391 Ft
 

Couple of questions for you FE guys that know something about FTs.

I have come across a 391 FT engine. If I understand correctly, the crank is forged and has a larger diameter snout and thicker rear flange than a 390 FE. The most notable thing about the block is the front and rear flanges where the intake rests. The casting is much thicker than a regular 390 block. My documentation also suggests the block was cast with stronger metals and alloys than the FE because of the heavy duty nature of the trucks these engines were used for. This also results in the block weighing approximately 10 lbs more than an FE block.

Having said this, if I were wanting to build a somewhat beefy 390ish to put in a car, can anyone give me some options and suggestions. I could have a machine shop turn the snout and flange down, change the timing chain cover and have a "heavy duty" 390. Would it be worth it? I have the original harmonic balancer and crank pulley, so should I consider using them and spare the added machine shop expense (I understand I would still have to thin the flywheel flange by 3/16")? Would I be better off scrapping it and going with a true FE? Questions, questions......

I am not interested in the low end torque this engine was originally designed for. Yet, I'm not ready for 800 horses either!

Thanks for any suggestions. As always, these forums are great!

I would suggest doing a search on the forums for that. I believe that the 391 FT was strictly a truck motor, and is much different from a 390 and does not accept most standard or aftermarket 390 parts. I could be wrong, but I think that's what I've read.

When using an FT block, there are several differences. The ones you mentioned are the most prominent....machining the crank, using a different balancer, and using a different front cover.

In most cases the front covers are cast iron and are just too heavy and bulky.

The crank work will cost you quite a lot. Yes they will have to turn down the snout, regrind the keyway, and machine the flywheel flange down.

It will be cheaper to buy an aftermarket crank for your purposes. If you're not going for broke on horsepower, you wouldn't need the forged crank anyway.

As for other differences, you will need a distributor bushing placed in the block as the trucks used different sized distributors.

The blocks for the most part are beefy. There are exceptions, but you'll find webbed mains and thick cylinders in most of them.

If you ditched everything but the block, the only part you would need would be the dizzy bushing. All other parts will interchange without a hitch.

A book I have says that the FE 390 is internally ballanced and the FT is externally ballanced. So you have to use the FT ballancer and flywheel or have the crank reballanced, which would be expensive compared to a good used FE crank.