391 truck

[michael1]

anyone know about 391's . don't know anything about them,and the types of lifters they came with?

[blykins]

The 361's and 391's were truck engines. Hydraulic cams. Some of them had oversized crank snouts for running accessories (hydraulic pumps, etc) and the distributor stubs were also a larger diameter. If you use a regular FE distributor in one of those blocks, you may have to buy a distributor bushing.

[Mark IV]

The "FT" engines often are forged cranks, but as stated have a larger diameter crank snout that can be turned down. The bottom ends are reputed to be stouter with thicker webs and some have the bosses cast in for the crossbolts.

The distributor hole is larger as the medium and heavy trucks used a cable drive tachometer that requried a larger diameter distributor shaft and thusly a larger housing diameter.

[Mr Jody]

[Just repeating some of the info already provided…was posted while I was looking up some info to refresh my memory and got caught up in the details.]

According to Steve Christ’s How to Rebuild Big Block Ford Engines, page 32, he says that hydraulic lifters are used on all FT engines, and have the standard FE oiling system with oil galleries drilled accordingly. Some other FT differences are:
Larger distributor shaft bore to accommodate a larger oil pump drive shaft.
Thicker main bearing webs and additional ribs in between.
Larger diameter crank snout (1.75” vs 1.375” for FE), and thicker flywheel flange.
Larger counterweights on forged FT cranks, and external balancing at the flywheel or damper is required because crankshaft to crankcase clearance is insufficient for even larger counterweights that are needed with the forged crank.
The pistons have a smaller compression height (wrist pin center to top of piston) of 1.757” vs 1.775” for the standard 390.

There are several other specifics and differences (ie, heads, valves, etc.) that I think you would just want to get the book, which has pictures, charts, etc., if you are considering using a 391. And you may want to check out ford-trucks.com and the FE Forum website for more info.

[Barry_R]

The large snouts were becaue many of the MD/HD trucks used the nose of the crank to drive pumps for the various chassis mounted accessories. Some FT engines have an extra return line for oil behind the filter - which must be blocked off for passenger car use (or comes in handy for blower drainbacks....). The heads and intakes are not interchangeable with normal FE stuff - but you would not want to use anything other than the block and maybe crank anyways.

[michael1]

thanks guys got some work to do here.

[PDUB]

I had one turned 20 years ago, and the machine shop had a heck-of-a-time... they said they had to resharpen the tool constantly, as the snout was so hard. They wanted to charge me triple the original quote... Not!!

They ate it...

[cobred]

I have one in my car. Has a 428 cobra jet crank and rods and is bored to 428 standard bore size.