The 1947 - Present Chevrolet & GMC Truck Message Board Network - View Single Post - when did GM put catalytic converters on Sierra 305s?

68GMCCustom · 01-06-2011, 10:39 PM

Don't feel like your alone...had some doofuss try to tell me the same for my '68! I had to laugh at the whole shop...as non of them knew it was 1975 models (for some '74) when things changed and regular leaded fuel was on its way out and unleaded was getting its start. Yes, from 1975 to 1980 there were both 1/2 tons and 5/8 tons (Big 10 and Heavy Half) sold. 1/2 tons had all the smog stuff....the 5/8 tons got HD hardware and no emissions.

01-06-2011, 10:39 PM	#12
68GMCCustom Truck and auto performance nut Join Date: Feb 2007 Location: McKinney,Texas Posts: 3,848	Re: when did GM put catalytic converters on Sierra 305s? Don't feel like your alone...had some doofuss try to tell me the same for my '68! I had to laugh at the whole shop...as non of them knew it was 1975 models (for some '74) when things changed and regular leaded fuel was on its way out and unleaded was getting its start. Yes, from 1975 to 1980 there were both 1/2 tons and 5/8 tons (Big 10 and Heavy Half) sold. 1/2 tons had all the smog stuff....the 5/8 tons got HD hardware and no emissions. __________________ Kurt - '68 GMC short step - NIB '09 LY6 6.0L crate motor w/mods, NIB '12 crate 4L85e w/billet 3k stall Circle D, 3.73 posi 12 bolt, DynaTech f-swap headers, 3/4 drop, handling mods, etc. - my toy '72 Chevy LWB C-10 Highlander - 350/350 ps/pb/tilt/ac - not original but close '06 Chevy TrailBlazerSS - LS2/4L70e - little black hot rod SUV - my DD '18 Kia Sorento - wife's econo-driver '95 Chevy S10 - reg cab shortbed, LS, 4.3, auto... my '68's powertrain and chassis build -links broken A surprise phase - carb to efi -links broken