Did metric fasteners get used on C3s?

In disassembling the interior, I keep finding that many of the smaller screws fit a metric socket better than an SAE socket, which is weird because the screws aren't rusted or rounded off, and I wouldn't have expected metrics to been in play in a 1979 GM vehicle.

 

Looks like the started to come in around 77/78.
https://www.corvetteforum.com/forums...ric-bolts.html
Keep in mind that a lot of the parts were not made by GM and those would/could be made in whatever the company that made them worked in. The gauges for instance came as a completed assembly, GM would only specify the mounting / interface sizes and not what went on inside
M

 

yes....78-82 have both! That whole 'metric initiative' that went bye-bye! Metricization

 

What about 68-77, were those still all SAE?

I keep hearing that 77 was kind of a "hybrid year" where things started to change and then 78-82 were kind of a "new C3" in many ways.

 

When I went from my ‘77 to my ‘80 was when I noticed I was running into metric sizing.

I also remember reading the word “gage” in the Owners Manual instead of “gauge.” My head exploded a little bit.
And, I remember trying to take the little plastic inserts out of the side gills and was introduced to “Torx” screws (and drivers) for the first time.

 

I was surprised to see torx screws in my 79 as well.

 

My 75 was a mixture of both....ended up buying a complete metric set to work on the car. has metric thread size as well...Ace Hardware still my favorite spot to get nuts and bolts, switched to stainless and grade 8 when I put it back together.

 

I did not find anything metric on my 68 or my 74. Metric shows up in places on my 80.

 

Although not DIRECTLY related to Corvettes, I bought a '78 Chevy Nova, brand new, and when I started tinkering with it, I noticed that it had both English and metric fasteners. So, I agree with what "vettebuyer6369" said, that the attempted "metric revolution" began in the late 70s.

 

Didn't Jimmy Carter try to push the metric system on the U.S.?

 

I've disassembled almost every part on my 75. No metric fasteners found yet.

 

I've found very few metrics in my late production '79 with nearly all of them in the cabin and all (I believe) were used in pre-built assemblies installed on the production line using SAE fasteners. The only TORX I recall are for seatbelt mounting where I believe they got their first automotive use years before.

 

I was a young engineer in a GM parts division when the metric change over was initiated. It was a corporate directive that all new vehicle programs, systems, subassemblies or components would be designed in the metric system. This occured in 75 or 76, I'm not sure which. Existing designs were not to be changed over, and were to continue using English specifications until obsolescence. For example, it didn't make economic or engineering sense to change the original Chevy V8 over to metric fasteners. I was involved with a new engine subsystem development in 1976 for a 1980 model year (start of production August, 1979). All product drawings were metric.
Drafting standards required products to be designed in "Hard Metric". Dual dimensioning (Engish and Metric) was not allowed. Of course, there were exceptions allowed in instances where there were issues relatedt to interfacing with a carry-over component.
This directive did not apply to production equipment, tools, fixtures, and gages. However, at the tool/part interface, metrification happened on an as needed basis. The extent of the production floor changeover varied by location.
And, justt for clarification, Torx fasteners are not indicative of metric threads. The Torx drive system was developed by Camcar Corporation in the late 60's to provide higher torque capability than the "Allen" head system. Torx heads were available in metric and English threads.