Switch to a Big Block - The 1947 - Present Chevrolet & GMC Truck Message Board Network

cobrajet21 · 02-21-2009, 08:30 PM

Can you put a big block in a truck with a low hump cab or do i need to change to a high hump? What other changes or problems would i run into?

**Palf70Step** · 02-21-2009, 08:44 PM

It is probably better that you do put in a high hump, but I do not thing it is mandatory. I thought some one said some came with low hump, but I cannot remember for positive.

spinning wheels · 02-21-2009, 08:48 PM

High humps were 4X4, 4 speed, or Turbo 400s.
You can put a big block in a low hump, the engine does not come in contact with the cab.

The humps were for clearance due to the trannys.

If your tranny hits the hump, you can always cut and modify your cab.

cobrajet21 · 02-21-2009, 09:03 PM

i am going to use a 700r4. will that make a difference?

Sinister · 02-21-2009, 09:18 PM

Quote:

Originally Posted by spinning wheels

High humps were 4X4, 4 speed, or Turbo 400s.
You can put a big block in a low hump, the engine does not come in contact with the cab.

The humps were for clearance due to the trannys.

If your tranny hits the hump, you can always cut and modify your cab.

Just to clarify, I have a TH400 in my '69 with a low hump.

Security guy · 02-21-2009, 09:31 PM

I've got a big block and 700r4 with a low hump floor. It fits great. Some people have said that it will hit, but i think thats because of cab mounts being worn out. As long as you have good mounts for everything, it should go in no problem. The only trouble I had was getting the motor and tranny in the right place. At first, my mounts were to far forward, so I had to move my mounts back a little. I did use all factory holes for mounting, so it shouldn't be a big deal.

**68350** · 02-21-2009, 11:12 PM

We had a 402/400 in a 72 sb. The only thing I recommend is to put new cab mounts on(doesn't hurt anyways to change) except it might misalign the panels, so it might turn into a larger project than thought. i'm not sure on the dimensions of a 700r4, but isn't it the same size as a th350? if it is, it should work out no problem.

Longhorn Man · 02-21-2009, 11:44 PM

where did the misconseption come from that says TH400 trucks had a high hump? I see it posted on here all the time.
High hump floors came in 4x4 trucks, 4 speed trucks, and big blocks with TH400.
A handfull of oddballs came out with the wrong floors, I have a 305 V-6/TH400 with a high hump, and there's beena couple bb/th400's documented on here with a low hump.

If you have good cab mounts, you should be fine.

*67/72junkie* · 02-22-2009, 12:03 AM

Longhornman has hit the nail on the head

,72,000 plus post .Thats alot of time on the board longhorn!

I don't think he has missed very much.

spinning wheels · 02-22-2009, 01:52 AM

Quote:

Originally Posted by Longhorn Man

where did the misconseption come from that says TH400 trucks had a high hump? I see it posted on here all the time.
High hump floors came in 4x4 trucks, 4 speed trucks, and big blocks with TH400.
A handfull of oddballs came out with the wrong floors, I have a 305 V-6/TH400 with a high hump, and there's beena couple bb/th400's documented on here with a low hump.

If you have good cab mounts, you should be fine.

Longhorn, you may be right. What GM has put out as model info, does not always end up being correct info. For example, I have a 70 RS Z28. According to GM, no A/C was available for my model year. Yet, I have factory installed A/C. Exceptions seem to be the norm when talking about GM products. Could be one of the reasons GM is on life support? I bet Honda has never screwed up on their info

02-21-2009, 08:30 PM	#1
cobrajet21 Registered User Join Date: Mar 2008 Location: Danville, VA Posts: 122	Switch to a Big Block Can you put a big block in a truck with a low hump cab or do i need to change to a high hump? What other changes or problems would i run into?

02-21-2009, 08:44 PM	#2
Palf70Step State of Confusion! Join Date: Jul 2002 Location: Gulfport, MS USA Posts: 47,083	Re: Switch to a Big Block It is probably better that you do put in a high hump, but I do not thing it is mandatory. I thought some one said some came with low hump, but I cannot remember for positive. __________________ Bill 1970 Chevy Custom/10 LWB Fleetside 2010 Toyota Tacoma PreRunner SR5 Double Cab - DD Member of Louisiana Classic Truck Club (LCTC) Bill's Gallery Life isn't tied with a bow, but it's still a gift. Live simply. Love generously. Care deeply. Speak kindly. Leave the rest to God!

02-21-2009, 08:48 PM	#3
spinning wheels Registered User Join Date: Sep 2001 Location: Hacienda Heights, California USA Posts: 474	Re: Switch to a Big Block High humps were 4X4, 4 speed, or Turbo 400s. You can put a big block in a low hump, the engine does not come in contact with the cab. The humps were for clearance due to the trannys. If your tranny hits the hump, you can always cut and modify your cab. __________________ '72 GMC custom camper 350/350

02-21-2009, 09:03 PM	#4
cobrajet21 Registered User Join Date: Mar 2008 Location: Danville, VA Posts: 122	Re: Switch to a Big Block i am going to use a 700r4. will that make a difference?

02-21-2009, 09:31 PM	#6
Security guy Registered User Join Date: Mar 2008 Location: Sarasota, Fl. Posts: 441	Re: Switch to a Big Block I've got a big block and 700r4 with a low hump floor. It fits great. Some people have said that it will hit, but i think thats because of cab mounts being worn out. As long as you have good mounts for everything, it should go in no problem. The only trouble I had was getting the motor and tranny in the right place. At first, my mounts were to far forward, so I had to move my mounts back a little. I did use all factory holes for mounting, so it shouldn't be a big deal.

02-21-2009, 11:12 PM	#7
68350 Senior Member Join Date: Jan 2002 Location: Williston, ND Posts: 2,999	Re: Switch to a Big Block We had a 402/400 in a 72 sb. The only thing I recommend is to put new cab mounts on(doesn't hurt anyways to change) except it might misalign the panels, so it might turn into a larger project than thought. i'm not sure on the dimensions of a 700r4, but isn't it the same size as a th350? if it is, it should work out no problem. __________________ 68 Chevy CST/10, 50th Anniversary, 327/th400, 373 posi, buckets 68 GMC Shortbox Stepside, 402/th400, Tilt, Tach, Bucket Seats, 3.08 Positraction 69 Chevy Camaro SS, 383, 4 speed, positraction 70 Chevy El Camino SS396, Triple Black, 454/th400, Tach 70 Chevy Shortbox Stepside 4x4, 350/th350, Tilt, Tach, Cab Lights, Bumper Guards, Tow Hooks 70 Chevy 3/4 Longbox, 350/auto, 70k, SURVIVOR 71 Chevy Blazer, CST, 350/auto 71 GMC Sierra K2500, 454, 4 speed, 4.10 posi, 37s 71 Custom/30, Open Road, 350/th400, tilt 72 Chevy Shortbox Fleetside, 496 Stroker/th400, Tilt, Tach, Bucket Seats, 3.42 Posi 72 GMC Sierra Grande 2500. 427/th400, tilt, a/c, tool and stowage, buckets/console, 3.54 posi

02-21-2009, 11:44 PM	#8
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Re: Switch to a Big Block where did the misconseption come from that says TH400 trucks had a high hump? I see it posted on here all the time. High hump floors came in 4x4 trucks, 4 speed trucks, and big blocks with TH400. A handfull of oddballs came out with the wrong floors, I have a 305 V-6/TH400 with a high hump, and there's beena couple bb/th400's documented on here with a low hump. If you have good cab mounts, you should be fine.

02-22-2009, 12:03 AM	#9
67/72junkie Account Suspended Join Date: Oct 2002 Location: NC Posts: 1,129	Re: Switch to a Big Block Longhornman has hit the nail on the head,72,000 plus post .Thats alot of time on the board longhorn!I don't think he has missed very much.



Register or Log In To remove these advertisements.

Register or Log In To remove these advertisements.