CONVERTING A 327 SMALL-BLOCK INTO A 350

This sleek ’65 Chevrolet truck is no stranger to the pages of this magazine, and owner Gilbert Lara, like most truck owners, is constrained to balance the budget between home life and the fun life. The decision to stick with the engine that came in the truck is one that many face while pursuing their own builds. In this case, the engine that came with the Chevy truck is a 1968 327-ci small-block. There’s little need to go into the virtues and history of Chevrolet’s legendary small-block engine. Suffice it to say that in 2011 GM claimed to have produced 100 million of these engines (and that does not include third party aftermarket blocks). With astronomical numbers like that,

rebuilding one of the most commonly used engines on the planet is the perfect way to save some cabbage.

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The larger sized main journal diameters of the 1968 327 small-block, 2.450, are the exact size of the later 350 small-block. The difference between the two is the length of stroke on the crank, 3.250 for the 327 and 3.484 for the 350.

Many performance truck owners lustily dream of super powered mills pushing their vehicles down local highways and boulevards, those are good dreams to have. Stomping the loud pedal and snapping the vehicle in a straight line like a rocket on rails is an E-ticket ride, and the best seat in the house is behind the wheel. However, as most know, purchasing that E-ticket will siphon money from a budget faster than the IRS can drain Willy Nelson’s accounts.

With that nasty “B” word on the tip of the tongue and foremost in the minds of many vehicle owners, breaking the budget is simply not an option. For some this might appear to be a handicap, when in reality, leaving well enough alone is often the best solution.

The connecting rod length from the 327 to the 350 is the same size, 5.703 for both engines.

The 1968 Chevy small-block that came with this project truck is one of the more desirable 327s that Chevrolet built. What made these engines better than the previous 327s were the larger diameter sizes of the main journals. An earlier 327 would have had a main journal size of 2.300, whereas the new and improved larger journal size of the 1968 is 2.450. This means that this particular 327 can easily be upgraded into a 350, which has become a standard in the aftermarket industry with tons of available parts. Refer to the chart on the previous page for side-by-side number comparisons.

In 1968 GM claimed that the 327 produced that year was putting out 250 hp. Take into account parasitic loss of about 70 hp from the flywheel through the transmission, driveshaft, rearend and finally the tires, and it’s a safe estimation that approximately 180 ponies were actually punching the pavement. An upgrade of 23 extra cubic inches will certainly help the old Chevy get up and go.

Besides the crank stroke, one of the main differences between a 327 and the 350 is cylinder volume. The 327s have a smaller cylinder volume of 40.861, while the 350’s cylinder volume is 43.803. The 327 has been bored and honed to match the volume of a 350 block.

The worn-out 327 found a new lease on life at Larry’s Track-Pro in Montebello, California. Shop owner Jim Escamilla says that the upgrade from a 327 to a 350 is simple enough. But what if the 327 is an earlier model year with the smaller journals? Even if the 327 is a pre-’68 with smaller journals, Larry’s Track-Pro informs us that they can still work the smaller journal 327 engines into a better-performing 350. All that is required from the end user is the casting numbers and their shop will provide the necessary parts for the upgrade that they can complete at their shop, fully assembled from oil pan to intake manifold; or Larry’s Track-Pro will ship all of the essential parts for the do-it-yourself builder at home. St

Arriving at Larry’s Track Pro, the block had already been prepped. The block was jet cleaned and the cylinders were rebored and honed. While the deck was CBN milled, the line bore on the main journals was checked, a fresh coat of black was added, and lastly, brass freeze plugs were installed.

The 350 crankshaft arrived the morning of the build. It was magnafluxed, reground .010 x .010 and micropolished; the oil holes have all been chamfered and deburred. Larry’s Track Pro technician José gives the cast 350 crank a final cleaning before installing and torquing down the two-bolt main caps at 70 ft-lbs.

The cam bearings and camshaft were already installed prior to the photo shoot. The cam duration comes in at .214 degrees intake and .204 degrees exhaust at .050 with valve lift at .420 intake and .443 exhaust.

After the cam sprocket is installed (20 ft-lbs), the double roller timing chain is next.

With the bottom half of the engine secured, our technician thoroughly cleans every cylinder prior to piston installation.

The connecting rods, wrist pins and bearings were also installed. The bearings are coated with assembly lube prior to installation.

New moly compression piston rings are gapped, installed and ready to go.

The new OEM-style cast flat top pistons with valve reliefs are carefully installed.

Both the right and left bank pistons are installed, and the new stock-style chrome timing chain cover is bolted on next.

A new Mellings high-volume oil pump, pickup screen and drive rod will pump the engine’s lifeblood for as long as the engine spins.

A stock 4-quart capacity oil pan is all that is required for this new 350.

New flat tappet hydraulic lifters are lubed and ready to go.

If the lifters are being reused, then each one must be put back in its original place. Since new versions are being used, and the block is newly machined, placement position doesn’t matter.

New gaskets from stem to stern are included in the rebuild kit.

The original 327 camel hump/fuelie heads were refurbished and put back on the block. The cylinder heads were jet cleaned and magnufluxed. The valve guides should be checked and replaced if necessary. New intake and exhaust valves, springs and hardened keepers finished off the job. The original camel hump heads had 160cc intake runners with 64cc combustion chambers, the intake valve is 1.94 inches and the exhaust is 1.50 inches. Since the heads were milled and surfaced, the combustion chamber may be a tick smaller at approx. 63-62cc.

The cylinder heads were torqued down first to 35 ft-lbs then 65 ft-lbs in a typical circular pattern.

OEM-style stamped steel rocker arms with a stock 1.5.1 ratio were used in this build.

New standard length 7.8 push rods were up next.

The valve lash is set on each intake and exhaust valve before the engine is shipped.

The unassuming stock 327 single plane intake manifold was cleaned, repainted and put back into service.

Don’t bother using the inadequate rubber intake manifold gaskets. A better seal is made using a silicone sealant like Permatex.

A Professional Products 6 ¾ damper and pulley replaces the worn stock version.

At this point, the build at Larry’s Track Pro has reached its zenith, and in only a couple of hours. The 327 long-block is ready to be dressed and installed. The advantage of sticking with the tried-and-true 327 that millions of Chevy trucks came with is a definite plus in the money-saving category.
Let’s recap: The 1968 327 was reported to come with 250 hp at the flywheel with an approximate parasitic loss of 70 hp from flywheel to the tires, with an actual 180 hp hitting the pavement.
Recently, a same-year 327 was rebuilt into a better performing 350, remade using only OEM-style parts to keep on budget. It’s now running 275 hp, 245 ft-lbs of torque with a pump-gas-friendly 9.25.1 compression. Take into account the 70 hp parasitic loss and 205 horses are pounding the pavement versus the original 180. That’s a gain of 25 hp just using OEM parts. There are some racers who willingly spend ten thousand dollars for an extra 25-hp gain, thankfully that isn’t essential in the case of this truck.

Our story hasn’t quite come to an end yet. After the build at Larry’s Track Performance, the engine and truck were brought over to Maloof Racing Engines where a few more tasks needed to be completed, like installing the engine in the truck.

The long-block was dressed to the nines at Maloof Racing, and owner Sammy Maloof recurved the distributor and tuned the small-block to get it purring like a kitten. The 327 is now topped with a Holley 670 carburetor and fuel pump, MSD ignition, wires and plugs, Tuff Stuff alternator, starter and water pump, Hedman headers and gaskets, K&N air and oil filter and Mooneyes valve covers and air filter cover.

Sources

Larry’s Track Pro
720s Maple Ave.
Montebello, CA 90640
323.869.9230

FREQUENTLY ASKED QUESTIONS

What casting differences exist between small and medium/large journal 327 engines?

Casting Differences Between Small and Medium/Large Journal 327 Engines

When comparing small journal and medium/large journal 327 engines, several casting differences stand out.

Small Journal 327 Engines (1967 & Earlier)

Journal Sizes: These engines feature 2.30” main journals and 2.00” rod journals.
Casting Design: The smaller journal sizes result in a unique block casting that differentiates it from the later models.
PCV System: A hole for a road draft tube or PCV valve is cast into the back of the block near the distributor. This hole is a distinct characteristic and is specific to the small journal engines.

Medium/Large Journal 327 Engines (1968 & 1969)

Journal Sizes: These blocks share the same design as 350 engines with 2.45” mains and 2.10” rods.
Block Casting: The casting for these engines accommodates the larger journal sizes, making them structurally different from the earlier small journal versions.
PCV System: The hole near the distributor seen in small journal engines is eliminated. Instead, these engines use a PCV valve integrated into one of the valve covers, streamlining the block design.

Additional Notes

Terminology Variance: Some refer to these medium journal engines as “large journal” due to their relative journal size, although this term is more commonly associated with even larger 400SB engines that feature 2.65” mains.

Understanding these differences helps in identifying and correctly working with specific 327 engine blocks, ensuring compatibility and proper functionality in various applications.

What are the differences in rod sizes between older and newer 327 engines?

Differences in Rod Sizes Between Older and Newer 327 Engines

The rod sizes in 327 engines have evolved over time. Older 327 engines typically feature rods that are 2.00 inches wide. In contrast, newer models have slightly wider rods, measuring 2.10 inches, similar to those found in 350 engines.

This increase in width addresses issues of durability and performance, allowing newer 327 engines greater stability and reduced wear over time. Whether you’re rebuilding an older engine or maintaining a newer model, it’s crucial to consider these size differences for optimum compatibility and performance.

Are the blocks of a 327 and a 350 Chevy small block engine the same?

The short answer is that not all 327 and 350 blocks are the same. While there are similarities, there are also key differences that set them apart.

Similarities

Block Casting: Some years of the 327 and 350 do utilize the same casting numbers, particularly the later 327s produced in 1968 and 1969. These models share the “medium journal” small block design, featuring 2.45-inch main bearings and 2.10-inch rod bearings.
Bearing Sizes: Both engines in their medium journal form use the same size bearings for the mains and the rods, making them compatible in that respect.

Differences

Journal Sizes: The 327 engine produced in 1967 and earlier uses “small journal” sizes with 2.30-inch mains and 2.00-inch rods. This makes for a different block casting compared to the medium journal blocks used in later 327s and all 350s.
Piston Stroke: The primary difference between the two engines lies in the crankshaft stroke. The 327 has a 3.25-inch stroke, while the 350 has a 3.48-inch stroke. Though both engines have a 4-inch bore and 5.7-inch connecting rods, the different crankshaft stroke results in a different piston design. The 350 has pistons with a slightly raised pin to compensate for the longer stroke.
Block Features: Early 327 blocks also have a machining difference. They include a hole for a road draft tube or PCV valve near the distributor, which was eliminated in the later 327 and 350 blocks that use a PCV valve in the valve covers.

Identifying the Engines

Casting Numbers and Suffix Codes: While some 327 and 350 blocks share the same casting numbers, the suffix code on the engine will help you identify the specific model.
Visual Inspection: Additionally, look for the presence of a hole near the distributor for early 327s. This feature is not present in the later medium/large journal blocks.

In summary, later model 327s (1968 and 1969) and 350s share more similarities, including block casting and bearing sizes. However, there are significant differences in journal sizes, piston stroke, and certain block features that distinguish the various models across different production years.

Is there a difference in piston diameter between 327 and 350 Chevy small block engines?

Absolutely! When comparing the 327 and 350 Chevy small block engines, you’ll find notable differences, but piston diameter isn’t one of them.

Key Differences:

Bearings: These differ between the two engine models.
Pistons: While the actual diameter remains the same, the pistons themselves have differences. Notably, the 350’s crank features a longer stroke by about 1/4″. This longer stroke affects the height and design of the pistons, but not their diameter.

To summarize, the piston diameter remains unchanged between the 327 and 350 engines. However, other components like bearings and crank stroke do vary, impacting the overall engine performance and design.

Do the 327 and 350 Chevy small block engines use the same flywheels?

Understanding the Differences: 327 vs. 350 Chevy Small Block Engines

If you’re comparing the 327 and 350 Chevy small block engines, it’s important to understand their components, especially when it comes to the flywheel.

Key Differences in the Engines

While there are similarities, the two engines have distinctive features:

Rod Measurements: The older 327 engines feature rods that measure 2.00 inches, whereas the newer 327 models and 350 engines have rods that are 2.10 inches wide.
Physical Dimensions: Though both engines share common block dimensions, the internal components such as the rods and crankshaft vary, affecting compatibility of some parts.

Flywheel Compatibility

When discussing flywheels:

Both the 327 and 350 small block engines typically use the same flywheels. This compatibility extends to many small block Chevy engines, thanks to the standardized bolt patterns and mounting locations.

However, always verify the specific year and model of your engine, as slight variations can exist. Whether you’re replacing or upgrading, double-checking the flywheel’s specifications ensures proper fit and function.

In summary, the 327 and 350 Chevy small block engines generally use the same flywheels. However, due to variations in other internal components, consulting a detailed engine manual or a trusted automotive expert can provide additional peace of mind.

What years of 327 engines use the same block as the 350 Chevy small block engines?

Understanding the 327 and 350 Chevy Engine Blocks

If you’re wondering which specific years of 327 engines share the same block as the 350 small block engines, the answer lies in the late 1960s. Specifically, the 327 engines produced in 1968 and 1969 are the ones that utilize the same block as the 350.

Key Details:

Medium Journal Blocks: Both the 327 and 350 engines from these years feature “medium journal” small blocks. These blocks are characterized by:
- Main Bearing Journals: 2.45 inches
- Rod Journals: 2.10 inches
Terminology:
- Some enthusiasts may refer to these blocks as “large journal” blocks. However, it’s worth noting that this term can lead to confusion, as others reserve “large journal” for the 400 small block, which has 2.65-inch mains.

This shared block design ensures compatibility and interchangeability of certain parts between these two popular engine models from that era.

How can you recognize a 327 from a 350 Chevy small block engine?

Recognizing a 327 vs. 350 Chevy Small Block Engine

Identifying whether you’re dealing with a 327 or a 350 Chevy small block engine can be tricky since they share many similarities. However, several key differences can help you distinguish between the two.

Bore and Stroke

Bore: Both the 327 and the 350 have a 4-inch bore.
Stroke: The primary difference lies in the crankshaft stroke. The 327 has a 3.25-inch stroke, while the 350 has a longer 3.48-inch stroke. This longer stroke accounts for the increased displacement in the 350.

Main Journal Sizes

Early Year Differences (Pre-1968):
- 327: Uses “small journal” blocks with 2.30-inch main journals and 2.00-inch rod journals.
- 350: Did not exist yet, so no comparison needed for pre-1968 350s.
Later Year Differences (1968 & 1969):
- 327 (1968-1969): These models transitioned to “medium journal” blocks with 2.45-inch main journals and 2.10-inch rod journals. Some refer to these as “large journal” blocks.
- 350: Utilizes the same “medium/large journal” blocks as the 327 during these years, also featuring 2.45-inch main journals and 2.10-inch rod journals.

Crankshaft and Pistons

Both engine types have 5.7-inch long rods.
327: Shorter 3.25-inch stroke crankshaft means the piston pin placement is different.
350: Longer 3.48-inch stroke crankshaft necessitates a different piston design with a higher pin placement to account for the extended stroke.

Casting Numbers and Suffix Code

Casting Numbers: In some cases, the block casting numbers for the 327 and 350 can be identical. This overlap adds to the difficulty of distinguishing between them based solely on this information.
Suffix Code: The most reliable way to differentiate between a 327 and a 350 is by checking the suffix code stamped on the engine. This code provides specific details about the engine model and its specifications.

Unique Features

Small Journal 327 (Pre-1968): These blocks include a hole for a road draft tube or PCV valve cast near the distributor. This characteristic was eliminated in the later “medium/large journal” blocks starting in 1968.
PCV Valve Placement: For blocks from 1968 onwards, a PCV valve is generally located in one of the valve covers instead.

By paying close attention to these distinct features, such as the crankshaft stroke, journal sizes, and suffix codes, you can accurately determine whether an engine is a 327 or a 350 Chevy small block.

How does the suffix code help differentiate between a 327 and a 350 Chevy small block engine?

Sure! Here’s a thorough explanation:

How the Suffix Code Differentiates Between a 327 and a 350 Chevy Small Block Engine

The suffix code, typically found stamped on the engine block, plays a crucial role in distinguishing between a 327 and a 350 Chevy small block engine. This alphanumeric code reveals key details about the engine’s specifications, origin, and model year.

Key Components of the Suffix Code

Identification of Displacement:
- The suffix code includes characters that indicate whether the engine is a 327 or a 350.
- For instance, a 327 engine might have a suffix like “JE”, while a 350 might bear “CSB”.
Manufacturing Details:
- The code discloses the manufacturing plant and the assembly date.
- This information is essential in verifying the engine’s authenticity and production period.
Model-Specific Information:
- Each suffix is unique to a particular engine model and configuration.
- Not only does this help in identifying the engine size, but it also aids in recognizing whether the engine has been modified from its original state.

By carefully examining the suffix code, enthusiasts and mechanics can accurately determine if they are dealing with a 327 or a 350, ensuring they have the correct information for repairs, restorations, or upgrades.

Are the casting numbers for 327 and 350 Chevy small block engines the same?

Yes, the casting numbers for 327 and 350 Chevy small block engines can be identical. However, these numbers alone may not provide the complete picture. To accurately distinguish between the two engines, the suffix code must be examined. This code, typically stamped on the engine, offers additional details that help identify which specific engine you’re looking at.

In summary:

Casting Numbers: Can be identical for both 327 and 350 engines.
Suffix Code: Provides necessary information to differentiate between the two.

What modifications were made to the pistons to accommodate the longer stroke of the 350 crank?

The new OEM-style cast flat top pistons with valve reliefs are carefully installed. Because the same engine block is used, compensating for the added piston travel is crucial. This is achieved by raising the piston pin in the piston, allowing for the longer stroke of the 350 crank without compromising the engine’s integrity. This meticulous modification ensures that the new pistons fit perfectly and operate smoothly, maintaining the performance and reliability expected from high-quality components.

What are the differences between a 327 and a 350 Chevy small block engine?

The larger sized main journal diameters of the 1968 327 small-block, 2.450, are the exact size of the later 350 small-block. The difference between the two is the length of stroke on the crank, 3.250 for the 327 and 3.484 for the 350.

Besides the crank stroke, one of the main differences between a 327 and the 350 is cylinder volume. The 327s have a smaller cylinder volume of 40.861, while the 350’s cylinder volume is 43.803. The 327 has been bored and honed to match the volume of a 350 block.

More Detailed Differences

Main Journal Sizes:
- 1968 & 1969 327s: These are “medium journal” small blocks with 2.45″ mains and 2.10″ rods.
- 1967 & Earlier 327s: These are “small journal” engines with 2.30″ mains and 2.00″ rods. These smaller main journals necessitate a different block casting.
Piston and Rod Details:
- Both engines feature a 4-inch bore and 5.7-inch long rods. However, due to the different crank strokes, their pistons differ.
- The 350 piston has a raised piston pin to accommodate the longer stroke, whereas the 327 does not require this modification.
Block Features:
- 1967 & Earlier 327s: Include a hole for a road draft tube or PCV valve near the distributor, a feature eliminated in later models.
- 1968 & Later 327s and 350s: Use a PCV valve in one of the valve covers, removing the need for the hole cast into the block.
Interchangeability:
- For “medium journal” 327s, you can swap in a 350 crankshaft and pistons to effectively transform it into a 350.
Casting Numbers:
- The casting numbers for 327 and 350 blocks can sometimes be identical. The suffix code is the key to distinguishing between the two.

Summary

Both the 327 and 350 small-block engines share many similarities, including the bore size and rod length. Yet, they differ significantly in terms of crankshaft stroke, piston design, main journal sizes, and historical block features. These distinctions are essential for engine enthusiasts and mechanics to understand for accurate identification and potential modifications.