L67 Fbird Revision B

81cutlass

Comic Book Super Hero
Feb 16, 2009
4,649
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Western MN
This is 75% dad's project but we're splitting the work. Hopefully this will be a quick one but we'll see what pops up as we dig in.

So a bit of background, we picked up a 97 red y87 3800 auto firebird in 2011 as my Winter beater. At the time my cutlass was basically too nice to winter drive, cold blooded so not a great fit for MN/ND winters and I wanted to play with something EFI.

This 97 was sitting with a rod hanging out the side of the block on a side street in Minneapolis that I saw on CL for $1000. Owner was going to put a SBC in it but got in over their head. Dad and I found a $250 L67 supercharged 3800 out of a rollover GP GTP and stabbed that in.

The car had ~120k on it when I picked it up and it was just starting to bubble rust in the floor pans and lower quarter in front of the rear wheels. We did a quick cosmetic touchup, got the L67 running and used it. It performed the duty of speed errand car, Winter beater and drag car for me and dad pretty much full time between 2011 and 2016.

Fall of 16 I took it in my first drag and drive, got it to the best of a 12.6x.
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It actually looked pretty decent
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And for like $3500 all in was a killer setup. 28mpg on 87, snow tires in the winter, drag radials and e85 and mid 12's in the summer along with TTops off cruising to the lake or the farm.
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But 2016 was about the peak. I transitioned to the wagon, 2+2 and cutlass and dad just drove it. It's up to about 200k now and the chassis is miled out.

The floor pans where the LCA attached are total swiss cheese
The seats are totally pounded out
It has several brake issues and dad fights to keep brake fluid in the thing.
The paint on the front end looks like poop. It got wrecked lightly like 3 times in the last 12 years and paint has faded differently as parts got swapped, clear has pealed and it got backed into a few times at dads work and has a hole on the bumper cover and a crease in the driver's quarter along with the quick paint touch up of rust totally exploding into a local tumor.

So the hunt for a new chassis was on. Having a 12 second capable drivetrain that's unique, compact, affordable and gets high 20s mpg is something we want to keep. Was thinking about a clean 2dr late production XJ but that's hard to find. We've looked at probably 4 98-02 4th gens to no avail, thought about RX8's, maybe a 98-05 S10 blazer.

But last week a $1000 black 99 y87 fbird roller came up for sale 50 miles from dad and needless to say it's in his driveway.

Bonus, it's essentially the same spec as the 97. Y87 so posi, 3.42, f41, 4wheel disk, t top auto, but none of the dump w68 TA cladding that makes 3800 fbirds look dumb.
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Cons? We have to de-hackify the aftermath of a failed LS swap. Yes, that makes 2 3800 cars that I've saved from V8 swaps lol.
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So plan:
Dads going to rip the drivetrain out of the red 97 first warm weekend when the driveway isn't covered in snow. He will deliver engine and trans to me.

I need to put a 3200 stall converter in that I've had since 16, send the injectors out for service, convert return less rail to a return regulator, change some seals and cleanup.

Need to swap the entire 97 dash harness and gages to the 99.
99- CAN gages, DBW throttle
97- Analog gages, DBC throttle

We didn't get a 99 dbw engine harness and the 97 already has a dbc set up L67. NA l36 throttle is too small to make power on a L67, and there's no room to put a stepper motor throttle on the blower. Plus, L36 f body dbw throttle is totally one off and reportedly no other larger options work. So hard and painful decision there.


Also picked up some qa1 used single adjustable coilovers off FB for $100.
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Goal is to have at least a 99 with engine in my driveway by May so I can plug away at it this summer. Trying to refine and fix some of the shortcuts and mistakes I made when I was 17 putting this together the first time.

Dad and I both need a fun rainy day car. People give 4th gens a lot of crap for being plastic fantastic but I'm a believer that the supply has dried up a lot in the last few years and I'm trying to get on a nice chassis before they are all wasted or $15k+.

Oh and if I end up with too much money in putting Y1 17" snowflakes on it.

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Updates coming when the snow melts.
 
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Oct 14, 2008
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Melville,Saskatchewan
The Firebird's are nice cars, as usual they looked better than the Camaro. My only issue was the spindly 7.5 rear and I didn't like certain model or years rear bubble butt tail lights. Looks fine on girls, not on a car. The Honeycomb WS6 rear lights look fine. I assume a 3.42 with the awesome Torsen posi? I didn't realize the later ones were drive by wire. Impressed you pulled out mid 12's with such good mileage. Did you have a 4L60E failure? Suprised if you didn't. I remember it failing on my BIL 95 Camaro and it wasn't mid 12's or high mileage. Sounds like a great Summer fun car.
 
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81cutlass

Comic Book Super Hero
Feb 16, 2009
4,649
13,565
113
Western MN
The Firebird's are nice cars, as usual they looked better than the Camaro. My only issue was the spindly 7.5 rear and I didn't like certain model or years rear bubble butt tail lights. Looks fine on girls, not on a car. The Honeycomb WS6 rear lights look fine. I assume a 3.42 with the awesome Torsen posi? I didn't realize the later ones were drive by wire. Impressed you pulled out mid 12's with such good mileage. Did you have a 4L60E failure? Suprised if you didn't. I remember it failing on my BIL 95 Camaro and it wasn't mid 12's or high mileage. Sounds like a great Summer fun car.

Yeah, 3.42. I know the 97 had a clutch but 99+ gets torsen for v8 and the y87 gt3800 cars which this one is.

No 60e failure. I've had good luck with 60e transmissions. My Rainier had an untouched 290k 60e and the 97 firebird had 120k on it when we got it and 200k now with just filter and oil changes.

I am concerned about the trans in this after we swap to the 99. Kinda want to refresh it but that's going to add $1500 and a month to the timeframe that we don't really want to spend.

Yeah looking forward to having a good summer car again that I'm not afraid to get wet. The cutlass is too nice and the 2+2 is too rare to risk hail dents so they don't get driven of it's 20% chance of storms at 4pm.
 
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81cutlass

Comic Book Super Hero
Feb 16, 2009
4,649
13,565
113
Western MN
Painfully no progress.

Winter has continued to stick around aggressively this year. At my house the snow has 2/3 melted but it's still to cold to work outside which I need to in order to drop the engine out the bottom.

Dad still has over 2ft of snow piled up and everything is buried. Can't get started on this project until he pulls the driveline out of the 97 and the loader tractor and car are snowed in. Looking like late April at this time before stuff is melted enough to get parts my way.


However I have been doing research on the wire harness.

The l67 in the 97 is inadvertently the goldilocks setup. Drive by cable and analog gages but OBD2.
The 99 is missing the engine harness. I could find a 99-02 harness but they are DBW and there is zero support for DBW throttle upgrades on 3800's. It's a dead horse that multiple people have beat with no results.
A 99 also uses serial data for the dash cluster. Oil pressure, tach, temp, all come from the ECM.
The 97 stuff uses all analog gages and DBC
The 98 stuff uses serial gages and DBC

I thought I might be able to get a 98 engine harness and repin/connect it into the 99 dash harness to retain serial data gages from the 99 but DBC in the 97 but that's also DOA. 98 gages are 1 yr only from what I have understood and not forward compatible.

So cost wise, it's fine as I have everything, but time wise I need to pull the entire dash out of both cars and swap the gage cluster and wiring harness. Not ideal but that's what it takes!!

Maybe the snow will melt and I'll have progress next month....
 
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81cutlass

Comic Book Super Hero
Feb 16, 2009
4,649
13,565
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Western MN
Or just abandon the project and give me the car. I want to build a new CMC car using a Pontiac.

You are MORE than welcome to drive up in about 2 months and take the 97 chassis.

I can't provide any type of warranty that the rear end will stay bolted in the car if you get tapped in a corner and spin out but I will say the shell should be about 5-10% lighter than the rest of the F body options that are rust free :p
 
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64nailhead

Goat Herder
Dec 1, 2014
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Amazing how cars that were considered basically undesirable have had a status change since Covid……..it must be chyna haha.

4th gens and G-bodies have jumped in value a crazy amount in the recent past.
 
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87National

G-Body Guru
Apr 15, 2009
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eastern SD
I am concerned about the trans in this after we swap to the 99. Kinda want to refresh it but that's going to add $1500 and a month to the timeframe that we don't really want to spend.
You are probably aware of the 60 deg block to sbc trans adapter that speedway sells....but adding the cost of the 4l80e, custom torque converter to mate up to the 3800 flex plate, shorten drive shaft....etc. It's not an affordable option.
 

87National

G-Body Guru
Apr 15, 2009
663
689
93
eastern SD
The 99 is missing the engine harness. I could find a 99-02 harness but they are DBW and there is zero support for DBW throttle upgrades on 3800's. It's a dead horse that multiple people have beat with no results.
Can you expand on this......why is DBW undesireable? I've got a complete 2000ish 3800 in the corner of my shed that I am planning to swap into a g-body some day.
 

81cutlass

Comic Book Super Hero
Feb 16, 2009
4,649
13,565
113
Western MN
You are probably aware of the 60 deg block to sbc trans adapter that speedway sells....but adding the cost of the 4l80e, custom torque converter to mate up to the 3800 flex plate, shorten drive shaft....etc. It's not an affordable option.

I'm not worried about a 60e in an under 400hp , under 3400lb car, more just the milage. It's got probably 190k on it, likely just needs a freshening up.

Can you expand on this......why is DBW undesireable? I've got a complete 2000ish 3800 in the corner of my shed that I am planning to swap into a g-body some day.

The dbw isn't undesirable for an NA 3800. Works fine. My issue is an L67 needs a larger throttle body and the NA L36 dbw is just too small.

There's no larger throttle options available for a L36 dbw.
 
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