A little help with Engine Mount Bolts

[Chris H.]

Re: A little help with Engine Mount Bolts

Ron, this thread may help.

https://www.forums.ncrs.org/showthre...ghlight=Hewitt

[Ron G.]

Re: A little help with Engine Mount Bolts

Chris, thanks for help. That was exactly what I wanted to see to confirm my thoughts.

[David L.]

Re: A little help with Engine Mount Bolts

Back to the subject of Engine Mount Bolts.
In searching for other parts in my garage I came across a set of engine mount bolts that I have no idea where that I got them so I cleaned them with my wire wheel. They are in very good condition and appear to have a black oxide finish or something similar.
The bolts measure 7/16"-14 X 4 9/16" with a pointed end (length = 4 3/4" including the "point") with a thread length of 1 1/8" long. The marking on the 5/8" hex washer head is a letter "T" attached to a letter "M" (the manufacturer) along with 8 radial line segments (grade 8).
The 11/16" hex flange nut is grade 8 (with the 8 "bumps" or "dots") and appears to be exactly like the NOS GM 6262212 nut as shown in photo #4.

My 1982 Corvette Parts Catalog (Nov. 1981) lists the following in Gr. 0.002:
72-82 Y........399803..........BOLT, ENG MT TO ENG BRKT (HEX. 7/16-14 X 4 7/16)
76-79 Y........334972..........BOLT, (7/16-14 X 5 1/8)(300M)
76-79 Y........6262212........NUT, ENG MT FLANGE HD (7/16-14)

The flange nuts appear to be correct for 1976-1979 Corvettes but I do not think that the bolts are Corvette because they each have the hex washer head or flange head.

I assume that these bolts are assembly line engine mounting bolts.

My 1978 Chevrolet truck parts catalog (Dec. 1977) lists the 6262212 nuts in GR. 0.002 but lists the BOLTS as GM # 460308 and described as 7/16"-14 X 5 3/16" (300M) where 300M = Grade 8.

Has anyone come across these type of engine mounting bolts?
Dave

[David B.]

Re: A little help with Engine Mount Bolts

399803 is an Oldsmobile design bolt which could be used by any division. 334972 & 460308 are Chevrolet

[David L.]

Re: A little help with Engine Mount Bolts

There is a pair of NOS 460308 bolts currently on eBay. They appears to be full thread 5" effective length plus "point".

https://www.ebay.com/itm/2-NOS-GM-460308-ENGINE-MOTOR-MOUNT-BOLTS-CHEVROLET-GMC-TRUCK-BLAZER-SUBURBAN-/113907080226