Chevy Impala SS Forum banner

1 - 11 of 11 Posts

·
Registered
Joined
·
1,557 Posts
Discussion Starter · #1 ·
Alright so i have a 96 9c1 with low miles on my 4.3. i have everything except the lt1 engine that the police package comes with (disc brakes, 3.23 gears, 8.5" reacrend, etc.) Exactly what would i need to complete a swap? does mileage matter if its going to be rebuilt for higher hp and torque?
 

·
Registered
Joined
·
581 Posts
Well first off get an LT1 from a 1996 vehicles(as it has additional crank sensor and different knock sensors than 1995 and older LT1 engines). Pull the L99 out and simply put the LT1 in its place. Then get the computer reprogrammed for the LT1 engine(as the fuel/air calibration tables are different but an L99 programmed computer will run an LT1 just would run it quite a bit lean but good for quick testing after the engine is in) and enjoy. You can keep the 3.23 rear end, no need to downgrade to the 3.08, unless you can get the 3.08 rear end for cheap and the computer out of the LT1 powered vehicle, so you wouldn't have to get it reprogrammed at all. That is one nice thing about the LTx/L99 series engines they are near identical outwardly just with internal differences(bore/stroke/combustion chamber size in the heads/injectors).

Also just for the record the 9C1 didn't necessarily come with the LT1 engine though is was popular, some big departments like NYC and LA used L99 powered vehicles for the many of their cars as in city driving don't need high horsepower just a big car to get around the city with that gets relatively good gas mileage(and when talking about a fleet of cars that does 30-40K miles in a year even a 1 or 2 MPG difference makes a huge difference). Actually the L99 engine was standard on all 94-96 Caprice sedans with the LT1 optional, though the LT1 was standard in all 94-96 Caprice wagons, Impala SS, Roadmaster, and Fleetwood. - Peter
 

·
Premium Member
Joined
·
2,705 Posts
Does the car have the single exhaust? If so change to duals and get an LT1 trans crossmember since it has the double hump compared to the L99 crossmember.

If buying a 96 LT1, get the PCM too and just reprogram it for the 3.23.
 

·
Registered
Joined
·
3,612 Posts
If buying a 96 LT1, get the PCM too and just reprogram it for the 3.23.
He can reprogram his just as easily.

If you're going to rebuild the engine like you say (and I recommend you do), just find a complete LT1 that runs without burning a lot of oil or making any bad noises. Who cares if its got over 100,000 miles on it. Expect it to need an 0.030" overbore, and maybe the crank turned 0.010" under. Any year LT1 will do. If you plan on keeping OBDII, either get a '96 or use the timing cover and crank hub from your L99. If emissions don't matter where you are, do an OBDI conversion. Programming is easier and cheaper.

Also, as others have said, you should go to dual exhaust. Also, install an upgraded 2-4 "Corvette servo" in the transmission.
 

·
Registered
Joined
·
1,557 Posts
Discussion Starter · #5 · (Edited)
the guy that usually gets the motors gets 94 to 95 caprices. what problems would i run into going that route? i havent really seen any 96 lt1s often.

if i wanted around 400 hp what should i get done to it as well?
 

·
Registered
Joined
·
1,812 Posts
Does the car have the single exhaust? If so change to duals and get an LT1 trans crossmember since it has the double hump compared to the L99 crossmember.
LT1 and L99 Cross member are identical. While the L99 does not have dual exhaust it still has dual cats that run under the cross member to a y pipe.

I went from L99 to LT1 in my car. All I did was swap the engine and computer. I also had a custom cat back installed. That is all that is required. If you have any questions let me know.
 

·
Registered
Joined
·
1,557 Posts
Discussion Starter · #7 ·
LT1 and L99 Cross member are identical. While the L99 does not have dual exhaust it still has dual cats that run under the cross member to a y pipe.

I went from L99 to LT1 in my car. All I did was swap the engine and computer. I also had a custom cat back installed. That is all that is required. If you have any questions let me know.
isnt it different since you have a 94 and i have a 96 9c1? i mean if i got the 94-95 i would try to get the pcm as well with it.
 

·
Registered
Joined
·
1,812 Posts
Isn't what different? Only difference between 94,95-96 that I know of is there is 4 o2 sensors in 96 and 2 in 94-95
 

·
Premium Member
Joined
·
2,705 Posts
96 has different knock sensors and also crank sensor on the timing cover.
 

·
Premium Member
Joined
·
2,755 Posts
isnt it different since you have a 94 and i have a 96 9c1? i mean if i got the 94-95 i would try to get the pcm as well with it.
Something seems to be getting lost in the translation. :)

For your purposes an LT1 is an LT1(though you want the vented opti). The differences come in O2's and knock sensors and computer. If you can, get and run the older OBD1 comp. If emissions require you keep your current OBDII just use the L99's timing cover/sensors on your new mill and have your comp reprogrammed.

Add duals, CIA, stir in headers and beehives and rockers, simmer and serve.
 

·
Registered
Joined
·
1,557 Posts
Discussion Starter · #11 ·
Something seems to be getting lost in the translation. :)

For your purposes an LT1 is an LT1(though you want the vented opti). The differences come in O2's and knock sensors and computer. If you can, get and run the older OBD1 comp. If emissions require you keep your current
OBDII just use the L99's timing cover/sensors on your new mill and have your comp reprogrammed.

Add duals, CIA, stir in headers and beehives and rockers, simmer and serve.
ok i comprehended most of it lol. the reason its not all clear to me is because im not the one whos doing the motor work whatever you guys tell me is needed ill tell my mexhanic to do lol. now ok emissions not really a problem as i get mine passed (shhhhhh) what id like to know is if i can get the lt1 with the pcm is there any additional stuff like parts wiring harness , and etc.

i have duals as i. Have stated and the stuff you listed is what i have in mind. you guys are doing a good job with the advice so keep it coming. im learning as we go
 
1 - 11 of 11 Posts
Top