Hi all,
I have a 75 highboy and am trying to figure out what i want to do with it. It has a 460 big block mated to a c6. I went ahead and put a floor shifter in it. I've been talking to my mechanic and he told me i could build out the 460 i have but for fuel economy he recommended swapping to a 5.8 351. Can I get the same horsepower (around 500-600) from the fuel injected 351 or should i keep my 460 and change it to fuel injection. Also my c6 is only a 3 speed and does not have overdrive. Are there any good substitutes that can be mated to a 460. Preferably a 4 speed auto with od. thanks!

 

A 351 based engine could produce that kind of power.. there are lots more aftermarket parts available for that engine platform at better prices than the big block, but it won't get better gas milage when it's all said and done. The motor will still have big block displacement.. you'll be stroking it out to a 408 or something similar, and you will need a different transmission... that is both good and bad as it gives you the opportunity to install one with an overdrive, but it will increase costs and work of course.

 

I agree with Paul, the 351W in any config is not much better than the 460 when it comes to MPG.

 

the only overdrive factory transmission that will mate to the 460 is the E4OD transmission. they came from the factory with the EFI engines. make sure to get one with the 460 bellhousing as they also were made with the small block bellhousing.

the only problem is that it is an electronically controlled , so you will need to add a control module and a throttle position sensor to make it work. there are a couple of different aftermarket offerings out there, Baumann is one. it is not that hard really, but not really cheap either. the E4OD transmission is a pretty stout tranny, it is basically a C6 with overdrive. they can be built to handle lots of power.

rgds
Mike

 

Considering the money it will cost to add an electronic 4 speed tranny you might think about a Gear Vendors overdrive.

 

no replacement for displacement. stick with the big block. there will be a lot of little things you will forget you need to buy if you go with the small block. brackets etc. I don't think what little mpg difference you MIGHT see will be worth it.

 

RE: Gas Mileage
Friend had a 79 F150 2wd C-6, with 460 engine. Didn't like the gas mileage. Went to a 351W...about the same mileage. Went to a 302, about the same mileage.
I have a 351W in my 86 F250 SC 2wd C-6 4.10 rear. A 460 in my 87 F250 SC 2wd C-6 4.10 rear. Both with a Holley 4 v carb.
The 86 351 gets about 8mpg loaded and pulling a loaded car trailer. The 87 460 under same conditions gets about 6mpg. Running empty the 351 gets about 11mpg, the 460 about 10mpg. The 460 has way more pulling power on the hills than the 351.