Small Block Chevy Engine Block Casting Numbers

The information found here will pretty much cover from 1955 -93.There will be more added as time and resources permit.

By far the fastest and easiest way to I.D. your small block Chevy is to use the casting number found on the drivers side rear of the block on the top flange that mates with the tranny bell housing.Numbers are raised approx 1/8 of an inch.The are about 3/4 of an inch tall.Even though you may have to scrap greese and dirt away,the numbers may be seen plainly while the engine is still in the car.

The casting date can also be very helpfull in idententification.Found normally on the top or the right side of the same flange that mates to the transmission belhousing.(Behind & below the distributor).They can also be located on the right side of the block next to a freeze plug.You will either find an alpha-numeric date code cast right into the block between the image of two screws cast into the block,these are from the screws that held the date code plate while the block was being cast.This code I.D.s the month,day,and the year of the casting,note that this does not mean that the casting date was also the model year of the vehicle that rolled out of the factory with said engine.

While there were a pile of minor changes in the last 40 years to the small block Chevy,the basic design has remained the same for the years we are looking at on this site.

The very first small block Chevy,a 265 CID overhead valve v-8,did not even have a provision for an oil filter!The familiar oil filter boss on the small block came around in 56,along with an all new casting.

The debut of the 283 in 1957 marked the end of the 265.Chevrolet went to an new motor mounting system placing the mounts near the freeze plugs on the side of the block.The old system had mounts located on the front of the block at either side of the timing cover.

Since around 1964 most small block Chevys have had two threaded holes at the rear of the block on the drivers side near the oil filter boss.These are to accomodate the clutch counter shaft for vehicles equipt with manual transmissions.Only one of the holes are required.Some vehicles used a counter shaft located approx 6" further to the rear,thus the need for the rear hole.Early blocks have only one hole and are pretty much worthless to a vehicle that require the rear hole for their clutch assemblies.

Before 63,small block Chevy engine used a "Road Draft Tube" to ventilate the crankcase.Featuring a large hole at the top rear of the block inside the lifter valley,these blocks are from the 50's through to the mid 60's.The PCV(positive crankcase ventilation system) replaced the daft tube in 1963.The vent hole disappeared in 68 when the system was redesigned to ventilate through the oil filler tube located at the front of the intake manifold.Later engine ventilated through the valve cover.

In 62 Chevy brought out the Chevy II,or Chevy Deuce.Using an inverted front suspension,the Chevy II had shock towers in the enginebay,which put the steering arms right where an oil pan would go.This little problem was solved for the small block applications (4 and 6 cylinder applications had no problem with this configuration) with a special block with a recessed oil filter boss,and an oil dipstick located on the passenger side.The problem was done away with in 68 with a new chassis and body style.The unique 64-67 blocks are in demand by collectors due to the recessed oil filter boss.

With the debut of the 327 in 62,Chevrolet fans were in heaven.Fitted with its own unique valve cover the featured a flat spot for a decal like "327 Turbo Fire".This design was used until around 1965 and is very popular with collectors today.1956-1967,small block Chevys also used a cartridge type oil filter inside a steel canister,joining other manufacturers in 68 with a spin on style oil filter.There are adapters available to update the older styleblocks to the newer style.

Several other changes took place to the small block Chevy in 67.It was the lst year of the 283 and the first year of the 350(Camaro only).It was also the first of three years for the very famous 302 Chevy(283 crank in a 327 block)

1968 was the year that Chevy started making the small blocks with large journal cranks,greatly improving strength and durability to the crank.This also means that small journal(pre 68) cranks do not fit large jounal block(post 68)Although this change did not occur until around March or April of 68.(This writer had a Mar 68 327 that was a small journal and has a may 68 327 that is a large journal.)

1968 marked the first year of the 307.The 307 utilized the stroke of a 327 and the bore of a 283.Chevy tried again with an economy small block with the 305,most are now boat anchors to the best of this writers knowledge.

1969 brough with it 4 bolt main bearing caps further strengthening the bottom end of the small block for high performance and heavy duty applications.69 also marked the last year on the 327 as well as the 302.

Growing to it's largest factory displacement of 400 cubic inches in 1970,these block required siamesed cylinders to gain the internal space for the displacement.Extra bolt holes were also drilled into the surface of each deck to promote cooling.It is also noted that for the use of a small block 400,you also need the small block 400 heads.Most of the crankshafts and connecting rods from the small block 400's ended up with a better life as part of a 383 build-up.

Another year of change was 1986.The two piece rear main seal was replaced with a one piece unit.Displacement of the block was also cast into the block next to the casting number.

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