Starter-Flywheel-Bellhousing Combinations Tom Parsons (DZAUTO) Starting with the VERY first Chevy V8 engine (265) in 1955, ALL Chevy V8 engines (and 6cyl engines beginning in 63) have the SAME BOLT PATTERN on the back of the block. Quick example. You can remove an original V8 from a 55 Chevy, install a 1990 454 (of course use the 454 flywheel), bolt it all together and drive it away. This interchange between the back of the block of all SBs, BBs and W-motors (348-409-427 Z11 engines---------now I KNOW that you all know what a Z11 is, right?) and all bell housings and auto trannys is the same. In the history of the Chevy V8 engines, there have only been TWO different sizes of flywheels-big (168teeth) and small (153 teeth). That's it, nothing else. Thus, only TWO sizes of bell housings. There have been MANY styles and configurations of bell housings, but they were still only for the big or the small flywheel. With the first V8 in 55, there was only ONE size flywheel and ONE size bell housing.Then in 63, the small flywheel and corresponding small bell housing was introduced. The EARLY flywheels, even though they were the big flywheel, only had a bolt pattern for a 10in clutch (except truck flywheels). There were no 10 1/2in clutches then (11in for big trucks). Up through 62, the starters bolted to the bell housing (63 on 409s). Some trucks also had bell housing mounted starters up to about 70. ALL bell housings that had the starter mounted to the housing were the open bottom type, as below. In 63, along with the new, small flywheel, all housings were the full enclosure type and they were alum (except some trucks as mentioned above). When the full enclosure bell housings were introduced in 63, the BLOCK MOUNTED starter was also introduced. Of course, there was an exception. Some early engines that were mated to the early Turboglide auto trannys, had block mounted starters. Otherwise, early engines did not have provision for mounting a starter to the block. MOST, but not all, 63-later V8s have 2 bolt patterns for block mounted starters straight across and staggered. The starter for the small flywheel has a straight across bolt pattern. The starter for the big flywheel has a staggered bolt pattern. Here is where you have to pay close attention. For engines with a BIG flywheel, which requires a starter with a staggered bolt pattern, THERE ARE 2 STARTER NOSE VERSIONS----------ALUM AND CAST IRON. The starter with an alum nose and staggered bolt pattern WILL ONLY WORK WITH AN AUTO TRANNY!!!! For a big flywheel and manual tranny, you MUST use a starter with a CAST IRON NOSE and staggered bolt pattern. The alum starter nose with staggered bolt pattern WILL NOT FIT into the starter bulge of a big bell housing (such as the 621 style, truck, etc). Here are starter nose comparrisons, cast iron and alum with staggered bolt pattern. Notice the iron nose is just slightly smaller than the alum nose and will fit into a big housing. Here are 2 straight across bolt patterns, but they are opposite. The right one is Chevy, the left one is Buick-Olds- The following pertains ONLY to GM-Delco factory type V8 starters. Aftermarket/mini starters are a different story. All starter motors are essentially the same and are interchangeable (Chev, Olds, Pont, etc). The difference, for example, between a starter for a Chev 283 and an Olds 455 is simply the nose. You can literally take a burned up 59 Chevy 283 starter, remove the nose and bolt that nose onto a starter for a 455 Olds engine. Also, there are regular and hi-torque starters, but the physical size and interchangeability of the starter motor is the same. USUALLY, the higher perf engines as well as all BBs routinely got the hi-torque starters. The simplest way to immediately identify the difference between a regular and hi-torque starter is to look at the lower terminal of the starter solenoid. The flat brass terminal coming through the starter case is attached directly against the lower terminal of the solenoid on a regular starter. The hi-torque starter has about a 3/4in spacer between the lower solenoid terminal and the flat brass connector. Here is a comparison. The internal components and armature of regular and hi-torque starters are different, so you can't swap the guts from a hi-torque starter into a regular starter. One last final thing. The bolts used to attach the starter to the block are SPECIAL. They are a special shouldered bolt to assure the starter is properly positioned in relation to the flywheel. There is a short, long and medium length bolt. The straight across bolt pattern nose uses one long and one short bolt. The ALUM staggered pattern nose uses 2 long bolts. The CAST IRON staggered pattern nose uses 2 medium bolts. It can be frustrating trying to locate these medium length bolts for the cast iron nose. The GM part number for the medium bolts is 3733289. Hope this helps. __________ Tom Parsons (DZAUTO)