Knowing the deck height may help when modifying the engine or doing a stock rebuild. Let’s answer, what is the deck height of a 426 Hemi?
The deck height of a 426 Hemi is 10.725 inches. The deck height is the distance from the centerline of the crankshaft to the deck surface of the block. It is the same for all the years it was produced, from 1964 to 1971.
This article will show you pictures of the block deck height. In addition, I’ll include the connecting rod length, stroke, the rod journal size and the main bearing journal diameter.
426 Hemi Deck Height
The 426 Hemi deck height of 10.725 in. is the largest height block of all the common big blocks during the muscle car era.
It shared the engine deck height with the other Chrysler RB blocks (tall deck) and was more than the low deck engines.
The deck height measurement is shown in the photo below.
Deck height can also be described as the distance from the center of the main bearing bore to the flat surface of the block where the cylinder head installs.
The deck or block height of an engine dictates the connecting rod length, crankshaft stroke and the piston compression height.
The following table indicates the 426 Hemi deck height, rod length, rod journal size, stroke and main journal size:
|426 Hemi (1964-1971)|
|Block Deck Height||10.725 in.|
|Connecting Rod Length (Center to Center)||6.861 in. (6.859″-6.863″)|
|Crankshaft Main Journal Diameter||2.75″|
|Connecting Rod Journal Diameter||2.375″|
During a standard rebuild of your original, unmolested Hemi, the deck height isn’t a critical measurement.
If the block was previously rebuilt and the deck surface was shaved (decked), the height is more important. This will affect the piston to deck clearance and the quench.
It’s a bigger concern in higher performance engine builds using stroker cranks, longer connecting rods or custom pistons.
The last thing anyone wants is the top of the piston getting to know the cylinder head by making contact. This may occur with the incorrect piston to deck clearance.
How is Block Deck Height Measured? 426 Race and Street Hemi
The most accurate and recommended way is to have it measured at a machine shop. All the cylinders should be measured because the height will vary between them.
Home builders will often measure the deck height in the following manner. Using a dial bore gauge and 12″ calipers:
- Install the main caps without the bearings.
- Measure the main bearing bore and divide it by 2 to find the radius.
- Hook the caliper jaw on the main bearing bore.
- Measure up through the cylinder to the deck surface.
- Add the caliper measurement to the main bearing bore radius.
Measuring is the same for the 426 cast iron or aluminum decks.
If you have any Hemi deck height questions, piston deck or about the post, you may send us an email found on our contact page.
I learned about Mopar block deck heights by first building my own 440 engine and a friend’s 426 Hemi. In addition, reading Mopar books, articles, magazines, seminars and watching videos for approximately 37 years.
Find out how to put Hemi (426) Heads on a 440 in my article, Can You Put Hemi Heads on a 440?
Read More Mopar Engine Articles
- Google books: How to Rebuild and Modify Chrysler Hemi Engines
- Wikipedia: Chrysler Hemi engine
- Google Books: Chrysler Engines 1922-1998