New ATP manual transmission flywheel. This is for 1-pc rear main seal 305/350 Small Block Chevrolet engines (1986 and newer). This is a 153 tooth (12 3/4" OD) flywheel, and is light weight (approx. 16 lbs) and is steel. This accepts the standard size clutch discs (10-10.4"), fits most bell housing. No balancing required. See all notes below to ensure you are ordering a correct flywheel. This works with most GM Muncie, T10, Super T10 transmissions, and T5 transmissions. This is not compatible with an LT1 engine and T56 transmission! As a general note, manual transmission flywheels require longer bolts than automatic transmission flywheels, so bolts are generally required and not included.
Small Block Chevrolet Flywheel Notes:
Selecting 153 tooth or 168 tooth : Depends on clutch size, bell housing size and starter type
153 Tooth is 12 3/4" OD, and accepts standard 10-10.4" clutches, requires 153 tooth starter (holes straight across), fits smaller bell housings
168 Tooth is 14" OD, and accepts 11"-12" clutches, required 168 tooth starter (holes offset), fits larger bell housings
Selecting 1-pc RMS or 2-pc RMS : Must match crankshaft bolt pattern! 1-pc and 2-pc rear main seal flywheel do not interchange, their bolt patter is different as well as how the flywheel is weighted!
2-pc rear main seal is 1985 and older (rear crank flange is not round where the flywheel bolts thread)
1-pc rear main seal is 1986 and newer (rear crank flange is round where the flywheel bolts thread)
Ensuring proper engine balancing :
ALL factory 2-pc rear main seal 305/350 Chevy are internally balanced, no weights on flywheel, no weights are required, ready to install.
ALL factory 1-pc rear main seal 305/350 Chevy are internally balanced, counterweight on flywheel, already balanced, ready to install.
ALL factory 400 Chevy are externally balanced, requires 400 specific flywheel with counterweight, requires balancing before install
Stroker combos must meet stroker manufacturer requirements, balancing may be required or special flywheel vs above statement, contact crankshaft manufacturer.
Selecting proper flywheel weight :
Standard weight flywheels are typically 25-30 lbs, and are used for bottom end torque
Lightweight flywheels are typically 15-20 lbs, and are used for higher RPM use.
If you still have questions, please contact us before ordering. If you are swapping a T56, please contact us for proper flywheel selection.