Re: More 840 head questions...
2.19/1.72 was the high performance valve package for rectangular port closed chamber cast iron heads until the 1970 model year when the 291 head was introduced. I don't know where the machine shop came up with a 1.88 exhaust, but I have never seen anything but a 1.72 in a pre 1969 cast iron head.
Your other question is a bit more difficult to answer. Did Chevy start using 291 heads during late 1969 (1970 model year)? I've never seen them on an original car and I've asked several other people who deal with these cars on a regular basis if they had seen 291s and their answer was "no" as well, but they didn't see a reason why it couldn't happen either... Obviously, you're right at the change over point so it is certainly possible.
Two points to add to the discussion...
I recently had a chance to look at a very low mileage 1969 L-71 Corvette at a show in MO. The car was in the 38,000 VIN range (very late build - it started down the assembly line on December 17, 1969) and had a little over 5,000 miles on the odometer. It had 840 heads although I have no idea what the valve size was.
What heads were used on the 1970 L-78 engines (don't have my resources handy)? What valve size? I had heard that only the LS-6 cars received the big exhaust valves anyway... Is this true or just urban legend?
Regards,
Stan Falenski
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