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will a SM420 bolt up to the 250-292 series of straight 6's? basic Q...lol, maybe an indepth answer. any advice is appreicated.
Sam
1967 Chevy II, 2-door post.
250, 3-OTT.
1969 GMC 1/2-ton.
307, 3-OTT.
DD.
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Joined: Jun 2002
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Short answer, yes. The SM 420 was standard GM equipment until after 1967 for light trucks. After that ['68-on] they went to the SM 465. Same bell housing -- almost. Smaller interior diameter on the pilot hole. Both bell housings fit L6s and SBCs. I don't have casting numbers at this hour, but I could look later.
I/I #4101
'71 GMC Jimmy 350, sm465, np205,3.73 posi.
'68 C/10 Stepside 292 (.030 over) Offy Intake, 500 CFM AFB,Clif headers, sm465, 3.73 posi.
'67 K/10 454 project.
'72 K/5 rolling frame project.
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Joined: May 2002
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I concur that the SM420 will bolt up, but you'll need the proper bellhousing. However, unless you already have a 420, you'd be better off with the 465, since parts are more available for the later tranny.
If your truck is a 68 (like your name), you may already have bellhousing mounts available on the frame. On my later 77, I had to come up with a different way to mount the 465, since the original bellhousing mounts weren't going to work.
I also went with a hydraulic clutch linkage, to replace the original rods & z-bar deal. It works great, but don't underestimate the amount of work. It took hours of looking just to figure out what to make....
One other thing, the starter used with the 465 is bellhousing mount, not block mount.
Greg
1977 Chevy C10 SWB
EFI 292
SM465
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if i'm right about my readings...there is an SM420 behind a 305 V6 on a '64 GMC. the truck is shot. but i'm hoping i can salvage the tranny, if it'll work. an OD would be nice, but for now, i just wanna get rid of the th350 behind a 292. i've been told that it will bolt up to a 235, 261, etc. that series..but not the 292-250. so...what all is involved w/ getting this to work??
1967 Chevy II, 2-door post.
250, 3-OTT.
1969 GMC 1/2-ton.
307, 3-OTT.
DD.
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Joined: Apr 2003
Posts: 229
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SM-420's have a std. Chevy bolt pattern, thus will bolt up to any chevy, GMC, etc., since about '39. There might be different retainer diameters? Be careful on the V6 one, make sure it has the short (Std) input shaft.
Good luck
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Joined: Apr 2004
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thanx ed. i've just been informed that the tail shaft, since its a 4wd tranny...well, it won't work. sooo...none the less, back to the drawing board.
thanx again.
Sam
1967 Chevy II, 2-door post.
250, 3-OTT.
1969 GMC 1/2-ton.
307, 3-OTT.
DD.
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Joined: Jun 2002
Posts: 315
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Well I dug up some casting #s from a couple of respective bellhousings.
SM 465 5-1/8" Dia. (GM5)(3925505)
SM 420 4-9/16" Dia. (GM11)(3815891)
I/I #4101
'71 GMC Jimmy 350, sm465, np205,3.73 posi.
'68 C/10 Stepside 292 (.030 over) Offy Intake, 500 CFM AFB,Clif headers, sm465, 3.73 posi.
'67 K/10 454 project.
'72 K/5 rolling frame project.
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