GMC'Ers
so I have ordered tWO flexplates so far ATP Z116 AND PIONEER FRA 102, I also tried a buick just because and nothing is matching up to the bolt patterns on the crank. Does anyone have an idea where to get one? Is there a used one out there? its quite difficult to break in an engine if you cant start it?

thanks
Grant

Mr. Boyd,
Thanks. I have one more heading to me in the mail. I will let you know, thansk

Yes that was the frustrating part, I rotated to where all lined up except 1. 5 out of 6 is not a bad thing but i really dont want to alter the holes on the plate. maybe I have bad holes on the plate?

Mr. Boyd,
Yes the weight goes out towards the torque converter. on a post recently i added some pictures so everyone can see. it is awfully frustrating as I cant dyno my engine and get it installed with out a flex plate.
any ideas?

Thanks
Grant

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?

So, here is what I found on the crank, I had to remove the pan and the oil as well as the crank as it needed to get balanced with the late model off hole location flexplate. reason for some reason in my 1972 455 block there is installed a 1968 -1969 odd ball nodular iron crankshaft that was only made for two years. Isn't that just my luck. so odd ball crack in a 1972 455 block, and now balanced with a flex plate with two hole drilled oversized as the only flex plate available for this crank is a sfi racing flexplate that is $350.00

1" wide.
397363 455 '68 - '70 Nodular iron. 'N' on front weight

so word to the wise not everything is what is should be and yes for some reason there are some engines out there that have mis matched parts.
so another $400.00 added to the engine build as it has to balance between the flexplate crank and balancer. $10,000 and climbing and no end to the bleeding. one of these days ill be able to drive my coach again.

Matt, is this asshole a GMC Person or just a local turd?

--johnny