Fakebacon

I was wondering.. 305 TPI in the 88 IROC vs. 305 TPI in a 89 T/A...

What makes the difference?!?!!?! My mom has an 88 IROC with the 305 and it hauls @ss! My girl has a 89 305 in her T/A and it just doesnt compare... is it as simple as the rear gears or does the IROC have a differen set of heads/cam?!?!

Tibo

iTrader: (15)

There will be a difference in how well tuned a car is of course, that aside it could be the gears. The other difference is on the 89 model years they did away with the cold start injector, but that would not make a difference. It could be mileage, lots of stuff.

Goumba T

Also they both have different intake designs. The camaros have a more straight path. Tech data page says this is worth ~10hp(?). Doubt you'd notice that as well as you say though.

In addition to what Tibo said, weight also. Does the TA have all power options? How about the IROC?

Also you didn't mention what transmission each had.

razor

Are they both automatics or is one a 5 speed. Different tranny=different cam in the 305's.

Fakebacon

I think they both share the 700R4. They also both have all the power options but cruz.

Orr89RocZ

iTrader: (20)

could be a few things.....

maybe the TA is a bit heavier???

maybe gearing in the Iroc is a bit higher

maybe tune up?

also it is said to subtract about 5 hp from the TA/firebirds cuz of the air intake design. that could affect some performance

83ho86tpi

same cam in 88-89 for 305 and 350 so no difference there, thats assuming no cam or engine replacment with non stock. Gears, posi, transmission, tires and how worn out / in tune will make up the rest of the difference. It is the same motor either way stock.

1MeanZ

iTrader: (9)

did everyone forget that TBI was the base engine for the IROC and i believe the TA as well? maybe the TA has an L03. otherwise it shouldnt be that much different. that iroc should have the peanut cam so i am sure it isnt that much of a stormer to begin with, and if the TA is that much slower it could be TBI.

83ho86tpi, i'm pretty sure the 305 and 350 didnt share the same cam untill the speed density years, 1990 and later.

Fakebacon

How about building codes in the glove box. You guys know any of the codes for the different rear ratio? Or the motor? TPI code vs. TBI code? I know the codes for my B body but are they the same GM codes on the F bodys?

Thanks again for all your help.

83ho86tpi

yup, same cam profile for 350 and 305 tpi for both years 88-89. That is what it says in my 1982-1992 camaro performance / history book. I would scan the page with all the cam details for the different years.....If I still had a scanner. My ex got that in the break up.

Vader

Look at the PROM in both.

NEEDforSPEED

wight is also a facter, the T/As where heaver

ZZsmpch

iTrader: (1)

You could have two identical IROCs and see a difference in performance. Besides the obvious gearing and weight, just the state of tune, age of plug wires, type of gas that was run through them througout their lifetime, etc. can have an effect on performance. What's the mileage of the cars, how were they broken in when new? There could be a lot of variables involved.

Zepher

iTrader: (1)

gears will be the most noticable. The T/A may have 2.73 gears which makes the car seem kinda dog slow.
The Iroc may have 3.23 or 3.42 gears, or even possibly 3.73 gears.
I know when my 88 formula went from 3.23 gears to 3.73 gears, it would haul *** from any speed.

86IROCTHD

actually the iroc only came with the tpi.... the TBI was the base for the r/s.... as far as the trans am as i am not sure what the "base" option was but i bet it was also the tpi and the firebird had a tbi

1MeanZ

iTrader: (9)

83ho86tpi, i will not dispute that, you have the book and i was going from memory LOL.

86IROCTHD, you are incorrect. the TBI engine was the base engine in the IROC and the Formula Firebird, so i assume it was the base engine in the Trans Am as well. the TBI 305 was the optional engine in the RS. I am not saying that the Trans Am in question here has TBI, but it would be a possibility.

83ho86tpi

I saw a iroc with tbi and swore it was a fake. I almost tore it apart trying to prove it was just a set of stickers and wheels. Everything else checked out on it but I still was not sure. The book I have just gives performance and upgrade info, so I am not sure if there is a tbi iroc. im sure the answer is on the history / restoration post though.

Silly question for you Fakebacon.... have you looked under the hood? Are they both tpi? Has one been replaced with a 350 from a previous owner?

BCdawg57

iTrader: (1)

The IROC's did come with the L03 as a base engine in some years. The TPI was an option.

Fakebacon

83ho~

Both motors have the TPI badge on the TB so I guessed they are the same in that aspect. The 89 T/A was just aquired this past summer and I don't know much about its history. The IROC on the other hand my mother has been the one and only owner. I fogot to mention, the Iroc is also a convertable, but I have always heard convertables are built a lil more sturdy so they won't flex as much and thus, making em more heavy.

mettalicirocz

If the 89 T/A is getting spanked by a drop top 305 IROC, then it is really out of tune or is just plain wore out.

IROCZTWENTYGR8

iTrader: (1)

That's weird. Convertables flex more and weigh more. Something's not right here. Do either have G92?

BTW, there were TBI IROC-Z's, but they were few. If we could only see pictures of both of these cars I'm betting it would be alot easier to solve.

swisscheese

The official imported IROCs in Switzerland have TBI, auto and 15"-wheels. But thats GM Europe...

Happy, mine was imported by a private person who knew what to order!!!

Fakebacon

G92?!?! What code is that for? Sorry if I sound dumb but I'm a lil new at the F~bodys.

As for pics... Ill take one right this sec of the T/A's motor. They will be the first few pics here...

www.mobog.com/fakebacon

Stay tuned for the IROC.

PS. Where the heck are the build codes on the T/A?!? They aren't in the glove box like in the IROC... Or under the hatchback like I thought they were.

ploegi

On the firebirds, the label is usually in the center console, glued to one side, or, in the locking compartment in the hatch, on the back of the door...... Mine fell off, so it resides in the Helms service manual...

swisscheese

G80, G92
one is for locking axle and one is for 3.23 gears.

Fakebacon

Yeah, the IROC is... Does one nice burn out if I say so myself. The T/A is a peg leg.