There have been many stories about these covers, from it being some kind of "Scotchman Special"
to having something to due with the "thriftiness" of the new 305E version of the V6 engine.
The Plaid covrs are found on some of the GMC Trucks built in 1963. They show up from all
The assembely plants & and through out the run. If you have a look at the
1963 VIN Listing
you will see they are scatered about in no real order, so it's a wild guess as to which trucks
built in 1963 will have the Plaid covers. The truck on the list with Plaid cover will have *.
The following is told by Jeff Middleton:
I came across your site while trying to verify a rumor I'd heard about the plaid valve covers.
A GMC owner near my dad said that there was a recurring problem with the valves or rocker arms
(I don't remember which), and that it was a warranty issue. He said that owners were bringing
their trucks back to dealers more than once for the same issue, so to identify trucks that had
already had the repairs done, they swapped the OE painted valve covers for the plaid ones. As I
said, I heard it from a friend, and haven't yet been able to verify the story, but that's what I heard.
The following is told by Bob Bray;
There was some discussion on the 305 plaid valve covers. They had long been a big mystery
to me as well, but I think I may have stumbled on an explaination some time ago. I was talking
to a retired G.M.C. truck engineer (I think it was Don Meyer that I heard this story from!) who
worked all through the 1960's and I asked him about those colorful valve covers and if they really
ment anything. He said that as you know, the V-6 had a reputation of not being an economical engine.
Many light truck customers, particularly those who had bought early 305A 1bbl. pickups, were not
pleased with the fuel economy. G.M.C. sought to improve the economy of the 305 in light duty trucks,
and was dyno-testing 305's with different carburetion and camshafts. Engineers in the dyno lab
identified the improved engines by putting adhesive shelf paper on the valve covers, and wouldn't you
just know it, 'Scotch Plaid' was what they were using. One day, some guys from marketing saw these
engines being tested, and though it would be a great marking idea to actually build them that way.
If you have a story as to why GMC used the Plaid design on the covers, I would like to hear it.
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Information About GMC Truck Drive Trains
GMC Big Block V6 |
1960-1966 |
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