351w motors come with either a 3/8 inch starter or 3/4 inch starter depth. You probably have the shorter one and need a longer one. Usually the 3/8 inch starter was for a manual transmission with 164 teeth flywheel. The 3/4 inch was from all automatics and manuals with 157 teeth.

 

My 1989 LX 5.0L with a swapped 351W and TKO 600 has been using the stock 1989 5.0L starter for 15 years without a single issue.

 

What trans, bell, flywheel? If it's manual regular mustang dimension stuff and starter should work fine. Some after market bells and block plate require some work.

 

UPDATE:

So I compared starter motors and sure enough, I have the "Short" version and the long version looked MUCH more like what I needed (shown below). I have all the plugs out of the heads (as I am checking for spark at the moment) so there is hardly any load on the starter.

Engages the flywheel perfectly and spins smooth. You can see the nice .380" of engagement in the picture below. No grinding or chewing anymore.

 

I'm on my 6th starter and 2nd flexplate trying to solve this problem, would you by chance have a part number for the correct starter? Thanks for doing the homework I wasn't bright enough to do on my own!

 

I know you resolved the issue but I thought I'd clarify things for the future. We go through this issue all the time on the vintage boards. How starts are listed is totally wrong. They are typically listed as either automatic or manual which is not true. Flywheels come in two sizes, 157 tooth or 164 tooth. The 157 tooth is listed as the "automatic" starter and the 164 tooth as the "manual" starter. 157 tooth flywheels are used in both automatic and manual. 164 tooth also are used for either. Starters should be listed either by flywheel diameter or tooth count, not transmission type.

A manual 157 tooth flywheel will have the ring gear stepped back about 3/8" while a manual 164 tooth the ring gear will be flush with the back side. Usually putting a 157 tooth starter installed on a 164 tooth won't engage at all. Some early small C4 flexplates were 160 tooth and used the 157 tooth type starter. Putting a 157 tooth starter on a 164 tooth flywheel will be disastrous.

Bottom line, go by tooth count, not transmission type. The 157 tooth has the longer snout with the drive gear mostly exposed while the 164 tooth has a shorter snout with the drive gear hardly exposed.

 

That's not really true. Autos on a small block ford are all the short snout. Manuals are tricky because they can be either depending on application. Most that came from the factory with a 3 or 4 speed are the short snout and factory 5 speeds are all long snout. All you have to do is look at the ring gear placement on the flywheel to tell what one you need. Ring gear to the engine side is short and to the clutch side is long. Bellhousing starter bolt placement is different for the larger diameter units along with having the correct block plate for the bellhousing and flexplate/flywheel size you have. The only difference in most sbf starters is how much the bendix is exposed. There were a few oddball 3 bolt ones that they tried that I have only ever seen pictures of. They really should list starters by the ring gear setback spacing 3/8" or 3/4". I had a 289 with one of those funky 160 tooth flexplates. I changed the bellhousing on my C4 so I could use a normal sized flexplate.

 

Anybody have pictures of both the 157 and the 164 fly wheels I have a Torino that I'm putting a c-4 automatic transmission in. The engine is a 1974, 302. I haven't been able to find the info as to what starter I need because I don't know what kind of flywheel I have as car is not drivable. Automatic in a 70s somewhere transmission.