250 crankshaft early vs late

[Johnsondawg]

Working on an EFI 250 project for my 66 Bronco. We started with a junkyard 78 block but just picked up a low mileage 70 block that’s in much better shape. The crankshafts have different casting numbers. I verified that there was indeed a change in 74 (according to tech archives). Does anyone know specifically what the change was? I have been scouring the internet for the answer this evening but so far I’ve not found any information.

 

[chad]

i'd guess metalurgy (nodular v forged or sompin) rather than dementional spec but have no idea w/o more research...sorry~
bubs build some @factory back then...he'll B along soon

 

[Econoline]

Year early 250 rods are forged. You can identify them by the parting line. The C9 rods are forged.

 

[Johnsondawg]

I did discover the forged rods. The crank looks to be cast. I’m mostly just curious about it and wondered if anyone had more information.

 

[bubba22349]

I don't know what difference's there is in the crankshafts all of my 250's were either 1975's and 1977 though I always wanted to get a hold of an early 1969 or 1970 version since they have all the best parts used in the short block. Since you have the 1970 and the 1978 you could lay the cranks on a table next to each other taking some good photos of them and posting them here. Also check the differances of the Rods (casting numbers) and Piston design. They used the orginal 1969 Forged Rod design unchanged for severial years into the 1970's. Both years of the Crankshafts are going to be of Nodular Iron to my knownage there weren't any forged crankshafts made for these six'es in the US market even in the industrial engine versions, still the Nodular Iron cranks are quite strong. There might be a counter weight difference (were they added some weight) if the later set of Rods and Pistons have much of a different in the combined weight than what the 1969 to 1974 250's had. If your not planing to balance your rotating assembly then it would probably be best to stay with the complete matched assembly i.e. Of The Crank, Rods, Pistons, from either the 1970 or the 1978 the Dampner is different early were 3 bolt later on they went to 4 bolt, Flywheel / Flex Plate wont mater since all years are Zero Imbalance on the rotating assembly. The person that might be able to tell you the differance is called the "NumberDummy" over on the ford truck site he is a retired Ford Parts Department Manager and has all the old parts books & Micro Fiche. Best of luck

 

[Econoline]

Sorry I misread your post.

 

[chad]

not sure he can help but as per bubba
Bill at FTE
https://www.ford-trucks.com/forums/member.php?u=368968

My bet? he'd love to hear from ya!

 

[Johnsondawg]

Thanks everyone, I’ll try contacting bill.