hey i was wanting to what's the major difference between the 390 and a 391, i know the 391 is a heavy duty motor, but what's the big differences?

thanks,
matt

 

391 is a FT series. webbed block, but interchangable with a normal FE block if an adaptor ring is used for the distributor. Distributor has a thicker base, but an adaptor ring is avalible to run the smaller FE unit. Forged crank, externaly balanced. crank has larger snout, so bigger hole in a cast timing cover. Crank can be used in a normal FE with either some minor machine work, or use of the FT's timing cover. The heads and intake manifold are diffrent, interchangable with a standard FE, but only as a set.

 

The 391 is a heavy duty FE with low performance heads and intake and big heavy cast iron timing cover that doubles as a motor mount. The block has higher nickle content and heavier block reinforcement. Some people use the blok and crank to build high power FE's. But like stated above you need the bushing for the FE dist and you need to have the crank turned down to fit in the FE timing cover. Most people have the crank internaly balanced.

 

also the 361 and 391 uses a steel crank and has 4 rig pistons real good pulling eng

 

not all are 4 ring. the FT engines are very low power low rpm low compression engines. they all make less power than the FE engines.

 

all 361 and 391's a 4 ring pistons

 

actually plenty had the C7 deep dish 3 groove pistons. 4 groove was a special thing for the mot part but common in dump trucks and water pumps.. U haul used both but mainly 3 groove. plenty of school buises are still running the 391 with 3 groove. both were common.

 

all i ever seen was 4 ring but who know's were talking about ford's so anything is posable

 

lol...thanks for the help, so it's pretty much a heavy duty 390...right? and same for the 360. what about the bore and stroke...are they the same? could i put 390 pistons in a 391 block?

 

yes you can use the 390 pistons. but i would use 360 pistons. the ft is different in lots of ways .