Help

[J kippin]

So I finally am getting around to putting a BBC in my 71. I am using 72 style mounts and everything is going pretty good. The transmission mount is in need of replacement so I crawl underneath to change it and I find the mount wont line up. It seems to be sitting to far back on the cross member. I am still using the TH350 that has been in the truck. I go back and check the engine and it is all the way forward on the mounts....
Before I burn this or sell it for parts any body got some ideas???

[elf w/capital T]

Not too knowledgeable with bbc, hope someone can help you!!

[71swb4x4]

Are you saying the transmission is farther back with the engine swap? If so move the crossmember. At most you will have four holes to drill, no big deal.
Or are you saying you got the wrong transmission mount? If so take the old one in with you when you go to exchange the wrong one.

[Hawghauler]

You have a few mounting positions on the crossmember for your motor mounts, and likewise with your trans crossmember. Look closely at the top of your frame where your motor mount perches are and you'll see an extra hole. This is spaced the same as where you are presently mounted. If it is in the right direction to line you up for the trans, your probably set. Likewise if you look at the frame where the trans crossmember is mounted you'll see some other holes as well, usually anyway. Good luck!

[J kippin]

What I see is the engine frame perches in the forward mounting holes. The holes in the perches are slotted and the mounts are as forward as they care allowed to go. The cross member was never moved and the mount which is the correct one does not line up. The mount now is sitting at the rear of the cross member instead of in the middle as it was intended to be. If I move the mount to the next set of holes back it will be too far now in the other direction. Also the slip yoke in the transmission is now bottomed out into the tail shaft whereas it was not before. Is this a normal issue when putting a BBC in front of a TH350 transmission?
Also just found my torque converter bolts don't line up with the flex plate...they are both 168 tooth. I don't remember having this many problems doing motor swaps when I was 20years younger maybe things have changed or just my memory has faded LOL.

[cheyenne shortstep]

First the flex plate issue, did you try both sets of holes in the flexplate and it still doesn't line up to either? As for the trans. crossmember I would probably be tempted to do as was mentioned and drill new holes in the frame, quick and easy. BB swaps or engine swaps in general can be frustrating, don't give up [I know the feeling] in the end it will all be worth while. I am pulling the BB out of the Super tomorrow and I will take some pics of the mount locations for you.

A couple years ago I bought a very original 70 Custom Camper 20 with the original small block that appeared to have never been removed, it was sitting on BB mounts with a BB fan shroud?? So looking to make a couple extra $$$ I decided to swap mounts and shroud for SB, sounds simple enough right. Well after about 4 hours of swapping mounts and shroud I lowered the engine back down only to find trans. didn't line up [similar to what you are describing]. I cut my losses and put the BB stands back in and called it a day with lesson learned.

[J kippin]

Thanks for the replies....I am pretty sure I tried both but maybe I skipped a set. Re drilling the frame would not be a big deal but I always thought the BBC motor mount to the rear edge of the block was the same length as a small block. I always thought the additional length was from the mount forward. That is why I don't understand why the trans is back from the original location.