Casting Info and Explanation
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There are several things that identify a casting! Everybody has heard the myths! Like, 'If the dip stick is on "X" side it's a 350' or 'If the block has a tiny pipe plug just above the timing cover it's a 350' or 'ALL 400's have 3 freeze plugs'. Others include, 'All trucks have 4-bolt mains and forged cranks' and so on and so fourth. The simple truth is that most of them are just not true! So before you lay out your hard earned cash you should at least know exactly what you are getting. I can't tell you how many "350's" have been brought to me for buildups that turned out to be 305's or other small undesirable displacement engines that were bought at a "sweet deal"!
Block InfoTo give you an idea of the possible engines you can get the following two tables show the displacement, bore, stroke, years cast and other info for both big and small block Chevy engines.
The truck blocks all have forged cranks and HD rods with 7/16" rod bolts but typically have large heavy 4 ring pistons and are not desirable for performance applications. There intake manifolds are also wider. As you can see there are lots of different displacements available and that 4-bolt mains are only available on a few kinds of motors. Also not all 4-bolt mains are desirable! The 70-72 400 small block was available with 4-bolt mains but these were prone to cracking when the motor was stepped on hard over a period of time. Here a 2-bolt block is more desirable. If you just have to have a 4-bolt you can have aftermarket splayed main caps installed on a good 2-bolt block. All GM castings be it small or big block, heads or cranks, intakes or even distributors have casting dates. A letter followed by a series of numbers denotes the month day and year the part was made. The letters are first and denote a month.
The first set of numbers denotes the day and can be 1 or 2 digits. The second set denotes the year and can be 1 to 4 digits in length.
e.g. When you combine the casting number and casting date you can determine the true year and application of most castings. If you had a casting date of F238 on a block with a casting number of 3931174 you can tell that this 307 block was cast on June 23rd of 1968 since that block casting was only available in the 60's and not the 70-90 years. Blocks also have a third ID marker. Suffix codes. A suffix code is stamped into the front of the motor at the end of the head on the passenger side just above the water pump to block passage on all small blocks and most big blocks, some big blocks have this number just above the center of the timing cover in a little flat recess. This code usually has a long series of letters and numbers. Generally they start with a letter than denotes what engine assembly plant they came from. F = Flint S = Saginaw T = Towanda V = Flint H = Hydramatic K = Canada M = Mexico They are then followed by the assembly date that is 3-4 digits long. The assembly date is usually stamped with the first 1 or 2 digits for the month and the next 2 for the day. V0822 = Flint plant August 22nd. The last 1-3 digits are the suffix code. The last 1-3 digits are normally letters but some 3-digit versions include numbers. A typical suffix code was used for several years and engines in several makes and model cars. Suffix codes typically can't be the only source of ID. Also since these numbers are STAMPED into the surface they can be faked and/or modified. Also most performance enthusiast have blocks decked. When they are machined this way it removes the suffix code. |