 14's generally i see 14.4's

 

As much as it freaks me out to find Mcdamit right...he may be. Did I wake up in an alternate universe today or what?

https://www.thirdgen.org/newdesign/tech/techdb.shtml in the camshaft data section has some clues.

1987:
305 AT (LB9 10088155* .350 .384 179 194 109.0 (108/-112)

305 5spd / 350 AT (LB9/ L98) 14093643* .404 .415 202 207 114.5 (115/-114)

305 (LM1 Police Pack.) 14093640* .383 .404 291 202 112 (108/-116)


1988, 1989:
305 AT 10088155* .350 .384 179 194 109.0 (108/-112)

305 5spd / 350 AT 10066049* .415 .430 207 213 117.0 (116/-118)


1990-1992:
305 5spd / 305 AT 10088155* .350 .384 179 194 109.0

305 G92 5spd / 350 AT 10111773* .413 .428 202 207 114.5 (116/-116)

 

interestingly enough, the 305 tpi motor will be better than a standard 305tbi, because of the heads?

What bout cams, are they both roller motors? or is the tpi the only one thats a roller? etc..

-steve

 

They are both roller cam motors. And, yes, that 60 HP difference between the 305 TPI and 305 TBI is all in the better heads and cam. Us TBI guys are stuck with "smogger" swirl port heads and a peanut cam.

 

cool.. so if i were to get this TPI longblock and throw the TBI intake and unit on it.. it should run pretty good then? more HP than stock, but yet, good for daily use?
-steve

 

yes but thats assuming that the GTA is a manual tranny car, if not your still getting a peanut cam just decent 081 heads

 

It would run OK, but not anywhere near it's potential, sadly. The stock PROM/chip in the ECM won't really be able to handle a stock 305 TPI motor. It's going to need a custom chip.

Instead of typing at all out again, check out my post in the TBI board (2nd post). It explains the different options you have:
https://www.thirdgen.org/techbb2/sho...hreadid=308482

That's the problem with most TBI motor build-ups, it seems. Most professional tuners won't touch TBIs because their too old and not nearly as popular as TPI, LT1, etc., and the common DIYer doesn't have the time and patience for PROM burning.

 

yea, its a manual tranny car..
- Steve

 

good, that means that most likely that LB9 has an L98 camshaft in it.

You'll need a custom chip reworked for the better heads and cam, other than that you're good to go.

The custom chip should cost a few hundred dollars if you get it done right - dyno tuned.

 

what about using a GTA's computer what would that do?
-steve

 

it would give you the ability to use that tpi, and no nothing would have to be changed but the mess of wiring

 

what i f i didnt change the chip in the car?
-steve