Motor and tranny swap questions - The 1947 - Present Chevrolet & GMC Truck Message Board Network

custom72c20 · 12-28-2008, 10:23 PM

Ok here goes. Im wanting to put a big block and th400 trans that I have in my 72 C20. My truck has a 350/350 in it right now. Can I just buy the engine towers and a new tranny crossmember and bolt it in? Will i run into any clearance problems with the cab, etc...? All help is appreciated. Thanks

thirdstreettito · 12-28-2008, 10:28 PM

I think you got it all covered. Not sure though.

primered_junk · 12-28-2008, 11:08 PM

You can run the small block towers if you swap them side to side, you have to drill 2 holes, but it works great. I did it on my 71 GMC 3 years back, never had any clearance issues at all, it got close on the drivers side header but never made contact. I have pics if you need them.

custom72c20 · 12-28-2008, 11:33 PM

Thanks for the input. I already have the towers and crossmember though. I just wanted to check to see if the tranny was going to clear the cab due to it being a low hump. Thank you again.

custom72c20 · 12-29-2008, 02:08 AM

Anyone else have any info?

Spray-Bomb · 12-29-2008, 02:12 AM

I see no reason for it not to fit

custom72c20 · 12-29-2008, 02:16 AM

ok cool. Now i just got to do it. haha

Tx Firefighter · 12-29-2008, 07:53 AM

I've done three big block conversions now. I found that a big block and turbo 400 will fit a low hump truck if you have fresh body mounts. Old saggy body mounts will allow the cab to rub the trans housing.

custom72c20 · 12-30-2008, 12:00 AM

Quote:

Originally Posted by Tx Firefighter

I've done three big block conversions now. I found that a big block and turbo 400 will fit a low hump truck if you have fresh body mounts. Old saggy body mounts will allow the cab to rub the trans housing.

Thank you for that. Good thing I have a new set of body bushings.

12-28-2008, 10:23 PM	#1
custom72c20 Registered User Join Date: Oct 2006 Location: Temecula,CA Posts: 309	Motor and tranny swap questions Ok here goes. Im wanting to put a big block and th400 trans that I have in my 72 C20. My truck has a 350/350 in it right now. Can I just buy the engine towers and a new tranny crossmember and bolt it in? Will i run into any clearance problems with the cab, etc...? All help is appreciated. Thanks __________________ Nick Old pic of my 72: http://img340.imageshack.us/my.php?image=img0435co5.jpg 04 Silverado Daily Driver 68 GMC short step http://67-72chevytrucks.com/vboard/s...d.php?t=379665 "I'll beat you to the gas station!!"

12-28-2008, 10:28 PM	#2
thirdstreettito Resident of Here Join Date: May 2008 Location: Wesley Chapel, FL, USA Posts: 7,716	Re: Motor and tranny swap questions I think you got it all covered. Not sure though. __________________ ~Bradley~ 2004 Black GTO LS2/T56 too much to list Miss having a truck

12-28-2008, 11:08 PM	#3
primered_junk ASE master tech/machinist Join Date: May 2008 Location: Blue Mound Texas Posts: 303	Re: Motor and tranny swap questions You can run the small block towers if you swap them side to side, you have to drill 2 holes, but it works great. I did it on my 71 GMC 3 years back, never had any clearance issues at all, it got close on the drivers side header but never made contact. I have pics if you need them. __________________ "I sit here and I pray in my broken down Chevrolet....."

12-28-2008, 11:33 PM	#4
custom72c20 Registered User Join Date: Oct 2006 Location: Temecula,CA Posts: 309	Re: Motor and tranny swap questions Thanks for the input. I already have the towers and crossmember though. I just wanted to check to see if the tranny was going to clear the cab due to it being a low hump. Thank you again. __________________ Nick Old pic of my 72: http://img340.imageshack.us/my.php?image=img0435co5.jpg 04 Silverado Daily Driver 68 GMC short step http://67-72chevytrucks.com/vboard/s...d.php?t=379665 "I'll beat you to the gas station!!"

12-29-2008, 02:08 AM	#5
custom72c20 Registered User Join Date: Oct 2006 Location: Temecula,CA Posts: 309	Re: Motor and tranny swap questions Anyone else have any info? __________________ Nick Old pic of my 72: http://img340.imageshack.us/my.php?image=img0435co5.jpg 04 Silverado Daily Driver 68 GMC short step http://67-72chevytrucks.com/vboard/s...d.php?t=379665 "I'll beat you to the gas station!!"

12-29-2008, 02:12 AM	#6
Spray-Bomb Texas Big Wig Join Date: Jan 2007 Location: Mineola, Texas Posts: 5,620	Re: Motor and tranny swap questions I see no reason for it not to fit __________________ Just not low enough... ----------------------------- Sinister Killer

12-29-2008, 02:16 AM	#7
custom72c20 Registered User Join Date: Oct 2006 Location: Temecula,CA Posts: 309	Re: Motor and tranny swap questions ok cool. Now i just got to do it. haha __________________ Nick Old pic of my 72: http://img340.imageshack.us/my.php?image=img0435co5.jpg 04 Silverado Daily Driver 68 GMC short step http://67-72chevytrucks.com/vboard/s...d.php?t=379665 "I'll beat you to the gas station!!"

12-29-2008, 07:53 AM	#8
Tx Firefighter Watch out for your cornhole ! Join Date: Jun 2003 Location: Azle, Texas Posts: 14,162	Re: Motor and tranny swap questions I've done three big block conversions now. I found that a big block and turbo 400 will fit a low hump truck if you have fresh body mounts. Old saggy body mounts will allow the cab to rub the trans housing. __________________ I'm on the Instagram- @Gearhead_Kevin



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