55-56 Chevy 235 2nd Series Engine

A Visual Guide for a 1955-56 GM 235 engine with Casting number 3836233.

In mid 1955 the Chevy 235 engine changed from the First Series (1947.2 – 1955.1) Advanced Design to the Second Series (1955.2 – 1962) Task Force Design.  Applications in Light-Duty and Medium Duty trucks.

Casting 3836233 incorporates these updated changes.

There may be differences in other blocks with the same casting number. See below on the Parts History page, this casting number had 5 different Part Numbers.

Differences depend if it is was originally for a Passenger Car or Truck Engine. It can also depend on which Transmission it was originally paired with Manual or Automatic.

This specific block is for a Truck with Manual Transmission using Solid Lifters.

55-56 GM 235 3836233 DETAILS

Specifications

Block Casting#: 3836233
Head Casting# : 3836848
Years :  1955-56
Engine: GM 235 Thriftmaster OHV 12V L6

Features

• NEW THRIFTMASTER  on rocker cover decal
• High Pressure Oiling System – Internal Lubrication
• Oil Pump Pickup is Floating, (not bolted to Third Main Cap).
• Oil Pan Baffle added to prevent surging on quick stops.
• Main Bearings change to Dowel Top and Tang bottoms.
• Insert-type Bearings
• Valves and Valtrain were modified
• Front Side Engine Mounts. Four-point system replaces previous three-point engine mounting.
• Longer Shaft Water Pump attaches with single 4″ hole instead of 2 small holes

Application Models 55-57

3100 (½-ton short)
3200 (½-ton long)
3600 (¾-ton)
3800 (1-ton)

Short Block

Here are a few shots of the engine block before the cylinder head and other parts are attached.

The 1954 and 1955 First Series oil pump Pickup Tube used a “box” that bolted to the Third Main Cap.  With the Second Series changes, 55 and later now use a “Floater” type oil pump and pickup tube, it does not bolt onto the main cap.

In the photos, you see how it attaches and “Floats”.  GM gives good information in the 1955 Chevrolet Truck Shop Manual 2nd Series page, a quick read.

Water Pump Opening Change

As part of the upgraded cooling changes, the engine block now has One 4 inch hole opening in the front of the engine block where the Water Pump attaches. The Impeller sits inside of the hole now, improving cooling.  This replaces the Two smaller hole version.

Later 55+ Water Pumps have a longer shaft.

I included a photo of the 1950-51 Engine Block, casting 3692703, for comparison.  You can see that blog post here, 50-51 GM 235 Engine

Sometimes people replace thier older GM 216 or GM 235 engine with a newer version.  They run into problems with mounting of the old pump due to height and clearance adjustments for the new longer pumps.

Modifications must be made, but they do sell Water Pump Adapter Plates to address the issue.  There are other remedies, but I’m not covering those in this post.

Chevy 235 Engines have various mounting positions.  It can be difficult to tell where a specific block mounts.  Older are Front Mount only, then we have Front Side Mount, and Middle Mounts in later years.  The middle mounts have two configurations; one like a Triangle and one that looks like an upside down backwards  “L”.  I will be adding more posts with different block casting numbers and photos so you can look at the differences.

I’ve got some close up shots so you know where a GM 3836233 engine mounts to the frame.

Most of the engines we rebuild or have for sale do not include the Engine Mount brackets or cushions.  So, I included a photo illustration from the 55-59 Chevrolet Truck Factory Assembly Manual, it shows where it attaches and what parts comprise the mount.

The other photo is from the 54 Passenger Manual, it shows how the opposite side has different hole arrangements similar to the 55 3836233 engine block.  That side also mounts the Generator bracket in the front, see the illustration.

I was able to dig up one photo of a 3836233 with a Front Mount Bracket on it.

Last, I included an illustration from the 1955 Chevrolet Features Truck Engineering Achievements book that has a write up of the new Front Mount feature.  Per the book “For improved supression of engine vibration, a four-point system replaces the previously used three-point engine mounting.

There are lots of numbers on an Engine Block. Some are raised and some are etched in.
The important numbers :

• Block Casting Number – Tells us the Year Range and Engine Size.
• Date Code – Tells the manufacture Date of the block.  This ties in with the Casting number.
• Serial Number – Tells us the Specifications pertaining to the block.

This photo is labeled so you know which numbers are which. Knowing what you are looking at makes it easier for you to identify your own Block numbers.

I decoded the various numbers with resources on the net and catalogs I have that tell what the numbers mean.

Many online sources state the Block Casting number is either 55-56 or 55-57.  I have no way of knowing which is absolutely correct.

GM 235 Serial Number

Here is a breakdown of the Serial Number from this block.  I included the Chevrolet Serial Number page from Chevrolet 1955 Specifications- Trucks Second Series book so you see how I got the information.  Cover and 1st page photos included.

I did check the Chevrolet Passenger pages for 1955 to be sure this was a Truck Block.  The Serial Number Format is a different layout, so I am sure this is a Truck Block.

At the bottom left of the page, that little circle with a line through it, it states “The first number of model year numeral group indicated 2nd series 1955 truck models.” . This corresponds to the same circle next to (On 6 cyl engines, 255 Φ) under the Engine Serial Number title.  This is when the format changed, adding a 2 in front of the year.

Parts History

While researching this GM Casting Number, 3836233, I found the Parts History catalog page that reference the number.  Turns out this casting number has 5 different Part Numbers.  Part numbers usually change when a change has been made.  Could be an upgrade, redesign, replacement, different material, inventory tracking, superseded, replace older stock, only GM knows.

I thought it was interesting, heres the page and book it came from, Chevrolet Parts History 65-73 P&A 30H.

Last two photos of different angles of the engine block

I feel I covered a lot of information on the changes that came to the 1955 GM 235 engine block.  There are many more upgrades pertaining to the vehicle that I did not cover.

We sell and rebuild Chevy 235 engines, so my focus is on the engine, not the rest of the car. My catalogs do have a lot of information though.

I hope these photos assist you in your research on the differences between the various GM 235 Engine Blocks.

If you want to Purchase a Chevy 235 engine, check out our Stock here.

If you want to rebuild YOUR Chevy 235 Engine, use the CONTACT form and send us the details of your engine for a rebuild estimate.

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