Editing Identifying 455 Engine

How to figure out the age of and type of Oldsmobile 455 engine:
Info gathered from the web on Sunday 14th March 2010


http://www.442.com/oldsfaq/ofe455.htm
General Information
Note: The information contained in all of the "Engine Detail" sections should be read before proceeding with modifications, etc., because some information that applies to all engines, or all small blocks or all big blocks, might not be duplicated in every section. 
The 455 was built from 1968 through 1976, produced from 210hp to 400hp, and were installed in just about every car Olds built in that period at one time or another, including the Cutlass/442, Delta 88's, 98's and Toronados (not the Omega, though). You can get a quick estimate of the year of the engine by looking at the 1" high casting letter on the lower-left corner of the block and/or head. 
If the engine is one of these high-performance motors, it's pretty easy to identify where it came from. If not, it's a little tougher. 
Other clues for identifying the engine, especially the later engines, are the carb numbers (stamped on the driver's side of the carb, usually something like 7040251), as the emissions regulations required carbs calibrated for the specific requirements of a particular model (basically 1973 and later), whereas all models before 1973 used the same carb numbers (again, aside from high-performance and Toronado engines). Likewise, the distributor number might be specific to the model it was installed in. 
The exhaust manifolds would also provide a clue as to where the engine was originally installed. If the passenger-side manifold has two openings, it's a single-exhaust application, and likely from an 88 or 98. 
Year Differences 
According to my trusty Olds engine book, the 455 was available in 310 hp, 320 hp, 365 hp, 370 hp, 390 hp, all street engines, with full manufacturers warranties. The 455 is a very forgiving and long-lasting engine. To eek out more HP you can go with higher compression, which will prevent pump gas usage (highest stock 455 comp. was 10.5:1). To achieve this, use flat top pistons (butterfly cut), milling heads, and decking the block. This will yeild CR in the 14 range. However, you have to pay for it in wear and tear. 
455 engines through the years have some differences. Some have lower compression pistons, not an issue if you are getting new ones anyhow. Later blocks, typically with an Fa casting ID have lost the boss where the clutch z-bar used to mount, which affects only manual trans applications. If you are using it in AT car, all 455 blocks are pretty much fungible for street use. Rumors of rear-face "F0" etc. codes having more nickel, but no one can seem to document that. Some are more likely to have a Nodular crank, might even have a forged crank. Not likely though. 

http://tech.classicoldsmobile.com/38.shtml
Big Block Unit Numbers
Pre 1968 engines also had an engine unit number stamped on to the machined pad at the front of the RH head. I believe that the Toronado 425's started with a T rather than a V. 
V 001001 1965   400 442's
V 100001 1966   400 442's
V 200001 G 1967 400 4V 442's, including W-30
V 200002 1967   400 2V 442's, [etc.?] Turnpike Cruiser 
1968 and up engines had an engine unit number stamped into the oil fill tube, the first digit of which will match the last digit of the car's year: 9012345 would be a 1969 engine [or 1979 small block]. Since this part is easily removed or replaced, use it for an indication, not a standard. No point in mentioning the oil fill tube decal with a 2-letter engine ID code, which is 99.99% of the time long gone, and easily replaced or faked anyway. 
Also starting in 1968, the VIN derivative of the engine's original car was stamped onto the vertical machined pad on the left side of the block, at the front, just under the head- block interface. It might look like "38M203456", where: 
3= Oldsmobile, GM's 3rd division [1=Chevy, 2=Pontiac , 4=Buick, etc.] 
8= year of issue last digit, like on oil fill tube [8=1968, 0=1970...] 
M= build plant [1, E, G, M, R, or Z; see below], and 203456= the last 6 digits of the original car's VIN. 
Build plant info was also used in the car's VIN plate [1 character] and body tag [up to 3 letters]. Some build plants were: 1 or OS= Oshawa, Canada, eh?; B or BA= Baltimore, MD; E or BL= Linden, NJ; G or FRA= Framingham, MA; K or KC= Kansas City, MO; LA, LAN, or M= Lansing, MI; R= Arlington, TX; BF or Z= Fremont, CA; 
That'll help ID the block year in case the heads are not original. 
For the purists: on the back of the block, near the distributor, is a 1 to 3 digit cast number, digits about 3/8", which is the Julian day of the year on which the block was cast [1 to 365]. It will generally match the Julian Day code cast into the heads, crankshaft, water pump, thermostat outlet, etc. within a few [up to 20-30] days, and precede the car's date of build by up to 30-40 days. 

Big Block Blocks 1965 - 1976


Big Block Identification
1.	A big block measures 14" between the heads at the manifold base. 
2.	Facing the front of the engine, at the top surface of the timing chain area, to the left of the oil fill tube, there is a code about 1.5" high followed by the casting number. A letter indicates a big block, a number indicates a small block. 
3.	Big blocks have a little hump in that area, whereas the small blocks are flat the whole way across. 

ID/                      Casting
Code   Year(s)     CID   Number   Notes
  A    '65         425   381917?? 1st year, big cars.
                         386525
  B    '65         400   389298   442 only, one year only.
  D    '66 - '67   425   389244   Big-car engine. Toro is different internally.
  E    '66 - '67   400   390925   442 engine [VERY rare].
  F    '68 - '72   455   396021   Most common big block. Two types of "F"
                                  letters: stick type, and one with two vertical
                                  hangers and a base.
  Fa   '72 - '76   455   396021   Very common big block.
  G    '68 - '69   400   396026   442/Vista/etc. engine.
  L    '76         455   231788   Motorhome, maybe marine also. GM made motorhomes
                                  from '73-8, maybe in all?
 Please refer to the Engines section as well! 
Look for the casting number and letter on the horizontal shelf right behind the water pump, just to the [driver's] right of the oil pressure sensor. The casting numbers are usually about ¾" - 1" tall, and the ID/Code is usually a bit larger, a little over an inch, and covered with schmutz. The most common block will be the standard 455: "396021 F" or "396021 Fa". The "a", as in Fa, is actually an upper case A, but about ¼ as big as the F, and subscript to the F [set lower]. Also, on the 231788L block, the "L" is the same size as most of the rest of the digits, whereas the center "7" is noticeably smaller. 
400's were bronze in color, most 425's and early 455's (1968, 1969) were red, while Toronado 425's and later 455's were blue. However, since engine color may have been changed, use this as supporting evidence only. 

Why Get a Toronado Engine?
Toronado engines were generally the cream of the crop; equivalent [or very nearly] to the 442 and W-30 engines, yet often priced the same as more common and lesser quality engines in the junkyards. Equipped with the best parts- aluminized valves, closer tolerances, etc. 
For instance:
·	Big valve heads, thru 1971 anyway. 
·	Highest compression pistons. 
·	Oil deflectors ['windage trays'] were used thru 1972 or so. 
·	Deeper oil pan holds an extra quart. 
Drawbacks to a Toronado engine: The oil filter mount will not fit other bodies; easy to change. The dipstick is slightly different in markings: the Full mark is the same, but the Add mark is about ¼" lower. Exhaust manifolds are not useful for any other application. 
[ Thanks to Chris Witt for this information ] 


How to Tell If It's a Toronado Engine
Several clues are built in to identify a Toronado engine. If it's in a Toronado engine bay, that's a good indication. Toro's usually have a very lo-rise intake manifold; the carb appears sunk in about an inch below the normal position. If it's a pre 1968 engine, the engine ID stamped into the front of the RH cylinder head will tell. The Toro oil pan has a unique shape- it's narrower side to side in the sump area, an inch taller, and there's a clearance 'dent' just in front of the sump, where the RH drive axle passes under the engine. Also, the oil filter mount is angled quite forward, and one of the attaching bolts is quite long [about 3"]. 
Other evidence would be exhaust manifolds, if still attached, likely to have a letter code from the early alphabet, like D, H, G, J... and will point more up and out than a typical A-C bodied car would have room for. There might still be a motor mount attached to the timing cover, behind the harmonic damper. If the heads are off, say, for inspection before sale, measure the intake valves. That's what you are really after, anyhow. If the pan is off, check for the Toro windage trays on the front main cap and on the #4-5 main cap, as well as the crank scraper which runs down the RH side of the oil pan.