Swap 6.2 for 6.5

[Flatlander6.2]

I am looking at putting a 6.2 engine out of a 1990 half ton, that is currently in a 1991 3/4 ton, into a 1994 with a naturally aspirated 6.5. I am planning on using the 6.5 fuel system and electronics on the 6.2 block. What affect will this likely have on my mileage? I am currently getting 25 to 28 with the 6.2 in a truck with over 350,000 miles on it.

[AKMark]

Should work, you might want to consider just running the fuel system already on the 6.2, as it's very reliable (in comparison to the pumps used in the 94). Mileage is a hard to say exactly what mileage will be because items such as transmissions, gear ratio's, 4x4, and other things will make a difference.

Why are you swapping motors? Hoping to get more mpg out of the truck? You could probably swap the heads and gain what you are hoping to get with the motor swap.

[Flatlander6.2]

I'm looking at swapping motors because I have a strong 6.2 in a very tired truck, and have found a 94 with a non turbo 6.5 in very very good shape for a very good price. But there is anti freeze in the oil on the 6.5. If the problem is more serious than a head gasket, I am thinking of dropping the 6.2 into it. However, the 6.2 fuel system is mechanically controlled, and the 6.5 is electronic, so to me the easiest way to make it work is to put the 6.5 fuel system on the 6.2. I don't foresee any problems as I think everything will transfer. One thing I am unsure of is the compatibility of the crank position sensor from the 6.5 onto the 6.2.

[DmaxMaverick]

Welcome aboard, Flatlander!

All else being equal, swapping only the block will result in little, if any difference. There is a bit of head design difference, depending on the model year, but it may not be noticeable. It will all depend on your use and habits. If you swap the 6.2 block and heads into the 94, and keep the fuel system, etc, the difference will likely be insignificant. A little less power and a little more economy, but that depends much more on your driving habits.

BTW....
You'll also have to swap the timing cover and harmonic balancer. The electronic version has the crank position sensor in the cover, and the reluctor wheel behind the 6.5 balancer. No big deal, since you are doing a complete engine swap, anyway. Any other components that may be different will have to stay with the vehicle, but it is all a direct bolt-on to the 90/91 engine.