I am rebuilding a 390 motor for my 1977 f-150. I have a complete ft motor also, and was wondering if there was any advantages to running the ft heads instead of my stock fe heads. my truck is street legal but used mainly for offroad. thanks

 

....no....

 

It's the other way around. Fe heads on an Ft is an upgrade (along with intake). Ft heads are terrible.

 

Ft heads will really choke up your RPM ability so it get really weak about 3500 or so rpm.

Although they could really do something in a rock crawler or something of the such where you high idle alot and need really snappy torque that a smaller head will help give. Kind of like the peanut ports Chevy used on there 454 in the 70's-80's trucks. Ford had the same thing on 460's.

But probily they would work quite the way you'd like, and stock truck FE castings with port matching, and exhaust polishing would be alot better.

 

You would need to use FT intake, and exhaust manifolds. The FT left-side manifold, I think, interferes with the motor mount perch (because FTs were installed using engine mounts on the timing cover and/or bellhousing, instead of on the side of the block).

Better to just use the 390 heads you have. They definitely flow better.

 

i installed a complete 391 in my 77 f350 and mated it to my np435 with a custom pilot bushing..The motor mounts bolt right up in there original location on the frame and you can use a set of exhaust manifolds from a 331 hd ft motor from a u-haul truck , specific to the F350 u- haul only.

 

Interesting info dragracer... got any casting #'s from those exhaust manifolds?

 

I have no part # to give . And i did this swap 20 yrs ago on a bet they said couldn't be done.If i recall i used the 331 flywheel that was smaller so it could fit the bellhousing of a FE engine to the motor. Because the 391 had a Clark 5 speed and the 435 wouldn't mate up to it. I had a pilot bushing made of silicon bronze to fit the back of the crank to accept the 435.The manifolds i bought off a u-haul dealer for i remember those 350 ford u-haul trucks had 331 md and hd motors in them and they bolted right up. ,for i needed them cause of the exhaust crossover.The drivers side looks like a y shape and the passenger side is a little diffrent from a standard 390 manifold.That is what i remembered . Oh ps i still have the truck.If you would like i could take some pictures.

 

Pics would be GREAT! And the casting numbers on the manifolds are out in the open, maybe they can be seen through the wheel wells?