1988 Monte Carlo SS
LS1/T56 Change-over page
2001 Project Updates
08/05/01 Clutch pedal assembly final installation
I want to get everything ready now for the final
installation of the drivetrain. I needed to get the clutch pedal assembly installed
Next I am moving to the AC/heater
shroud for removal of my damaged unit. This thing is a pain!
08/12/01 Begin final assembly
I am really trying to get serious this week and see if I
can get the car ready to fire-up this next week so I apologize in advance for having
limited updates and pictures this week. I will go back after the fact and add
pictures with text for this weeks' update since I will be spending a lot of time in the
- I finished building a locating/weld jig for close tolerance
motor mount fabrication. I test fitted a completed pair of mounts in the chassis to
verify jig accuracy and the LS1 motor was a perfect fit. I will be offering these
motor mounts which are specifically designed for the G-body for $145 + shipping. I
will later verify if they fit other vehicle applications too. This pic shows a
completed motor mount.
- The AC/heater shroud has been removed and replaced.
- I removed the F-body fuel rail and replaced it with the
'97-'98 C5 dual line unit.
- The oil pan was re-installed with a new gasket.
- I found a location on the LS1 (same location as a std. SBC)
for an oil pressure sending unit. I had to drill a fitting on the block which is
left unused on the F-body but appears to be an oil temperature sending location in the C5
LS1. I drilled the fitting with an 11/32" drill and tapped this unit for
1/8" NPT threads and installed
my L69 oil pressure sending unit.
- I also added a temperature sending unit to a spare hole
location in the passenger cylinder head directly adjacent to the #8 cylinder head. I
oversized the hole using a 37/64" drill bit and tapped the hole for the correct
3/8" NPT threads. I then installed the stock L69 temperature sending
unit. Not knowing if the LS1 PCM oil and water temperature lead wires provide a
digital signal or not I will have the analog sending units available just-in-case!
shows the original cylinder head threaded plug, compares it to the sending unit and shows
the sending unit installed.
- I re-installed the modified LS1 wiring harness back onto
- Since I had taken out my power steering box when I painted
the engine bay I elected to take this opportunity to replace it with a 3rd Gen F-body IROC
"XH" steering box designed with adjustable stops to prevent the front tires from
rubbing at full turn.
- I installed a new throttle cable from a '99 F-body.
The F-body unit is a lot longer to reach the throttle body up front. This view
compares the L69 vs. the longer LS1 cable. I had to slightly enlarge the existing
firewall hole using a 13MM drill bit (just over 5/8") to fit the round shaped
retaining clip as opposed to the stock G-body rectangular shaped unit.
- The motor mounts were bolted in the chassis using (4) 10M x
1.5 bolts for each mount.
- I replaced the stock F-body pressure plate, clutch disc and
flywheel with P/N 12562765 from the 2001 LS6.
- Prior to connecting the transmission to the motor I went
ahead and also replaced the clutch hydraulic slave unit located on the front of the T56
with an upgraded P/N 15046288 which is from a 2001 F-body.
- With the engine and transmission bolted together as a unit
I carefully lowered the assembly into the chassis. I left the driver side exhaust
manifold and starter off of the motor to make the installation a bit easier since this
provided additional clearance at the rear of the motor mounts since with the transmission
attached I needed a steep installation angle to clear the front radiator support with the
oil pan and transmission yoke at the firewall/transmission tunnel. I installed the
rear Crossmember brackets, rear Crossmember and installed the engine mount through bolts.
08/13/01 Final assembly continued
Final mechanical assembly continues....
8/14 through 8/18/01 Final assembly continues
- I refused to use any portion of the worthless crimped stock F-body drivers side Y-pipe
after the CAT on my car so I mocked up the proper fit of the exhaust routing between the
CAT and my existing G-body exhaust pipe with a piece of 2-1/4" flex-tube.
shows how I tack welded a couple metal strips to the flex-tube so that it would retain
its shape long enough to enable a local muffler shop to properly bend a replacement pipe.
- This view shows where I had to cut the stock
G-body Y-pipe and how the new head pipes and CATs will look once installed. I also
needed about a 5" section of pipe to splice together the passenger side exhaust. I
proceeded to weld the pipes together under the vehicle. The exhaust system is now
- I had the flexible stainless steel fuel lines fabricated to connect the frame
mounted hard fuel lines to the intake manifold mounted C5 fuel rail at the same local
Industrial Hose supply shop that brazed the ends of my frame mounted hard fuel lines This
view shows the stainless flex lines installed.
- Since I was not installing the EGR valve (interfered with my A/C bracket & when I
modify the motor with the LS6 intake manifold it doesn't use an EGR valve either) I had to
plug the EGR tube inlet hole at the intake manifold behind the throttle body. I stopped by
the local hardware stock and bought a tapered
rubber plug which fit perfectly into the EGR intake manifold tube end fitting once I cut
off the EGR tube. I installed this rubber plug with high temperature silicone sealant
where the tube was removed to prevent a potential vacuum leak. I then installed this
assembly back onto the intake manifold with the OEM O-ring and 8MM bolt
- I still wasnt really satisfied with the minimum clearance (about ¼") between
the rear of the passenger coil bracket and the A/C-heater shroud. I removed the passenger
side valve cover and ground
away part of the raised boss which retains the coil bracket to gain about an
additional 3/16" of clearance. I also ground part of the bracket here and the
attaching bolt face adjacent to the shroud to maximize clearance.
- Since the #8 coil was now turned approximately 45* to again maximize clearance, the
spark plug wire was about 1" too short. I went to the local Chevy Dealer and bought
one new spark plug wire for a 99 & newer 5.3L truck since they are ~2.5"
longer than the F-body OEM wires and have the exact same special connector end for the
- Next in I installed the A/C condenser with the passenger side A/C hose connection
fittings which came out of the mid-80s Olds G-body in front of the radiator.
- To save a few more pounds up front I installed a new aluminum (as opposed to the stock
heavy brass) radiator designed for an 89 IROC Z. This unit also comes with
lightweight plastic side tanks and virtually bolts right in without any modifications
- I installed an 86/87 GN/TR electric fan and top radiator trim plate which
retains the radiator. This is a two speed fan which has the speed controlled by routing
the power feed through a large resistor for slow speed operation and directly to the fan
for high speed. Two relays are required to operate the fan in the two speed mode.
- I found a pair of electric relays with the correct wiring connector for the GN/TR fan on
a wrecked 88 Midsize Olds. I mounted the
relays on top of the A/C-heater motor blower with an existing bolt. I also found an
85 Monte Carlo OEM passenger side inner fender mounted battery
terminal power junction block which attaches to pre-existing piloted holes on the
engine compartment side of the fender to provide positive12V power to these relays. I
connected the 12V positive PCM lead for the fan to these relays and also the correct low
speed and high speed PCM fan leads to the corresponding relay.
- Trying to determine placement of the F-body PCM was a little frustrating because of the
limited length of the stock F-body engine wiring harness so I would not be able to locate
it inside of the passenger compartment where the L69 computer resided. I determined which
wires I wanted routed to the interior passenger compartment and then installed the
passenger side inner fender with a new battery box too since my original one showed severe
signs of corrosion. I really couldnt find a good place to put The LS1 PCM "out
of sight" so I elected to mount the PCM
on the passenger side inner fender top directly adjacent to the A/C accumulator where
the stock G-body radiator overflow bottle is mounted. I will have to relocate the overflow
bottle next to the radiator and find another overflow bottle to work here.
- I found a mid-80s Celebrity overflow bottle which could be fitted in front
of the battery next to the radiator. I will use this as a temporary set-up until I have
time to determine what other options exist.
- The re-wired LS1 engine harness came with a fuel pump relay and positive lead wire for
the tank mounted electric fuel pump. I extended this line back to the fuel pump by
grafting an OEM fuel sending harness body mating end and integrating this "+"
lead, attaching a ground wire and splicing the fuel sending unit wire to connect to my OEM
body harness connector.
- I installed my fabricated A/C bracket and LT1 compressor after I had the aluminum
bracket bead blasted and clear satin lacquer finished for a nice protective finish which
matched the look of the other aluminum engine components.
- The original mid-80s G-body V-8 Olds A/C hoses didnt want to fit now
due to the computer location. I found an A/C hose assembly from a mid-80s V-6
Olds set-up that seemed to work just fine now except I later found out that the connection
at the compressor is different even though it appears to bolt up properly.
- The intake system in front of the throttle body required some specialized pieces to
function properly. I went to my local fuel line fabricator and found a special
90° rubber elbow which had a 4" diameter end to fit the throttle body on one end and
a 3.5" end for the Mass Airflow Sensor (MAF). I also found a 3.5" to 4"
diameter reducing sleeve that would connect to the balance of the metal intake tract
and air filter. I went to a local muffler shop that has Mandrel pipe bending capabilities
and had a 4"
metal tube specifically bent per my specifications to route the intake air from the
MAF through the radiator support for fresh air to the motor. I attached a 4" inlet
diameter K&N conical filter end (P/N R-40-0008 RAM) to this intake pipe. It looks very
intimidating in the flesh!
- Since I did not plan on using the F-body OEM Intake Air Temperature (IAT) Sensor due to
my intake tract plumbing I inserted a 4.7K ohm 1/2 watt resistor into the wire harness end to
simulate a constant 57° air intake temperature and then sealed the end with electrician's
- I waited until the intake system was installed to judge clearance requirements for the
upper radiator hose. I had a local Auto Parts store get a stock 99 F-body upper
radiator hose (w/o power steering cooler) for me so that I could verify fitment. It was
too short on the end where it needed to connect to the LS1 water pump. I used this as a
data point and went back in their stock room with an idea of what I wanted and found a
hose which I believed would fit (NAPA P/N 7620). I then test fitted the hose and cut each
end to fit properly.
- For the lower radiator hose I ordered up a hose designed for a 99 & newer 5.3L
truck. I trimmed it to fit on both ends and it worked out just fine. I used the plastic
protective shield that came with this hose and installed it on the upper radiator hose
next to the MAF sensor to prevent potential contact during engine torquing.
- I pulled the PCM wires into the passenger compartment where the L69 computer sits and
connected a 12V "+" continuously hot lead for PCM memory and a switched 12V + to
- I debated on what to do with the existing Monte Carlo engine wiring harness. I finally
decided to just eliminate the wires which were no longer required. The only remaining
wires that I used are the starter leads, water temperature sending unit, tach lead, volt
gauge lead for the alternator, oil pressure sensor and a power and ground lead for the A/C
since it has the correct connector end to mate with the existing A/C wire harness which
comes through the A/C-heater shroud.
- I routed the vapor canister hose around the brake booster and connected it with a
¼" reducing plastic connector to the LS1 vent valve vacuum solenoid located on the
- The 1/8" vacuum line for the A/C-heater was routed and connected to the 1/8"
vacuum line which came off of the rear of the LS1 intake manifold.
- The heater hoses were connected and I elected to route these under the A/C bracket to
keep the engine bay looking less cluttered directly to the fittings on the water pump.
- Work in the engine bay is basically complete now with the exception of connecting the
A/C hoses properly connected and system charged. Since I need to be able to have the
water pump functioning properly I elected to install the stock F-body serpentine belt which
would not activate the newly located A/C compressor until I have the system finalized.
- The stock 99 F-body battery cables that came with the motor were a perfect length
and bolted right up to the battery.
- At this point the hood was re-installed by aligning the scribe marks that I made on the
underside of the hood at the hinges prior to removal. This made the fitment perfect.
- Moving on to the interior, I made a cardboard
template based on the 93 F-body console boot to cut out the stock Monte auto
shifter console trim piece to accommodate the T56 shifter. I proceeded to cut the hole out
with a die grinder and then finished the net trim with a reamer attached to a drill. The
boot assembly now just snaps in place! I temporarily fit the C5 T56 shift knob onto the
shifter end by forcing it onto the stick until the undersized threads were ready to
engage. The stock console bolted down in the rear in its stock location! I will still need
to install the front bracket to anchor the front half of the console.
- The proto-type 200 MPH speedo and 8000 RPM tach were installed and the rest of the gauge
cover components. I noticed that my OEM plastic bracket which secures the light knob was
cracked and actually broken in all three mounting locations. I bought a new piece (GM P/N
14086212 for ~$3) through my local Chevy Dealer. I would recommend getting this part while
it is still available! I will still need to connect a speedometer adapter/calibration box
which uses a VSS signal from the PCM to drive a mechanical cable for the speedo to work
correctly. More details here will be forthcoming soon.
- The brakes were bled since I had installed the 8.5" rear end and disconnected the
- The hydraulic clutch was also bled to remove air in the system caused by drilling out
the restriction point and installing the new slave unit in the transmission.
- Fluids just need to be filled now for the trans, engine, power steering, brakes, clutch
reservoir & radiator!
08/19/01 My LS1 breathes it first air
in a G-body!
First off let me say that I apologize for the lack of
detailed updates this past week. I was on a mad rush to get the car ready to go to
the local Pacific Northwest High Perf Chevy Show at Seattle International Raceway (SIR)
today and missed attending by about 6 hours :>( oh well! Working
on the car and posting web updates just didn't give me the time I needed. This next
week I'll try to get all of the updates from this past week updated and current. Now
on to the good stuff!!!
- After filling all of the fluids as a safety precaution I
rolled the car out of the garage before attempting to start it.
- Once the wiring was connected with the proper "hot
& ignition on" for the PCM I turned the ignition key to only the "on"
position, heard the fuel system & pump relay run for 2 seconds like it is supposed
too, cranked the starter and NO START! I thought, what the heck is up with this?
- I blew the 10 AMP Ignition/ECM fuse after I could hear the
fuel pump prime the fuel system. I replaced the fuse several times and blew several
more. Hmmmmmmmmmm.......very frustrating after getting the mechanical portion of the
installation this far.
- I consulted long distance with "Crazy Bill" (as
he is affectionately know on the "Monte Mailing List" since he is a "Jedi
Master", well seasoned TPI/LT1 G-body retrofitter) to explore my concerns regarding
the LS1 PCM wiring and fuses and he suggested a 20 AMP fuse based on the LT1's. The
PCM/ignition fuse in a G-body has only a 10 AMP OEM fuse for the L69 ECM and the LS1 PCM
apparently needs a larger fuse too!
- Installed a 20 AMP fuse and music to my ears!!!!!!!!
The LS1 fired up and ran smooth as silk! It is very,
very quiet even with real dual exhaust. Very different tone as compared to the SBC
- I checked for leaks and noticed that everything seemed fine
with the exception of a small oil leak where I had located an external oil pressure sensor
above the LS1 oil filter. Since this was dripping oil on the drivers side CAT I
elected to not test drive the car until this is fixed.
- I washed the car and took this pic
while still wet so that you can see it in running condition!
- I also snapped this interior view
of the Shifter, pedals and although hard to see clearly, the killer proto-type 200 MPH
speedo & 8000 RPM tach installed.
- Once dried off, I engaged the clutch and LS1 self-powered
the car into the garage!
The debugging process will begin now to ensure everything
performs as expected. I know that I have trouble codes since the SES light is on (as
expected) so I will need to isolate all of the issues so that the car will run properly.
I purchased an ATAP to aid in
the diagnosis. I will also have to get the A/C a new set of hoses and have the
system charged before installing the pulley belts. I'll be driving shortly!!!
I was up until 3:30 AM last night trying to get things
ready to go and was up before 9 AM this morning and it is pushing Midnight now so needless
to say I am a bit tired. I have spent a lot of time with the car this past week so I
will spend some quality family time this week too so please be patient with updates.
And yes it feels great to have it running!!!!!!
8/25/01 The LS1/T56 takes its first flight!
I was able to fix the oil leak by removing the driver side CAT and tightening the
fitting into the oil pan side adapter fitting. I also discovered a very minor leak at the
fuel filter inlet, which required a slight turn on the fitting to stop. I was cautious
tightening everything early on to ensure not stripping any threads. I always figured that
I could give things a final tightening if leaks were discovered. As it turned out these
were the only two leaks of any kind and were easily fixed!
- Just installing the L69 oil pressure sending unit as I initially did directly into the
adapter caused an interference with the CAT. This view shows the plumbing
(1/8" NPT 90° street elbow, 2.5"L threaded tube & female connector) required
for the oil pressure-sending unit to clear the CAT.
- The attached harmonic balancer for the front input shaft on the
Driveshaft did not want to adequately clear the factory body pan brace. I took this opportunity to
fabricate a Driveshaft safety loop to bolt in its place. This view compares the
sheetmetal brace with my welded ¼"Tx2"W unit that bolts into the same
underpan factory bolt holes using longer bolts to compensate for the added thickness.
- In order to secure the air intake tube/filter assembly properly I welded on
a 1/8"Tx1/2"W metal tab to the side of the intake tube and attached it to
the upper radiator support using an existing hole and placing a nutplate here for an 8MM
- In order to obtain full throttle I had to unbolt the accelerator pedal and put it into a
vice to enable bending the top cable receiving end about 1-1/4" to take up the
additional slack caused by the longer F-body throttle cable. A quick re-installation
verified full throttle now with the accelerator fully depressed!
- I was concerned that the radiator fan didnt come yet since the water temperature
(according to the factory gauge) was about 220°. I shut things down to prevent overheating
and consulted the 99 F-body service manual and noted that the primary electric fan
was supposed to come on at 223°. I fired up the motor again with a cooking thermometer in
the radiator and sure enough, at the designated temperate the fan came on! Now were
ready to drive!
- I backed the car out of the garage wheeled around the driveway, stopped, then and turned
onto the street. As I eased out the clutch again and gave it only a small amount of
throttle the car accelerated very smoothly and quietly. As I upshifted I noticed that the
T56 shifted effortlessly!
- After a quick stop at a local gas station I proceeded to run the car through the gears
at a somewhat brisk ¼ to 1/3 throttle acceleration. WOW!!!! The sound created by
the huge 4" intake tube/K&N filter assembly is wicked and actually overpowers the
sound of the DynoMax dual mufflers and the combination of the two emitted the sweetest
high performance authoritative roar that sounds similar to a NASCAR type sound that just
brings the biggest grin to my face and has made this whole effort worth every dime spent
and hour worked!!!!!!!!!!
- Next I went onto a lightly travel local the freeway for a few full throttle blasts. I
ran the car in 2nd & 3rd gears until rev limiter kicked in to
determine where I should guestimate shift points on my tach face since my tach currently
reads about 60% slow until I install and have the Abbott Electronic Ratio Adapter box
connected and calibrated to account for the LS1s unique square wave tach signal. I
ran the car again at full throttle and noticed a very nice pull throughout the upper RPM
..definitely 13 second ET material!!! YEHAW!!!!!!!!
- I stopped by a local weigh station while I was out driving around to establish the race
weight of this combination. The car with the LS1/T56 (without driver) now weighs 3380 with
¼ tank of gas (3580 w/driver) compared to 3480 (w/o driver) with the L69/TH200R4
drivetrain. The LS1/T56 changeover accounted for an overall reduction of 100 pounds, all
off of the front end!!!
- I probably need to wait a few weeks for the suspension to settle properly up front
because right now the front end of the car sits about 1" higher than before.
Additionally, I also noticed that now with the IROC steering box installed that my front
tires no longer touch the rear of the lower A-arms (courtesy of the huge P275/40x17
tires!) when the steering wheel is fully cranked.
- Before calling it a day, I went ahead and also installed the C5 Fuel Rail
Covers (FRC's) and they make the motor look awesome!
Next up on the agenda is to finalize the remaining details. This will include getting
the tach calibrated, speedometer connected and calibrated and the Air Conditioning lines
fabricated to fit the LT1 compressor properly and connect to my existing A/C condenser and
accumulator. I will also be going back and updating this web page with the remaining
pictures and details missed this past two weeks.
8/28/01 Updates to Web page
I added in pictures and updates for the days between 8/13/01 and 8/19/01 above and
inserted them into the proper chronology date-wise above.
8/28/01 PCM SES trouble code diagnosis
I installed my AutoTap software onto a laptop and connected it to my PCM ADL connector.
I received the following trouble codes:
- PO107 Manifold Absolute Pressure [MAP] Sensor Circuit Low Voltage
- PO405 EGR Valve Position Sensor Circuit Low Voltage
- PO412 AIR Solenoid Relay Control Circuit
- PO418 AIR Pump Relay Control Circuit
- PO449 EVAP Emission Control System Vent Valve Circuit
- PO452 EVAP Pressure Sensor Low Voltage
- PO463 Fuel Level Sensor Circuit High Voltage
- PO645 Air Conditioning [A/C] Clutch Relay Control Circuit
I expected all of these codes except for the PO107 based on my installation. After
further analysis of what causes PO107 with the MAF, it could be caused by problems
detected with the EGR system so this makes sense. My first reaction is to want to delete
all of the PCM functions for these codes with the exception of the PO107 for the MAF and
the PO645 for the A/C since I dont have the A/C connected properly. I was waiting
for the release of LS1_Edit Software to do this myself, however, I understand it is
still being BETA tested. I am reviewing my options for reprogramming the PCM now.
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© 2001 by John Bzdel