1958 Heater Hose Routing

[Jack M.]

For anyone that might be interested, I found this drawing in an original 1958 Corvette AIM.
Itz a 'Supplement to Deviation', with a date of 12-19-57 (highlights & notations added).
This may give owners some insight into early 1958 production changes.

1958 Corvette AIM - Suppliment to Deviation (12-19-57).jpg

[Richard M.]

Re: 1958 Heater Hose Routing

Jack, Very interesting find.

It would be good to hear from owners of the 1958's if any have that 3741203 bracket installed. Likely early cars.

Rich

[Jake M.]

Re: 1958 Heater Hose Routing

Was the change due to moving the hood support from right to left side?

[Richard M.]

Re: 1958 Heater Hose Routing

Was the change due to moving the hood support from right to left side?

Jake, Not directly. The Deviation Title calls out the reason because the generator moved to "new forward" location near mid production.

This new location also according to Dan Holstein's document on page 1 & 2 HERE.

But this was also done around the same time as the hood support moving over to the left, so yes it is somewhat relative to the hood support change.

What is confusing is on the Deviation sheet, that lower bracket has no reference part#. We think that's the one that mounts to the lower forward generator manifold bracket mounted under like all later cars, but unsure, as the depiction doesn't even show the generator.

The main purpose was to move the heater hose routing. They moved the 2 hoses more forward by rotating the 3741203 clip 180*. That clip never shows up in the AIM, only the lower one, a different part # because the mount hole is very large for the bolt that attaches it. The upper clip is held by a screw, also holding the fresh air hose bracket.

Until we find some original "early" cars with this hose routing and upper clip and hose position, the mystery will continue.

Rich

[Jake M.]

Re: 1958 Heater Hose Routing

So 12/7/57 would mean 1710 '58s had been produced.
Would this mean we're looking for those in that range?

[Jack M.]

Re: 1958 Heater Hose Routing

Jake- Since the deviation is dated 12-19-57, and they were still awaiting the revised bracket to be manufactured/tested/supplied... I was speculating that the earlier 3741203 clip, as well as the 3752946 bracket, could possibly be found on 25-30% of 1958 Corvette production.

[Jake M.]

Re: 1958 Heater Hose Routing

What would be the definition of "early"?

[Jack M.]

Re: 1958 Heater Hose Routing

Jake- I must confess... I know next to nothing about C1s. After purchasing the AIM (which I believe is an original), I found this drawing in the contents. Unless there was a previous hose routing, why wouldn't every 58 Corvette built prior to the 12-19-57 deviation drawing, be configured with the parts noted? Again, I'm just providing the documentation for review and consideration... as I don't believe this has been addressed in the past.

[Richard M.]

Re: 1958 Heater Hose Routing

What would be the definition of "early"?

I used the term "early" but.....

EDIT- New information coming....
I'm now thinking that maybe only a certain "unknown" quantity of cars in the December/January timeframe may have been built with this deviation, as we don't know when the "revised bracket" was actually available. The deviation doesn't state the part# of the revised bracket either.

The 3741203 bracket does not show up on any 56-62 AIM. In fact, it doesn't show up on any parts list for 56-62 Corvette either. The only reference I ever saw was for a 1967 Camaro with C60. AIM PDF HERE

C60 page showing the Clip here. Item# 2.
Screenshot_2022-12-19-11-28-54_resized.png

The 3741203 was superseded to 3825416 in 1979. HERE

Ref 1958 AIM Heater Hose page(attached below)

Rich

[Richard M.]

Re: 1958 Heater Hose Routing

Jack and I spent some time reviewing this and we believe we came up with some new information. This is speculation, but it makes sense. We had concluded that cars from the start of production had 2 unique parts until some time in late December or early January. This would therefore show two different configurations of this area.

Additionally, the above deviation would also mean that a third configuration would also have occurred, between Early and Later builds.

Opinions welcomed.

Jack found the document he posted at thread start in a original AIM he acquired. This is a example of a special note for the production floor. Here's the AIM Deviation as Jack found it, hidden away in the AIM.
1958-59 Corvette Assembly Manual-11.jpg

THEORY:
From the beginning of 1958 production, we believe that the 3752946 Fresh Air Hose Bracket and 3741203 Clip was used on all cars, until the 3753930 revised bracket became available. Some time after this Deviation was written the new bracket arrived on the production floor. This new bracket had a relief to allow the hoses to pass under it, which also deemed the 3741203 clip unnecessary. Note that the 3741203 Clip or the 3752946 Bracket was never available in service. It was only used in production.

As the Deviation shows, the 3752946 bracket lower area just above the mount screw was flat and also used the 3741203 Clip, both attached to the inner skirt with a screw. On all of these first built cars, the Clip was positioned at the 3 o'clock position as shown, with the hoses routed to the right of the mount screw.

The Deviation was written to move the clip/hoses to the left of the mount screw to the 9 o'clock position. Notice the dashed lines for the hoses and the note "existing". The description states to move the hoses to clear the Generator when it moved forward, a known production change, however, the actual date of the generator change is uncertain. These changes happened simultaneously. Once the generator moved, the hoses and clip had to move. So one can ascertain that the generator likely moved forward at the same time in December when this Deviation was written. I've added a few notes on Jack's image to help the explanation.
1958 Corvette AIM - Suppliment to Deviation (12-19-57)Mod.jpg

This is what the new 3753930 bracket looked like(reproduction shown), with the noticeable relief for the hoses to pass underneath.
CC_3753930mod.jpg

SPECULATION - REASON FOR THE DEVIATION:
The rear pivot mount of the generator was likely too close to the clip and hoses after it moved forward.
Here is a generator showing the pivot mounts. The rear pivot is shown at the left.
GeneratorPivots.jpg

Here is a view of a 1960, which also would be similar to the later 1958 after the Generator moved forward. I've simulated where the clip would be, by showing the plane of the the generator rear pivot(yellow line), and the area where the hoses & clip would have been before the deviation. The clip would have likely interfered with the pivot.
1960_2Mod.jpg

Here's a reference photo of the above car before assembly. It's a tight area in there once all items are there. You can see the holes where the lower screws for the 2 brackets are installed.
1960Misc.jpg


Once the new 3753930 bracket was available, and since the 3752946 was removed from assembly operations, it was decided to also remove the 3741203 clip. The hoses now were held under the new bracket.

However..... If you look at the 1958 and later AIMs, it appears the new bracket is shown, with its relief for the hoses, and the clip removed, but the hoses are not routed "under" the new bracket. We believe this is a error in the AIM.
1958AIMHoses.jpg

Here's a estimated timeline for these events

• Generator moved forward 3/4", likely in the Dec 1957 timeframe.
• Dec 19, 1957 - Deviation written to gain generator clearance. Move the hoses and clip more forward until new bracket is available.
• New 3753930 bracket now available for production. Possibly late December 1957 or January 1958?
• Production now uses 3753930 bracket. Clip 3741203 removed from production. Hoses routed under the new bracket.
• All 1958 to 1962 cars are now configured this way in production. 3753930 bracket now available in service.

SUMMARY:
Since this appears to be a official GM document, albeit hand written, it may shed new light on the configuration of early 1958 production regarding the subject area.

If you have a 1958 built before the December 1957 timeframe, please share the information on your cars configuration in this area. If we can show that THREE configurations exist, we can publish this for future review with the appropriate Judging personnel.

Configuration 1 - Early builds - Start of production to Dec 1957. Generator in early(not forward) configuration. Early(flat ended)Fresh Air Hose bracket and clip used. Clip at 3 o'clock position.

Configuration 2 - Dec to ?? builds - Generator in 3/4" forward configuration. Early(flat ended)Fresh Air Hose bracket and clip used. Clip at 9 o'clock position. This is the Deviation build timeframe.

Configuration 3 - Late Dec/Jan beyond builds - Generator in 3/4" forward configuration. New Fresh Air Hose bracket used. Clip removed. Deviation eliminated.


Thanks,

Rich & Jack

[Jack M.]

Re: 1958 Heater Hose Routing

GREAT job, Rich... THANX for all your help and work on this thread.
With any luck, we can bring more insight into early 1958 production changes.

[Richard M.]

Re: 1958 Heater Hose Routing

Glad to help Jack. Always fun to learn more about these cars.

I found one of my original Fresh Air Hose brackets in my pile of parts. It's the smaller front bracket, part#3746149. Note the original manufacturers stamp - AAC
0502231137_resized.jpg 0502231138a_resized.jpg

I'd suspect that stamp will also be found on the 2 other original versions of the rearward brackets.

Rich