From: jlg@zycor.lgc.com
Newsgroups: rec.autos
Subject: Re: Formula (was Re: BETTER? 92 Camaro...)
Date: 11 Nov 92 21:03:22 GMT
Article-I.D.: lgc.1992Nov11.210322.20230
Distribution: na
Organization: Landmark/Zycor  (Austin TX)
Originator: jlg@jason.zycor.lgc.com

>        I think the cheesy rear-end had problems with the jolts
>associated with manual shifting under the extra torque, as well.
>The 1LE cars got the aussie-built 7.75" unit.
>
>>
>>>  Also, the 4 wheel disc's were standard on any Firebird with a TPI
>>>engine (5.0L or 5.7L).  It looks like in '89 they started putting
>>>bigger discs on the rear, along with dual exhaust past the cat's.
>>>It was good for another 10 hp.
>>
>>On my build sheet rear discs are an option.
>>
>>Hmmm. I have seen some TPI examples with (ugh) rear drums, but this is
>>Canada. What year is your Pontiac catalog for? I thought the dual cats
>>were standard on the GTA and optional on TPI FORMULAS & T/A's
>
>        The firebird literature in (88-90? memory fade) claimed that
>the 4 wheel disks were a required option on the TPI 'birds.  It
>also said that 5.0 TPI 5 speeds and 5.7 cars got the dual cats.
>I seem to recollect a recall on TA's or GTA's that didn't get the
>dual cats....they were re-fitted with the proper setup.
>
>        Despite what the literature says, I've seen (usually late
>in the model year) TPI firebirds with the rear drums.  But the scariest
>thing I saw was a 5.7 IROC with rear drums and 15", non-speed rated
>GT +4's!  A car that would go 145 MPH with tires that go to mush
>at 120....hope that thing had a speed limiter...
>
>        Just for laughs, what axle ratios do your cars have, and
>what are the 'G' codes on your option sticker?
>
>--Ken


1LE f-bodies are not the only f-bodies to have the Borg-Warner 'australian',
9 bolt rear end.  All '87-'89 5.7 IROC's and all '87-'89 5.0 G92 5 speed IROC's 
have the BW rear end.  WS6 Firebirds went the BW rear end one year earlier (1986).
1989 was the last year for any BW f-body rear end.

In addition, all 5.7 IROC's ('87-'90) and 5.7 Z28's ('91-'92) required rear disc 
brakes and the 16 inch wheels.  The same was true for all 5.0 TPI G92 5 speed 
IROC's ('87-'90) and all 5.0 TPI G92 Z28's ('91-'92).

The only TPI powered f-bodies (a lot of them) that have rear drums are 5.0 non-G92
automatics and 5.0 non-G92 5 speeds.

The 5.7 IROC you saw with rear drums and 15 inch wheels was likely not a 5.7.
I have seen several 5.0 IROC's rebadged as 5.7 IROC's.  To be sure, always
check the VIN:

                    Engine codes: (8th digit of VIN)

                           H : LG4 (5.0 4bbl)
                           7 : LU5 (5.0 Cross-fire)
                           E : L03 (5.0 TBI)
                           G : L69 (5.0 4bbl H.O.)
                           F : LB9 (5.0 TPI)
                           8 : L98 (5.7 TPI)

Starting in 1989, rear disc brake equipped (J65) f-bodies got larger 11.65 rotors
replacing the previous 10.5 rotors.  The front discs remained 10.5 rotors.  The
1LE package however would replace the front 10.5 rotors with 11.86 rotors.

The first dual-cat (N10) equipped f-bodies were available in 1989; ordering the
G92 option (performance axle ratio) determined whether dual cats N10 were installed.
In 1989, both 5.0 and 5.7 TPI could be had with or without the G92 option so you
will see 1989 5.0 and 5.7 TPI f-bodies with or without the dual cats.  The situation
changed for '90-'92 when only one axle ratio was available with the 5.7: 3.23 non-
BW.  All these 5.7 cars are G92 and have the dual cats.

If interested, join the f-body mailing list (f-body-request@boogie.ebay.sun.com) 
where such topics are discussed regularly.


John Gravell


-- 
Yr Model        Engine      Displacement   HP      Torque  Induction
---------------------------------------------------------------------
85 IROC-Z (man.) L69         5.0 (305)    190       240    4BBL H.O.
87 IROC-Z (man.) LB9         5.0 (305)    215       295    TPI