got the 10024361(67cc chamber/165 runner)Dart iron eagles installed to replace tired old '624s: running good now after a little trouble on the first shakedown run-discovered stainless steel valves don't play well with iron guides-they will gauld and stick in iron guides-use bronze guides for SS valves...used chrome stem valves 2nd round MK2 Vortec stem seals fit iron eagle iron guide heads,and the rocker cover gasket surface is raised ~1/2" vs original heads,so plenty of clearance under the '84 magnesium covers for roller rockers.Machine work perfect on these heads including the valve jobs.Used #1094 shim gaskets for tight quench and no rattling when engine lugged-probably ~9.5 c/r with the stock TRW forged flattops.Does seem to be minor performance improvement idle-4000,but will see about higher RPM once weather clears again.

 

What is a "MK2 Vortec"?

 

-2nd gen Vortec,96 up-1st gen would be '87-95 "swirl port "vortec" The Iron Eagle heads have similar"heart shaped" chamber design to 2nd gen Vortec

 

Did GM or the Chevrolet Division use the "Vortec" name for any V-8 prior to the 1996 5.0 and 5.7 versions?

So far as I know, prior to '96 model year, the only "Vortec" was a V-6. The swirl-port LO3 and LO5 that you describe were never called "Vortec", and Chevy never called the '96 L31 or the 5.0 stablemate a "MK2"..

Am I wrong?

 

GM Marketing has called the swirl port heads "Vortec" since 1985.

 

here and there you will find discussion on pre-1996 "Vortec"SBC heads-my '06 Canyon has a "vortec 2900" The SS valves used in the ill-fated 1st shakedown were Ferrea-can say those can take a lot of heat-had to get a rosebud torch tip in the port and heat it bright orange hot to straighten it enough to get the keepers off-bought another exhaust valve to have complete set to use in a future bronze guide head someday.Used Melling valves 2nd time-those made in Brazil,about as good as you can get these days.