Was wondering, how is it that the factory used different frame mounts to offset big block motors to the passenger side, and in doing so, uses a different transmission crossmember (atleast for muncie 4spds), and still has the shifter coming up in the same location? Also, how does this effect the drive shaft and rear differential? I have tried to think about this and visualize what was happening, but I could not figure it out, I suppose if I actually did the conversion, it would make sense???

Thanks for the help in advance.


(ps I wasnt sure where to post my question)

You need to use the big block shifter mount (repros are available), that goes between the trans and the shifter. It puts the shifter back to were it should be. The driveshaft u-joints are not affected by the offset of the trans.

anyone got a link to these big block shifter mounts? or a photo???

The output shaft of the transmission must be parallel to the rear differential's pinion shaft. By using a big block transmission crossmember, it is matching the offset to the passenger side of the engine and it is parallel.

Many people think that they know what is best, and they " think" by putting the engine on center, that everything is inline. The pinion shaft on all GM rears is offset to the passenger side by 1/2".

The Big Block offset, does put the rear pinion in line in the horizontal plane. In the vertical plane the transmission's output is parallel with the pinion shaft.

With a small block the transmission output shaft is parallel in both planes, but never inline.

If you attempt to use a small block transmission crossmember (on center) with Big Block frame mounts the result is a crooked engine and thence the shafts are not parallel.

Small block mounting plate

http://i263.photobucket.com/albums/ii152/tjs69_photos/Transmission%20ID/shifterplateforsmallblock.jpg

Big Block mounting plate

http://i263.photobucket.com/albums/ii152/tjs69_photos/Transmission%20ID/shifterplatebigblock.jpg

You can see an offset to the mounting points.

A Big Block Bell Crank (Z-bar) is also needed.

http://i263.photobucket.com/albums/ii152/tjs69_photos/Transmission%20ID/BellcrankSB.jpg

http://i263.photobucket.com/albums/ii152/tjs69_photos/Transmission%20ID/BellcrankBB.jpg

The transmission crossmember difference.

http://i263.photobucket.com/albums/ii152/tjs69_photos/1st%20gen%20crossmembers/trans_xmember_sb_bb1.jpg

http://i263.photobucket.com/albums/ii152/tjs69_photos/1st%20gen%20crossmembers/comparo.jpg

Broc, sorry you asked??? After all, this is the Camaro information age site.:thumbsup:

To complete this, the 67-68 factory shifters mounted on the cross-member. The mounting holes on the sb and bb were in the same locations (see the photos already posted) so the shifter is in the same location with respect to the hole in the tunnel. The difference in engine/trans mounting is taken up by the shifter rods.

Martin

the drive shaft is also longer on a big block car with the frame mounts being more foward

thank you all for the responses, things are making sense somewhat.....few more questions regarding this though


does this mean if doing a small block to big block conversion....you would need a new drive shaft?

Also...I should have realized that yes, muncie shifters mounted to the crossmember, I guess I was thinking about the hurst competition plus shifters (ie not stock) what difference in shifters/mounting/or hardware is there?

If someone was to do a conversion from small block to big block....what would they need? assume 67 or 68 camaro........saying that it has a 4spd muncie and one already has the correct bellhousing, cluth press. plate flywheel......

--big block heater core and housing
--big block frame mounts (motor mounts are the same right?)
--BB (assume 4spd muncie) crossmember
--BB z bar (how do you tell the difference from bb to small block? - bb is longer right?)
--a BB drive shaft???
------anything I'm missing???

anyone have a link for what the shifter plate bracket looks like for a 67 68....Hurst Competition Plus (to fit console) I already have the shifter and small block linkage, what would it cost do make it a bb shifter?

I am considering going to a big block (454) and I guess I want to know what it would cost to do the complete swap over.

Is the drive shaft different?

Does anyone know if there is a height difference in the 69 camaro crossmembers? I've seen the photo above for the offset, but not anything on a variance in height of the trans mounting surface.

The reason I ask is I have a 6 degree difference between the trans shaft and the pinion shaft (nose is down). This is how I bought the car and I'm working thru setting everthing up correctly and wanted to know if the correct stands and crossmember changes the angle that the engine and trans sets that might help fix my problem. It currently has a 454 on small block stands, 350 trans on small block crossmember, 8.5 rear end with multileaf perches, 3 leaf springs.

The rear is now out and I checked the spring perch to pinion angle ands it's right on 5.5 degree with the nose being up. So I don't know how the nose could be down 6 degrees in the car relative to tran.

I'd like to know about needing a longer driveshaft as well if anyone knows.

Thanks, Mike

Based on the template above, it looks like it would be rather simple to convert a small block crossmember in to a big block crossmember. Any one ever go through the trouble to do it?

thats the same thing i was thinking. I was thinking about finding a small block crossmember and trying it.......any help with my 2nd set of questions tho???

thank you all for the responses, things are making sense somewhat.....few more questions regarding this though


does this mean if doing a small block to big block conversion....you would need a new drive shaft?

Also...I should have realized that yes, muncie shifters mounted to the crossmember, I guess I was thinking about the hurst competition plus shifters (ie not stock) what difference in shifters/mounting/or hardware is there?

If someone was to do a conversion from small block to big block....what would they need? assume 67 or 68 camaro........saying that it has a 4spd muncie and one already has the correct bellhousing, cluth press. plate flywheel......

--big block heater core and housing
--big block frame mounts (motor mounts are the same right?)
--BB (assume 4spd muncie) crossmember
--BB z bar (how do you tell the difference from bb to small block? - bb is longer right?)
--a BB drive shaft???
------anything I'm missing???

A simple solution for the crossmember is to fab a flat plate about 3/16" thick, that will mount to the transmission in between the Transmission and the transmission mount with the offset holes in the plate.

http://i263.photobucket.com/albums/ii152/tjs69_photos/engine%20and%20frame%20mounts/sbctobbc.jpg

anyone have a link for what the shifter plate bracket looks like for a 67 68....Hurst Competition Plus (to fit console) I already have the shifter and small block linkage, what would it cost do make it a bb shifter?

I am considering going to a big block (454) and I guess I want to know what it would cost to do the complete swap over.

Is the drive shaft different?

The Hurst aftermarket shifter, rods, and mount plate is the same for BB and SB but uses one install kit for 67-68 and a different kit for 1969 BB and SB.

The Hurst 67-68 mount plate is different then 69

On a side note, the early 427 Camaros built by Yenko, Motion, Dana, Nickey, etc used the small block engine mounts and trans cross member and other SB parts. The DS exhaust manifold and heater hoses don't fit very well but the thats how they were built before the factory BB became available. They used headers squeezed in the heater hoses on early BB conversions.