Chevy 350 4 Bolt Main Identification [Answered with Image]

The talk-over between 4-bolt and 2-bolt main is a joint discussion among car enthusiasts. But are you aware that only 6 out of 10 people can quickly identify a four-bolt main in a Chevy 350?

Chevrolet Block Identification number locations

A four-bolt main has on each center caps four bolts and is mainly preferred when building an engine. At each main cap on the block, the four-bolt denotes the number of the crank that the main bearing cap bolts. Please stick through to the end to find out the Chevy 350 bolt in detail.

In 1967 Chevrolet Camaro first used 4-bolt mains. The first car engine to use four-bolt main bearings was the V12 Maybach Zeppelin of 1928.

All Chevrolet’s siblings of the period (Buick, Cadillac, Oldsmobile, and Pontiac) designed their own V8s.

Main Block Definition

The perfect definition of the main block is it has large ports, valves, and bores to deliver improved power production.

chevy 350 4 bolt main block

But before being routinely added to most passenger vehicles, it was designed originally for trucks and larger vehicles.

 It may sacrifice acceleration for power due to the ability to add weight to the front axle of a car. Nonetheless, the main block engine has a large size overall with both 4-bolt and 2-bolt mains.

But the fact remains that different drivers prefer either of them for various advantages.

What is a Four Bolt Main?

Are you having trouble figuring out what a four-bolt main is? Well, I have a clear explanation for you here. A four-bolt main is the number of the crank the main bearing cap bolts on the block at each mani cap.

It has four bolts on either side of the center caps with two bolts for each cap at the main caps on an engine. More abuse holds firmly, using the four bolts as the crank’s main bearing caps. 

Racing applications and big trucks have two extra bolts for extra heavy duty. But some are cross-bolted four bolts for additional strength.

what does a 4 bolt main look like

 Conversely, a four-bolt main is a desirable block for heavy-duty or racing applications since the main bearing caps on an SBC have four bolts that hold them in place. 

Note: The V6 Nissan VQ engine also uses 4-bolt mains. Toyota UZ engine and Toyota MZ engine, Ford Modular V8 engines use 6-bolt mains. It prevents crankshaft flexing with its aluminum block or during high-stress applications.

How do I know if I have a 4 bolt main 350?

You can tell a 4-bolt main 350 by pulling the pan to check the numbers.

Similarly, truck 010 blocks are mainly four-bolt main from the suffix stamping code at the flat machined pad. It will tell you what is behind it, looking at the pass side of the engine above the timing cover.

Please note that the plant can goof the stamping codes.

Alternatively, you can tell if the engine is original or not using the suffix code on the block. You will guarantee a four-bolt block if four bolts hold them in with three center main bearing caps.

You will notice two bolts at the front and rear caps. 

How do I know if I have a 2 bolt main or a 4 bolt main?

Looking at various aspects, you can distinguish between a two-bolt main and a four bolt main.

A 2 bolt will take 550 hp without strain, while a big block four-bolt main will reliably take 800 hp since the factory rods are the weak point.

Because of the beefier bottom end in big leagues, you can get away with a lot more. 

A two-bolt main has two bolts holding the main caps on, while a four bolt main has four. You will figure this out if you look at the caps that hold the crank by pulling the oil pan.

chevy 350 4 bolt main horsepower

However, all four bolts are parallel and can be drilled straight into the block, while a two-bolt has the bolts drilled at an angle with two more on the outside.

 The two-bolt main is appropriately driven and built for the utmost reliability, while the four-bolt main is prone to cracking at the inner bolts of the caps on the block in the main cap area.  

Pictures of a 4 bolt main:

A 4-bolt main is substantial since it will be more stressful to rip it off than a 2-bolt main. You will get an increased crankshaft load anytime you increase the cylinder pressure and horsepower. 

Chevy 350 4 bolt main identification

Chevrolet Block Identification number locations

140029 Small Block V8 1980-1984 350, 2 bolt

14010209 Small Block V8 1980-1985 350, 4 bolt

14011064 Small Block V8 1983 350, 4 bolt

14016379 Small Block V8 1977-1979 350, 2 bolt or 4 bolt

14079287 Small Block V8 1986-1990 350, Truck

14088526 Small Block V8 1987-1989 350, roller cam, 1-piece rear seal

14088548 Small Block V8 1986-1988 350, 2 bolt or 4 bolt


Is a Chevy 350 Vortec a 4 bolt main?

Yes. It has a better-quality oil pump flow and ensures a long cylinder bore life with the new hyper eutectic pistons coated on the sides. You can check the casting at the back if it’s a four-bolt main or check a square 1/8 NPT pipe plug towards the passenger side above the water pump.

How to tell 2 bolt or 4 bolt main?

There are differences between a two-bolt and a four bolt main. A two-bolt main holds down using two bolts on each main cap, whereas a four-main bolt uses four bolts. It implies less likelihood that the crank will at high power or RPM push itself out of the engine’s bottom in addition to more clamping force.  Two-main bolts work best if you stud them on a typical 350 Chevy less than 450 hp, while four-main bolts are best in an SBC with 650 hp. 

How to identify a 4 bolt main 454?

You can quickly identify a 4-bolt main 454 by looking at the side of the block on the size of the hole. It will be a four-bolt; suppose the hole is large and a two-bolt if it is small. Undoubtedly, it is the most straightforward identification of a 454 4-bolt main.

Can you make a 2 bolt main into a 4 bolt main?

Of course, you can make a 2-bolt main into a 4-bolt main. Besides, it will turn out better since it makes your engine stronger than a four-bolt made in the factory. Don’t hesitate; turn your two-bolt into a four-bolt main conversion kit from the plenty of two-bolt main lying idle in your junkyard. It will possibly cost you less money with less hassle. 

How much HP can a 4 bolt main Chevy 350 handle?

A four-bolt main 350 can handle 350-375 hp upwards before surpassing the components’ readability. It can make an area of about 400-475 hp for a big block with similar features. Additionally, it can handle upwards of 500 hp before the stock cast piston’s reliability exceeds. 

Why is a 4 bolt main better?

A four bolt main is better because it is more vital than a two-bolt main. It makes it difficult to remove the four bolts in the main compared to the two-bolt main. Also, you will increase the crankshaft load anytime you increase the cylinder pressure, torque, and horsepower. So if you are in for a solid main, the for-bolt main is a perfect choice.


Now you know the identification of a Chevy 350 4-bolt main after reading this article to the end. Conversely, bolts secure the bearing caps to the lower half of the main bearing.

 They then have caps that have four bolts on the engines to make it a four-bolt main. Please note that the machine can withstand higher RPM or power output from the additional bolts that increase its strength.

It ultimately makes it more robust compared to the 2-bolt main. Stay safe! 

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