Flywheel

There are several flywheels that can be used with the adapter depending on the specific bellhousing to be used. The bellhousing, and the attending starter location, determine the flywheel diameter and ring gear tooth count.
The typical passenger car small block manual transmission bellhousing will use the 130 tooth count flywheel. Vans and pickup trucks from the 1970’s and 1980’s typically use the 143 tooth flywheel, however, only the flywheels with an 8-bolt pattern can be used. It is not advised to redrill a 6-bolt flywheel for the 8-bolt pattern.

This photo shows the difference in overall diameter between the 426Hemi flywheel (130 tooth count) on the left and a later 3.7 / 4.7 style flywheel (143 tooth) on the right. This photo also shows the modifications to the 143 to add the older 8-bolt crank flange pattern and to also rebalance for use on a forged crankshaft..

This photo shows a typical 146 tooth flywheel as used on pre-1962 v-8 and flathead inline 6 and 8 cylinder engines.

All pre-62 flywheels are directly mounted to the crankshaft, whereas post-62 flywheels require a crank flange adapter.

This photo shows the typical pre-62 flywheel with the 4-bolt pattern.

This photo shows the typical pre-62 flywheel with the 6-bolt pattern.

Pre-1962 flywheels were also found with the even larger 172 tooth count ring gear. This flywheel was found in a D-600 truck with a 413 engine. The ‘171’ noted on the flywheel is an apparent mis-count of the ring gear teeth.

When using any pre-62 flywheel on a crankshaft that is not drilled for a pilot bushing the easy fix is to mount a bearing or even a bronze bushing in the flywheel itself. In this photo you can see that a ‘reducing bushing’ has been pressed into the flywheel which then accepts a ball bearing. There are many suitable bearings available, the only requirement is the the bearing ID must be compatible with the input shaft pilot OD.

In certain applications there may also be the need to reduce the length of the pilot so the shaft does not bottom out in the crank.
In any trans swap project the critical relationship is that the input shaft splines should engage the clutch disk splines 100%. There may be some variations in the clutch disc hub design so you may not achieve 100% engagement but it should be close. This relationship is generally controlled by the thickness of the block adapter.

Also, note the design of the ‘clipped’ head bolt that is required for this flywheel. Most pre-62 flywheels have this style attaching bolt with the nut secured on the engine side of the flange. Yes, they are a PITA to work with. If you choose to install a capscrew, also pictured, the machined shoulder will have to be enlarged so that the cap screw can seat flush. Spot facing or counter boring 1¼” at each hole also provides the required clearance.

…last thoughts on flywheels….or, how to make a useful change…
The flange on the crank can be welded up and machined to copy the dimensions of the late model A-LA-B-RB crank flange and by doing so, you now have access to the more plentiful, and infinitely cheaper, 6-bolt flywheels and flexplates. Although not an inexpensive modification, it compares favorably, overall, with the high cost of, and sometimes difficult to source, LateHemi parts. If you want to discuss this modification with your crank repair shop we can help answer any questions that arise.