340 to 360 Harmonic Balancer Swap?

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kenicb

kenicb

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i am swapping parts off a 340 to a 360 long block

1) I have a 340 harmonic balancer with the "use for 340 cast crank only"
stamped on it. will this particular balancer work on the 360?

2) will the 340 flex plate work on the 360?

3) will the torque coverter need to change as well?

thanks so much. Godspeed

keni
 
WELCOME TO FABO

forged crank 340s were internally balanced up to about 71. 360 are externally

i dont know if an externally balanced 340 72+ would work on a 360 though.

There is a Mopar book on small blocks that might be your best bet for an answer. i will look in mine tonight and repost if i find anything

I am sure someone else here will know for sure.
 
In theory since it is for the cast crank, it should be externally balanced. Therefore it should all work. Not sure if the bolt patterns are different.
Interested to see what others think.

I skipped all the guess work on my 360, and ordered a Mopar Performance 360 balancer, and B&M 360 flex plate.
 
the 340 external balance is not the same as the external balance of the 360's, so no on the dampener, diff stroke/piston weight.
more arm requires...more counter balance...
The flex plate will work but the convertor need to be balanced for the 360, or you must use the external balance 360 convertor.
 
1wild&crazyguy said:
the 340 external balance is not the same as the external balance of the 360's, so no on the dampener, diff stroke/piston weight.
more arm requires...more counter balance...
The flex plate will work but the convertor need to be balanced for the 360, or you must use the external balance 360 convertor.
Click to expand...


...340 cast crank balancer is for a 340 cast crank...that is why it is written on balancer for 340 cast crank....
 
kenicb said:
i am swapping parts off a 340 to a 360 long block

1) I have a 340 harmonic balancer with the "use for 340 cast crank only"
stamped on it. will this particular balancer work on the 360?

2) will the 340 flex plate work on the 360?

3) will the torque coverter need to change as well?

thanks so much. Godspeed

keni
Click to expand...
I have a 360 oem balancer and a 360 oem torque convertor if your interested. they came off of a 74 charger 360. my engine is now internally balanced so I do not need these.
 
"340 cast crank balancer is for a 340 cast crank...that is why it is written on balancer for 340 cast crank...."

Yes thank you. I should have thought of that. remember, everything is easy when you know how to do it. So it sounds like the flex plate off the 340 is good to go as long as I can get an oem 360 balancer and torque converter.
 
yepp the flex plate will work. are you puttin a 360 in place of a 318? there is a aftermarket flex plate to do that so you don't need a new convertor
kenicb said:
"340 cast crank balancer is for a 340 cast crank...that is why it is written on balancer for 340 cast crank...."

Yes thank you. I should have thought of that. remember, everything is easy when you know how to do it. So it sounds like the flex plate off the 340 is good to go as long as I can get an oem 360 balancer and torque converter.
Click to expand...
 
1wild&crazyguy said:
the 340 external balance is not the same as the external balance of the 360's, so no on the dampener, diff stroke/piston weight.
more arm requires...more counter balance...
The flex plate will work but the convertor need to be balanced for the 360, or you must use the external balance 360 convertor.
Click to expand...

thank you. that makes sense to me now. If the cranks are interchangeable, it didnt make since to me why the balancer was specific to just the "cast 340 crank" I didnt think about the piston components being different weights..
 
"yepp the flex plate will work. are you puttin a 360 in place of a 318? there is a aftermarket flex plate to do that so you don't need a new convertor"

the 360 is replacing the 340 which i pulled to work on. So I hear you saying if I buy the aftermarket balanced flex plate, I can keep the torque converter?

If i were to look for the flew plate at summit what would i ask for? A "balanced flexplate for a 360"?
 
no nevermind, keep that convertor with the 340 i do believe it is diffrent than a 360 one
kenicb said:
"yepp the flex plate will work. are you puttin a 360 in place of a 318? there is a aftermarket flex plate to do that so you don't need a new convertor"

the 360 is replacing the 340 which i pulled to work on. So I hear you saying if I buy the aftermarket balanced flex plate, I can keep the torque converter?

If i were to look for the flew plate at summit what would i ask for? A "balanced flexplate for a 360"?
Click to expand...
 
You running a 904 or 727 ?

B&M External balanced 360 flex plate:
904 part #10239
727 part #10236

360 balancer P5007301
 
I believe the flexplate part numbers johnny offered up are "if" you have a 318 or internallybalanced 340 ,273 or 318 to install externally balanced 340 or 360 with neutral balance convertor....hell I'm gittin confused now....
Johnny Dart said:
You running a 904 or 727 ?

B&M External balanced 360 flex plate:
904 part #10239
727 part #10236

360 balancer P5007301
Click to expand...
 
Everything I listed is for a 360 only.

I switched from a 318/904 to a 360/904. I bought the Mopar 360 balancer P5007301 from the local Dodge dealer and the B&M 904 360 externally balanced flex plate #10239
from Summit. Works perfect.

Lol.....This can get confusing, thats why I took all the guess work out of it and bought 360 only (externally balanced) parts.
 
OK thanks Johnny. That certainly simplifies matters. I found a 360 balancer. So all i need now is the B&M 904 360 externally balanced flex plate from Summit. The torque converter can stay the same correct?
 
kenicb said:
OK thanks Johnny. That certainly simplifies matters. I found a 360 balancer. So all i need now is the B&M 904 360 externally balanced flex plate from Summit. The torque converter can stay the same correct?
Click to expand...

As long as it is "0" balanced.

The B&M flex plate is designed to couple Externally balanced engines with
"0" balanced torque converters. There should be no weights on the converter.

For example: The 1973 cast crank 340 had 4.22 ounces of weight added to the converter. So........

I used a 904 Mopar Performance converter I got off E-bay for cheap. If you need some part#'s let me know.
 
OK Got it all figured out. Here's where i got confused. The 340 with cast crank is EXTERNALLY balanced. From the factory that would mean the harmonic balancer was the special "use for 340 cast crank only" and a balanced torque converter.

However, the 340 I pulled had an aftermarket balanced flex plate on it. Meaning the torque converter had been replaced w a neutral one.

Thats good news for the 360 Im putting in. I kept the neutral torque converter in and used the stock 360 harmonic balancer and bought a 360 balanced flexplate from B&M that would bolt to the 904

So, thanks for all the help. I got it together. will give you pics soon.

God bless
keni
 
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