71 front motor mounts

[Pete B.]

During the process of my body off resto on my SB, I replaced the broken mounts with the only thing that was available...Import mounts purchased from NAPA.

My engine now sits too low and at times the fan rubs on my shroud.

Last week at Nationals we had a 300 mile bowtie car on the lift and I measured that mount. Mine is 1/4 (shorter) lower than the bowtie car (meaning the dim from the block mounting surface to the centerline of the bolt where it mounts to the frame)

I am out of adjustment on the shroud and need to do something else. Does anybody know of mounts that are not so short?

PS I saw the "new designed one" at the Corvette Central booth...same dimension as my short one...So watch out!

TIA Pete

[Jim T.]

Re: 71 front motor mounts

Pete do you still have the mounts you removed from your car? Were both of them unable to hold the engine down? If only one was unable, install it on the passenger side and the old good one on the drivers side. This will keep your fan from hitting the shroud until you find adequate replacements.
I have the original mounts I removed from my 70 20 years ago when I installed a ZZ crate engine. I am going to continue keeping them after reading about what is available today.

[David L.]

Re: 71 front motor mounts

I have a pair of NOS 3980701 mounts (used on 1970 Corvettes only) and the measurement from the center of the hole to the block mounting surface is about 1 11/16" or 1.7". I also have pairs of aftermarket 2267 and 2285 mounts and ther measure the same.

Dave

[Dick W.]

Re: 71 front motor mounts

Peter, you could have the core support shimmed up too high, which will cause the same problem.

[Pete B.]

Re: 71 front motor mounts

Dave, the Bow tie car was 2.00 mine are about 1.75...so maybe I have a shimming issue...as Dick mentioned....

I have a pair of NOS 3980701 mounts (used on 1970 Corvettes only) and the measurement from the center of the hole to the block mounting surface is about 1 11/16" or 1.7". I also have pairs of aftermarket 2267 and 2285 mounts and ther measure the same.

Dave

[Scott K.]

Re: 71 front motor mounts

I have a pair of NOS 3980701 mounts (used on 1970 Corvettes only) and the measurement from the center of the hole to the block mounting surface is about 1 11/16" or 1.7". I also have pairs of aftermarket 2267 and 2285 mounts and ther measure the same.

Dave

Our new locking motor mount has the same measurements, appearance and functionality as GM p/n 3980701. Here is a link to more information on these mounts: http://tech.corvettecentral.com/2011...vette-central/

[Joe L.]

Re: 71 front motor mounts

Our new locking motor mount has the same measurements, appearance and functionality as GM p/n 3980701. Here is a link to more information on these mounts: http://tech.corvettecentral.com/2011...vette-central/

Scott-----

Thanks for "stepping up to the plate" and giving folks a much better option for motor mounts than has been available for quite awhile.

[Joe L.]

Re: 71 front motor mounts

I have a pair of NOS 3980701 mounts (used on 1970 Corvettes only) and the measurement from the center of the hole to the block mounting surface is about 1 11/16" or 1.7". I also have pairs of aftermarket 2267 and 2285 mounts and ther measure the same.

Dave

Dave-----


The GM #3980701 was used in PRODUCTION for 1970-72 Corvettes. However, it was only available in SERVICE during approximately the 1970 model year. After that, the 3990916 became the SERVICE part number for Corvettes. The difference is that the 3980701 is the part number for the mount, alone, and was sold just that way during 1970. The 3990916 is a UNIT which consists of 1 GM #3980701 mount + through bolt, engine mounting bolts, lock nut, and washers. So, why did GM stop selling the individual mount and start selling it only as a kit? Well, the 3980701 mount became the SERVICE mount for all 1963-69 Corvettes. However, when used on those applications, a longer through bolt was required. So, I suppose that GM figured it would be best to sell the mount as a UNIT which included parts needed for installation on the 63-69 applications. They probably had gripes from dealers or mechanics that purchased the 3980701 mount and then found that they needed other part(s) to make it work for the 63-69 applications.

By the way, the 3990916 was discontinued from SERVICE in February, 1977 and replaced by GM #6258154, the mount UNIT originally cataloged in SERVICE for 1973 and later Corvettes. The 6258154 was the same as the 3990916 EXCEPT that it contained a GM #330973 motor mount instead of the 3980701 included with the 3990916. The 330973 was the motor mount used in PRODUCTION for 1973-82 Corvettes.

So, what's the difference between a GM #3980701 mount and a GM #330973? Well, the only difference that I've been able to discern is that the 3980701 uses oval shaped spacers which are either cast or forged and somehow "spot-welded" to the mount's frame. The 330973 uses spacers which are fabricated from steel bar stock and are MIG-welded to the mount's frame. This difference is virtually indiscernable when mounted on the car.