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Ford Flexplate Identification Guide

1/13/2023
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Whole Lotta Shakin’ Going On
You'll find Ford crankshafts that are both internal and external balance depending upon application, aftermarket crankshaft, and more, so do your homework!

Bolting up the wrong flexplate in most Ford applications is going to induce some major driveline vibrations. This is because Ford often switched from internal to external balance or from one balance weight spec to another throughout an engine family’s history. So, knowing what year your engine was built is critical to knowing its balance weight (if external). To toss another wrench in the works, most small block Ford stroker kits will change the engine’s balance as well, taking a late-model 5.0L V8 from 50 ounce balance back to the earlier 28.2 ounce balance. These stroker engines can even be custom neutral balanced right in the crankshaft, necessitating zero weight SFI flexplates and crankshaft balancers! So be sure of your Ford’s engine internals/build history before bolting up that new flexplate (and balancer!).

What Flexplate Tooth Count Does a Small Block Ford Use?

Ford’s small block engine family (commonly referred to as the Windsor engine family due to the Windsor Engine Plant where many were assembled, though Ford’s Cleveland Engine Plant built small block Fords as well) has always been an externally balanced engine from the factory. However, over the course of 41 years of production there have been changes to the external balance amount, flex plate tooth count and even bellhousing bolt pattern. One thing that is consistent with small block Ford flexplates are the requirement to use a starter with a 3/4-inch starter depth/offset. The shallower 3/8-inch depth starter is for manual transmission use (except for T-5 five-speeds, which use the automatic depth). We have available a larger version of the starter graphic shown below that may help.

Ford Starter Depth To Flexplate/Flywheel
Small block Ford flexplates come in 157- and 164-tooth variants.

While the small block Ford ranged in size from 221 cubic inches to 351 cubic inches, the most used small block Fords still found being built today are the 289 (1965-1967), the 302 (1968-2002), and the 351W (1969-1996). These three engines can all be found with either a 157-tooth or 164-tooth flex plate. In the case of Ford flexplates, the tooth count is related to the automatic transmission that was used.

The 157-tooth is used for the C4 three-speed transmission in most cases, but you may come across a 164-tooth flexplate with a C4 bolted up. The 164-tooth flexplate is found when the engine was backed by a C6 three speed transmission or the later four-speed overdrive models like the AOD, AOD-E, E4OD, and 4R70W. You can confirm tooth count with a simple measurement, the 157-tooth is 13.28 inches (call it 13-1/4 inch OD) and the 164-tooth is 14-1/4 inch OD.

All Ford V8 engines use a block plate, sometimes referred to as a starter indexing plate and it must match the block bolt pattern and flexplate tooth count.

Of importance to note is that there are specific engine block plates for these tooth counts. If you use the wrong plate the starter could be too far away from the Ford 302 flexplate or cause it to crash into the flexplate when engaged. Using an aftermarket engine block plate is a great solution for a missing plate or when switching from 157-tooth to 164-tooth flexplates, as they incorporate both starter mounting locations. In a nutshell, the transmission, flex plate, block plate, and starter must all match.

Also included in the overall discussion of small block Fords is the 335 series engines built between 1969 and 1982. The most famous being the 351C (C for Cleveland, the plant most of them were built at), but also including the two tall deck variants, the 351M and 400. These engines used the same 164-tooth flexplate just like the 351W small block. One thing to note is that the 351C used the standard small block bellhousing bolt pattern (making transmission swaps/upgrades rather easy), while the tall deck models used Ford’s 385 series big block bellhousing bolt pattern.

What Flexplate Does a Big Block Ford Use?
Ford's FE big block uses a 184-tooth flexplate that is exclusive to this engine family.

Ford’s two big block families, the 385-Series/Lima 429 and 460 (1968-1998), along with the popular FE series (390, 427, and 428 to name the more popular displacements built between 1958 and 1976) have different flexplates specific to these engine families and cannot be mixed with the small block Ford flexplates due to balance differences (more on that in shortly). The 385/Lima series big blocks use a 164-tooth flexplate while the FE big block engines utilize a 184-tooth flex plate. The Ford 460 flexplate is not the same as the small block Ford, even though it has the same tooth count. You might read about a 176-tooth flexplate, but that is a manual transmission flywheel found on some 429/460 applications. Of special note is that these two Ford big block engine families have different bellhousing bolt patterns, so you cannot easily swap an automatic from a 460 to a 428 FE for example.

Ford’s big block families use a starter block plate, often referred to as a starter index plate, just like the small block Ford engine. It is important in Ford applications this plate is used to properly index/seat and support the starter. If your 385-Series or FE big block plate is missing, you can usually source one used online. There are a few specialty retailers offering reproduction block plates as well. Wherever you source it, don’t forget to install it BEFORE your flexplate. There’s nothing worse than dropping that fresh engine and trans down on the mounts only to turn around and spot the engine block plate sitting on your workbench. Been there, done that, earned the T-shirt!

Are Ford V8 Engines Internally or Externally Balanced?

Yes, they are. OK, we got the sarcasm out of the way. The serious answer is that Ford has produced both internally and externally balanced V8 engines over the decades and the externally balanced engines use various balance weight specs. The easiest way to sort them all out is via this handy list we created.

Ford Small Block (289/302/351W)

Externally balanced via weighted damper and flexplate

  • All 289 and 351W engines use 28.2 oz balance
  • 1968-1980 302 engines use 28.2 oz balance
  • 1981-2002 302 engines (5.0L) use 50 oz balance
When internally balancing a small block Ford you will need a zero balance (also called neutral balance) flexplate and balancer.

For externally balanced engines you do have the option of having your machine shop/engine builder converting to internal balance via aftermarket crankshaft upgrades or balancing with “heavy metal” and then using a neutral/zero balance flexplate and balancer. These are usually SFI flexplates, which provide an extra layer of security when pushing the rpms at the track.

The popular small block Ford 331 and 347 stroker cranks change the factory 5.0L 50oz balance back to the earlier 28.2oz, so watch out for that when building a stroker engine.

(Note: the late-model 5.0L V8 balance will often change to the earlier 28.2 ounce when a stroker kit is installed. This requires the use of an aftermarket balancer and a 164-tooth 351W flexplate is the perfect solution when fitting up a modern overdrive transmission like the AOD or 4R70W. Most of these balancers are “flat faced” and will require a pulley spacer to maintain belt alignment.)

An externally balanced small block Ford may be internally balanced using Mallory slugs, often referred to as "heavy metal" by engine builders. The only way to know for sure will be to pull the pan and look for the weight slugs in the crankshaft.

335-Series (351C/351M/400)

Externally balanced via weighted damper and flexplate

  • All engines use 28 oz balance

385-Series/Lima Big Block (429/460)

Internally balanced crankshaft

  • All 429 engines
  • 1968 to mid-1979 460 engines

Externally balanced via weighted flex plate and add-on “hatchet” weight behind damper

  • Mid-1979-1998 460 engines use 24 oz balance

(Note: If unsure, check your 460 block casting numbers. D1VE, C8VE and C9VE are the early internally balanced engines. Block casting number D9TE-6015-AB is the late externally balanced 460. Note this assumes your block still has the original crankshaft. It is possible to interchange crankshafts between early and late engines.)

FE Big Block (390/427/428/etc.)

Internally balanced crankshaft

  • All 332, 352, 360, 390, 406, 427 engines

Externally balanced via weighted flex plate (428CJ uses “hatchet” weight at damper)

  • All 330, 361, 391, 410, 428 engines use 28 oz balance
What Torque Converter Bolt Pattern Does Ford Use?
For small block Fords the 157-tooth flexplate will use the smaller Ford torque converter bolt pattern, while the 164-tooth will use the larger.

Finally, we have some good news to share with you. Ford kept things simple with their torque converters no matter if it is a 3-speed or 4-speed automatic. Ford has used only three patterns in their overhead valve pushrod V8 engines over the years and one of them is so unique you’ll most likely never see it.

Ford Torque Converter Bolt Patterns/Associations

  • 141-tooth measures 9.375 inches (exclusive to 74-78 Mustang II C4 transmission only)
  • 157-tooth measures 10.50 inches
  • 164-tooth measures 11.438 inches (equivalent to 11-7/16, some call it 11-1/2 inches)

For those Ford old hands out there much of this info is ingrained in their gray matter, but if you’re new to the Blue Oval then we hope this information has been helpful in ensuring that your Ford engine and transmission are happily married and vibration free to provide your ride with many years of fun on the road!

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