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Old 07-23-2017, 02:12 PM   #1
randy500
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Join Date: Jul 2016
Location: Tacoma, WA
Posts: 6,873
Big Block install differences...from small block

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.
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