BB 402 into 72 K20 Problems???? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**w314speed** · 11-20-2007, 07:25 AM

Thinking about putting a BB 402 in to 72 K20. What problems will I get into??
What is the easy way!!!!!!!!

Thanks,

Dan

Bishops Trucks · 11-20-2007, 07:38 AM

This is what I just wrote to another member doing a similar swap.
You need the big block towers that bolt to the frame, bigblock radiator, bigblock fan shroud, You might need to upgrade your fuel line to 3/8. Is the motor stock? You might need to install heavier springs in the front. Make sure you get all the brackets and pulleys. I'm sure I left some things out but someone else will jump in and help you.

1969k10stepside · 11-20-2007, 08:50 AM

The distributor and valve covers will probably hit the firewall.Some dent the firewall,some add a body lift,some move the motor forward and the t-case crossmember the same amout to solve the issue but have to get custom drive shafts since the stocks one would be to short and too long.But,some people don't have a bit of issues.Valve cover type,and distributor type are factors.I believe you can use the regular small block 4wd motor crossmember.

**w314speed** · 11-20-2007, 08:41 PM

I am also considering installing a GearVendors overdrive unit that I have had for years. If I can use it with an adapter, I will. I originally bought for a TH400 Truck, adapting to the np205 may be more than an adapter.

earl87gta · 11-21-2007, 05:27 AM

there were no 4x4 72 BB trucks so you have to use the SB cross meber or an after market one. if 73 to 87 came with a BB you could also use a cross member from one of them.

bdozeraz · 11-22-2007, 01:23 PM

Use short valve covers and you may still have to bump out the fire wall. Use your small block motor mounts on the big block and it will drop right in. You can use the same fan shroud but you will have to cut it back an inch or two. Use a four core radiator. We did this exact same swap on my dad's 71 GMC along with a 700r4 which only required moving the transfercase back 2 inches. We used the advanced adapters short output shaft in the 700r4.

11-20-2007, 07:25 AM	#1
w314speed Senior Member Join Date: Jun 2005 Location: atlanta Posts: 2,315	BB 402 into 72 K20 Problems???? Thinking about putting a BB 402 in to 72 K20. What problems will I get into?? What is the easy way!!!!!!!! Thanks, Dan

11-20-2007, 07:38 AM	#2
Bishops Trucks KEEP ON TRUCKIN' Join Date: Jun 2005 Location: Sterling, Va. Posts: 5,730	Re: BB 402 into 72 K20 Problems???? This is what I just wrote to another member doing a similar swap. You need the big block towers that bolt to the frame, bigblock radiator, bigblock fan shroud, You might need to upgrade your fuel line to 3/8. Is the motor stock? You might need to install heavier springs in the front. Make sure you get all the brackets and pulleys. I'm sure I left some things out but someone else will jump in and help you. __________________ JIM '97 GMC Sierra K1500 '95 Chevy Silverado C1500 '71 Cheyenne Z71 / LT1 & 4-Speed SWB K/10 Father/Son Project http://www.youtube.com/watch?v=4l689JKXPnA http://67-72chevytrucks.com/vboard/payments.php "LIVIN' FREE FOREVER" Last edited by Bishops Trucks; 11-20-2007 at 07:38 AM.

11-20-2007, 08:50 AM	#3
1969k10stepside Registered User Join Date: Mar 2006 Location: USA Posts: 21,019	Re: BB 402 into 72 K20 Problems???? The distributor and valve covers will probably hit the firewall.Some dent the firewall,some add a body lift,some move the motor forward and the t-case crossmember the same amout to solve the issue but have to get custom drive shafts since the stocks one would be to short and too long.But,some people don't have a bit of issues.Valve cover type,and distributor type are factors.I believe you can use the regular small block 4wd motor crossmember. Last edited by 1969k10stepside; 11-20-2007 at 08:53 AM.

11-20-2007, 08:41 PM	#4
w314speed Senior Member Join Date: Jun 2005 Location: atlanta Posts: 2,315	Re: BB 402 into 72 K20 Problems???? I am also considering installing a GearVendors overdrive unit that I have had for years. If I can use it with an adapter, I will. I originally bought for a TH400 Truck, adapting to the np205 may be more than an adapter.

11-21-2007, 05:27 AM	#5
earl87gta Senior Member Join Date: Dec 2003 Location: Kingsport TN Posts: 4,641	Re: BB 402 into 72 K20 Problems???? there were no 4x4 72 BB trucks so you have to use the SB cross meber or an after market one. if 73 to 87 came with a BB you could also use a cross member from one of them. __________________ Earl 68 2500 4x4 GMC Burb

11-22-2007, 01:23 PM	#6
bdozeraz Registered User Join Date: Jun 2007 Location: Phx, Az Posts: 51	Re: BB 402 into 72 K20 Problems???? Use short valve covers and you may still have to bump out the fire wall. Use your small block motor mounts on the big block and it will drop right in. You can use the same fan shroud but you will have to cut it back an inch or two. Use a four core radiator. We did this exact same swap on my dad's 71 GMC along with a 700r4 which only required moving the transfercase back 2 inches. We used the advanced adapters short output shaft in the 700r4.



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