Big Block Tower/Motor Mount Problems!!!

[6600DURAMAX]

Finally got around to installing the big block last night and have run into some major problems! The mounts are suppose to be for the 71-72 trucks and mine is a 72 but after bolting the cups/ mounts / towers to the motor the holes in the frame rails to not align. The holes all appear to be off by 3/4'' or more.

The motor is tight to the tranny (a 4 Speed which hasn’t been moved since the small block was pulled) and the rest of the driveline is bolted up as normal(driveshaft, rear end).

Where is the problem???? Can the rubber bushings be turned around??? A member here sold me the BB towers and cups and tells me they were for this year truck. Also from some other pictures, they appear to be correct.

I have tried to pry/jack the motor back to make the holes line up but it only causes the driveline to bind really really bad and the hole still don’t line up. Should I just drill all the holes where the motor sits now or is something wrong???

NEED HELP

Thanks guys

[6600DURAMAX]

No one has any help on this. Who has dropped in a BBC in place of a SBC

thanks

[1970 CST Short Wide]

I just did the same thing this week-end. I had to move my trans back 1 inch and shorten my drive shaft. I had a 350/350 and used the 72 mounts. I thought everything was supposed to line up and not have to move anything, WRONG !!!!!

I finally have it in and running, Pic's to follow in another thread.

Good luck

[6600DURAMAX]

Thanks CST Short Wide

But I am still confused on why this is a problem, if push come to shove I might try to use some small block mounts, really dont want to mess with the driveshafts. Or could I just drill ALL new holes in the frame??

But that still does not answer why we have this problem and that is what I would like to find out???

Thanks

[1970 CST Short Wide]

I'd like to know too. I undersatnd you can use SB mounts but you have header problems if you do. My headers fit perfect. I used Dynomax ceramic (Thanks for the info Bill) I was able to drill new holes in my Xmember and not drill the frame. I beleave its due to the fact that BB had 400,s behind them and I'm useing a 350 ?????

Let me know how you come out

[purple gas]

In a truck mag this summer ( wish I could find it) they showed all the 4 differnt motor mounts for our trucks. I-6,, small block, big block, and '72 big block. I needed small block myself, so I don't know what the differnce is between a regular big block, and the '72 big block. But maybe this is the problem. Could you possibly have a combination of parts that aren't compatable? Found the article. Classic Trucks/June 04, page 66. Ill try scan & post, but that could take a year. The 2 big block style mounts look VERY differnt from each other. Hope this helps.

[meathead95]

do you have a part number for those dynomax headers?

[1970 CST Short Wide]

I ordered them right out of Jegs Part #289-86022
Cerama-Coat Headers for Trucks with 396-454ci,
1/2-, 3/4-, 1-Ton Pickup 2WD 1967-87
Blazer/Jimmy 2WD 1968-87
$239.99

[NO LONGER DISTURBED KONCEPTZ]

The big question is do you know for sure if they frame mounts were from a 71-72 big block truck. Because some people with sell the 73-87 mounts as them and not know the difference. The 73-87 mounts will move the whole drive tran 1" back towards the firewall.

[Longhorn Man]

well 71 is completely different from 72. Apples to oranges here.
Do you have the ability to post pics?

[kwmech]

I have asked the same question in the past and never really got the answer I thought was correct. I have a 68 longhorn with a big block turbo 400. The trans bolts up to the rear holes in the frame. I have a small block with a turbo 400 in a 69, and the trans bolts up to the front holes in the frame --both are 1 tons. So my thought would be that the big block pushes the trans back 1''. BUT the center line of the motor mounts to the bellhousing face is the same small and big block.----------ssssssooooo?

[Longhorn Man]

How about the dimentions from the center line of the motor mounts, to the front of the engine?
I always figured they moved the tranny back instead of putting the fan too close to the rad.

[racer face]

I think the problem is in the bell housing. your running a T-10 Toploader to
a chevy bb. If you contact Advance Adapters they will steer you in the right.
If I remember right from my jeep days, sb to T-10 toploader took a longer
bellhousing than when we ran bb to T-10. If you were running all chevy
stuff the swap would be no problem, all holes would be predrilled at the factory. I'm doing a 68 1 ton dually with a 327/th400 and swapping the 327
for a 502.Having done this before (sb to bb) everything lined up,but the bb
did use one different hole on either side if I remember right. hope this helps!

[hobby67stepside]

I've installed a BB in a '67 and I had the same problem going on here. I just took the plunge, ordered BB towers, BB engine mounts, mounted the towers in the front holes in frame (had to do a little grinding on frame to get them to fit) and went from there. I fabbed my own trans mount and knew I would have to have custom drive shaft done.

[kwmech]

It is not the bellhousing, the difference seems to be in the towers. I asked the same thing before when I had a question about a serpentine belt conversion. Dammit-where's my tape measure?-----

[kwmech]

OK---- from the back of the block to the lower motor mount center hole is 16'' both small and big block. Using the same hole to measure a frame reference [ I used the front x-member]. I got a 1'' difference in motor placement, thus the big block towers push the trans and engine assy back 1''. So somebody doing a conversion to a big block using big block towers will have to move the trans back and redo the driveline, linkage, and exhaust. On a different note, if you want to do a serpentine conversion on a small block the water pump pushes the fan forward 1-1/8''. I even used the same tape measure to ensure accuracy