it will say 445 on your air cleaner if it's a 401 if it's a 425 it will say 465, and i think the 401 was painted silver and the 425 green.
look for the casting numbers here ya go Greg :beer Block Cast # Year Displacement 1169334 56-59 322 1173201 59-61 364 1174372 59-61 364 1185484 59-60 401 1185404 61-66 401 1196546 61 401 1196547 61 364 1340146 63-66 425 1346046 61-66 401 1349046 62-66 401 1354713 64-66 425 1354714 64-66 425 1364704 63-66 425 1364705 64-66 401/425 1364707 63 425 1364714 64-66 401
Got a lead on a local 425. I know little about nailheads. I assume the casting numbers are on the front on the block? What is the range of price to pay for a core 425?
Look at the top front of the block--right behind the thermostat housing on the surface where the valley pan gasket meets the top of the block. There will be numbers stamped there. On the left is the 2 letter engine id number, and on the right is the VIN number for the vehicle it was in. If it is a 425, the second letter in the id will be W or X (w is single 4bbl, X is 2-4bbls.) The first letter is the year (J=63, K=64, L=65, M=66). If it is a 401, it will have an R or a T for the second letter (T=most all 401s, R=specific code for the 401 in the '65 and '66 Skylark GS). Check out this website for all the details and a complete list of everything: http://www.buicks.net/shop/reference/engine_ident_63_75.html
In '66 The Nailhead went red. Brian the X codes were factory until late March, BUT you could still get them (duals) as a dealer installed optioned after, along with the aluminum finned valve covers. Yours is prob. a 401 unless it's a transplant, they weren't offered in '63 :3gears:
Actually the 425 was offered late in '63. I have seen with my own eyes a '63 Wildcat 4-speed car with a factory installed 425 in it. The original owner still had it when I saw it (he had it for sale when I saw it). He ordered it late in the model year and they had the 425 available. Very rare in a '63 though. It was a single 4bbl. engine. And yes, my '65 GS came with an LR code 401 in it.
Red didn't come along until '66. All 340's were red--both 2bbl. and 4 bbl. versions. All 425s were red, and the 401 only in the '65 Skylark GS was red. The 225 V6, 300 2bbl. (no 4bbl. 300 available in '66), and the 401 in anything but the skylark GS was painted green. Another interesting note--all 425s that came in '66 Riverias had a spreadbore intake and a rochester Quadrajet carb on them.
