external balanced engine ?
Thread Starter
Instructor
Joined: May 2006
Posts: 144
Likes: 0
From: Stockbridge GA
external balanced engine ?
I am thinking of replacing the harmonic damper on my 383 stoker in hopes of getting rid of some vibration at high rpms when i installed the engine i put the cheapest damper i could on it so i could focus on bigger issues i had at the time. My question now is i see that prices range from $98 to $417 for a new damper is it worth buying the $417 one? Also I need to know if I can install right out of the box or do I have have a machine shop check the balance of the engine and add counterweights to the damper
Melting Slicks
Joined: Dec 2009
Posts: 3,229
Likes: 656
From: Thunder Bay
If your 383 is externally balanced, you have to make sure you get the damper for an externally balanced engine. Balancers should be balanced as part of the rotating assembly when the engine is built. If you need to replace the damper, and you are sure the outer ring has not slipped, you can get the balancing shop to balance the new one the same as the old one. If you are replacing it to cure a vibration problem, I think you are in a crap shoot. If you really want to cure your vibration problem, you're going to have to disassemble the engine and balance everything properly. Otherwise, you're just guessing.
Safety Car
Joined: Aug 2000
Posts: 3,711
Likes: 43
From: San Antonio TX
Some (most) 3.75 strokers are externally balanced. You need to know what balance you have before you get a damper/balancer. The root cause of your vibration could be putting on the wrong balancer (internal or neutral balance damper on an external balance crank).
When you buy a damper, you will see they have internal and external balance. The external balance damper will have the balance offset built in and you won't need to do anything more.
The cost difference is usually reflective of the intended use. The cheaper dampers are for most applications. The $$ dampers are the ones that have an SFI certification for class racing, some technology and marketing that may or may not have any relevance to your situation.
When you buy a damper, you will see they have internal and external balance. The external balance damper will have the balance offset built in and you won't need to do anything more.
The cost difference is usually reflective of the intended use. The cheaper dampers are for most applications. The $$ dampers are the ones that have an SFI certification for class racing, some technology and marketing that may or may not have any relevance to your situation.
Thread Starter
Instructor
Joined: May 2006
Posts: 144
Likes: 0
From: Stockbridge GA
Some (most) 3.75 strokers are externally balanced. You need to know what balance you have before you get a damper/balancer. The root cause of your vibration could be putting on the wrong balancer (internal or neutral balance damper on an external balance crank).
When you buy a damper, you will see they have internal and external balance. The external balance damper will have the balance offset built in and you won't need to do anything more.
The cost difference is usually reflective of the intended use. The cheaper dampers are for most applications. The $$ dampers are the ones that have an SFI certification for class racing, some technology and marketing that may or may not have any relevance to your situation.
When you buy a damper, you will see they have internal and external balance. The external balance damper will have the balance offset built in and you won't need to do anything more.
The cost difference is usually reflective of the intended use. The cheaper dampers are for most applications. The $$ dampers are the ones that have an SFI certification for class racing, some technology and marketing that may or may not have any relevance to your situation.
Race Director
Joined: Apr 2000
Posts: 17,676
Likes: 201
From: Who says "Nothing is impossible" ? I've been doing nothing for years.
I remember that the kit I bought had a fly wheel that the shop said was balanced for my engine but I had to buy my own damper. I am pretty sure I bought a external balance damper especially since the vibration is not that bad. Is there a way to tell what kind of damper you have by looking at it . If not can any one recommend a good external damper for street use
Thread Starter
Instructor
Joined: May 2006
Posts: 144
Likes: 0
From: Stockbridge GA
So you never got the assembly balanced in the first place ? Or if you did it is quite possible you might have an internally balanced damper. THere will be a notch in an externally balanced damper where some weight has been taken out you will not see this on an internally balanced damper .
Burning Brakes
Joined: Feb 2005
Posts: 894
Likes: 91
Internal vs. External
I bought a unassembled short block kit from larrys performance they said it was balanced so I did not pay my engine builder to balance it once it was assembled. I just hope that if I do have a internally balanced damper I can just buy one and throw it on with out pulling the engine and having the whole thing balanced ( which may not be a bad idea if I ever had another reason to pull the engine out of the car).
Contrary to the post above about "most 383's are externally balanced", this is really incorrect, out of 100 builds (here) only one may end up "external". I don't even recall the last one through here!!
(Add) The price you pay for any damper is irrelevant, you need one that will correct the problem, it's that simple. Call "Larry"!!
Thanks, Gary in N.Y.
P.S. The main reason for "external" balancing is the lower costs normally associated with the job. The reason we try to avoid this is to avoid your exact dilemma, you cannot beat an "internal" balanced unit, makes choosing/changing components fairly simple! Any "zero" balanced damper and/or flywheel will get the job done.
Last edited by GOSFAST; Mar 2, 2013 at 07:56 PM.
Drifting
Joined: May 2005
Posts: 1,968
Likes: 44
From: East TN
Are you sure the damper is the cause of your vibration? Did you do any other work that might be the issue, such as replacing the u-joints on the driveshaft, replace clutch/ flywheel, motor/ trans mounts, etc?
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Melting Slicks
Joined: Dec 2009
Posts: 3,229
Likes: 656
From: Thunder Bay
You have a "potential" major issue, not knowing the correct components used to balance the unit initially, "Larry" may be the only guy that has the answer??
Contrary to the post above about "most 383's are externally balanced", this is really incorrect, out of 100 builds (here) only one may end up "external". I don't even recall the last one through here!!
(Add) The price you pay for any damper is irrelevant, you need one that will correct the problem, it's that simple. Call "Larry"!!
Thanks, Gary in N.Y.
P.S. The main reason for "external" balancing is the lower costs normally associated with the job. The reason we try to avoid this is to avoid your exact dilemma, you cannot beat an "internal" balanced unit, makes choosing/changing components fairly simple! Any "zero" balanced damper and/or flywheel will get the job done.
Contrary to the post above about "most 383's are externally balanced", this is really incorrect, out of 100 builds (here) only one may end up "external". I don't even recall the last one through here!!
(Add) The price you pay for any damper is irrelevant, you need one that will correct the problem, it's that simple. Call "Larry"!!
Thanks, Gary in N.Y.
P.S. The main reason for "external" balancing is the lower costs normally associated with the job. The reason we try to avoid this is to avoid your exact dilemma, you cannot beat an "internal" balanced unit, makes choosing/changing components fairly simple! Any "zero" balanced damper and/or flywheel will get the job done.