496/T56 to LS3/6L80E
Thread Starter
Teching In
Joined: Mar 2024
Posts: 3
Likes: 0
496/T56 to LS3/6L80E Hello all,
I will hopefully soon begin converting my car from a 496 big block Chevy backed by a T-56 magnum to an GM Connect & Cruise 430hp LS3 backed by a 6L80E. Some background on the car and why I'm doing this:
- 1968 Impala convertible
- 3.73:1 rear axle ratio
- The T-56 already required extensive transmission well modification
- I already have an in-tank electric fuel pump that will supply enough fuel/hour for EFI
- The car has a four-row aluminum radiator with dual Spal e-Fans, which should work fine for the LS3
- The car was originally a 396/TH400 car and I wanted to keep it true to its big block roots. The engine just proved to be a little too much - I'm not racing an open top car. The T-56 was fantastic on the open road but an absolute nightmare when negotiating city traffic or even moving it around in my driveway.
I'm more looking for specific feedback about the LS3/6L80E Connect & Cruise system if I can get it. I understand the obstacles to integrating a modern powertrain into a classic car. Thanks for any feedback.
I will hopefully soon begin converting my car from a 496 big block Chevy backed by a T-56 magnum to an GM Connect & Cruise 430hp LS3 backed by a 6L80E. Some background on the car and why I'm doing this:
- 1968 Impala convertible
- 3.73:1 rear axle ratio
- The T-56 already required extensive transmission well modification
- I already have an in-tank electric fuel pump that will supply enough fuel/hour for EFI
- The car has a four-row aluminum radiator with dual Spal e-Fans, which should work fine for the LS3
- The car was originally a 396/TH400 car and I wanted to keep it true to its big block roots. The engine just proved to be a little too much - I'm not racing an open top car. The T-56 was fantastic on the open road but an absolute nightmare when negotiating city traffic or even moving it around in my driveway.
I'm more looking for specific feedback about the LS3/6L80E Connect & Cruise system if I can get it. I understand the obstacles to integrating a modern powertrain into a classic car. Thanks for any feedback.
TECH Apprentice
Joined: Jan 2015
Posts: 313
Likes: 127
From: Austin area
If you're set on the 6L, Connect and Cruise is great. If you want to go up a little in budget, check out Blue Print Engines. I run their LS3 w/ 4L70e in my Chevelle and it works great. A bit more power too (550). On the freeway, I can cruise at 80 around 2700 RPM (I have a 3.70 Ford 9" rear). Also comes with a complete front end accessory drive, which you would have to add to the GM kit.
Another option is to run the 8hp70 transmission, its an 8 speed that shifts extremely fast and has a 700ftlbs rating stock. Ive seen alot of issues with the 6l80&90e transmissions and they cant even compete on shift speed. Theres a thread in this section that explains all the details. Good luck, cool car
Thread Starter
Teching In
Joined: Mar 2024
Posts: 3
Likes: 0
If you're set on the 6L, Connect and Cruise is great. If you want to go up a little in budget, check out Blue Print Engines. I run their LS3 w/ 4L70e in my Chevelle and it works great. A bit more power too (550). On the freeway, I can cruise at 80 around 2700 RPM (I have a 3.70 Ford 9" rear). Also comes with a complete front end accessory drive, which you would have to add to the GM kit.
TECH Apprentice
Joined: Jan 2015
Posts: 313
Likes: 127
From: Austin area
It has a little lope. Especially on cold start. But it's relatively mellow. Has a good sound, but very far from the, "uuuhhhh, not sure that can stay running" lope of a huge cam. I can take a video if you want.
