• When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.

440/727 need help understanding

kinghs95

Well-Known Member
Local time
9:23 AM
Joined
Nov 29, 2015
Messages
79
Reaction score
18
Location
Bartlesville, Oklahoma
I have a 1978 cast crank 440 Bored 30 over, I think 30/30 crank might be wrong, and mild cam ....Which is externally balanced due to cast crank and harmonic balancer. I was wanting to know what torque converter and flexplate I need? Also what’s the difference btw having teeth on flexplate and having them on torque converter? Also I have already bought a mini starter for it but will that effect which on I need teeth on, and or what size of torque converter I can have? I haven’t gotten a 727 yet but I know I want an automatic.

5B2CFBF5-A8C3-41A3-85A5-E9F588ECF181.jpeg
 
You need to know what cam you have that will help you to know what stall you need on the torque converter. Others that are more smartererr will chime in. But essentially any big block mopar 727 torque converter should have the same teeth and the mini starter should work either way.
 
look up the cam manufacturer and it will list you cam by number including whether you need a higher than stock torque converter to go with it. Generally the 10" wide torque converter seems to be the one everyone wants behind a 440. I'm not an expert though and perhaps some of the racers will chime in.
 
I'd get the b&M flexplate for your external ballanced 440 (not the 6 pack one unless you have a 6 pack crank- check the front balancer
that way you can use a neutral balanced converter
now converter will depend on your cam- any details
remember the factory used the smaller HP converter even on non HP cars due to the low grunt torque of the low compression motors
what gears?
since you have a 78 do you have a lock up converter trans?
What the other guys said
do you have a low compression motor- what exhaust manifolds?
any cranking compression numbers or how far down are the pistons if you have had it apart
cheers
 
Unless I missed a memo, all 440's are internally balanced... but I have lived under a rock for awhile :moparsmiley:
 
Externally balanced engines will have a significant weight placed off center on the harmonic absorber and flywheel. If your flywheel just has the normal drill pecks in a couple of places then it might be safe to say it's internally balanced. I am also unaware of any 4340 cranks requiring external balancing. From meep-meep.
 
all cast crank 440's are externally balanced. the big fat balancer is usually marked . that also means it came with 2 20gram weights welded on either side of the drain plug on the converter. as mentioned, you can also use a flex plate that replaces the weights on the converter and use one without weights. get you a 10" converter.
 
The B&M counterweight flexplate is a good choice. It allows using any neutral balance converter with any of the different bolt patterns.
The starter ring gear for the automatic is on the converter.
Mini Starter, no problem, just need to remove the off-set connector/adaptor piece.
Best to connect starter wires before installing the starter because they sort if face the block.
 
we really need more info

for discussion sake, I'll continue

what is the intended usage of the car/engine combo ?
what is you final goal ?,
the answer may be a huge deciding factor when choosing
engine/camshaft, heads, exhaust, ignition, gears, torque converters
& many other components to make a combo work together

the V8 Dakota style "mini starter" works on any V8
that are Small block LA, Magnum or Big Block B-RB
(except new gen. 3 & up hemi's)
sometimes if the starter isn't clock-able,
you may need to trim down the main 1/4" 12vt stud,
so it doesn't contact the block & able to get the battery cables on & off
without removing the starter

as said multiple time here already
with automatic 727tf/904tf etc. the starter ring-gear
is on the torque-converter, both on BB or SB

not knowing your camshaft or rear gears
or even the induction/fuels system needs
it's hard to recommend a Torque Converter (TQ)
specifically for your combo
the OE style "Flexplate" is sort of a cloverleaf shape,
it has no starter ring gear on it
many externally balance engines
are balanced with weight on the TQ &/or harmonic balancer ecentric
you can use a full circle flex plate (not a flywheel, that's a 4 speed or manual)
like a B&M, the starters "ring-gear" is still on the TQ, not the flexpalte

(if you use a neutral balance torque converter,
from/intended for a steel crank equipped 383, 440 or 426
)
& have a cast crank in your 440, all cast cranks are externally balanced
unless custom "internally" balanced at the machine shop
the external balance full circle style flex plate,
like a B&M also
(has a 6 bolt crankshaft pattern, has 8 holes, 2 pairs of 4, for different size converter bolt patterns)
will have a half-moon chunk out of it for the external balance,
for an external balance, cast crankshaft

disclaimer;
#'s below are just used for references/information purpose,
they're not necessarily a recommendation


as to the converter choices
if you have a steeper higher numerically rear gear
&/or a camshaft with 284* advertised duration,
a min. of a 10"-11" TQ a 2500-2800rpm stall speed
is a good idea, so the car won't lunge or creep in gear...

again it all depends
on what your final use for the car is

"albeit"
the more camshaft, especially in regarding more duration
& more steep the rear gear (or higher numerically) you have
"generally speaking"
(like a 3.91:1 - 4.30:1 gear ratios) on a street/strip combo
the more stall speed you can use,
like a 3000-3200 or 3500rpm stall speed
gear multiplications/has mechanical advantages of the steeper gears
(especially higher numerically rear gears)
lessons the affects of the TQ stall speed on take off,
the car will move much easier, even with a higher stall speed with steeper gears
like a 4.30:1 vs a 3.55:1

(a heavy car can effect stall speeds a lot too)

you can get more effective stall speed,
lets say you have a 11"-11.5" 2200-2500rpm converter street/strip
if it's on/in a car equipped with 3.55:1 rear gears,
vs the 4.30:1 steeper gears
(it may actually stall/flash rpm more like 2600-2700rpm, before the car moves hard)
mainly because of the mechanical advantage of
steeper gear & torque multiplication
with the same converter & a 4.30:1 gear, the car will want to move easier
or quicker, it may still flash to the advertised 2200-2500rpm stall speed,
but the car will already react much quicker, less/lower effective stall speed
(the converter really needs to match your whole cars combo, to be effective/efficient)

the more HP & Torque you engine puts out
the more critical the camshaft, gears & converter combo plays
in selecting a proper TQ, can make or break your combo/performance

if any of that makes any sense

good luck
 
Last edited:
Also I have already bought a mini starter for it but will that effect which on I need teeth on, and or what size of torque converter I can have?

No, it shouldn't. Fortunately, as a company with it's roots in solid engineering, founded by a man who surrounded himself with talented engineers, designers, etc they got that right the first time.
 
Sorry it’s a 1976 440 going in a 1972 satellite that I’m putting a 8 3/4 rearend in with 489 third-member with clutch sure-grip, 3.55 gears, 1350 yoke that I bought from dr diff, and have hooker headers. I don’t currently have a 727 yet and a lot of other parts but working on it. Just trying to educate myself on what I need or what is best. It has a mild purple cam but no 100% what it was bc I bought the 440 a few years ago and can’t remember.

22EED369-A78B-4C2D-BD6E-625F8E58E780.jpeg B3610598-05A0-4A34-AB77-7BA2E518FA39.jpeg 72DBB673-5609-4B56-8F66-24664E7B12BF.jpeg
 
can you check the lift on the purpleshaft
a lot of the purple shafts used the same spring- check it out
any idea what your cr and cranking compression are/ were?
 
a lot of the purple shafts used the same spring- check it out
any idea what your cr and cranking compression are/ were?

I think it was 8:2:1 but not 100% sure
 
Auto Transport Service
Back
Top