Basic details on starter motors
How a engine starter works
Exploded view of a starter:
- Starters/Alternators from Super Starter Shop.
Block mounted SBC/BBC starters
Basically there are two different starter noses used. The difference in the starters is to accommodate the two different diameter flywheels/flexplates ("flywheel" will be used unless otherwise specified) normally encountered in passenger car/light truck applications.
First, the 12-3/4" 153 tooth flywheel uses a starter with the bolt holes across from each other, 90 degrees to the crankshaft. The larger 14" 168 tooth flywheel uses a starter w/the holes offset diagonally from one another (see drawing below).
Blocks from about 1962 up are drilled with three holes for either starter. In my experience, the only two engines that may be a problem (other than the early blocks that used a bellhousing mounted starter) is the 229 V6 Chevy and the SBC 400. The 229 V6 may have only the side by side bolt holes and not enough "meat" to drill the offset hole. The SBC 400 may have only the offset holes. It can be drilled for the other hole pattern- but this needs to be carefully done for obvious reasons.
I have heard rumors there is a cast iron starter nose that has all three mounting holes on the nose. There are aftermarket high torque gear reduction-type starters that have four holes. They are made to be used with either the 153 or 168 tooth flywheel, depending on which holes are used.
To prevent broken starter noses or cracked block mounting holes, always use a starter brace and knurled attaching bolts as sold by GM. Torque the bolts to 35 ft/lb.
The GM starter-mounted solenoid can be resurrected if it becomes sluggish. The terminals inside the solenoid become burned and worn over time, but these terminals can be removed, rotated 180 degrees, and reinstalled to provide the internal contact disc of the solenoid brand new terminal contacts.