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Old 11-05-2012, 12:52 PM   #1
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L31 Harmonic Balancer

Stock balancer is shot.

I have an internally balanced motor, not external

I have cross references this motor with other applications and it appears the best xreference data on it is the 96-02 c1500 express van. When I check listings like Summit racing I do not see any listing for a Fluidampr unit(which is what I desire)

I will assume that basically any SBC gen 1 balancer will work but its a matter of keyway clocking for timing marks.

The stock elastomer unit is an 8" but I want to run a much better quality Fluidampr in a 6.8" which is simular to what I did on an extenally balanced L05 motor I had years ago.

Can anyone please help confirm Im doing the correct thing buy putting this Fluidampr unit onto the L31 motor?

http://www.summitracing.com/parts/flu-670100

Dean
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Old 11-05-2012, 03:03 PM   #2
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Re: L31 Harmonic Balancer

Nevermind.

I call the tech @ Fluidampr and asked the same question and even he was not sure. He said he;'s never had anyone try and put one on a Vortec head crate motor.

He seems to think it will fit fine also, but I might have timing mark issues just like I also assumed.
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Old 11-05-2012, 04:04 PM   #3
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Re: L31 Harmonic Balancer

Really the timing mark is the only issue. Where is it located on your current motor? The location of the timing mark on the vortec is clocked off to the driver side. A lot of older SBCs are straight up and town.
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Old 11-05-2012, 05:32 PM   #4
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Re: L31 Harmonic Balancer

Quote:
Originally Posted by SlickTrackGod View Post
I call the tech @ Fluidampr and asked the same question and even he was not sure. He said he;'s never had anyone try and put one on a Vortec head crate motor. .
Time they got a new tech ;
Vortec crank is just a reg 1 pce seal SBC crank , no different to a late L98 or LT1 crank

Quote:
Originally Posted by SlickTrackGod View Post
I will assume that basically any SBC gen 1 balancer will work but its a matter of keyway clocking for timing marks.
Keyway didn't change , the position of the timing tab did ( and thus the position of the line marked on the balancer )

"Timing tags from 1955 through 1968 the mark on the balancer was 2 degrees of the keyway
1969 till the mid 1980's the timing mark was 10 degrees off the keyway
from the mid 1980's the timing mark was moved 30 degrees of the keyway."


Balancer you selected should work fine
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Old 11-05-2012, 06:34 PM   #5
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Re: L31 Harmonic Balancer

A real Vortec balancer has a snout about 1/8" shorter than earlier engines because of the added thickness of the factory crank trigger wheel taking up space between the balancer snout and timing chain gear.

If your application does NOT use the Vortec crank trigger wheel (like a crate motor or an original Vortec engine where all that factory crank trigger stuff has been removed) you can indeed use a plain 'ol gen1 balancer like off a 70s/80s-vintage small block. You can't use a 90s-vintage LT1 dampener in either case, however. Different animal.
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Old 11-05-2012, 10:15 PM   #6
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Re: L31 Harmonic Balancer

Thank you for the info both of you^^^.

yes I was surprised a tech could not answer what I thought was a simple and very common issue. There are tons of Vortec crate motors used in hotrod apps out there just prior to the LS craze. I find it hard to believe that Fluidampr never had to answer this question to someone wanting to spin a L31 motor up a little more in the RPM range. It is common reading to find the stock dampers on the crate motors will slip with a little abuse.

As for the longer snout, if I am in fact sitting out an 1/8" further it is no issue at all for me-Why?- I run an electric waterpump and an underdrive dual serp crank pulley running only a powersteering pump 5 rib on one side and a 6rib Alt on the other side of the motor- both are adjustable mount units in the fore and aft positions from March Performance. I have about 1" adjustment on the pump to keep it lined up with either a short or long snout waterpump even though I don't need it for that.

Timing is an easy fix. I generally run 3* advance off base timing so I will set the motor to 0 advance with this current dampner and then switch to the new unit and record the "new zero" at whatever degree it reads in my little notebook of modifications (I should say big notebook 78 lincoln mark7 rotors, 86 svo rear calipers, chevelle balljoints, 1330-1350 conversion u-joints, etc etc etc. I something ever happened to me no one would know what the heck this vehcile takes in replacement parts- I try to keep what I can under direct vehicle reference for future maintinance- hence why I asked for advice but I see I'm pretty well versed already on my choices.

Thank you guys

Dean aka Vetruck
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Old 11-26-2012, 05:14 PM   #7
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Re: L31 Harmonic Balancer

GM L31 #12555879 & 12341915 TAB

However I have the L31 and just bought the PROSTREET #24266 8" It has a removable weight for Neutral or Ext balance
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Old 11-26-2012, 05:14 PM
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