swapping out 8" balancer
Thread Starter
Racer
Joined: Sep 2004
Posts: 495
Likes: 0
From: berwick pennsylvania
swapping out 8" balancer
need some help here fellas. i want to swap out my oe 8" damper for my externally balanced 383 with a 7.25" fluidampr. what will i need to do to make this happen? balance match the fluidampr to the old 8" one or nothing at all?
all help is greatly appreciated.
thanks,
chris
all help is greatly appreciated.
thanks,
chris
Large Impressive Member
Joined: Jul 2003
Posts: 65,811
Likes: 71
From: Good health is merely the slowest possible rate at which one can die
St. Jude Donor '04-'05-'06-'07
I'm not sure about your L98(?) but the LT1, although externally balanced in the rear is internally balanced in the front, hence the damper should be neutral. If this is the case then you should be good to go. 
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
The L98 is neutrally balanced, front and rear, but a non-internally balanced 383 has the same imbalance as a stock 400, externally balanced (imbalanced) at both ends. The OE, C4, damper isn't 8". The OE 400 CID damper IS 8". The Corvette L98 damper is closer to 6 3/4" to 6 7/8". If the 383 going in, isn't internally balanced, you will need a damper with the imbalance of a stock 400 CID engine. If the engine was properly built with that 7 1/4" damper, and it has the 400 imbalance, it has the proper balance. The 7 1/4" diameter is a definite "maybe". There was a recent thread on here, where just that question was addressed. I believe that the consensus was that the 7 1/4" damper cleared the cross member in most, if not all, cases.
RACE ON!!!
RACE ON!!!
Thread Starter
Racer
Joined: Sep 2004
Posts: 495
Likes: 0
From: berwick pennsylvania
cfi-efi,
the balancer is not my oe l98 balancer is is a 8" balancer for a ext balanced 400. the motor is in the car and running and running great! the x member is clearanced for the 8" balancer .i would like to use a fluidamper to more accuratly control the tortional vibration and reduce some rotatating mass.so what u r saying is if i get a 7.25" fluidamper for for an ext balanced 400 it will work with no additional balancing
the balancer is not my oe l98 balancer is is a 8" balancer for a ext balanced 400. the motor is in the car and running and running great! the x member is clearanced for the 8" balancer .i would like to use a fluidamper to more accuratly control the tortional vibration and reduce some rotatating mass.so what u r saying is if i get a 7.25" fluidamper for for an ext balanced 400 it will work with no additional balancing
Race Director
Joined: Feb 2004
Posts: 12,518
Likes: 19
Chris, I built a 383 for sami85l98. He used a 6 3/4 (I think) balancer from summit. SFI approved, nice quality and a silly cheap price of $125 bucks or so. Check on this before you buy. I have never seen a quality, external balancer that looked that good and was priced so well.
Le Mans Master
Joined: Jan 2002
Posts: 9,036
Likes: 13
From: Edmonton AB
I recently contacted Fluidampr with a similar question and received
a very prompt reply as follows:
To Fluidampr
sami85l98 provided details on a 6-5/8" damper for Summit and
eguyett1985 reported:
a very prompt reply as follows:
To Fluidampr
> > I have a GM crate engine that came with an 8" damper (#12498008).
> >
> > Is someone able to tell me whether the Fluidampr 720111 or
> > 790100 externally balanced dampers (26oz imbalance) are
> > suitable replacements?
Their Reply> >
> > Is someone able to tell me whether the Fluidampr 720111 or
> > 790100 externally balanced dampers (26oz imbalance) are
> > suitable replacements?
> > Hi Ken,
> >
> > If the 8" damper that came with your crate engine has a counterweight
> > on it, then our part number 720111 or 790100 will work on your engine.
> > Sometimes GM puts an internal balance 400 crank in their crate
> > motors and sometimes they use an externally balance crank. If
> > your damper has a counter weight on it then it is externally
> > balanced.
> >
> > The outside diameter of p/n 720111 is 7-1/4" & p/n 790100 is 7-3/16"
> > diameter. I hope I have answered all of your questions,
> > let me know if there is anything else I can help you with.
> > Thanks.
> >
> > Dan
From a recent thread,> >
> > If the 8" damper that came with your crate engine has a counterweight
> > on it, then our part number 720111 or 790100 will work on your engine.
> > Sometimes GM puts an internal balance 400 crank in their crate
> > motors and sometimes they use an externally balance crank. If
> > your damper has a counter weight on it then it is externally
> > balanced.
> >
> > The outside diameter of p/n 720111 is 7-1/4" & p/n 790100 is 7-3/16"
> > diameter. I hope I have answered all of your questions,
> > let me know if there is anything else I can help you with.
> > Thanks.
> >
> > Dan
sami85l98 provided details on a 6-5/8" damper for Summit and
eguyett1985 reported:
Originally Posted by eguyett1985
I have a 7 1/4" Fluidampr on on my 408 and there are
absolutely no clearance problems with the crossmember.
absolutely no clearance problems with the crossmember.
Thread Starter
Racer
Joined: Sep 2004
Posts: 495
Likes: 0
From: berwick pennsylvania
so as long as the new balancer has the same amount of imbalance as the old one i am good to go? if a am reading that correctly. sorry to sound so stupid bout this just got a lot of money tied up in this engine.
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Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
I had written a detailed response, before the previous three posts appeared, but apparently, I clicked on the wrong icon and it is lost in cyberspace. You seem to have your answer.
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