How To Identify a 426 Hemi: Easy Hemi Identification

There are many ways to identify the iconic Hemi. Sometimes a quick visual inspection will tell you, how to identify a 426 Hemi?

A 426 Hemi engine is identified by its casting #2468330. It has wide black valve covers with the spark plug wires through the center. The engine has its distributor in the right front at an angle. It has two four barrel Carter carburetors mounted in tandem.

There are more ways identifying a Hemi assembled or taken apart can be accomplished. This article will cover them in detail including how to tell their different years.

How To Identify a 426 Hemi

There are many ways to identify an engine as a 426 Hemi. Let’s start with the most obvious, a quick visual identification. If that’s not enough to determine, the remainder of the article covers details unique to the engine and certain years.

A Quick Eye Examination of an Assembled Engine

A quick visual inspection to identify an assembled engine as a 426 Hemi will reveal the following four details:

A Hemi has wide black valve covers (rocker covers) with the spark plug wires leading through the middle of them.
The spark plug wires come from the distributor mounted at an angle in the front of the engine on the right side (passenger).
The intake manifold has two four barrel Carter carburetors mounted inline.
The carbs are covered by either a round chrome air cleaner, oval orange air cleaner or a shaker hood scoop.

Just one alone doesn’t make it a 426 Hemi. In some situations all four details are not enough and a further inspection must be completed.

If you’re still unsure how to identify the engine or its year, let’s examine more details about it.

426 Hemi Engine Block Casting Number

Another way to identify the engine is by the casting number. It is located on the left side (driver’s side) of the block. The numbers are raised and not stamped in.

The casting number is the same for all 1964 to 1971 Hemi blocks. The casting number is:

2468330

If there is the letter “M” at the end of the casting number, it is a Mopar block produced after 1971 during the 1990s to early 2000s. The M block won’t have a casting date near the casting number.

A generation 2 factory block will also have a casting date near the casting number. This date indicates the day, month and year the block was cast.

If the casting date is 11 21 70, it means the block was cast on November 21, 1970. However, this block would be for the 1971 model year.

The casting date year and model year will not always match. Typically, if the block is cast after July, it is intended for use in the next model year.

If the block is cast before July, then the casting year usually matches the model year of the car.

Block ID Pad

The ID pad is located to the right of the distributor hold down clamp in the front of the engine. The pad is flat and measures approximately 2″ x 3.”

The pad typically has 2 rows of stamped numbers and letters on it. The first row contains 2 letters and the number 426 like this, F H 426. In this example F stands for the year, 1970, H for hemispherical and 426 for the cubic inches.

The 426 street Hemis used the following letters for each year:

B for 1966
C for 1967
D for 1968
E for 1969
F for 1970
G for 1971

The 2nd row of numbers identify the month, day and which number engine it was built for that day.

For example, if the 2nd row was 3-17-15, it would stand for the engine being built on March 17th and the 15th engine built that day.

Other letters or symbols on the ID pad may include the following:

WT indicates water tested.
A Maltese cross on the ID pad will indicate .001″ undersized main bearings. Any numbers following the cross indicate the specific bearings that were undersized.
A Maltese cross and X indicate the same as above but .010″ undersized bearings.
The letter A on the ID pad indicates .020″ oversize cylinder bores.
A diamond symbol on the ID pad indicates all the tappets are oversized by .008″
The letters O.S. on the ID pad indicate .005″ oversize valve stems.

Most 1968 blocks don’t have the letter or 426 on the pad.

Partial Vin on the Block

Partial vin numbers are stamped on Mopar blocks beginning in 1968. It can be found on the right side (passenger) near the bottom just above the oil pan.

It is stamped on a long, smooth narrow pad. The partial vin are the last 8 digits of the car’s vin number the engine was installed into from the factory.

Having the partial vin on the block is golden because it could match the engine to the car it came in or verify it is original to your car.

The 1st number indicates the model year. For example, a number 9 would indicate the year 1969.
The 2nd digit is a letter indicating what plant the car was built.
The last 6 digits (numbers) indicate the vehicle sequence number at the plant.

1968 Hemi blocks have a partial vin number stamped at the top rear of the block near the oil sending unit. It will be where the transmission or bell housing bolts up.

Therefore, 1969, 1970 and 1971 Hemi blocks will have it on the lower side.

Some 1969 blocks may have the full vin instead of the partial vin.

Engine Identification Number (EIN) on the Block

The EIN started in 1968. Therefore, you won’t find them on the older Hemi blocks.

426 Hemi blocks have the engine serial numbers stamped on the cylinder block oil pan rail at the left rear corner below the starter opening. With the engine installed in the car, they will be facing the ground.

The engine serial number contains 14 characters and digits. The first letter or two indicate the assembly plant.

A 426 Hemi block should start with MN or MV, which is where they were built.

The engine plant codes are as follows:

MV or MN: Marysville
W: Windsor
PM or M: Mound Road
PT or T: Trenton

The next three digits are the cubic inch displacement. For a 426 Hemi, it would be 426. Therefore, a 426 Hemi EIN should begin with MN426.

The next 4 digits represent the 10,000-day calendar. This indicates the exact date it was built.

The last 4 digits or numbers of the EIN are the daily sequential number of engines built.

Having an EIN is nice although it doesn’t inform you about the car it was installed into from the factory.

Valvetrain and Rocker Arms

If the valve covers and spark plug wires were removed a Hemi may be identified by inspecting the valve gear.

A Hemi head has two shafts which the Hemi rocker arms pivot on. One shaft is for the intake side and the other for the exhaust.

The shafts are parallel to each other spaced inches apart. The four spark plug holes can also be seen in the center of the head between the shafts.

The intake rocker arms will be shorter than the exhaust rocker arms.

Older Hemi engines, generation l, look similar but can be easily identified because their distributor is located in the rear of the engine, instead of the front.

A big block Wedge engine will only have one rocker shaft due to the valve configuration.

Identifying the Cylinder Heads: Street or Race

If the heads are removed, flipping them over will reveal the large, domed combustion chambers with the valves opposite each other. The tip of the spark plug hole is in the middle of the chamber.

Other RB-series big-block Mopars and LA-series small-block engines have their valves next to each other, parallel to the camshaft, a flatter combustion chamber with the spark plug hole off to the side.

Hemi heads doesn’t have a heat crossover which the other big blocks have in the middle of the head.

The casting number of the head can help figure out which head is on the engine.

The casting number for all street Hemi cylinder heads from 1966-1971 is:

2780559

For a complete breakdown of all 426 Hemi head casting numbers, check out my article, 426 Hemi Head Casting Numbers.

Pistons

If the heads are removed the factory Hemi pistons are raised (domed) and flat at the top. The sides of the raised area are slanted for valve clearance.

Engine Block

If most of the engine has been disassembled, inspecting the following block details may help identify it as a Hemi.

The middle three main bearing caps have 4 bolts each. The extra two bolts are cross threaded in through the sides of the block visible from the outside.

Their purpose is to prevent the cap from walking. All other big block Mopars have 2 bolt mains from the factory.

The valley of the block has cast cylinder head bosses. The top four (intake side) cylinder head studs fit through the bosses and are secured from underneath with nuts. All other big block Mopars don’t have these bosses.

For intake pushrod clearance, there are recesses at the top of the valley to the sides of each boss stud hole.

The Hemi deck surface has holes for the exhaust pushrods to fit through from the lifter, through the head and to the rocker arms.

Other Wedge or big block Mopars don’t have these. Their exhaust pushrods don’t fit through the block, only from the lifter through the head to the rocker arms.

Each deck surface of the block has two oil drain back holes. They are located in the lower left and right corners.

This is necessary because of the shape of the head. A wedge block doesn’t have the oil drain holes because their heads allow the oil to drain back down the valley of the block.

An unmodified factory block has a 4.25″ bore. So does the Max Wedge but they won’t have all the characteristics described above.

Check out my article here, The Differences Between a 426 Max Wedge and a Hemi.

Any questions or if you have more information you’d like to contribute, send us an email found specifically on our contact page

For the past 40 years, I’ve been studying and researching Mopar engines like the 426 Hemi. I’ve assembled and disassembled its engine parts, read books, articles, magazines, watched videos, attended seminars and spoken to other Mopar experts.