Original long bolts for 1969 L/78 motor mounts

[nuch_ss396]

Original motor mount to engine block bolts:

Note that the left side bolts ( 3768390 ) are longer than the right side bolts ( 3748038 )
to compensate for the thickness of the stop bracket.

[nuch_ss396]

WHEW!    Glad that's over with. 

OK, now for some observations & questions:

1) Were the motor mounts assembled to the block prior to the BB painting process at Tonawanda?
    Would there have been any orange over spray on these motor mounts ( see the original mounts at the beginning of this thread )?

2) Were the BB motor mounts 3920627 ( 3937930 ) used throughout the 1969 production year?
    When were these mounts discontinued from production use?  Why do these mounts have two different part numbers molded on them?
    When was the left side stop bracket assembly discontinued from production?  Did it make it into the 1970 model year?

3) When did the BB engine frame brackets 3980941 & 3980942 replace 3950113 & 3950114?

4) Using the AIM as a reference, no part number could be found for the right hand long motor mount bolt.
    Extrapolating on the information I could find, it appears that possibly the standard 8 cylinder long motor mount bolt: 3980716 appears to be
    the correct part number for use on the passenger side motor mount of the 302, 350, 396, and 427.  See AIM – page 87.  Can someone
    reference a 1969 parts manual and tell me if I am correct in my assumption?

So sorry to all the Z/28 & L/48 guys here.  Until I got into the research on this topic, I didn't know that the these cars used a similar stop bracket.  Odd that
a thru bolt and nut assembly was used on the Z & SS and the big block used the threaded receiver.  Are there any Z/28 or L/48 owners here that can post images of
their motor mount components?  I'd like to see them for comparison purposes.

OK - I welcome responses.

Nuch

[1968RSZ28]

Nice job Steve!  I think your ready to write a CRG report on this topic...   

Paul

[Pex68]

Ok, so obviously this is a 69 only thing so I can't offer any help specifically to the parts.  Was is interesting to me though is upon looking in my AIM for 68 there is a little bracket 3945413 listed as STOP-ENG MOUNT L.H. & specific bolt called out for it 3786494.  It was added 3-5-68 so I guess that why I don't have it on my car (12D) Assuming these things (stop brackets) were GM's first attempts to cure the breaking mounts?  I clearly see how the 69 mount worked (although think it would have just ripped the bolt out as there's really not much thread contact in that 69 mount) but what the heck was that little bracket supposed to do in 68???



Also, Steve, I beleive if the AIM shows an assembly process, then it was done on the engine dress line and at that point the engine would already have been painted so no overspray on the mounts.  I looked at this way when doing mine, NO AIM process for valve covers, distributor, or bell housing and they all had overspray on them.

Wish I could help more with this...69 guys need to chime in!!!

[JohnZ]

Also, Steve, I beleive if the AIM shows an assembly process, then it was done on the engine dress line and at that point the engine would already have been painted so no overspray on the mounts.  I looked at this way when doing mine, NO AIM process for valve covers, distributor, or bell housing and they all had overspray on them.

Wish I could help more with this...69 guys need to chime in!!!

That's correct - anything illustrated in the Assembly Manual with a part number callout was installed at the car assembly plant; that's the easiest way to determine which part was installed where.

[nuch_ss396]

Makes sense - so how did they keep orange paint from clogging the threaded bolt holes for the motor mounts?

Steve

[JohnZ]

Makes sense - so how did they keep orange paint from clogging the threaded bolt holes for the motor mounts?

Steve

They didn't - there was no attempt made to mask any of the threaded holes in the block during engine painting - only the fuel pump attaching area was masked.

[nuch_ss396]

John,

Got it - thanks.

Did you ever see the engine painting process using the reported vac-forms that masked the aluminum intakes from paint? 
This topic has long been talked about over on the NCRS.org forum and is one of those research topics I am quite interested in. 

Steve

[JohnZ]

Did you ever see the engine painting process using the reported vac-forms that masked the aluminum intakes from paint? 

Yes - I worked at the Chevrolet Pilot Line, almost next-door to Flint V-8, from 1966-69 (a friend of mine ran the Flint V-8 Piston Department); Flint V-8 made the vacuum-formed plastic masks in their toolroom.

[nuch_ss396]

John,

To the best of your recollection, has anyone ever documented that process
with pictures taken during the engine painting process?  Did any of these masks
make it out of Tonawanda and into someones collection?  I'd love to see one......

Steve

[crobjones2]

Did you ever see the engine painting process using the reported vac-forms that masked the aluminum intakes from paint? 

Yes - I worked at the Chevrolet Pilot Line, almost next-door to Flint V-8, from 1966-69 (a friend of mine ran the Flint V-8 Piston Department); Flint V-8 made the vacuum-formed plastic masks in their toolroom.

John
were several different motors built at the same time?  for instance the Corvette motors alongside the Camaros?

[JohnZ]

John,

To the best of your recollection, has anyone ever documented that process
with pictures taken during the engine painting process?  Did any of these masks
make it out of Tonawanda and into someones collection?  I'd love to see one......

Steve

If I had known 40 years ago it would be important today, I'd have taken pictures . No, I don't have any photos of the Flint V-8 paint process, have never seen any, and the GM Media Archives doesn't have any either. The only photo I have is of the Tonawanda paint line, but it doesn't show the masks - the only engines Tonawanda built that used intake masks were tri-power and solid-lifter big-blocks.

[JohnZ]

John
were several different motors built at the same time?  for instance the Corvette motors alongside the Camaros?

Yes. Both Flint V-8 and Tonawanda built 300-320 engines per hour, 16-18 hours per day (one every 12 seconds), and they typically ran 30-40 different suffix codes every day, with a mixed schedule.

[Pex68]

What's the correct finish for the motor mount through bolts and nuts?  I always thought they were black phosphate but just ordered a set from AMK and their both clear zinc!!!  Is that right???  Also just have a simple "A" on the head with GR 5 marks...what's correct?  Speaking of 68 396 application. 

[firstgenaddict]

Here is an Original Early 69 Z Engine Mount, this was on the right side of the 10D 69 Z I am restoring now.
I assume the left would have originally been the same with the limit assembly including the long bolt and spacer, however this car had a later interlocked one on the left.
It also uses a threaded reciever which is blind so I have no idea what the nut reference is in the AIM.





The difference from the BB is the chunk of rubber with the threads is opposite and the BB doesnt have the elongated cutout along the bottom where the lower hole is.