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1957 Plymouth 318 crank damper part 1821 410
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FURY
Posted 2017-10-15 1:02 AM (#550316)
Subject: 1957 Plymouth 318 crank damper part 1821 410



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Hi does anybody have a 1957 Plymouth 318 crank damper part 1821 410 in good condition that they would part with?
If this part is being replaced, and it is from a balanced engine, are there any issues in using a second hand damper from a different engine that was not balanced with the rest of the assembly?
Glenn
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58coupe
Posted 2017-10-15 9:46 AM (#550327 - in reply to #550316)
Subject: Re: 1957 Plymouth 318 crank damper part 1821 410



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Did you have your engine balanced before assembly? I would think that on an internally balanced engine the damper would not be any different.
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FURY
Posted 2017-10-16 1:59 AM (#550368 - in reply to #550327)
Subject: Re: 1957 Plymouth 318 crank damper part 1821 410



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Location: Auckland, New Zealand.
Yes the internal components were balanced separately along with the vibration damper.
I had the damper revulcanised locally prior to balancing but I noticed on the weekend that it has a bad wobble now. I would rather get a good used one than go down that track again as it hasn't done more than 10,000 miles and it looks like it has failed already..
Glenn.

58coupe - 2017-10-16 1:46 AM

Did you have your engine balanced before assembly? I would think that on an internally balanced engine the damper would not be any different.
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wayfarer
Posted 2017-10-16 10:01 AM (#550377 - in reply to #550316)
Subject: Re: 1957 Plymouth 318 crank damper part 1821 410



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You can install any replacement balancer if it is from a forged crank engine. Since you have a rebalanced assembly the replacement should be checked.
If this is not a 100-point car then any A or LA part can be used.
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57chizler
Posted 2017-10-16 2:06 PM (#550393 - in reply to #550377)
Subject: Re: 1957 Plymouth 318 crank damper part 1821 410



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On the 318, forged or cast crank makes no difference in balance.
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wayfarer
Posted 2017-10-17 10:29 AM (#550457 - in reply to #550316)
Subject: Re: 1957 Plymouth 318 crank damper part 1821 410



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...you might double check that ......
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57chizler
Posted 2017-10-18 12:02 PM (#550546 - in reply to #550457)
Subject: Re: 1957 Plymouth 318 crank damper part 1821 410



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No 318, even the later Magnum, ever used external balance.
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mstrug
Posted 2017-10-18 5:49 PM (#550564 - in reply to #550316)
Subject: Re: 1957 Plymouth 318 crank damper part 1821 410



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Maybe:

https://www.ebay.com/itm/Mopar-Chrysler-Plymouth-Dodge-Poly-318-Harm...
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mstrug
Posted 2017-10-18 5:53 PM (#550566 - in reply to #550316)
Subject: Re: 1957 Plymouth 318 crank damper part 1821 410



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info:

Building a 318 Polyhead Motor β€” LA and A Parts Interchange
A lot of parts interchange between the 1962 to 1966 polyspherical A 318 engine and the LA series of Mopar motors (318, 273, 340, 360), including:

Thermostat
Thermostat housing
Internally balanced 273-318-340 harmonic balancers
Valve springs, retainers and keepers
Main bearings (NOT 360 though)
Rod bearings
Crankshafts (reground 360's included)
Flywheel
Starter, both standard and high torque
318 LA ring set
timing chain and sprocket
fuel pump
oil pump
oil pan (not 360) β€œThe 360 front and rear seal/front timing cover is bigger than those of the 273/318LA/340 to accommodate the larger main bearings.” ” Bill P.
distributor pump drive gear
distributor, standard points or electronic


Though reported as interchangable in several references, apparently the timing covers are not exactly the same.

http://www.1962to1965mopar.ornocar.com/poly318_1.html
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wayfarer
Posted 2017-10-25 10:06 AM (#551004 - in reply to #550546)
Subject: Re: 1957 Plymouth 318 crank damper part 1821 410



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57chizler - 2017-10-18 9:02 AM


No 318, even the later Magnum, ever used external balance.


If someone would guide me through the process I'd be happy to scan and post a copy of page 51 in the 9th edition of the Mopar Engine Manual
where it clearly lists the 74-89 318 as a cast crank with service part number 3751831.
I would be remiss if I did not also mention that the list differentiates the 318-4 bbl with a different pn.

Did MaMopar internally balance a cast crank??

Edited by wayfarer 2017-10-25 10:08 AM
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57chizler
Posted 2017-10-26 2:20 PM (#551094 - in reply to #551004)
Subject: Re: 1957 Plymouth 318 crank damper part 1821 410



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There's no debate that Mopar made 318 cast cranks (actually several of them) but the 318 cast crank doesn't require external balancing like the 340 and 360. The lighter reciprocating weight of the 273 and 318 rod/piston allows the crank counterweight to balance the assembly without external weights. Thus, the dampers will work on both forged and cast crank 318's.

I think you'll find that the main difference in 318 damper interchangeability is the location of the timing mark, it changed with front cover design.

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