Guys I need some advice on a flywheel application please. I’ve built a 383 stroker using a 1989 5.7 block with a scat 383 kit. The crank and block are a one piece seal. I’m going to go with a t56 transmission and understand that they use a 153 tooth flywheel! I believe that the 1989 5.7 block used a 168 tooth flywheel. If I go with the t56 transmission will my starter turn the flywheel???? Thanks

Iirc you need a 153, look at spec clutches for externaly balanced one piece rear main. Or centerforce and McLeod has them too. I’d get it sent to your machine shop for balancing with the rotating assembly.

Blocks don't use flywheels.

Transmissions do. More specifically, bell housings.

Both diameters are available that will fit your motor. Once you determine how it's balanced, there's plenty to pick from, of either size.

so what you’re telling me is the starter bolts to the transmission and not to the engine block????

No Lisa. The starter bolts to the engine. However the starter is designed for either a 153 OR a 163 tooth flywheel. Not interchange able. Clutch flywheel size is usually determined by bell housing size. These cars used the 153 flywheel because of the small tunnel. Now you did state your using a Scat crank . Is it a "forged crank" or cast? If its cast then it is external balance which means external weighted flywheel and harmonic balancer. As stated you really should have it balanced by a reputable balancer. They will tell you what flywheel you should use because it needs to be balanced along with the rest of the lower end.

No.

The starter bolts to the engine.

You pick the starter to match the flywheel size you need.

You pick the flywheel based on the transmission, bell housing, etc.

The block does not care. At least, blocks after about 78 or so, don't; before that (the introduction of the 12.8" wheel) they only had the right bolt pattern to fit the starter for the 14" wheel. To put modern transmissions on older blocks often requires drilling a bolt hole for the later model starter. With your 89 block that's not an issue, it has the bolt pattern you need.

A 153 tooth flywheel and starter allow a little exhaust clearance.
An LT1 T56 153t flywheel uses an 11" clutch.
A third gen 153t V8 flywheel can use up to a 10.75" clutch. Many are 10.5".
Both the above have bellhousings which need a smaller starter. A third gen V8 T5 starter fits. A 4th gen LT1 starter fits. A third gen 5.7 starter does not. Any starter for a 168 tooth flywheel does not.
So if you listen to the old fellas who tell you to go with the 168, they won't be able to outline one advantage to it.

As I said in your earlier thread, if your 383 accepts a stock balance flywheel, that keeps options open.

To a point... before you buy ANYTHING, you HAVE TO KNOW what your motor was balanced to.

It's easy enough to "unbalance" a stock flywheel, if needed. The stock 12.8" wheel for 86-up (1-pc rear main seal) motors isn't neutral balanced anyway. Butt you HAVE TO KNOW what your motor was balanced to before you bolt everything up. Either a 14" or 12.8" wheel can be made to work with a "stock" 305/350 balanced engine, or can be modified to work with one that ISN'T internally balanced like the 305/350 were, as many 383 rotating assemblies are NOT, or whatever. Regardless, you HAVE TO KNOW what your motor was balanced to. Only way to get that info is to talk to the people that built it.

Nearly all T-56 flywheels (the 93-97 ones are not the same as for other transmissions, apart from outer dia) are 12.8".

Also a good thing to know is when getting a starter that 153 tooth ring gear will need a starter with 11 teeth on the bendix drive gear. 168 tooth ring gear is nine teeth. The parts stores have given me the wrong one in the past.