SBC to BBC Swap in 71 4x4? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

ljbear · 06-09-2003, 09:34 PM

I came across a big block and decided that I can't live without it. I currently have a perfectly good 350 in my 71 Chevy SWB 4x4 and need to know what's involved in the swap. I'm running a NV4500 5 speed with 205, and would really like to leave it right where it is. Will a big block drop in? When I purchased the motor mounts for the truck, the guy at Brother's said the 4x4 and big block mounts were the same, and that's what I have under the 350. I know this has been addressed before, but the information in the FAQ and search didn't help. Any help is greatly appreciated.

Larry

GMC71k20 · 06-09-2003, 10:17 PM

what you need to do to put in the nv4500? did you use parts from advance adapters?

ljbear · 06-09-2003, 10:49 PM

The NV4500 was quite an experience. The adapter is from Advance, but that was the easy part. The input on my 205 was from a 4 speed and was a 10 spline male. I had to change to a 32 spline female to tie to the NV. The 32 spline is the same input that goes with a TH400 and uses a larger bearing than the 4 speed and TH350's. The transfer case had to be bored to accept the larger bearing. The clutch was changed (my choice), to hydraulic, and required a new style 168 tooth flywheel and newer style bell housing. The biggest problem is that the newer style hydraulic clutch has the slave assembly on the passenger side and without a suspension lift it would interfere with the front driveline. Now that it's done I'm happy, but during the process I was thinking the 4 speed wasn't all that bad.

Larry

GMC71k20 · 06-10-2003, 03:04 PM

thanks for the info, thissummer i might be out hunting for a nv4500 and maybe even a np205 that was originally behind a th400

Longhorn Man · 06-10-2003, 03:56 PM

While I do not know the details, I think the 4X4 guys have said you need a body lift to do this.

6772king · 06-10-2003, 04:14 PM

yes body lift will do it with no modification to the fire wall, if you dont want to use a body lift then you can dent the fire wall in (behind the divers side valve cover about 1")

GMC71k20 · 06-10-2003, 04:36 PM

can you run an HEI without the bodylift?

ljbear · 06-10-2003, 08:32 PM

A body lift or modification to the firewall isn't a problem, the cab is off the chassis right now anyway. The concern is the dimension of the BB. Is the side motor mount to the bell housing dimension the same on a BBC as a SBC? How about this? Can someone with a BBC measure the dimension from the rear of the motor to the center of the bolt holes for the mounts?

Larry

6772king · 06-10-2003, 08:35 PM

yes, that part of the fire wall isn,t bad. the problem spot is right below your throttle cable if you post your e-mail i can send some pics as i dont know how to get a pic on now. is your transfer case in the original spot and is the nv4500 the same length as the sm465?

ljbear · 06-10-2003, 08:43 PM

6772King,

The motor is in the stock location. The bell housing is the same depth as the original, but the NV, adapter, and 205 moved the rear crossmember is back just shy of 2". Here's my email Wheels for pictures. Thanks for the help.

Larry

6772king · 06-10-2003, 08:43 PM

ljbear, just went out and measured for ya. it is 16" on both.

ljbear · 06-10-2003, 09:00 PM

6772King,

Thanks. I was pretty sure it was close. The only experience I have with BBC's is when I pulled one out of my 57. I put in a SBC and don't recall having to do anything to get it in.

Larry

**Yukon Jack** · 06-11-2003, 10:15 AM

I had to make some adjustments for header clearance and oil pan clearance. Check out this thread for more info on that issue. http://64.246.42.114/vboard/showthre...hlight=fitment

06-09-2003, 09:34 PM	#1
ljbear Registered User Join Date: Jan 2003 Location: Emmett, Idaho Posts: 858	SBC to BBC Swap in 71 4x4? I came across a big block and decided that I can't live without it. I currently have a perfectly good 350 in my 71 Chevy SWB 4x4 and need to know what's involved in the swap. I'm running a NV4500 5 speed with 205, and would really like to leave it right where it is. Will a big block drop in? When I purchased the motor mounts for the truck, the guy at Brother's said the 4x4 and big block mounts were the same, and that's what I have under the 350. I know this has been addressed before, but the information in the FAQ and search didn't help. Any help is greatly appreciated. Larry __________________ Larry 72 Chevy SWB 4x4 71 Chevy SWB 4x4 My Work Truck "Don't confuse enthusiasm with capability"

06-09-2003, 10:49 PM	#3
ljbear Registered User Join Date: Jan 2003 Location: Emmett, Idaho Posts: 858	The NV4500 was quite an experience. The adapter is from Advance, but that was the easy part. The input on my 205 was from a 4 speed and was a 10 spline male. I had to change to a 32 spline female to tie to the NV. The 32 spline is the same input that goes with a TH400 and uses a larger bearing than the 4 speed and TH350's. The transfer case had to be bored to accept the larger bearing. The clutch was changed (my choice), to hydraulic, and required a new style 168 tooth flywheel and newer style bell housing. The biggest problem is that the newer style hydraulic clutch has the slave assembly on the passenger side and without a suspension lift it would interfere with the front driveline. Now that it's done I'm happy, but during the process I was thinking the 4 speed wasn't all that bad. Larry __________________ Larry 72 Chevy SWB 4x4 71 Chevy SWB 4x4 My Work Truck "Don't confuse enthusiasm with capability"

06-10-2003, 04:14 PM	#6
6772king Registered User Join Date: Feb 2002 Location: grove city pa usa Posts: 628	yes body lift will do it with no modification to the fire wall, if you dont want to use a body lift then you can dent the fire wall in (behind the divers side valve cover about 1") __________________ 67 chevy short step 2wd 427 71 chevy short fleet 4x4 396 72 gmc jimmy 2wd 377 71 chevy blazer 4x4 454 69 chevy longhorn 5.9l cummins 72 chevy 400 2wd custom camper 67 chevy lwb 4x4 454-in pieces 67 chevy panel soon 4x4-400 67 gmc dump 4x4 1 ton-305 WTF!! 72 chevy 3/4 ton 4x4 burb 350 70 chevy panel 2wd 302 5 speed tko "THERE IS NO REPLACMENT FOR DISPLACMENT"!!!!!!!

06-10-2003, 08:32 PM	#8
ljbear Registered User Join Date: Jan 2003 Location: Emmett, Idaho Posts: 858	A body lift or modification to the firewall isn't a problem, the cab is off the chassis right now anyway. The concern is the dimension of the BB. Is the side motor mount to the bell housing dimension the same on a BBC as a SBC? How about this? Can someone with a BBC measure the dimension from the rear of the motor to the center of the bolt holes for the mounts? Larry __________________ Larry 72 Chevy SWB 4x4 71 Chevy SWB 4x4 My Work Truck "Don't confuse enthusiasm with capability" Last edited by ljbear; 06-10-2003 at 08:37 PM.

06-10-2003, 08:35 PM	#9
6772king Registered User Join Date: Feb 2002 Location: grove city pa usa Posts: 628	yes, that part of the fire wall isn,t bad. the problem spot is right below your throttle cable if you post your e-mail i can send some pics as i dont know how to get a pic on now. is your transfer case in the original spot and is the nv4500 the same length as the sm465? __________________ 67 chevy short step 2wd 427 71 chevy short fleet 4x4 396 72 gmc jimmy 2wd 377 71 chevy blazer 4x4 454 69 chevy longhorn 5.9l cummins 72 chevy 400 2wd custom camper 67 chevy lwb 4x4 454-in pieces 67 chevy panel soon 4x4-400 67 gmc dump 4x4 1 ton-305 WTF!! 72 chevy 3/4 ton 4x4 burb 350 70 chevy panel 2wd 302 5 speed tko "THERE IS NO REPLACMENT FOR DISPLACMENT"!!!!!!!

06-09-2003, 10:17 PM	#2
GMC71k20 Registered User Join Date: Aug 2002 Location: mass Posts: 1,277	what you need to do to put in the nv4500? did you use parts from advance adapters?

06-10-2003, 03:04 PM	#4
GMC71k20 Registered User Join Date: Aug 2002 Location: mass Posts: 1,277	thanks for the info, thissummer i might be out hunting for a nv4500 and maybe even a np205 that was originally behind a th400

06-10-2003, 03:56 PM	#5
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	While I do not know the details, I think the 4X4 guys have said you need a body lift to do this.

06-10-2003, 04:36 PM	#7
GMC71k20 Registered User Join Date: Aug 2002 Location: mass Posts: 1,277	can you run an HEI without the bodylift?

06-10-2003, 08:43 PM	#10
ljbear Registered User Join Date: Jan 2003 Location: Emmett, Idaho Posts: 858	6772King, The motor is in the stock location. The bell housing is the same depth as the original, but the NV, adapter, and 205 moved the rear crossmember is back just shy of 2". Here's my email Wheels for pictures. Thanks for the help. Larry __________________ Larry 72 Chevy SWB 4x4 71 Chevy SWB 4x4 My Work Truck "Don't confuse enthusiasm with capability"

06-10-2003, 09:00 PM	#12
ljbear Registered User Join Date: Jan 2003 Location: Emmett, Idaho Posts: 858	6772King, Thanks. I was pretty sure it was close. The only experience I have with BBC's is when I pulled one out of my 57. I put in a SBC and don't recall having to do anything to get it in. Larry __________________ Larry 72 Chevy SWB 4x4 71 Chevy SWB 4x4 My Work Truck "Don't confuse enthusiasm with capability"

06-11-2003, 10:15 AM	#13
Yukon Jack Post Whore Join Date: Feb 2000 Location: Rose Hill, KS, USA Posts: 12,684	I had to make some adjustments for header clearance and oil pan clearance. Check out this thread for more info on that issue. http://64.246.42.114/vboard/showthre...hlight=fitment __________________ 1970 Blazer with a 400 sbc and 4" lift 1980 Pontiac Trans Am, 455 Oldsmobile 2012 Kawasaki Concours 14



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