The 1947 - Present Chevrolet & GMC Truck Message Board Network - View Single Post

J_T · 03-08-2021, 01:12 PM

Looking for a little guidance on what to do with my BBC 396.

I Bought a running 1972 GMC Jimmy. Needs some body work but everything else is functional and usable so I haven’t had much motivation to disable it to start fixing it up. I figured I can start working on the drive train and do it in pieces so I can keep using it.

BUT someone swapped in a Big Block, numbers read GM 1967 396 with Th350. The swap appears out of a Similar aged Pickup using stock parts as nothing appears custom and if BBC was an option in the Jimmy It’d appear factory (but plate reads SBC350). It has the Standard 12Bolt rear end (don’t know ratio yet it but I assume it hasn’t been touched.)

Since its already not a numbers matching I’m not as motivated to keep everything stock. What I want is whats best for long term reliability and some fun factor to use with my family without going high dollar as its not going to be a show vehicle. I’ve read about 6.2L LS swap with 4l60E but the price is considerable to obtain and then rebuild and also adding electronic control but that’s the reliability I’d like for this vehicle.

The 396 runs fine with some oil burn and standard chevy leaks. I’d like to go with a Holley Sniper- or similar type fuel system, something self contained, instead of the current weber. I do occasionally pull ATV/motorcycle trailers or boat with my other vehicles so want to keep that option. It would be nice to have the overdrive so maybe 700R may be better if I keep the 396. But I could make the 396 look like a stock Chevy under the hood.

Questions:

need guidance to decide if I should go through LS swap or should I have the 396 refreshed (and heads and cam) and maybe see if more can be massaged out of it without spending an arm and a leg.
What performance comparison can I expect between the LS 6.2L and a rebuilt 396 with cam, heads and throttle body fuel injection. I'm coming off a 12V cummins so no racer but i'd like something that can stand up to the exhaust rumble that it'll have. I know this will be tough as 50+ year old technology but I've seen amazing things with BBC but never owned one so don't know what it'd take to liven it up.
Which would cost more to get the comparable results compared to the other? (comparing stock 6.2L LS, 4L60E, electronic control etc and conversion parts, vs to rebuilt 396 and maybe 700R, and fuel injection)
Can the 12bolt rear and Dana 44 front handle anything a sensibly built 396 give it? (My first big block trying to decide between rebuilding them or ¾ ton axle swap are in the future. (my past fun vehicles have been ¾ ton diesels so I liked the robustness and bullet proof factor and simplicity but they were pickups and not family fun vehicles)

03-08-2021, 01:12 PM	#1
J_T Registered User Join Date: Mar 2007 Location: TN Posts: 18	Refresh my BBC396 or Swap to LS Looking for a little guidance on what to do with my BBC 396. I Bought a running 1972 GMC Jimmy. Needs some body work but everything else is functional and usable so I haven’t had much motivation to disable it to start fixing it up. I figured I can start working on the drive train and do it in pieces so I can keep using it. BUT someone swapped in a Big Block, numbers read GM 1967 396 with Th350. The swap appears out of a Similar aged Pickup using stock parts as nothing appears custom and if BBC was an option in the Jimmy It’d appear factory (but plate reads SBC350). It has the Standard 12Bolt rear end (don’t know ratio yet it but I assume it hasn’t been touched.) Since its already not a numbers matching I’m not as motivated to keep everything stock. What I want is whats best for long term reliability and some fun factor to use with my family without going high dollar as its not going to be a show vehicle. I’ve read about 6.2L LS swap with 4l60E but the price is considerable to obtain and then rebuild and also adding electronic control but that’s the reliability I’d like for this vehicle. The 396 runs fine with some oil burn and standard chevy leaks. I’d like to go with a Holley Sniper- or similar type fuel system, something self contained, instead of the current weber. I do occasionally pull ATV/motorcycle trailers or boat with my other vehicles so want to keep that option. It would be nice to have the overdrive so maybe 700R may be better if I keep the 396. But I could make the 396 look like a stock Chevy under the hood. Questions: need guidance to decide if I should go through LS swap or should I have the 396 refreshed (and heads and cam) and maybe see if more can be massaged out of it without spending an arm and a leg. What performance comparison can I expect between the LS 6.2L and a rebuilt 396 with cam, heads and throttle body fuel injection. I'm coming off a 12V cummins so no racer but i'd like something that can stand up to the exhaust rumble that it'll have. I know this will be tough as 50+ year old technology but I've seen amazing things with BBC but never owned one so don't know what it'd take to liven it up. Which would cost more to get the comparable results compared to the other? (comparing stock 6.2L LS, 4L60E, electronic control etc and conversion parts, vs to rebuilt 396 and maybe 700R, and fuel injection) Can the 12bolt rear and Dana 44 front handle anything a sensibly built 396 give it? (My first big block trying to decide between rebuilding them or ¾ ton axle swap are in the future. (my past fun vehicles have been ¾ ton diesels so I liked the robustness and bullet proof factor and simplicity but they were pickups and not family fun vehicles) Last edited by J_T; 03-08-2021 at 01:24 PM.