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#1 |
Registered User
![]() Join Date: Jan 2011
Location: laconia NH
Posts: 196
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72 BB motor swap wont drop/ 2wl dr/ halfton
I am swapping out a 350 for the 402.
For whatever reason the mounts on the engine and the BB 72 engine stands dont even come close. I've got the engine bolted up to the existing 350 TH tranny, and the 72 only engine stands are not lining up. Is it because of the smaller tranny ? Are there different stands ? Would 4x4 have the same stands. I have hit the wall. Pulling out what few remaining hairs I have. I have a set of BB 71 towers I am going to try on Mon. I may be overlooking something stupid. Anyone with any experience with this issue ? Thanks !! |
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#2 |
VA72C10
![]() Join Date: Mar 2008
Location: Midlothian, VA
Posts: 25,269
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Re: 72 BB motor swap wont drop/ 2wl dr/ halfton
Have any pictures? Where are the mounts attached on the frame? Using clamshells I assume....
I know factory they had 400's but not sure that would have made a difference.... Bump anyways for you!
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Looking for a 67-72 swb or blazer project in or around VA. ![]() |
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#3 |
Project Junkie! Fishing Poor!!
![]() Join Date: Dec 1999
Location: Olympia,Wa. 98512
Posts: 10,770
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Re: 72 BB motor swap wont drop/ 2wl dr/ halfton
Bolt the engine where the stands belong and move the transmission crossmember. The frame should be drilled for the new location. WES
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On-line catolog Classic Heartbeat Pickup Parts WEHEPP@comcast.net Call us Toll Free (888) 338-2502 Like Us on Facebook No appointment necessary. 72 BB Chevy Custom Deluxe / Custom Camper 67 I-6 (Soon to be 5.7 LS1) Panel 68 BB Chevy Short Bed 72 6.0 LQ9 Short Bed Chevy 4X4 Olympia's fastest growing truck parts supplier. Olympia's home for Wayward Chevys |
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#4 |
Registered User
Join Date: Nov 2008
Location: orange ca
Posts: 9
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Re: 72 BB motor swap wont drop/ 2wl dr/ halfton
I went form a 327 to a 468 i moved the motor to the forward holes on the frame. i had to move the trans cross member forward to fit. You will also have to locate some BB motor mounts too. Hope this helps
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#5 |
Registered User
![]() Join Date: Jan 2011
Location: laconia NH
Posts: 196
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Re: 72 BB motor swap wont drop/ 2wl dr/ halfton
Thanks,
I thought I did my homework. Same model year(72) engine. 72 BB mounts, Clams, .I cant believe GM would make me move crossmembers, fudge bolt holes etc. The only thing that does not belong on the truck is the TH350, and the 350ci bolted to it and, fit on its mounts fine. |
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#6 | |
Account Suspended
Join Date: Jan 2007
Location: Tucson
Posts: 2,183
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Re: 72 BB motor swap wont drop/ 2wl dr/ halfton
Quote:
here's a series of photo's that took a 67 stepside frame built for the six cylinder/Th350 auto combo to a HUGE tall deck big block/TH400 combo without drilling ONE new hole! The closeup of the front crossmember shows all of the factory holes for small block, big block and six cylinder engine stands. The second shows how the trans crossmember was moved to the matching rearward holes to make up the difference in length for a big block motor mated to a TH400 trans. All parts used ARE STOCK, over the counter GM. Note that the trans crossmember moved back almost 6 inches. |
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#7 | |
Registered User
Join Date: Nov 2010
Location: Grand Terrace, Ca.
Posts: 1,607
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Re: 72 BB motor swap wont drop/ 2wl dr/ halfton
Quote:
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#8 | |
Account Suspended
Join Date: Jan 2007
Location: Tucson
Posts: 2,183
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Re: 72 BB motor swap wont drop/ 2wl dr/ halfton
Quote:
The only other fit problem was the power brake booster. I had to replace the 10 in stock unit with a 7 in dual diaphragm unit to clear those monster valve covers. Not much difference between the 502 and 572....your truck should run like a scalded dog. Mine does! ![]() |
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#9 |
Registered User
Join Date: Nov 2008
Location: orange ca
Posts: 9
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Re: 72 BB motor swap wont drop/ 2wl dr/ halfton
The bolt holes are already there in the frame for the cross member
Do you have any pic you can upload? |
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#10 |
Registered User
![]() Join Date: Jan 2011
Location: laconia NH
Posts: 196
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Re: 72 BB motor swap wont drop/ 2wl dr/ halfton
The engine / frame mounts line up fine in the frame bolt holes. But lowering the engine on to them does not line up.
Taking pictures of the wiring prior to removeing the sb , my camera got knocked off the bench and guess what. That was One heck of a day. |
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#11 |
Registered User
![]() Join Date: Jan 2011
Location: laconia NH
Posts: 196
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Re: 72 BB motor swap wont drop/ 2wl dr/ halfton
I know tarditionally GM makes it easier for these changes. Thats why i couldnt imagine having to do any drilling. Like I said, I hope it may be a dum dum on my part. Taking a day off will give me another perspective. If not, bring on the TNT !
I will take these pics down tho the shop tonight and have another go. Thanks for the great help. |
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#12 |
6>8 Plugless........
![]() Join Date: Sep 2007
Location: Prairie City, Ia
Posts: 17,140
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Re: 72 BB motor swap wont drop/ 2wl dr/ halfton
GM didn't put any holes in my frame for my 6 cylinder swap!
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Ryan 1972 Chevy Longhorn K30 Cheyenne Super, 359 Inline 6 cylinder, Auto Trans, Tilt, Diesel Tach/Vach, Buckets, Rare Rear 4-link and air ride option Build Thread 1972 GMC Sierra Grande Longhorn 4x4 1972 Chevy Cheyenne Super K20 Long Step side tilt, tach, tow hooks, AC, 350 4 speed 1972 C10 Suburban Custom Deluxe 1969 Chevy milk truck 1971 Camaro RS 5.3 BTR STG3 Cam Super T10 1940 Ford 354 Hemi 46RH Ford 9" on air ride huge project Tired of spark plugs? Check this out. |
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#13 |
Registered User
Join Date: Jun 2011
Location: Montana
Posts: 78
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Re: 72 BB motor swap wont drop/ 2wl dr/ halfton
when i swapped a 396 in place of a 350 in a '72 GMC 1/2 T, it was just as others have said. remove the rivets for the trans crosmember and move it back to another set of holes.
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#14 |
Registered User
Join Date: Feb 2011
Location: Crowley TX
Posts: 979
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Re: 72 BB motor swap wont drop/ 2wl dr/ halfton
well this may not be your problem .cause mine is a small block and i put solid mounts on it and when i went to sit motor on frame it wouldint sit down all the way down on pedistals and the 2 long bolts lacked abit lining up after checking i found out they made a shorter solid mount . i got it and it fixed my problem . maybe you have same deal on your b-block..i think they were only like 1/2" difference but might as well been a mile. good luck.
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#15 |
My Carbon Footprint
Join Date: Oct 2008
Location: Orygun
Posts: 5,527
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Re: 72 BB motor swap wont drop/ 2wl dr/ halfton
FITZ.......572? You suck!!!! lol
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#16 |
Roadtrip!
![]() Join Date: Feb 2003
Location: Grand Rapids MN
Posts: 13,721
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Re: 72 BB motor swap wont drop/ 2wl dr/ halfton
Are you sure you have the correct stands and mounts? If you had a V-8 in there already, a big block shouldn't change the trans location. Did the truck used to be a 6 cyl?
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#17 |
Account Suspended
Join Date: Jan 2007
Location: Tucson
Posts: 2,183
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Re: 72 BB motor swap wont drop/ 2wl dr/ halfton
A big block will most certainly change the location of the trans. The cylinder size and spacing changes the length of the block but the lands for the motor mounts are all the same distance from the front face of the block to maintain clearance up front for stuff like fans and water pumps. That means the trans has to move back and, in my case, it moved back almost 6 inches.
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#18 |
Registered User
Join Date: Mar 2004
Location: Oklahoma
Posts: 28
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Re: 72 BB motor swap wont drop/ 2wl dr/ halfton
Actually the big blocks are the same distance between the motor mounts and the bell housing mating surface as the small block. A big block will stand taller in the engine compartment and will extend closer to the radiator in front.
In many of the old cars (not trucks) swapping between the big block and small block is pretty simple because the transmission stays in the same place and the motor mounts are in the same place, everything bolts right up. From what I've been told the reason the factory moved and raised the motor mounts for big blocks in the trucks was for exhaust clearance. |
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#19 |
Always on the hunt...
![]() Join Date: Sep 2006
Location: Portland, OR.
Posts: 5,602
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Re: 72 BB motor swap wont drop/ 2wl dr/ halfton
As others have said, mount your big block & 72 bbc towers in the forward set of holes and then move your trans and rear crossmember. Mel
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#20 |
Registered User
![]() Join Date: Jan 2011
Location: laconia NH
Posts: 196
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Re: 72 BB motor swap wont drop/ 2wl dr/ halfton
What about the drive shaft ? Wont it be too long ?
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#21 |
Account Suspended
Join Date: Jan 2007
Location: Tucson
Posts: 2,183
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Re: 72 BB motor swap wont drop/ 2wl dr/ halfton
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#22 |
Registered User
![]() Join Date: Jan 2011
Location: laconia NH
Posts: 196
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Re: 72 BB motor swap wont drop/ 2wl dr/ halfton
I am thinking of putting the original TH400 on the new rebuild and then see where the tranny crossmember wants to line up on the frame. That will eliminate the only invariable being the 402 on the current T350 .
I am blown away with all the help. Thanks all...... |
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#23 | ||
"I ain't nobody, dork."
Join Date: Sep 2007
Location: Whidbey Island, Washington
Posts: 8,936
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Re: 72 BB motor swap wont drop/ 2wl dr/ halfton
Dredging the waters? 4.5 year old thread.
![]() Gary
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'cuz chicks dig scars... My 1972 GMC 1500 Super Custom (Creeping Death) "long term" build thread. The Rebuild of Creeping Death after the wreck Quote:
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