Can You Put 426 Hemi Heads on a 440? Hemi Heads

The heads on a 426 Hemi is what gives the engine its true power. The Hemi Heads are designed for more power than 440 heads. For this reason many people ask, can you put 426 Hemi heads on a 440?

Stock 426 Hemi heads cannot be placed onto a factory stock 440 engine block without extensive modifications. This is due to the differences in the inner mounting bolt locations, pushrod locations, different oil drainage holes and water hole passages.

This article will cover in more detail the reasons why the head will not fit on a 440 wedge block. In addition, I’ll explain how Hemi heads and a 440 block were modified to make this combination work properly.

Why 426 Hemi Heads Can’t Go on a 440

Head Bolt Pattern

The inner head bolts, studs, on a Hemi are mounted through bosses in the lifter valley and secured with nuts from underneath.

The 440 block doesn’t have these bosses and the wedge block threads are in different locations than the Hemi.

Oil Drain Return Passages

The Hemi block deck has two oil drain back holes which allow the engine oil from the top of the head to drain back down to the oil pan.

A 440 block doesn’t have the return oil passages. The oil on a wedge drains back down through the lifter valley.

Water/Coolant Jackets

The outermost water jackets on the wedge block will not line up properly to the Hemi heads.

Engine Bracket Mounts

A stock Hemi exhaust manifold won’t fit properly on the driver’s side of a 440 block because their mounting ears will get in the way.

426 Hemi Heads on a 440

Although putting factory Hemi heads on a factory stock 440 is not possible, modifications have been made in the past where it got the job accomplished.

Hemi Interchange

Racers in the early 70s modified 383 B blocks to receive Hemi heads to work their way around new racing rules and regulations.

A company, Stage V Engineering, made Stage V Hemi conversion heads for years. The price of the conversion head and valve train sold for approximately $4,000 to $5,000. Additional costs were required for machining the block modifications discussed below.

The Stage V Hemi head conversion enabled modified aluminum (not factory) Hemi heads to be used on a 440 block.

Unfortunately, the kit is no longer available. It was developed during a time when Hemi blocks were harder to come by.

A Good Idea?

When I owned a 440 I thought about installing Hemi heads onto the block. I thought it would be cool and improve horsepower. I quickly realized I was better off getting a whole Hemi Block which became easier to obtain aftermarket. Also, it was not any cheaper to put the heads on the wedge block.

You can do this, but you will be better off for a street Hemi type of setup. The 440 bottom end is not as strong as the Hemi. One example is the two bolt main bearing caps.

A higher rpm horsepower engine would be better for a Hemi and less machine work on the wedge to strengthen it up.

Interchange Differences

They used a standard 440 wedge block, when mounted with the aluminum Hemi heads, appeared just like a 426 Hemi Engine.

The stock Hemi intake manifold and exhaust manifolds would bolt right up to the Hemi heads. This combo looks like a real Hemi Engine. Although it’s not, let’s look at the interchange differences.

On the lower part of the wedge block, the engine mount ears have to be modified on the driver’s side to make clearance for the Hemi exhaust manifold. This is why Hemis used different k frames and engine mounts.

Another modification to the wedge block is grinding away the valley walls to make clearance notches for pushrod clearance.

Since 440 bores are larger than a Hemi, stock Hemi pistons won’t work. Therefore, boring and aftermarket pistons to match are required.

Since the wedge block doesn’t have oil return holes in the deck, the conversion heads must use external oil return lines. This requires drilling the block and installing fittings as shown in the picture below.

Their conversion rocker gear wasn’t factory. The rockers were rollers and mounted on dual shafts. The rocker shaft mounting stands positioned the exhaust rocker shafts 1/2 inch closer to the engine centerline. This was to straighten the exhaust pushrods and move them away from the block’s lifter valley.

The exhaust rocker arms were also made longer to compensate. The valve angles and chamber volumes are identical to stock Hemi heads.

Original Hemi blocks have cast bosses on the walls of the lifter valley to accept the heads inner head bolts. Since the wedge block doesn’t have the bosses, the conversion inner head bolts are bolted from the floor of each intake port. Supposedly this doesn’t interfere with intake flow.

Those are the main differences between the wedge heads, Hemi block, Hemi head and 440 block for the Hemi interchange to work out properly.

Find out about the intake manifold torque specs and sequence in my article, Hemi Intake Manifold Torque Specs.

The video discusses 426 Hemi Heads on a 440 block.

Find out how to properly torque a factory Hemi head in my article, 426 Hemi Head Torque Sequence and Specs.

Was there ever a 440 Hemi?

Chrysler never produced a 440 Hemi. The 440 always had a wedge design cylinder head. The Chrysler Hemi head design was only placed on the 426 block from 1964 to 1971 and earlier engines in the 1950s.

I wrote a whole article on those early 1950 engines which you can check out here.

I learned about 426 Hemis and 440s by reading Mopar books, articles, watching videos, talking to knowledgeable people and attending seminars. The research and knowledge I acquired has accumulated for 40 years. The first Mopar I owned had a 440.

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