The 1947 - Present Chevrolet & GMC Truck Message Board Network - View Single Post

**1774btcrew** · 05-25-2017, 04:09 PM

I will weigh in here. My dad and I did a 4BT in my 77 crew cab short bed. It has a 4l80e with compushift controller, 3.73 gears and 295 50 15 tires. I get 25-26 MPG highway and 19-20 in town. Neither is with towing anything. Top speed is around 85 with this set up. I really don't have any desire to go any faster but I am sure with a couple minor mods it would improve the top speed. As said above, it is noisy at idle but at freeway speeds it is hardly noticable and I haven't even done any sound deadener.
We have done 7 Cummins conversions in Chevy trucks in years ranging from my 77 all of the way up to 2002. Of those 2 were 12v 6BTs and the rest were 4BT conversions. They are great engines and super reliable with easy to get parts. The only thing I may have changed on my conversion is running a NV4500 instead.

05-25-2017, 04:09 PM	#12
1774btcrew Senior Member Join Date: Jun 2009 Location: Phoenix AZ Posts: 4,604	Re: Who has done a 4BT swap? I will weigh in here. My dad and I did a 4BT in my 77 crew cab short bed. It has a 4l80e with compushift controller, 3.73 gears and 295 50 15 tires. I get 25-26 MPG highway and 19-20 in town. Neither is with towing anything. Top speed is around 85 with this set up. I really don't have any desire to go any faster but I am sure with a couple minor mods it would improve the top speed. As said above, it is noisy at idle but at freeway speeds it is hardly noticable and I haven't even done any sound deadener. We have done 7 Cummins conversions in Chevy trucks in years ranging from my 77 all of the way up to 2002. Of those 2 were 12v 6BTs and the rest were 4BT conversions. They are great engines and super reliable with easy to get parts. The only thing I may have changed on my conversion is running a NV4500 instead. __________________ AZPartsLocators on Instagram 1972 Cheyenne Super Short Bed big block "Blackie" 1977 Crew Cab GMC Short bed with 4BT Intercooled Cummins Diesel and a 4L80e "The Junkyard Dog" 1985 Crew Cab Chevy dually with 5.9 Cummins "The Big Dog" This is what my dad liked to be called by the grandkids before he passed so it seems fitting for his old truck.