360 Internal or External Balance??

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pastortom1

pastortom1

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On a 74 360, was the balancing internal or external?

I have to guess external like the 318's, but I know the 340's were internal......

I want to make sure the car I'm working on is correct.......I feel a little harmonic vibration in there, but not at idle........Could be the torque converter............Internal or external???
 
All 360's are externally balanced. The newer Magnum 360 are also externally balanced, but take a little less external weight because of lighter internal components.

All 318's are internal.
Forged crank 340's are internally balanced.
Cast crank 340's are externally balanced, but even less than a 360 Magnum.
 
Yep, Locomotion Is Correct--one Note Is All 318's Are Cast Crank Thats Internally Balanced Therefore The Same Balancer As Forged Cranks[yes There Were A Few Forged Steel Crank 318's-marine-industrial Etc. But For Most Part Were Cast Cranks That Were Internally Balanced] Heard Rumors That There Were Some 360 Forged Cranks But Never Seen One Or Know If They Exist, Very Possible Knowing Some Of The Strange Things Chrysler Did....
 
Well, the 318's are a surprise........I thought for sure they were external.......

I'm feeling a vibration similar to a mismatched converter..........I wonder if the previous owner put a neutral balance on there..........Gotta go under I guess.
 
Clarify this for me please? I thought 273, 318,340 were all internally balanced, but you guys say some 340's were externally balanced? Please claify if you can positively verify, Walt
 
ALL 360S WERE EXTERNAL BALLANCED.340s made in 1973 and newer are cast cranks,and EXTERNAL BALLNACED.318s went to cast cranks in 1970 or 71.That is debateable,because ive got 2 71 318s that came out of one owner cars and there both forged cranks.Now 318s in straight drive applications remained forged for a few years,im not sure when that stopped,but i have a book that tells for sure somewere.The book "How to hotrod smallblock Mopars"Is a good place to find specific years and casting numbers for cranks that your not sure if its cast or forged.Also,all 273s had forged cranks.As most of you know,but some may not,you can put the forged crank from a 273 right in any 318(premagnum)or 340 if you currently have a cast crank engine.Then you can run the thinner,lighter internal ballance harmonic ballancer.Now knowing that 273,318,and 340 all had pistons that weigh different,its hard to believe they are ballanced correctly from the factory,but thats how production stuff goes i guess.As a side note,All 383 bigblocks had forged cranks,and they are the same stroke as 400 b blocks,so they are a direct replacement for the stock cast crank 400s.
 
There were cast crank 340 engines in model year 1972. But it seemed like a lot of leftover parts from 1971 continued into 1972 until they were used up.

Here are some helpful links on what to look for.

http://www.moparts.org/Tech/Archive/smallblock/5.html

http://www.moparts.org/Tech/Archive/motor/8.html

http://www.moparts.org/Tech/Archive/conv/8.html

There obviously were a lot more forged crank 340's built because they were manufactured from 1968 into 1972. Cast crank 340's were only manufactured from 1972 through 1973, which was the last year for the 340.


To add a little to what tobysoldblue said - while 273 cranks can be installed in a 318 and/or 340, it would be wise to rebalance the rotating assembly. Different cranks have different weights. A casting is also lighter than a forged piece. This actually makes the counterweights lighter and requires external weights in most Mopar applications. 318's are an exception. Piston and rod weights can be different in different years also.


Also, I forgot the transition year, but very early 273 cranks had a smaller converter register and will not accept the newer/modern torque converters which had a bigger "snout".
 
I forgot about this one (I'm a small block guy.): 440 Six Pack engines are the only forged crank Mopars I can think of that are externally balanced.
 
pagilman said:
Are you guys saying only forged cranks are internally balanced?
Click to expand...

No.

All 273's used a forged crank and were all internally balanced.

All 318's were all internally balanced and used both forged and cast cranks depending on the year they were made.

340's with a forged crank were internally balanced but later 340's that used a cast crank were externally balanced.
 
whether or not a crank is internally balanced has nothing to do with cast or forged...

it has to way the weight of the piston/rods in comparison to the weight of the crank....

cast cranks are not as heavy as forged...they weight less...so weight must be added by some means...hence...weight added to balancer and converter.

if light weight pistons and rods are used with cast crank...it is possible that weight is not needed on balancer/converter...

so...it depends....
 
It wouldn't hurt if you have the time and space. It's just a matter of finding a customer. But there are a few people who occasionally look for whole 273's for other parts or to race in class.

But as mentioned before, very early 273's had a small converter snout register which will not accept the common, later converters, unless someone machines it out. I just don't remember the transition years. But either way, anytime you start swapping parts around - 273, 318 or 340, the rotating assembly needs to be checked for proper balance.
 
locomotion thanks for the input. where you located in florida, I'm leaving on the 4th for ocala taking the camper and then on down to the keys untill Jan, doing some fishing and snorkeling. Walt
( I just retired in oct and am making a pest of myself on the site)
 
So 318la does not need a weighted flex plate or converter ? I’ve pulled apart many 318 cars and all had weights on the conveters
 
It's been a while since I've seen an OEM converter. Perhaps they have small weights to fine-tune the "neutral" balance. Only LA 360's and cast crank 340's were externally balanced. 360 Magnums had less weight than LA 360's. Don't recall details on Magnum 318's.
 
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