85 K5 Diesel Swap. NEED OPINION

[6btor4bt]

I have an 85 K5 blazer an want to put a new diesel in it. either a 4bt or 6bt it has automatic 700r4 and i need help so any advice would be nice thanks.

[NH2112]

Well, if you're going to keep the 700R4 I'd say you're pretty much limited to the 4BT. The early 700R4s were marginal behind 6.2ls, there's no way it'll handle a 6BT without a high-dollar performance rebuild, and even that's questionable. Even a slightly warmed 4BT will push a 700R4 to its limit. Where will you be getting the engine? 4BTs used in bread trucks usually had a TH400 or SM465, due to no overdrive you'd be limited to maybe 55mph depending on your truck's gearing (3.08, I'd guess) but you'd know the tranny was matched to the engine.

[Edahall]

You’ll also need to use heavier duty axles from a ¾ ton especially if you end up going with a 6BT. They weigh around 1100 lbs with all the accessories. But first off, you need to decide which engine you’re going to go with. The 6BT is very hard on automatic transmissions due to its extreme low rpm torque. With this engine you would be much better off going with a manual (NV4500, NV5600, G56) unless you are willing to spend big bucks to get an automatic transmission built up to withstand the power.

[Harvey_Cannon]

Got a 85 4x4 stanard 4 speed pickup with the 4bt. The motor starts the first roll over and does good. The motor in the pickup was the 6.2 (that made it to 250K) so the change over wasnt all that bad. You will have all kinds of room to work with. The motor has maybe more power slow than the 6.2, just wont rive up very fast(top speed is 68mph with the 373). The motor I have is total stock, with power to do what I do. The fuel milage is always over 20 mpg so I am not going to change anything. I am not telling you what to do, just telling you how it is working for me. Good luck.