You may be wondering what the difference between 305 and 350 is, be it you have a new car and are unsure of the engine, or you need to find parts for the one you have? Most drivers come to find the only significant difference between the Chevrolet 305 and 350 cubic-inch engines is the size of the cylinder bore.
The engine ID number must be compared to a list of suffix codes that specify the specifics of the engine in issue, including initial application, horsepower, year of manufacture, and technical characteristics, to identify any Chevrolet small-block V-8 engine. Thus, it is a struggle to find the 305 vs 350 identification for most owners of these engines.
Luckily, there is a wealth of info regarding the Chevy 350 vs 305, yet it is buried deep inside user forums. Luckily, we have done all the hard work to help. There are visible identifying techniques, such as tags and labels on the engine or in the engine compartment.
However, it’s possible that these labels have worn or that the engine has undergone modifications, making the tags useless for sure-fire engine identification. In our guide, if you haven’t found out what your engine and transmission is, you can run through our user posts that date back years and were originally posted for the very same reason. (Read Can A Bad Alternator Cause A Misfire)
By the end, you should have a better understanding to know which engine you have, or at least tell the difference.
Quick Guide To Block Casting Numbers
Here’s a quick starter on how to decipher the numbers once you have found their location:
1. Look for your engine ID number.
Small-block Chevrolet engine ID numbers are located on the left (passenger) side of the engine block, forward, below the cylinder head, and next to the alternator, according to a Chevrolet Engine Identification website. To view the number, the alternator may need to be loosened or removed.
2. Decipher the ID number prefix.
There are at least eight slots in the ID number stamped on the block. The prefix component of the number starts with a letter, then four numbers that represent the month and day of manufacture, according to the website.
The engine production facility is mentioned in the letter. February 25 is represented by the number “0225”.
3. Identify the suffix portion of the ID number.
The last three letters of the engine ID number are what Nasty Z28 refers to as the suffix part. When compared to the suffix identification charts published on the site, complete identifying information is offered.
Driver #1 Post: Camaro Engine Identification
While going on a fun parts search for an engine build, this driver was asking for advice on how to tell the difference between a Chevy 305 and a Chevy 350. Often, it takes a casting number book to identify as there are so many Chevy Camaro blocks in existence.
You may find the oil dipstick on the driver’s side for a Camaro 305 and the passenger side for 350 at least that’s the difference between a blazer and Camaro. If you haven’t found it, the dipstick will be on a lot by the drivers’ side on engines up to 1980 or 1983.
After these dates, you’ll find it on the passenger’s side for the 305 and 350 engine sizes. Also, you can spot it cast on the motor where the transmission bolts onto the side of the block and sits above the oil pan rail. (Read 350 Tbi Idles Up And Down)
Conclusion:
In the difference of engines manufactured in the same year or very close to it, telling them apart might be difficult. The driver’s-side bellhousing mounting area on later engines features the 5.0 or 5.7 cast into the block is one way to tell.
GM switched to a single-piece rear main oil seal in 1986, which caused oil pan variations; in 1987, they switched from perimeter bolts to center bolts on their rocker covers.
Over time, there have been other shifts as well. The best way to tell is to find a decent small block Chevy reference book that has listings for casting numbers and stamping numbers, then compare those numbers with the engines you’re inspecting. It’s not foolproof, but it’s as close as it gets most of the way.
Roller Cams
There are certain blocks that, based on the casting number, appear to be roller cam engines, but don’t let that mislead you; roller cam engines were only installed in a small number of high-performance cars.
From the late 1980s until GM stopped producing a standard small-block Chevy engine, roller cam engines were widely used in a number of applications.
Cars and light trucks alike made use of them for various purposes. Both the metal lifter retainer plate in the intake manifold and the camshaft retainer plate in the front cover are telltale signs of a roller engine.
Bore Measurement
Tear down the head and pulling the bore measurement after removing the head is the easiest way. A 350 has a bore of 4 inches, while a 305’s bore is just 3.736 inches. Once you know what to look for, the difference is striking.
Compared to the 3.48-inch stroke of a 305 or 350, the 3.27-inch stroke of a 327, or the 3-inch stroke of a 302, the 400’s bore is 4.126 inches and its stroke is 3.75 inches (IIRC). The first year that oil filter bosses were originally posted appeared on small blocks was 1957; on early Chevy II blocks, the boss was moved to a higher position in the block.
Around the same time, General Motors went from a 168-tooth flywheel to a 153-tooth one, so make sure you have the right starter. Transmissions made for the 153-tooth flywheel may not be compatible with the 168-tooth piece.
Also, because the 400 is externally balanced, it cannot use the neutral balanced flywheel of other small blocks without rebalancing both the engine and the flywheel. Between 1986 and 1987, General Motors used the roller cam block instead of the one-piece seal block they had previously used.
Not all engines and heads installed during this period feature roller cam, but they all allow for the cam valley spider to be installed so that the factory roller cam valvetrain can be used. (Read Can I Sleep In My Car With The Ac Running)
Driver #2 Post: Engine Identification and Location
Is disassembling the heads the only way to tell them apart? They were told the 305 had been swapped out for a 350 and that the car was used.
Conclusion:
To determine the model year and engine displacement, you must locate the engine’s RPO code. The RPO can only tell you want it was in the first place. For the current block identity, ya find the casting numbers on one half of the block.
You’ll find the suffix number location in front of the passenger’s head or the casting number behind the driver’s head to identify vehicle. Note: It has been originally posted the suffix number is difficult to decipher, and it will be eliminated if the block has been decked.
Blocks for the 305 and 350 have various casting numbers since their bore sizes differ, thus offering different power from the rods and bores. You may need to take off the valve covers to check the casting number on your cylinder head’s location, and I would bet, if you see 5G, it is supposed to be 5.0.
The center bolt valve covers and rods on the engine indicate a more recent block design. It could be wrong to feel underpowered, although you may wonder if you can use a 305 computer and throttle body.
Blown Gaskets:
It could end up being bad news. A blown head gasket in a 305 could make it unfeasible to continue driving the engine, and depending on the damage, it could be a local junkyard for an entire engine and transmission.
Again, the easy way to tell between a 305 and a 350 is crucial.
You can pull a head and measure the bore width, or you can try to find the casting numbers. Since there is likely to be a lot of Camaros to check, and since pulling a head can take some time, you’re going to have to rely on casting numbers.
You may need to check the casting numbers originally posted to tell the difference.
The valve covers location help as there are four bolts, one in each corner of the 305, whereas the 350 has ribbed covers and four bolts that through the valve covers top.
You can’t use it since my 350 V-covers are secured with bolts in all four corners. The casting number can be found on the block’s bottom, usually around the exhaust manifold.
If it is spotless, you may read out the embossed numbers “305” or “350” on the block or heads. The serial number, or casting number, can be seen on the back of the block. Driver’s side, behind the valve covers.
You may hope to find a motor in a junkyard location, so find one that has been in a fire or major road accident from the rear, and ask the guy for a discount, and then you may figure out how to fix the engine, to at least you’ll have a good idea if you have a good engine. (Read Temperature Gauge Goes Up And Down)
Driver #3 Easy Way To Check Car Motor
The current owner claims the car’s former owner told him it had a 350 engine when he acquired it from him 12 years ago, but the VIN shows it came from the factory with a 305 engine size and a 5-speed manual.
Conclusion
Any guy in the same situation may not care which engine they have, yet knowing which one it is in their car is important. So, is there a quick way to tell between them? Seeing the casting mark on the front of the block and looking it up is about all you can do without disassembling it.
By the size of the bore, the block casting numbers are variable. The numbers 5.0L and 5.7L printed directly on the side of several of the blocks make everything a breeze.
On the bell housing flange of the driver’s side of the engine block, near the oil filter area is another location you may find your answer of identification.
