C3 Safety Locking Motor Mounts

[Sheldon S.]

Has anyone found a good replacement motor mount for C3's. I have tried Paragon, Zip and Napa. They are allreal bad repo's. Besides not looking good, they are so flimsy looking I'm not sure I even want to put one on my BB. Thanks for any info.
Sheldon

[Don W.]

Re: C3 Safety Locking Motor Mounts

Have you looked at Dr Rebuild catalog; page 106?

[Joe L.]

Re: C3 Safety Locking Motor Mounts

Has anyone found a good replacement motor mount for C3's. I have tried Paragon, Zip and Napa. They are allreal bad repo's. Besides not looking good, they are so flimsy looking I'm not sure I even want to put one on my BB. Thanks for any info.
Sheldon

Sheldon-----


I've checked this out exhaustively in the past. I don't think there's an original configuration and quality motor mount manufactured today. All that I am aware of are of foreign manufacture and are, to say the least, "less than impressive".

[Bill L.]

Re: C3 Safety Locking Motor Mounts

May I add that if you seek an NOS mount, make sure it is not the second design. The original long bolt that goes through the frame will not work and the motor mount is clearly different albeit maybe a little stronger with the second design. The mount does not follow the contour of the frame so GM just welded what amounts to a washer on each ear.

Ask me how I know





Bill

[Joe L.]

Re: C3 Safety Locking Motor Mounts

May I add that if you seek an NOS mount, make sure it is not the second design. The original long bolt that goes through the frame will not work and the motor mount is clearly different albeit maybe a little stronger with the second design. The mount does not follow the contour of the frame so GM just welded what amounts to a washer on each ear.

Ask me how I know





Bill

Bill-----


Are you talking about the difference between the non-locking mounts (i.e. 1963-69) and the locking mounts (1970-82 and SERVICE for 63-69)?

Of the locking style mounts GM GM used only 2 different part numbers, GM #3980701 (after 1971 available in SERVICE only as part of mount KIT GM #3990916) which was used for 1970-72 Corvettes and SERVICE for 63-69 Corvettes. GM #330973 was used for 1973-82 Corvettes and was available in SERVICE only as part of KIT GM #6258154. The 6258154 kit became SERVICE for 70-72 (and 63-69) after February, 1977.

I have many NOS examples of the 3980701 and 330973 and there are only very minor apparent differences between them. I have found either one to work perfectly. I only wish they were still available.

[Bill L.]

Re: C3 Safety Locking Motor Mounts

Joe,

Now you have me thinking maybe my mount is not a corvette mount. It is a safety mount for sure. It is just much wider than the original mount where it attaches to the frame. Instead of the ears being bent in to match the contour of the frame it has two oval and thick washers welded to the mount. If I use a longer bolt it would work fine. It is just that the original bolt is too short with this mount.

I cannot imagine it would pass judging. If I cannot find a good used original I may have to use it and get another bolt.

I threw away the GM tag with the part number. If the part number is on the part I will post it.

I posted on the corvette forum trying to find a good used original mount.




Bill

[Joe L.]

Re: C3 Safety Locking Motor Mounts

Joe,

Now you have me thinking maybe my mount is not a corvette mount. It is a safety mount for sure. It is just much wider than the original mount where it attaches to the frame. Instead of the ears being bent in to match the contour of the frame it has two oval and thick washers welded to the mount. If I use a longer bolt it would work fine. It is just that the original bolt is too short with this mount.

I cannot imagine it would pass judging. If I cannot find a good used original I may have to use it and get another bolt.

I threw away the GM tag with the part number. If the part number is on the part I will post it.

I posted on the corvette forum trying to find a good used original mount.




Bill

Bill------


The mount you describe sounds like the 70+ Corvette mount. The welded-on spacers are necessary to make the locking style mount work with the Corvette frame brackets which were not changed when locking style mounts were introduced. The original GM mounts used for 70+ all had these. In fact, the spacers are the only feature I've found that differs between the 3980701 and 330973 mounts. The 3980701 has spacers which appear to be some sort of forging. The 330973 uses spacers which are fabricated from bar stock with a more-or-less butted joint.

The bolts for the non-locking style mounts are necessarily different than the locking style. The locking style MUST be longer. The 63-69 bolt, GM #3817224, was 3-3/4" OL. The 70-82 bolt, GM #399803, was 4-7/16" OL.

Most 70+ GM motor mounts have the part number embossed on the rubber portion of the mount, either 3980701 or 330973. It will be seen in fairly small size font.

[Bill L.]

Re: C3 Safety Locking Motor Mounts

Joe,

Well I looked and could not find a part number anywhere on the mount.

Assuming that both the original mounts were on the car with only the driver's side broken, this replacement mount is different.

Both the originals and this "NOS" mount are the safety locking type. I have a non locking mount to have as a comparison.

Both original mounts are identical and the ears are bent to the exact profile of the frame where they attach without spacers. The reproductions are all shaped like my original but are of much lesser quality as you say.

I have had someone speak up and may have an original I can buy. Hopefully I can get a pic to make sure.

If I could figure out how to post a pic maybe that would help.

Now I am even more curious.



Bill

[Joe L.]

Re: C3 Safety Locking Motor Mounts

Joe,

Well I looked and could not find a part number anywhere on the mount.

Assuming that both the original mounts were on the car with only the driver's side broken, this replacement mount is different.

Both the originals and this "NOS" mount are the safety locking type. I have a non locking mount to have as a comparison.

Both original mounts are identical and the ears are bent to the exact profile of the frame where they attach without spacers. The reproductions are all shaped like my original but are of much lesser quality as you say.

I have had someone speak up and may have an original I can buy. Hopefully I can get a pic to make sure.

If I could figure out how to post a pic maybe that would help.

Now I am even more curious.



Bill

Bill-----


Attached are photos of an NOS GM #3980701 motor mount [not for sale]. This is the EXACT mount that was used from 1970-72. It is POSSIBLE that VERY early 1970 used mount GM #3967767. However, it was discontinued from SERVICE in October, 1969 which strongly implies that it was not used for 1970 PRODUCTION and I seriously doubt that it was ever used for 1970 PRODUCTION. I know nothing of the configuration of the 3967767 mount, though.

If the configuration of your old mount differs from this mount, then I don't know what you have.

[Joe L.]

Re: C3 Safety Locking Motor Mounts

Joe,

Well I looked and could not find a part number anywhere on the mount.

Assuming that both the original mounts were on the car with only the driver's side broken, this replacement mount is different.

Both the originals and this "NOS" mount are the safety locking type. I have a non locking mount to have as a comparison.

Both original mounts are identical and the ears are bent to the exact profile of the frame where they attach without spacers. The reproductions are all shaped like my original but are of much lesser quality as you say.

I have had someone speak up and may have an original I can buy. Hopefully I can get a pic to make sure.

If I could figure out how to post a pic maybe that would help.

Now I am even more curious.



Bill

Bill-----


The attached photos show an aftermarket, Korean-manufactured locking-style Corvette mount. It does appear a bit lighter duty than the GM mount. However, this particular mount, purchased quite a few years ago from Dr. Rebuild, is, based on my evaluation of dozens of other mounts available on the market today, the apparent best one out there by a long shot. I don't even know if this mount is still available. If it is and I was in need of a mount, this is the one I'd be looking for.

[Larry S.]

Re: C3 Safety Locking Motor Mounts

Bill,

Have a look at the motor mounts supplied by Ecklers in Titusville Fl.

I got new ones from them for my '66 BB and they are much heavier than the ones that I will not use from Corvette Central. The Ecklers version didnt have a country of manufacture on them that I could see, but Ecklers say they are a heavy duty mount.

[Bill L.]

Re: C3 Safety Locking Motor Mounts

Joe,

Thank you for the pics.

The NOS mount I purchased is exactly as the one in your pics of a correct GM motor mount. I will check to see if there is a part number again.

Now it seems that at some point maybe both of my original mounts were changed out and the ones that were in there are not original. I am a little surprised in that so much of the hardware on my 70 is orginal.

Did they ever make a safety mount that was compatible with the short bolts?

Bill

[Bill L.]

Re: C3 Safety Locking Motor Mounts

Well I figure I better ask about bolts for the mounts.

What head mark should I have and in what finish for both the bolts that attach mount to engine and the bolts that go through the mount and frame.

My frame bolts appear to have 5 lines and what looks like an o in the middle.

The indented hex head bolts ,for mount to engine with captured lock washers, all appear to be I think EH or maybe CH.



Thanks again.




Bill

[Joe L.]

Re: C3 Safety Locking Motor Mounts

Joe,

Thank you for the pics.

The NOS mount I purchased is exactly as the one in your pics of a correct GM motor mount. I will check to see if there is a part number again.

Now it seems that at some point maybe both of my original mounts were changed out and the ones that were in there are not original. I am a little surprised in that so much of the hardware on my 70 is orginal.

Did they ever make a safety mount that was compatible with the short bolts?

Bill

Bill-----


I don't know of any like that. However, the 3967767 MIGHT have been such a mount. Is this car a very early 70? Also, have you thoroughly examined the mount for any evidence of a part number?

[Bill L.]

Re: C3 Safety Locking Motor Mounts

It is a June build date Joe. I will pull the other motor mount once I obtain the correct hardware to check on a part number.

I did look at what I bought as an NOS part. It does have a part number but I will need a better pair of eyes to read it. I believe it is the PN you referenced as the GM # in the pic you posted.

Just as an aside. Were the bolts plated bright zinc or typical black/gray phosphate for all the mount hardware? Do you know what head marks I should have on the hardware?


Thanks,



Bill