tm9-801.com

The front motor mount for a G508 is pretty much the same as for all GM I6s in the 40s. A 4 part deal that sandwiches a rubber vibration dampener between two plates and a grease/oil shield.

From the SNL:



The parts are readily available.. but not from a single source.



The most common issue is that the SHIELD [C] is missing... its a simple stamped part and its job is to keep the oil/grease off the rubber. Oil will soften the rubber and it will lose its vibration dampening properties. There is a SPECIFIC measurement, adjusted by grinding the RETAINER [E] flanges to fit. The process is not in the TMs that I can find, but its in the civvy service manual for 48-51 235. My 42 Chevvy shop manual does not address the spacing.

Here is the parts breakout for the CCKW mount:


mount to crossmember bolts


Timing cover bolts


This is different from the civvy mount as the CCKW/G506 uses a slotted nut an cotter pin to retain the mount.

Well, this is interesting.

The REAR motor mounts I got that 'fit' the G506 and G508 are a bit unique. The G506 SNL does not go into the mount bolts... but the G508 SNL is explicit.





Part L, or the bolt: 9/16-18NF-3 x 1 1/8.

Smart readers will say 'hey.. that's to many numbers for a bolt spec!'. No. NF is 'National Fine' the -3 is a thread classification:

"Threads are also designated by Class of fit. The Class of a thread indicates the tolerance allowed in manufacturing. Class 1 is a loose fit, Class 2 is a free fit, Class 3 is a medium fit, and Class 4 is a close fit. Aircraft bolts are almost always manufactured in the Class 3, medium fit. "

That's why a normal 9/16-18NF bolt 'almost' threads... the thread tolerance it to lose... it needs a -3 fit.

Shouldn't be to hard to find

Found an NF-3 bolt.. its a cap screw.. and $6 per.

Code: Select all

http://www.fastenal.com/web/products/fasteners/sockets/socket-cap-screws/_/Navigation?term=&termca=&termpx=&sortby=webrank&sortdir=descending&searchmode=productSearch&zipcode=&filterByStore=&filterByVendingMachine=&r=~|categoryl1:%22600000%20Fasteners%22|~%20~|categoryl2:%22600039%20Sockets%22|~%20~|categoryl3:%22600040%20Socket%20Cap%20Screws%22|~%20~|attrdiameter:710|~%20~|attrlength:1350|~%20~|sattr06:^Fine$|~

Class 3A... just what you need.