Small Block to Big Block Swap - The 1947 - Present Chevrolet & GMC Truck Message Board Network

MudBug · 01-23-2007, 05:02 PM

What is needed to replace a small block with a big block? I have a 1970 GMC long wheel base and a freebee 402 big block that needs a good home.
Thanks

cruiserman · 01-23-2007, 05:34 PM

2WD or 4WD?

You need motor mounts for one thing

.

Longhorn Man · 01-23-2007, 05:37 PM

you just wanting to stuff this sucker in there, or are you trying to make it look like it came this way?
There's a few ways to do it, some better than others.

matthufham · 01-23-2007, 05:44 PM

fan shroud if desired, motor mounts, exhaust manifold/headers, if you have a th350 it'll work but i'd swap that for a th400, you might want a larger cfm carb too. anything else?

krue · 01-23-2007, 06:03 PM

Welcome to the board from South Mississippi!

MudBug · 01-24-2007, 12:24 PM

I would like to keep it stock looking but aint afraid to use new parts.The truck is a 70 model GMC 2 wheel drive with a 350 motor and trans and leaf spring rear suspension.Do you change the motor stands on frame or will a blig block drop on the same stands?

novajess1972 · 01-24-2007, 12:36 PM

Quote:

Originally Posted by MudBug

I would like to keep it stock looking but aint afraid to use new parts.The truck is a 70 model GMC 2 wheel drive with a 350 motor and trans and leaf spring rear suspension.Do you change the motor stands on frame or will a blig block drop on the same stands?

You can use the SB motor mount brackets if you are using stock exhaust manifolds. I had to go with BB motor mount brackets to make my Hooker Headers work. The BB brackets have a recessed area to allow for the aftermarket headers. I had to locate BB P/S pump brackets and BB alternator brackets. Be sure to find a 4-row radiator if you dont already have one.

That's all I can think of at the moment.

Good Luck!!!

MudBug · 01-24-2007, 12:45 PM

Thanks , I'm already got a alinumin dual pass radiator thats the same kind we use on a stock car with a 431 small-block, If that don,t work i'll try something different.I got the 402 from saleing a street stock and the guy didn't have enough cash. I put the motor on a run stand and it sounds great, no knocks or weird noises, and pretty good oil pressure. Can you notch the motor stand for headers to fit? Thanks

cduster · 01-24-2007, 02:30 PM

I couldn't get my stock manifolds to fit using the smallblock stands. Ended up getting the BB stands. That was my expirience.

Dan

novajess1972 · 01-24-2007, 02:43 PM

Can you notch the motor stand for headers to fit? Thanks[/QUOTE]

You CAN notch the stands, but I wouldn't recommend it. I'm no expert, but I would think notching would sacrifice the integrity/strength of the stand. And none of us want an engine to let go under acceleration. It may not happen right away, but it may happen down the road. Just spend the money to get the correct ones. If not new, there are some members on here that have used ones availalbe in the classified section.

Good luck

Longhorn Man · 01-24-2007, 04:03 PM

i have actually been told that with headers, you can use small block stands... naturally, that will depend on the brand/model of headers. Bit to run the correct manifolds, you will need the correct stands.

meathead95 · 01-24-2007, 05:14 PM

i have a set of nos bbc 68-71 stands if your interested pm me. also welcome to the board. where are you in tennessee?

krue · 01-24-2007, 05:46 PM

Please restrict buying and selling to parts boards and pm's.

01-23-2007, 05:02 PM	#1
MudBug Registered User Join Date: Jan 2007 Location: tennessee Posts: 159	Small Block to Big Block Swap What is needed to replace a small block with a big block? I have a 1970 GMC long wheel base and a freebee 402 big block that needs a good home. Thanks

01-23-2007, 05:34 PM	#2
cruiserman Registered User Join Date: Dec 2006 Location: Idaho Posts: 210	Re: Small Block to Big Block Swap 2WD or 4WD? You need motor mounts for one thing . __________________ 72 C2500 LWB 402 Sierra Grande 05 Odyssey 08 Tundra

01-23-2007, 05:37 PM	#3
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,690	Re: Small Block to Big Block Swap you just wanting to stuff this sucker in there, or are you trying to make it look like it came this way? There's a few ways to do it, some better than others.

01-23-2007, 05:44 PM	#4
matthufham Registered User Join Date: Feb 2005 Location: Carl Junction, Missouri Posts: 2,061	Re: Small Block to Big Block Swap fan shroud if desired, motor mounts, exhaust manifold/headers, if you have a th350 it'll work but i'd swap that for a th400, you might want a larger cfm carb too. anything else?

01-23-2007, 06:03 PM	#5
krue Designated A-hole! Join Date: Mar 2003 Location: South Mississippi Posts: 36,448	Re: Small Block to Big Block Swap Welcome to the board from South Mississippi! __________________ "If it ain't broke, fix it 'til it is!" Being stupid ain't illegal. We're Still Debt Free Except for the House!!! www.daveramsey.com 70 GMC SWB Stepside project "Green Booger" soon to be 6.0l/4l80e 93 S-10 "Poppaw's Truck"

01-24-2007, 12:24 PM	#6
MudBug Registered User Join Date: Jan 2007 Location: tennessee Posts: 159	Re: Small Block to Big Block Swap I would like to keep it stock looking but aint afraid to use new parts.The truck is a 70 model GMC 2 wheel drive with a 350 motor and trans and leaf spring rear suspension.Do you change the motor stands on frame or will a blig block drop on the same stands?

01-24-2007, 12:45 PM	#8
MudBug Registered User Join Date: Jan 2007 Location: tennessee Posts: 159	Re: Small Block to Big Block Swap Thanks , I'm already got a alinumin dual pass radiator thats the same kind we use on a stock car with a 431 small-block, If that don,t work i'll try something different.I got the 402 from saleing a street stock and the guy didn't have enough cash. I put the motor on a run stand and it sounds great, no knocks or weird noises, and pretty good oil pressure. Can you notch the motor stand for headers to fit? Thanks

01-24-2007, 02:30 PM	#9
cduster Registered User Join Date: Oct 2002 Location: S.W. Michigan Posts: 403	Re: Small Block to Big Block Swap I couldn't get my stock manifolds to fit using the smallblock stands. Ended up getting the BB stands. That was my expirience. Dan __________________ Good Judgment comes from experience. Most experience comes from bad judgment.

01-24-2007, 02:43 PM	#10
novajess1972 Registered User Join Date: Sep 2006 Location: Houston, Texas Posts: 190	Re: Small Block to Big Block Swap Can you notch the motor stand for headers to fit? Thanks[/QUOTE] You CAN notch the stands, but I wouldn't recommend it. I'm no expert, but I would think notching would sacrifice the integrity/strength of the stand. And none of us want an engine to let go under acceleration. It may not happen right away, but it may happen down the road. Just spend the money to get the correct ones. If not new, there are some members on here that have used ones availalbe in the classified section. Good luck __________________ 1985 SWB Silverado 1/2 Ton 1972 Chevy SWB 1/2 Ton (sold) 1972 Chevy Chevelle SS (sold) 1971 Chevy Nova (sold) 1967 Chevy El Camino (sold) 2001 Mustang Bullitt (sold) 2019 Toyota Tundra Crewmax (daily)

01-24-2007, 04:03 PM	#11
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,690	Re: Small Block to Big Block Swap i have actually been told that with headers, you can use small block stands... naturally, that will depend on the brand/model of headers. Bit to run the correct manifolds, you will need the correct stands.

01-24-2007, 05:14 PM	#12
meathead95 computer illiterate Join Date: Jan 2001 Location: Des Moines, IA Posts: 6,440	Re: Small Block to Big Block Swap i have a set of nos bbc 68-71 stands if your interested pm me. also welcome to the board. where are you in tennessee? __________________ 72 2wd blazer 72 swb 4x4

01-24-2007, 05:46 PM	#13
krue Designated A-hole! Join Date: Mar 2003 Location: South Mississippi Posts: 36,448	Re: Small Block to Big Block Swap Please restrict buying and selling to parts boards and pm's. __________________ "If it ain't broke, fix it 'til it is!" Being stupid ain't illegal. We're Still Debt Free Except for the House!!! www.daveramsey.com 70 GMC SWB Stepside project "Green Booger" soon to be 6.0l/4l80e 93 S-10 "Poppaw's Truck"



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