Motor mount

[pfarber]

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:

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

rP9260228.JPG (140.06 KiB) Viewed 7975 times

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.

civmount.PNG (172.41 KiB) Viewed 7975 times

[pfarber]

Here is the parts breakout for the CCKW mount:

cckwmount.PNG (87.52 KiB) Viewed 7969 times

mount to crossmember bolts

cckwbolts.PNG (80.82 KiB) Viewed 7969 times

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.

[pfarber]

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.

snlmm.PNG (122.83 KiB) Viewed 7962 times

rmm.PNG (42.35 KiB) Viewed 7962 times

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

[pfarber]

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$|~

boltclass.PNG (53.55 KiB) Viewed 7961 times

Class 3A... just what you need.