[Durney]

I've found multiple threads here and excellent data within the Corvette restoration community that implies the very early 71 big blocks may have left with chrome valve covers.
Tonawanda clearly built these simultaneously and there's no reason they wouldn't have continued until supply/changeover was complete.
When I purchased my 71 I was lucky enough to have contact with the son of the original owner and retrieve info and some missing parts. One thing I left behind was chrome VC because I just "knew" they were incorrect(and very rusty).

The question is ....when did they stop? NCRS seems to use the 5900 number which puts it in first week of Sept.

Any Data here that can be shared ?

 

[Cam]

I tend to think the Corvettes had chrome v.c. phased out in '71 (BBC vette chrome v.c. usage confuses me a little).
As for '71 Chevelles, I say NO to factory chrome valve covers. IF they actually made an LS-6 Chevelle in '71, it would've used the chrome versions.

 

[zookpr]

Chome covers were not unique to the LS6 in '70. All factory '71 LS6 vettes that I have seen had painted covers.

 

[Durney]

There are numerous documented original 71 Corvette LS5 (and 6) with original chrome covers. They are accepted and correct up to the first almost 6000 cars built.

 

[Shift4x]

Yes, early 71 LS5’s came from Tonawanda with chrome valve covers (non notched left side used on Chevelles as Corvettes would have a notched valve cover for clearance reasons). I have a 3rd week production Chevelle with original chrome valve covers. My S/N engine was assembled prior to start of the 1971 production run at Oshawa. As far as the cut off date, that I don’t know, but some were given the Chrome treatment.

 

[Cam]

Those are interesting points. A 3rd week production Chevelle from Oshawa no less.
In the early big block years Oshawa would sit on a batch of engines from Tonawanda as the big blocks were fairly rare in Canada and would trickle them off. For instance, for 1965 they were putting 409s (very few) into big Chevies & Pontiacs in Oshawa until depleted, right to the end of build-out.
The situation was changing in Oshawa by 1969 as more cars were going both ways across the border. Allocations to factories were being rationalized. I figure it would have changed the way they drew on engine stocks.
Ste. Thérèse in Quebec was something else again... They built U.S. spec B-bodies for U.S. sales. This was done to offset what was coming into Canada from the U.S. in the form of Cadillacs, Electras, GS400s, 98s, Toronados, 4-4-2s from Michigan or wherever, plus later all those lovely COPOs from Baltimore. (Ste. Thérèse built 40 SS427 coupes for '67.)

I'd love to hear from some judges or from former members of ACES or NCOA on this. GM was into saying in print that models, prices and equipment are subject to change without notice.