Engine Mounts Bolt

[Orjan S.]

I want help with the assembly of the engine mount.
When I read in AIM, you should use flat washers.
When I read Judging Manual I should use lock washers.
What is correct?
It is the long bolt between the frame and the engine mount.
I'm grateful if anyone has a photo of a correct bolt, nut and washers.

Orjan

[Edward J.]

Re: Engine Mounts Bolt

Orjan, there should be flat washers on bolt and nut sides, the nut is a self locking nut.

[Joe L.]

Re: Engine Mounts Bolt

I want help with the assembly of the engine mount.
When I read in AIM, you should use flat washers.
When I read Judging Manual I should use lock washers.
What is correct?
It is the long bolt between the frame and the engine mount.
I'm grateful if anyone has a photo of a correct bolt, nut and washers.

Orjan

Orjan------


The bolt is a standard, trimmed (i.e. non indented head) bolt of size 7/16-20 X 3-7/8". It is zinc finished and 1-3/4" of thread. It has a piloting tip (i.e. slightly tapered) to ease insertion. Natural steel FLAT washers are used on either end (i.e. under the bolt head and under the nut). The nut is a slotted type lock nut. No lock washers are used in the assembly.

[Leif A.]

Re: Engine Mounts Bolt

Orjan,
A picture of the bolt, washers and nut that Joe described for you.

[Mike E.]

Re: Engine Mounts Bolt

I'm not sure what edition 68-69 JG you are reading, but 5th edition, p. 165 and 6th edition p. 168 both indicate flat washer with locking nut.

I want help with the assembly of the engine mount.
When I read in AIM, you should use flat washers.
When I read Judging Manual I should use lock washers.
What is correct?
It is the long bolt between the frame and the engine mount.
I'm grateful if anyone has a photo of a correct bolt, nut and washers.

Orjan

[Orjan S.]

Re: Engine Mounts Bolt

Mike


I have 67 JG 7th edition on page 97 it says "Each mount is secured to the frame with cadmium or zinc plated hex-head bolts without specific head marks, split lock washers and hex nuts"
It should be the same as 68-69?

[Edward J.]

Re: Engine Mounts Bolt

Orjan, what year is your car? There maybe some differences. Plating of bolts and washers,

[Leif A.]

Re: Engine Mounts Bolt

Orjan, what year is your car?

It says '67 in the heading of his original post.

[Edward J.]

Re: Engine Mounts Bolt

It says '67 in the heading of his original post.

thanks Leif. I should have seen that.

[Joe L.]

Re: Engine Mounts Bolt

Mike


I have 67 JG 7th edition on page 97 it says "Each mount is secured to the frame with cadmium or zinc plated hex-head bolts without specific head marks, split lock washers and hex nuts"
It should be the same as 68-69?

Orjan------

The same bolt, washers and nut were used for all 1963-E69. The GM #3817224 bolt was as I described above and of GM 280-M material grade (3 lines). The GM #103342 FLAT washers were "plain" finish (i.e. natural steel), the GM #272876 slotted locking nut was zinc plated.

I don't know why the 67 JG describes the assembly as a bolt with no head markings, lock washers, and an (apparently) conventional hex nut. The bolts at least had 3 lines. No lockwashers were used as assemblies with locking nuts rarely also include lockwashers. Even more surprising, while the text does say just as you mention, the adjacent photo shows a zinc plated bolt head with some sort of markings (indistinguishable in the photo) and what are obviously FLAT washers. The nut is not shown. So, the photo shows exactly what I would expect given what GM specified and what I have experienced while the text is contrary.

addendum: It occurs to me that, perhaps, the text in the JG is referring to the bolts that attach the motor mount to the block. Those 3/8-16 X 1" bolts are used with lockwashers.

[Nick C.]

Re: Engine Mounts Bolt

Orjan------

The same bolt, washers and nut were used for all 1963-E69. The GM #3817224 bolt was as I described above and of GM 280-M material grade (3 lines). The GM #103342 FLAT washers were "plain" finish (i.e. natural steel), the GM #272876 slotted locking nut was zinc plated.

I don't know why the 67 JG describes the assembly as a bolt with no head markings, lock washers, and an (apparently) conventional hex nut. The bolts at least had 3 lines. No lockwashers were used as assemblies with locking nuts rarely also include lockwashers. Even more surprising, while the text does say just as you mention, the adjacent photo shows a zinc plated bolt head with some sort of markings (indistinguishable in the photo) and what are obviously FLAT washers. The nut is not shown. So, the photo shows exactly what I would expect given what GM specified and what I have experienced while the text is contrary.

addendum: It occurs to me that, perhaps, the text in the JG is referring to the bolts that attach the motor mount to the block. Those 3/8-16 X 1" bolts are used with lockwashers.

Re: Front Engine Mount Assemblies and Ground Strap, 1967 TIMJG 7^th edition second printing

We have already submitted revised text reflecting key elements of this discussion for inclusion in subsequent editions of the 1967 TIMJG. In the frame to mount attachment, we recognize the uniqueness of the Marsden nut and tapered end bolt, as well as installation of flat, not lock washers on both ends, as listed and illustrated in AIM UPC 6 sheet B5.

Several items remain unresolved;

First, may we believe claimed as known FOEM installations include split lock washers on the 3 cylinder case mounting screws? They are not shown or listed in the AIM UPC 6 sheet B5. File photos we have, and some survey reports appear to indicate their presence.

Second, referring AIM UPC U69, sheet A3, a star washer for the ground strap is shown as expected for an electrical connection, installed between the frame and ground strap lug, yet many original appearing images and reports show the star washer installed on the screw side. Refer to image M 1-1, pg 97 of the 1967 TIMJG 7^TH edition, second printing. The significance of claimed FOEM unmolested engine installation makes this discussion quite relevant to those concerned.

[Joe L.]

Re: Engine Mounts Bolt

Re: Front Engine Mount Assemblies and Ground Strap, 1967 TIMJG 7^th edition second printing

We have already submitted revised text reflecting key elements of this discussion for inclusion in subsequent editions of the 1967 TIMJG. In the frame to mount attachment, we recognize the uniqueness of the Marsden nut and tapered end bolt, as well as installation of flat, not lock washers on both ends, as listed and illustrated in AIM UPC 6 sheet B5.

Several items remain unresolved;

First, may we believe claimed as known FOEM installations include split lock washers on the 3 cylinder case mounting screws? They are not shown or listed in the AIM UPC 6 sheet B5. File photos we have, and some survey reports appear to indicate their presence.

Second, referring AIM UPC U69, sheet A3, a star washer for the ground strap is shown as expected for an electrical connection, installed between the frame and ground strap lug, yet many original appearing images and reports show the star washer installed on the screw side. Refer to image M 1-1, pg 97 of the 1967 TIMJG 7^TH edition, second printing. The significance of claimed FOEM unmolested engine installation makes this discussion quite relevant to those concerned.

Nick------


The GM #3748038 bolt assembly used for the motor mount-to-block application included a captured lockwasher. Therefore, no lockwasher is shown in the AIM. This bolt assembly was never available in SERVICE. The captured lockwasher is a PRODUCTION convenience. In SERVICE separate bolt and lockwasher can be used and no one will ever know the difference once installed. The bolt was a rather unusual GM 275M material grade.

[Orjan S.]

Re: Engine Mounts Bolt

Thanks for all the help and comments.
It seems that Leif's thread # 4 to be the correct bolts and nuts.

Joe
Were the bolts motor mount-to-block zinc plated or black phosphate?

[Gary B.]

Re: Engine Mounts Bolt

Orjan,

Black phosphate for the motor mount to block bolts.

Gary

[Joe L.]

Re: Engine Mounts Bolt

All-----


By the way, this is the through bolt that GM says was used for all 1970-82 Corvettes. It's also the bolt that should be used when using locking-style mounts (which I HIGHLY recommend) on any 1963-69 Corvette. Of course, manufacturer's ID mark will vary. Head style and material grade markings will not vary.


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