How do you tell the defference between a hi or low compression 400/430/455 motor just looking at it compaired to a 350.I'm wanting to change over to a BBB in about a year from now I will be checking a local salvage yard that has alot of older cars soon. Thanks, o No:
a year one catalogue in the front has the stamped codes with the horse power ,compression and torque ratings :Smarty:
But if you don't have the book handy, here is some tips. First off, all Big Blocks have five bolt valve covers, 350s have six. All have the distributor in front. Now you know your looking at a big block. All 400/430/455 have the engine size printed on the top rear of the engine on the little valley between the two top tranny bolts. If its a 400 or 430, its got high compression pistons. So now you read it and it says 455. It can only be a 1970 through 1976. Is it Blue? Its a 1975 or 1976. Is it Red and does it have smog rails on the intake manifold? Its a 1972 through 1974. No smog rails? 1970 or 1971. This is a simple "At a glance" Formula to help you narrow it down. Consult that book or ask here when you are closer. Good Luck!!!
the sixth digit of the VIN number will tell you the year of the car from 67-76. the 'high compression' motors would be the 1967-69 400s/430s and the 1970 455. these will have two digit block codes with the first digit ranging from 'N' to 'S'. a valid code will look something like 'NR' to 'SF'. the oversize Stage valves only get you ~1/2 point and the standard 455 in 71 dropped to 8.5:1. if you want Stage valves ... first of all, good luck. second, you'll have to check the block for a two digit code ending in 'S'. it will be 'SS' to 'ZS' for the 1970 to 74 engines. the 67-69 400 and 430 were not available with oversize valves (shrouding issues with the smaller bores) and the Stage option was discontinued after the 74 model year. the first digit of the block code is for the year, the second digit is the application. some of the Riv's and Centurions are supposed to have shipped with oversize valves but there isn't any way to tell without pulling the heads and looking at them ... head casting #s are the same for normal and Stage heads. on the plus side, you can put Stage valves in ANY standard 400/430/455 head and as long as you pay attention to the water passages between the block and head you can use that head on any 455 block. do you intend to keep your engine fairly stock or are you going to be putting some money into it?
Something Buick fairly stock under $1500 325-375hp good sounding cam with headers is good enough for me. :3gears:
