Big Block install differences...from small block

[randy500]

So we all know a big block factory install requires the following parts

Big block frame stands and engine mounts
Big block fan shroud
Big block frame transmission linkage bracket, commonly called TH400 frame bracket since all big blocks had s TH400 transmission.

All that stuff is required because the big block is placed in the engine compartment about 3/4 of and inch back from the small block location. It also sits down or up by 3/4 of an inch or so (I will verify this with a picture later)

In 67 all automatics were TH400's and maybe 68 too.
Some small blocks in years after, I think until 69 could be had with a TH400, those will have the same frame bracket as a TH350 since the commonly called TH400 frame bracket is actually a big block frame bracket.

The reason I am writing this is that I just discovered that the TH400 frame bracket is actually a big block frame bracket.

I discovered it when I placed my big block up to my 71 which had a small block and TH350, when I removed the small block I left the transmission connected to the crossmember and the shift linkage in place.
When I bolted the big block to the transmission the frame stands were 3/4 of an inch forward of the frame bolt holes. To line up the frame stands I took the bolts out of the trans crossmember and mount, lifted the engine and trans together and ligned up the engine frame stands, after bolting in the engine I found the trans linkage out of alignment.
I corrected the shifter linkage alignment with the commonly called TH400 frame bracket, it corrected the shift linkage alignment even though I had the TH350 bolted to the big block.

Pictures to follow.

[randy500]

Another reason I am writing this is to also prove that there must be a big block manual transmission crossmember or bellhousing which is cast or machined different for the big block engine placement.

Our member Ghalperin is building s big block short bed step side with a 3spd overdrive transmission and is having problems with z bar alignment.
He has installed NOS big block frame stands and a small block bellhousing crossmember.

I have gathered parts to make my big block 71 manual transmission too.
Right now I have a small block z bar frame bracket and the correct big block ball stud and they are in perfect alignment.
From Ghalperins posted problems I will not attempt the SM 465 install and will instead use a transmission with a rear mount instead of the bellhousing mount, not sure is a nv4500 will work for that or if I will use a T56 when I change over to manual trans.

[randy500]

Another pic of z bar alignment, I don't have a z bar but hopefully you can see the alignment I have with the frame bracket and engine ball stud. The aluminum ruler goes through the frame bracket and is touching the center of the ball stud. The round thing to the right on the engine is the 1/2 in threaded bolt head which mounts the ball stud pivot bracket to the engine block.

[randy500]

Another pic.

[Mike C]

There is a big block manual trans crossmember. It is a different shape than the small block one because it mounts higher up the frame and closer to the front. Unlike the auto trans x member that can be slid forward and backwards, the upward curve of the frame requires a different size/shape for the big block bellhousing crossmember.

Some of the clutch linkage components are different as well. I think the z bar pivot bracket the same but mounts further forward. Both sets of holes should be in the frame.

High hump also has the 4 speed shifter opening cut in a different location and I believe the big block shifter cane is different as well because it is so far under the dash.

[67 chevelle]

turbo 400 was not the only automatic transmission option in 67-68

[randy500]

Originally Posted by 67 chevelle

turbo 400 was not the only automatic transmission option in 67-68

Right, forgot about the powerglide...