Car building has experienced a wide variety of engine combinations and changes in design in the past few decades.
The choices between big blocks, small blocks, LS, LT, Flathead, Cleveland, Windsor, Y blocks, FE, MEL, Hemi, Wedge… it can be a little overwhelming sometimes, but typically we know what we like and will go with what we know..
Regardless of which you choose, it’s important to know your engine set up and how it works with the wide variety of transmissions available today.
One of the biggest challenges is knowing your engine balance, to ensure the correct flywheel is bolted on the first time.
You may be thinking that this seems like a “no-brainer”, but you are not alone if you just aren’t 100% sure of what you’re working with.
The following information will help you choose the correct flywheel.
Should you need information on something not found below, there will likely be a little more research to be done
Feel free to call us 208-453-9800
In addition, engine balance there are two other important factors to consider.
- Crank flange bolt pattern/sealing arrangement
- Ring gear tooth count.
These are the critical elements to making sure you can properly attach your engine to your chosen transmission.
Each engine manufacturer has its own specific set-up.
So deciding which engine to use is the first step.
This is especially important because not everyone refers to things the same way.
Two engines might both be part of the “small block” family but are completely different when it comes to which flywheel they use.
You will want to gather as much possible information as you can before you set out on your parts-gathering journey so that you can find the right parts in one trip!
GM engines are used in a wide variety of builds not just Chevys.
The crank flange bolt patterns of Gen I (two-piece rear main seal),
Gen II (one-piece rear main seal), and Gen III, IV, V (LS style) are all different and will not permit any interchange between them.
These bolt patterns became successively smaller with each generation. Gen I and Gen II Chevy engines featured two available diameters of flywheels and two corresponding tooth counts of 153 and 168. Gen III, IV, V LS/LT series engines feature only the large diameter, 168 tooth flywheels, and flexplates, but carry either a 6, 8, or 9 bolt crank flanges.
Early GM(Chevrolet) Small Block Engines
- Built from 1955-1985.
- Displacements were 265ci. up to 400ci.
- 2pc rear main seal design crankshaft with 6 bolt flanges.
- 153 tooth and 168 tooth ring gears- many of the factory bellhousings will only accept the 153-tooth size, typically the aftermarket bellhousings will accept both sizes.
In many cases, if you’re changing from one size to the other you will also need a new starter that is paired for that ring gear. - All had an internal or “0” balance EXCEPT 400 Small Block- which is externally balanced.
Late GM Small Block Engines
- Built from 1986-2003 for factory vehicles, still available through GM’s crate engine program.
- Displacements were limited to 305ci. or 350ci. (the L99 262c.i. was a rare exception)
- 1 pc rear main seal design crankshaft with 6 bolt flanges.
- 153 tooth and 168 tooth ring gears- many of the factory bellhousings will only accept the 153-tooth size, typically the aftermarket bellhousings will accept both sizes. In many cases, if you’re changing from one size to the other you will also need a new starter that is matched to that ring gear.
- Engines will be either internally or externally balanced with the external balance being most common.
The GM (Chevrolet) Big Blocks
- The early 454ci.design used a 2pc rear main seal and had its own specific balance.
- The later (after 1990 or Gen V) 454/502 ci. engines were all 1-pc rear main seal and externally balanced.
- All other big-block displacements used a 2-pc rear main seal, internal or “0” balance, and 168 tooth ring gear. They will accept the same flywheel as the early small-block engine.
- All Big Blocks can use the 153 tooth flywheel when the engine block is drilled for starter type.
LS/LT series engines 1997-present (Gen 3, 4, & 5)
- All engines use a 168-tooth ring gear.
- All engines are internally balanced.
- Series LS1,2,3,6,7 have 6 bolt crank flange bolt patterns.
- The LSA, LSX (aftermarket), and the new LT1 & LT4 engines have 8 bolt crank flange patterns.
- The LS9 uses a special 9 bolt crank flange pattern.
- Early 4.8L & 6.0L LS engines have an extended crank flange that requires a specific flywheel.
Ford used three different balances, so you must be conscious of engine balance when choosing a flywheel.
Many aftermarket stroker kits will carry their own balance that is different from the original.
Ford Small Block Engines
- They have either 157 tooth or 164 tooth ring gear
- 221ci 1962–1963 28.2 oz-in
- 255ci 1979–1982 50 oz-in
- 260ci 1962–1964 28.2 oz-in
- 289ci 1963–1968 28.2 oz-in
- 302ci 1968–1980 28.2 oz-in
- Boss 302ci 1969-1970 28.2 oz-in
- 302ci 1981–2001 50 oz-in
- 351W (Windsor)1969–1997 28.2 oz-in
- 351C (Cleveland)1970–1974 28.2 oz-in
- With a 6-bolt crank flange
Ford FE & Y Block Engines
- FE blocks were built from 1958-1976.
- Unique crank flange bolt pattern and balance.
- With 184 tooth ring gear.
Ford Big Block Engines
- Have displacements of 370, 429, & 460ci.
- Also referred to as the 385 series of engines sold between 1968–1997.
- With a 176-tooth ring gear.
- All are internally balanced.
Ford Modular & Coyote Engines
- Built from 1990-present.
- Check for 6 or 8 bolt crank flanges.
- 4.6L, 5.0L, 5.4L common displacements.
- There was one variation for the Mustang Shelby GT500 at 5.8Lthat will be different than the others.
- All are internally balanced.
- With 164 tooth ring gear.
Mopar Small /Big Block & Early Gen 1 & 2 Hemi Engines
- Check for 6 or 8 bolt crank flanges.
- With 130 tooth ring gear for most, some bigger displacements may use 143-tooth.
- You will need to check for the internal or external balance.
- Engines mated to automatics from the factory are not machined for a standard Mopar pilot bushing, will require special bronze bushing to run manual transmission.
Mopar Gen 3 Hemi
- This covers the 5.7, 6.1, & 6.4L engines.
- These will have an 8-bolt crank flange.
- They are Internally balanced.
- With 130 tooth ring gear.
- Caution: some engines have a flush ring gear mount and others are offset by .850” from the factory. If incorrect set up is used the starter will not engage properly.
If you have more questions about which flywheel you need, please check out our site or reach out to our specialists!
Modern Driveline can help you get the right flywheel and has most other parts you will need to build your Ride.
208-453-9800 www.moderndriveline.com
