Crossmember Mounting Holes Question

[mark johnson]

Well, first off, please overlook the crud on the belly of the beast. I'm in the process of shoving my LS-6 454 and Super Muncie M-22 into my Biscayne and am wondering which set of transmission crossmember mounting holes to use. My assembly manual shows the upper set of holes being the correct ones but I'm using an ancient, but massive RC Industries scattershield that only permits me to use the lower mounting holes because of floorpan interference. Just kind of curious if anyone know why there are two different mounting positions and what their intended usaged are for. Thanks, fellas.

 

[Fathead Racing]

Don't know why there was a choice for the cross member in the first place? Must have been for stick or auto car, never had thought about it before. I'm sure lot's of guys here know. I think the important thing is the angle in dgs that the engine sits in relation to the carb float setting when the car is sitting on level ground and where the driveshaft enters the driveshaft tunnel under the car/U joint angle. There may be distributor clearance issues also.

 

[PAINTJOHN1]

Mark,if my memory serves me right,back in 1970 I installed a 396ci big block in my 64' Chevy Convertible for towing.I used a Lakewood bellhousing at the time.I believe I used the bottom holes,nothing really changed for me.I drove the car with that engine for a year or so,changing to a 427ci engine with no problems ,no vibrations,clearence from the floor or whatever for almost 4 years.Only problem was changing the starter,motor had to be jacked up right hand side and header(Doug 1st engine,,then to Hooker 2nd engine) dropped down to get the starter out.As far as the top holes,they could possibly be used for Turboglide or maybe Powerglide trannies.I'm sure one of the other guys will chime in on this. John

 

[gearhead409]

Mark, use the bottom holes, the only time the top holes are used would be with the std. three speed tranny without overdrive.

 

[mark johnson]

Thank you very much, fellas! The bottom holes are what I was hoping for. I'm leaving the house right now to go discipline a trash-talking, Shelby GT500 Mustang with my Z06 and then I'm gonna come home and get back to work on this thing!