Reply to "351C flex plate"

> Flex plates should be interchangeable with other Small Block Fords.

No. You'll find there are 157 teeth and 164 teeth versions, along with
28.2 oz-in and 50 oz-in flex plates (also neutral balance if you include
the 300 truck six which shares the same bolt pattern). There were small
and large C4 bell housings. The small used the 157 teeth flex plates
while the large used 164. There was also a smaller C4 used in the
Pintos and Mustang II's (I've seen 141, 143 and 148 teeth claimed at
various times but have never come across any of those). Also the 157
teeth flex-plates have a 10.5" converter bolt pattern, while the 164 tooth
flex-plate is 11 7/16".

351C's came with 28.2 oz-in 164 teeth flex plates. If you try to use
a stock size starter with a 157 teeth, it will not clear the oil pan
lip unless you roll it back. I've done that before but it's better to
use a mini-starter. The small bellhousings are nice as they have more
clearance for headers.

Google Moneymaker Racing (Alex Denysenko) and he can set you up with
the right flex plate for you application. Below I've added a few C4
notes from the write up I did after I did a C4-to-AOD swap in my
mom's Mustang convertible.

Dan Jones


Balance Factor Information
--------------------------

1981-and-up 5.0L - 50.0 oz-in
Pre-1981 289/302 - 28.2 oz-in
351W and 351C-400 - 28.2 oz-in

C4 and AOD Dimensions
---------------------

Overall Length (bellhousing to tailshaft housing end, flat-to-flat):
AOD - 30 3/4"
C4 - 30 1/4"

Notes:
"Engine Swapping Tips and Techniques" lists C4 length as 27 3/4" (C6 length
28 1/2" or 28 3/4"). I may have measured to the end of the output shaft,
not to the end of the tailshaft housing.

Distance from Bellhousing to Insulator Mount (flat to mounting hole centerline):
AOD - 21 3/4"
C4 - 19 3/4"

Torque Converter Stud Spacing (centerline-to-centerline)
AOD/C4/164 teeth flexplate - 8 1/4" between closest studs, 11 7/16" between
farthest studs (stud pattern diameter)
C4/157 teeth flexplate - 7 3/4" between closest studs, 10 5/8" between
farthest studs (stud pattern diameter)

Transmission Lengths from "The E4OD", Ford High Performance, April 1995

Trans Bellhousing Overall Length
Face to Trans From Bellhousing
Mount Length To Tailshaft End

C4 20 1/4" 30 1/2"
C6 22 1/2" 33 1/2"
AOD 22 1/4" 30 3/4"
E4OD 29 3/8" 37 1/2"

Torque Converter Snout Diameter (from early SVO catalog)
289, 302, 351W/C/M, 400, 429/460 - 1.375"
FE series and early '68 Lincoln 460's - 1.848"

Flexplate Diameters
164 teeth - 14 3/16" (13" converter)
157 teeth - 13 1/4" (11" converter)
141 teeth - ?

Mustang II used 148 teeth flywheels and 141 teeth flexplates.

C4 Variations
-------------

C4 detachable bellhousing, case, and tailshaft housing.

Large bellhousing - smooth flair case, twin bolt circles (case to housing,
outer secures bellhousing to trans case, inner secures oil pump to case),
3 locating tabs, 14 3/16" flexplate, 13" converter, no dipstick hole in
main case (dipstick goes into right front corner of pan), used in small-block
powered large cars and light trucks.

Small bellhousing - step case, single seven bolt circle (case to housing),
13 1/4" flex plate, 11" torque converter, dipstick hole in case (seals with
an O-ring), five bolt ('64 1/2 and early '65 Mustangs, etc.) and six bolt
versions, used in small and medium small-block powered cars.

Trans-Dapt supposedly makes adapters for six bolt blocks to five bolt
transmissions (need to check on details).

Top bellhousing bolt holes are 5 1/8" apart.

"C" intermediate servo (289 hipo applications) is largest but rare.
"H" servo is next largest, used on 302 4V engines from 1968.
"A" servo is typical stock unit.

Pinto governor allows highest rpm shifts, p/n D7ZZ-7C063-C.

C5 pan interchanges with C4 and is deeper.

There was a revision in mid '70's to nine mounting bolts for the valve body,
previously used 8 bolts.

Main cases and bellhousings for large and small versions are not
interchangeable. 5 and 6 bolt small bellhousings are interchangeable between
each other (on the case side).

Entire 6 bolt (small or large bellhousings) transmissions, except for
dipstick locations, are interchangeable in many cars (some smaller cars
require the small bellhousing variant).

C5 bellhousing looks similar, but has a completely round hole in the front
pump area and is not interchangeable with C4 bellhousing.

Standard Tailshaft - 13 1/8" long, most applications.
Short Tailshaft - 6 5/8" long, some pickups and vans.

Input Shaft Spline Count (8 cylinder and some 6 cylinder applications)
'70 and later - 26 splines
pre-'70 - 24 splines

Note: Some 1970 input shafts have 26 splines on both ends ('71 and later have
24 splines on one end and 26 on the other), making them the most desirable
for drag racing applications.

Need to add C4 valve body variations (green-dot, cruise-o-matic, etc.) and
AOD shift sequence

Four and six cylinder versions are light duty (fewer clutch plates).

Some C4's (late '60s, early 70's Mavericks? need to check details) had
full-manual valve bodies.


Major C6 variations
-------------------

C6 integral bellhousing (case and bellhousing are one piece) with tailshaft
housing:

FE big blocks - round bellhousing opening with top bolts 6" apart,
often have stiffening ribs on top of case/bellhousing

302/351W/351C - bellhousing opening is squared off on top, case opening
is 16 3/4" tall, top bolts are 5 1/8" apart, no ribs

351M/400/429/460 - bellhousing opening is squared off on top, case opening
is 17 3/4" tall, top bolts are 7 3/4" apart, has ribs


Transmission Weights
--------------------

AOD (without converter or fluid) - 150 lbs
AOD stock torque converter - 34 lbs
C4 (without converter or fluid) - 110 lbs
C4 torque converter - ? lbs
C6 (without converter or fluid) - 140 lbs
C6 torque converter - 30 lbs small block, 31 lbs big block
FMX (without torque converter, unknown fluid level) - 160 lbs
FMX torque converter - 32 lbs
Ford-o-Matic (pre-FMX), cast iron case - 228 lbs

Notes:

- AOD and C4 weights are as measured by me using a standard bathroom scale.
- FMX and C6 torque converter weights provided by Steve Grossen (also used
bathroom scale).
- Ford-o-Matic weight is an assembly line weight provided by my Dad.
- C6 weight is from "Engine Swapping Tips and Techniques" which also lists
the C4 at 109 lbs.