"Safety" Motor Mounts

[Peter M.]

1)When did the Safety type motor mounts become standard for Corvette ?

2)Was the introduction the same period for SB and BB ?

3)As far as the safety part - if the engine mount separated - would the safty prevent the block from droping down on the cross member - jumping through the hood - or both ?

[Joe L.]

Re: "Safety" Motor Mounts

Peter----

1) The "safety" style motor mounts were first used in PRODUCTION on Corvettes for the 1970 model year;

2) They were used for both small blocks and big blocks from the outset of the model year;

3) Primarily, the purpose of the safety mounts was to prevent a "rise" in the engine if the elastomer on the mount failed. This could cause damage to the fan shroud, hood, or other parts of the car.

I recommend only the use of safety style mounts on ANY 1963-82 Corvette, even though these mounts were not original for 63-69 models.

[Peter M.]

Re: "Safety" Motor Mounts

Joe - Did original "non-safety" mounts have a high or known failure rate when Vettes were new - or did GM fail to recommend changing them after say 100K miles. If they were a problem - whey did it take them 7 years to intro the new type ?

[Joe L.]

Re: "Safety" Motor Mounts

Peter----

I have no idea why it took GM so long to deal with this problem and I certainly don't know what the failure rate was of the original design motor mounts. However, in 1969 a safety recall was issued for many Chevrolet cars. The campaign involved the installation of a "cable and bracket" system to prevent significant movement of the engine in case one of the mounts broke. There were quite a few kits designed and issued for this campaign in order to suit various chassis and motor mount configurations. I'm sure that this campaign cost GM a "bundle", and I'm quite sure that they would not have done it without very good reason.

Beginning about January, 1970, Chevrolet discontinued all of the old-design motor mounts from SERVICE and replaced them, for all applications, with the "locking" style, safety mounts. After about that time, you could no longer purchase the non-safety mounts from a GM dealer, although they continued to be available in the aftermarket.

[Michael H.]

Re: "Safety" Motor Mounts

Joe,

I should know better by now than to get involved in C3 discussions but.... wasn't 69 the first year for the safety interlocking mounts? Only going from memory here but I do remember that the lower ignition "V" shielding changed in 69 to accept the new configuration mount. The 63-68 design would not fit with the new mount.

[Joe L.]

Re: "Safety" Motor Mounts

Michael-----

Well, I know for sure that a 1969 Corvette built in mid-September 1969 was originally built with the non-locking style mounts. It's possible that some built after that were built with the locking style. In any event, the vast majority, if not all, 1969 Corvettes were built with the non-locking style.

The ignition shields used for 1969, including the lower V shields were the same as earlier. They will not fit the locking style mounts without modification.

The 1969 AIM does show a new motor mount, GM #3967767, replacing the earlier mount, GM #3886466, with a drwing revision dated sometime in 1968. However, I don't think that this was a locking style mount. I think that it was an "interim" design mount which was of the same configuration as the 3886466 but, perhaps, of some improved construction. In any event, no change to the lower "V" ignition shields is shown in the 1969 AIM and they are the same as used from 1963.

The 1970 AIM shows the 3967767 being replaced by the GM #3980701 with a revision date of 6-2-69. I don't think that the 3967767 was ever used on a 1970 model since I believe that the 3980701 was used from the outset of PRODUCTION. The 3980701 is DEFINITELY the locking style mount. I suppose it's possible that some very late 1969s got the 3980701 mount.

The 1970 U-69 shielding drawings show only the later style shields. However, I believe that there were earlier sheets (with revisions) that were replaced and are not included in the copies of the AIM we have today (at least, the one I have).

[Michael H.]

Re: "Safety" Motor Mounts

That's interesting. I remember all of the activity at GM in late 68 on the motor mount failures and the campaign that followed but I was pretty sure it included the new design mount for 69. Possible that the Corvette was not included in the original 1969 SOP change to the new safety style mount for all pass cars.

I have an NOS GM radio installation kit (minus the receiver) for a 69 Corvettte and the "V" shields are definitely the 2nd design with the rotated reinforcement at the motor mount bolt location. May have been a middle of the year released kit though, which may explain the 2nd design.

By the way, the cars that suffered the broken mount/engine lift problem the worst were the full size pass cars, not Corvette, for some reason. I've had the old original dangerous non lift stop mounts in every Corvette I've ever owned since 1964 and never had one that allowed the engine to lift. Just lucky I guess.

[Mike Cobine]

Re: "Safety" Motor Mounts - Lawsuit

As best I remember, there was a case of a big block Chevy on a drag strip that the engine torqued over in the chassis when a mount broke. It jammed the throttle open and the driver lost control, crashing. The story I remember is that it crashed into a crowd of spectators.

I remember my dad getting the recall notice for a '65 Chevy BB wagon he had around 1970. One of the salesmen he was friendly with also told us that same story.

I think there were two recalls - the first to attach a restraining cable from the engine to the frame and the second to replace the mounts. It would be easy enough to look up the recalls on the web, if you are interested.

[Peter M.]

Re: "Safety" Motor Mounts

Michael - to your point - found this on Goggle -

2. Engine mounts: General Motors recalled 6.7 million cars and trucks in 1971 because of an engine mount that sometimes separated, allowing the engine to lift and push down on the throttle, causing the vehicle to take off like a rocket. Models affected were Belair, Brookwood, Camaro, Caprice, Chevrolet, Chevy II, G Series, Impala, Kingswood, Nova, P Series, C Series and Townsmen.

[Michael H.]

Re: "Safety" Motor Mounts

Interesting that the campaign did not include Corvettes built prior to 1969 but that was the way I remembered it. I thought it was all passenger car applications prior to the 69 model year. The bulletins from engineering first came down in about mid 1968 and at that time, only mentioned the new design mount assy released from engineering that would be installed on new 1969 pass car units. There was no mention of a campaign for past models (1968 and older). Soon after the first bulletin came in, a new one arrived that clearly stated, "ALL V8 engine equipped passenger vehicles built prior to 1969" will be involved in a campaign to install either a new design mount assy or an "engine lift stop" kit, which consisted of a bracket and cable assy. I well remember the campaign in 1969, for 68 and older cars, that continued into 1970 but I didn't remember it as late as 1971. It was one of the first GM Chevrolet campaigns. (Chevrolet didn't like the word recall)

I have a 1969 printing of the GM Corvette parts book and it shows 3886466 for 1968 and earlier, and 3980701 for 1969. The 701 is definitely a locking style mount assy but, as Joe Lucia said, it may have been later in the model year when this part was actually used in production. The number is too high, numerically, to be correct for start of production 1969.

Does anyone have a 69 AIM handy? I'm looking for the part numbers for the two "V" ignition wire shields that bolt to the lower sides of a small block.

[John H.]

Re: "Safety" Motor Mounts

Michael -

Concurrently, the 1969 Camaro A.I.M. shows a "phased response" to the problem; all optional V-8's show a change to add the "Stop" reinforcement between the left engine mount and the block (3977781 on L-48 and Z/28 and 3977783 on L-34/35/78) during the first week in June '69, and the new "safety" mount assy. shows as added to the base V-8 in mid-August '69 ('69 Camaro production went through November, 1969).

[Stephen W.]

Re: "Safety" Motor Mounts

I owned an original 69 Z/28 in 1971 and received the letter from GM about the cable restraints. I was the 2nd owner of the car.

[Michael H.]

Re: "Safety" Motor Mounts

This discussion is bringing back memories of that particular era and I remember what seemed like every other piece of paper that came across my desk had to do with the engine mount campaign. By late 1969, the quadrajet fast idle cam problem and the engine mount campaign seemed to be the only thing that engineering was concerned with. Funny how a little media attention can bring out the best in a major corp.

I vaguely remember receiving something in the mail in 1969 about the engine mount in my 68 Z28. I think everyone received this notice about the same time because every Chevrolet dealer service dept in my zone was booked for weeks in advance. Every dealer parts dept was over stocked with the "quick fix engine lift stop" kit. Most aggressive campaign since the Power Glide downshift rod problem in 67 or 68. Must have had something to do with Ralph Nader.

[John H.]

Re: "Safety" Motor Mounts

Michael -

Does this look familiar?

[Michael H.]

Re: "Safety" Motor Mounts

Been a lotta years since I've actually seen one installed on a car. I still have several of these cables in my junk drawer somewhere. Think of the money GM could have saved if they would have just made a correct mount to begin with.