Identifying Chevy engines

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by: Cobalt327, Jon, Mortec, T-bucket23
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[edit] Overview

Identifying Chevy engines isn't that difficult if all that's needed is to know whether it's a BBC or SBC, or a six or V8, etc. But to get into the finer points requires digging deeper.

[edit] Block casting numbers and codes

Locations of Chevy V8 block ID numbers and codes

One of the easiest way to identify a Chevrolet engine is by the casting number (c/n) that is cast into the castings (not stamped). Chevy engine casting numbers has additional info including links to several sites that have casting numbers broken down to application, etc.

The Chevy V8 block casting number is generally atop the transmission mounting area of the block. The date code will usually be found in the same area, sometimes on the opposite side from the casting number, but not always.

Warning Note: It is common practice to use just the last three numbers of the c/n when dealing with casting numbers, i.e. block c/n 10243880 would be called an "880" block. Usually the last three numbers aren't repeated, but there are cases like the SBC head c/n 462 that- for some unknown reason- was reused 5 times! Fortunately this is rare.

[edit] SBC engine casting numbers

[edit] BBC casting numbers

[edit] Suffix codes

Suffix codes are stamped into a small boss on the front passenger side of the block where the head and block meet. There will sometimes be two lines of numbers and letters, later engines had just one line of numbers and letters.

Small block Chevy engines used different size pads for the engine suffix/partial VIN. Mid '70s-up blocks use the short, fat pad (top example in the picture below). Early engines use the middle pad. Blocks from the '60s through the mid '70s use the bottom pad.

Suffix pads.jpg

Beginning about 1969 the suffix code became (mostly) three characters instead of one or two.

[edit] Date code

The date code is most often found back by where the transmission bolts to the engine block, on the top side of the block.

The date code generally has a letter followed by two or three numbers. The letter is the month. The next number or two numbers will be the day of the month. The last number is the last digit of the year.

Example: C124
  • C = March (A = Jan., B = Feb., etc.)
  • 12 = day of the month
  • 4 = year ending in 4, i.e. 1964, 1974, 1984, etc.

[edit] Factory hydraulic roller SBC block ID

Hydraulic roller valve trains were used beginning in 1986. During this period, there were both roller and flat tappet (non roller) equipped engines available.

Some blocks came completely machined for a mechanical fuel pump. Others have either partial or no machining of the block to use a mechanical F/P.

It has been said that most or all of the c/n 638 blocks are ready to use a mechanical pump. In EFI applications, these engines will have a block off plate covering the mechanical pump area. Casting number 880 blocks have been seen both with and without mechanical pump provisions, and casting number 148 is mostly without the mechanical pump provision.

Blocks with a 4" nominal bore diameter (as used on the 350/5.7L SBC engines) that are equipped to use the factory hydraulic roller valve train, are casting numbers:

  • 10243880 (common casting number of a 5.7L Vortec engine)
  • 14011148
  • 14088526
  • 14093638

Some of the 1986-up Chevy small block engines used flat tappet (i.e. non-roller) cams. 350 cid/5.7L flat tappet blocks are casting numbers:

  • 10054727
  • 14079287
  • 14088548
  • 14101148

These flat tappet blocks may have the provisions for a roller cam (i.e. bosses present and drilled/tapped for the spider and for the cam plate, etc.), but also may not be equipped with the drilled and threaded bosses needed to use a factory roller valve train. In any event, these blocks originally had a flat tappet cam and non-roller lifters, no spider, and no cam thrust plate. These blocks are fine if you don't care about the roller cam.

Warning There is a flat tappet block and a roller block with casting numbers that both end in 148. 14101148 is a flat tappet truck block, 14011148 is a roller provisioned block.

[edit] Vortec block cylinders

The newer Vortec era blocks (1996-up) have a slightly shorter bore at the bottom, nearest the cam tunnel, as shown below left. This isn't a problem in most cases, but if a stroker crank is being considered, this should be looked into to be sure there'll be no issues due to the lack of piston support at BDC.


[edit] SBC Head casting numbers

[edit] Dampers/balancers

[edit] SBC

The earliest SBC 265 dampers had a riveted on crank pulley (red arrow) attached to a steel hub, as shown below.

SBC 265 damper hub with attached pulley, front
SBC 265 damper hub, back

On other SBC engines, including internally balanced stroker engines, the dampers are neutral balanced. The differences will be in the location of the TDC line, weight, thickness and diameter of the dampers.

On the 400 SBC and externally balanced stroker engines, an OEM damper will have a scalloped portion to the outer ring which is easily seen. Aftermarket dampers usually use a bolted on counterweight, which is also usually easily seen.

Not as easily seen is the gap or void in the SBC 400 main bulkhead webbing.

OEM 400 balancer. Note scalloped outer ring
Void in 400 main webbing

[edit] BBC

[edit] Damper/balancers

The 396/402 and 427 ci BBC engines were internally balanced. The 454 BBC engine is externally balanced. The 454 can be ID'd by the balancer having the inner hub cast with an integral counterweight (see image below). A 454 will also have a different flexplate/flywheel, having an added counterweight that is missing from the other displacement BBC engines. Like the SBC aftermarket dampers, the counterweight of a 454 damper might be bolted to the hub.

BBC 454 balancer with inner ring scalloped

[edit] BBC notched bores

A BBC block may have bores notched to clear the intake valves. Not present on all BBC engines. BBC 454 BLOCK NOTCHED BORES.jpg

[edit] BBC external cues for 2- or 4-bolt bottom end

While not 100%, a Mark IV BBC engine can sometimes be ID'd for being a 2- or 4-bolt bottom end by looking above the filter mount: Bbc 4-bolt vs 2-bolt fittings id.jpg

[edit] 396 block boring

Some 396 blocks will take an overbore to 4.250". One way to tell if the block has sufficient metal to do this is by removing a center freeze plug from the side of the block, then see if a ~1/4" wooden dowel (a pencil will do) will fit in between the cylinder jackets. If it fits the walls are probably not thick enough to bore to 4.250".

Warning Note: This is not meant to be a replacement for sonic testing the bore thickness. It is only to judge whether the block is a candidate for sonic testing.

[edit] Tall deck BBC

The 10.2" deck height tall deck (TD) BBC was made in two different sizes: 366 and 427 cid. These engines were made to stand up to heavy duty use like bus and dump truck, etc. right up to where a diesel would be used. The tall deck height was to facilitate the height of the four ring piston used in the TD BBC engines. The bottom ends were forged and the rods were heavy duty-and heavy in weight.

These engines can be made into good performing engines without going to too much trouble or expense. Here is a thread showing a budget build up of a 427 tall deck BBC.

If the engine is assembled, the stock intake had two thermostats on it and the intake is also wider due to the taller decks. The distributor is different and may have a different oil pump drive arrangement.

One of the easiest ways to tell a tall deck BBC block from a standard 9.8" deck height BBC block is to check the distance from the top water pump bolt hole to the block deck. A standard block (below left) will have very little space between the hole and deck; a tall deck block will have around 1/2" between the hole and deck (below right).

454 deck.JPGBbc tall deck.jpg

[edit] BBC 502

A production Chevy 502cid block can be a Gen V or VI. It will have "8.2" cast into the block, and will have 4-bolt mains with a one piece rear main seal.

A 454 bore diameter will be about 4.25". A 502 will be about 4.5".

[edit] Resources

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