72 BB motor swap wont drop/ 2wl dr/ halfton

[HDBOB]

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 !!

[VA72C10]

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!

[Classic Heartbeat]

Bolt the engine where the stands belong and move the transmission crossmember. The frame should be drilled for the new location. WES

[streetstrip1972]

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

[HDBOB]

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.

[Fitz]

Originally Posted by HDBOB

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.

It's not a question of fudging holes as much as building a frame that can acommodate a very broad selection of engine/trans combo's. The 327 & 350 share a common mount as do the 396/402 and, the six! The great thing about the way Chevrolet built it's cars is almost any combination of block transmission and frame can be assembled using stock parts without drilling the frame. Try that in a FORD!
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.

[ItsRandy]

Originally Posted by Fitz

It's not a question of fudging holes as much as building a frame that can acommodate a very broad selection of engine/trans combo's. The 327 & 350 share a common mount as do the 396/402 and, the six! The great thing about the way Chevrolet built it's cars is almost any combination of block transmission and frame can be assembled using stock parts without drilling the frame. Try that in a FORD!
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.

You're my hero (572 BB)! What headers are those? I have a 502 in my truck (couldn't get the wife to "ok" the 572) and used Hooker supercomp headers. I had a bunch of clearance issues I had to correct, head bolt interference, lower control arm on driver's side touched a primary tube...it was a mess. I used all the stock mounts and factory holes.

[Fitz]

Originally Posted by ItsRandy

You're my hero (572 BB)! What headers are those? I have a 502 in my truck (couldn't get the wife to "ok" the 572) and used Hooker supercomp headers. I had a bunch of clearance issues I had to correct, head bolt interference, lower control arm on driver's side touched a primary tube...it was a mess. I used all the stock mounts and factory holes.

I used Sanderson Headers. Stacey David had the first set made up to fit Copperhead---ZZ572 in a 67 fleetside so when I did my stepside I just called and asked for the same ones. They are long tube headers which slip right in. Since the 502/572 use the same heads they will fit your truck. You will have to relocate the oil filter, though. Bit pricey...around $350.00

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!

[streetstrip1972]

The bolt holes are already there in the frame for the cross member

Do you have any pic you can upload?

[HDBOB]

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.

[HDBOB]

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.

[Dieselwrencher]

GM didn't put any holes in my frame for my 6 cylinder swap!

[Monty]

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.

[mightymouse]

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.

[prostreetC-10]

FITZ.......572? You suck!!!! lol

[too much stuff]

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?

[Fitz]

Originally Posted by too much stuff

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?

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.

[Fasglas]

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.

[Classic Bowties]

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

[HDBOB]

What about the drive shaft ? Wont it be too long ?

[Fitz]

Originally Posted by HDBOB

What about the drive shaft ? Wont it be too long ?

Yes. I had to cut mine down to 37 inches!

[HDBOB]

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......

[GASoline71]

Dredging the waters? 4.5 year old thread.

Gary