Sir, the 68 cast in the rear of the block is the Julian date (1-365) of the year the block was cast. Since yours is Fa it is 72-76 nothing strange
there. It looks like if you were to rotate the flywheel about 5* ccw on the crank then 5 bolts would line up and one would be off center 5* cw which
it should be and you should have the correct flywheel according to the #'s.. I still think you just need to rotate the flywheel on the crank till all
6 bolt holes line up. Just keep turning it to a new hole and somewhere all 6 will line up. Make sure the welded weight is facing outside toward /
against the torque converter.
On the date built it is on some cars stamped with VIN number on oil fill spout then painted over. I have not found any on motorhome build engines as
the oil fill tube end is motorhome only. Has a fill hose instead of spin on fill cap. If you do find a number the first # is the year, should be
2-6.
Husker92592 wrote on Thu, 26 March 2020 13:54
> Not sure on any of these as my engine builder is supposed to be a BOAT guy. I picked up the engine from a local GMC'er and quickly took it to get
> built. So relaying on my builder probably is not a good idea. there was not and origianal flex plate so this is where I am at. I suppose it is time
> to remove the engine pan again and do some research.
>
> 396021 fa is the casting number next to the oil filler tube, according to the "oldsmobile FAQ site The block is "common" but the back casting is a
> 1968 not a 72 on, obviously there is something wrong.
>
> ID/ Casting
> Code Year(s) CID Number Notes
> A '65 425 381917?? 1st year, big cars.
> 386525
> B '65 400 389298 442 only, one year only.
> D '66 - '67 425 389244 Big-car engine. Toro is different internally.
> E '66 - '67 400 390925 442 engine [VERY rare].
> F '68 - '70 455 396021 Common big block. Stick type F (sans serif).
> F '70 - '72 455 396021 Common big block. Serif type F. Two vertical
> and a base serif.
> Fa '72 - '76 455 396021 Very common big block. Marine also (L VIN derivative).
> G '68 - '69 400 396026 442/Vista/etc. engine.
> L '76 455 231788 Motorhome, marine and irrigation. GM made motorhomes
> from '73-8, maybe in all? Casting number appears
> as "231 [tiny 'L'] 788" on the block.
>
>
> so much for a solid rebuild. seems I need to find a new crank. and who knows what else. I will do some research and be in touch. thanks
>
> I could have put a diesel in my coach by now.\
>
>
> New photos:
>
>
http://www.gmcmhphotos.com/photos/engine/p67122-engine-castings.html
>
>
http://www.gmcmhphotos.com/photos/engine/p67123-engine-castings.html
>
>
http://www.gmcmhphotos.com/photos/engine/p67121-engine-castings.html
>
>
> block casting under heads: 33M730673
>
> 3= oldsmobile
> 3= 1973
> M = Lansing
> 730673= vin of car block comes from
>
> Crank?