Who has done a 4BT swap?

[Dieselwrencher]

It varies, but after the swap is always better. My wife's V10 excursion went from 6-11 to 18-20. An 89 V2500 suburban with a TBI 350 to a 12v was 8-12 before, and 15-18 now. And that truck has 3.54 gears with 35" tall tires. He tows a 10k dump trailer with it and a pretty good sized enclosed trailer with it and said he could never go back to the gas engine in it. My 72 I can't tell you before because it didnt run when I got it. But it was a 402 4 speed truck. It gets 17 with a mix of highway and in town driving. I hauled a skid loader a hour and a half away, which was 23k loaded. When I filled the tank from that trip it averaged 14.8. I was running 70-75 on the interstate. It would get better if I pulled some fuel back. It is pretty over fueled right now. I have not dyno'd it but it pulls like any other 600-650hp truck we've built. You have to watch your skinny pedal. The rotary pump 12v's do better on mileage than the P-pump 12v's. But the p-pump engines still get great mileage too.