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Author Topic: harmonic balancer size ??  (Read 4550 times)

Offline jaysons

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harmonic balancer size ??
« on: November 03, 2010, 04:04:50 pm »
 So I'm i bit new here, but not to these trucks & engines.
    I've got a Freshly rebuilt 355ci. to put in my 4x4. Bought the engine already bored out, & in pieces. Had the local machine shop do the heads & put the bottom end together. Just got the exterior pieces to put on & it's ready to go in. None of the boxes of parts that came with it had a harmonic balancer in it. I've got one all cleaned & painted, ready to go on; But the one I took off the 350ci. that I took out of the truck, has a much larger one on it.
    The painted one is 6 & 3/4 inches in diameter. The one off the 350 is 8 inches in diameter. So my question is...... which one is required?

   The engine is bored .060 over, Has a Lunati 350 hp cam, beefier valve springs, new piston & rings, new wrist pins, ...126 heads, Weiand intake, Edelbrock 600 carb, & as far as I know, stock crank & connecting rods.
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'87 4x4 ~10 inches of lift on 35" General Grabber MT's ~ 350 -.060 over ~ T.H.400 ~ N.P.203 ~ Dana 44 front ~ 12 bolt rear ~ 3:73's ~ Future upgrades ~Dana 60 rear ~ N.P.205 ~ 5:13's or 5:88's ~ etc.etc.etc. ~ The list seems to get longer every week or so

Offline motion427

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Re: harmonic balancer size ??
« Reply #1 on: November 03, 2010, 05:37:49 pm »
Ussually the trucks had the bigger 8".
check your timing chain cover for the location of the timing tab.
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86 K10,350 Roller Cam,T350,NP205,10 bolt posi,12 bolt posi,33" tires.
85 K30,454,T400,NP205,Dana 60,14 bolt,being built now.
04 Avalanche Z71,6.0L,TVS 1900,Dynatech,Corsa,etc...
06 TBSS,AWD,6.0L,Kooks,C6 fan kit,etc...
75 Nova SS,502,T350,12 bolt

Offline reallyrusty

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Re: harmonic balancer size ??
« Reply #2 on: November 03, 2010, 07:00:36 pm »
In general... The smaller (lighter) the balancer, the higher rpm/performance, the application.
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Offline VileZambonie

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Re: harmonic balancer size ??
« Reply #3 on: November 03, 2010, 08:53:35 pm »
For your 4x4 run the 8" balancer
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74 GMC, 75 K5, 84 GMC, 85 K20, 86 k20, 79 K10

Offline jaysons

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Re: harmonic balancer size ??
« Reply #4 on: November 03, 2010, 10:15:11 pm »
So what I'm gettin is that either one will work, right? The cam is supposed to help give it more bottom end torque, so the 8" would be better.
   But if I was running it in sand drags or something similar, then I should run the smaller 6 3/4" one.  Is that about right?
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'87 4x4 ~10 inches of lift on 35" General Grabber MT's ~ 350 -.060 over ~ T.H.400 ~ N.P.203 ~ Dana 44 front ~ 12 bolt rear ~ 3:73's ~ Future upgrades ~Dana 60 rear ~ N.P.205 ~ 5:13's or 5:88's ~ etc.etc.etc. ~ The list seems to get longer every week or so

Offline VileZambonie

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Re: harmonic balancer size ??
« Reply #5 on: November 07, 2010, 06:09:12 pm »
Run the 8" balancer. Pounding on the engine other than mild stock applications you'll want the 8"
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,                           ___ 
                         /  _ _ _\_
              ⌠ŻŻŻŻŻ'   [☼===☼]
              `()_);-;()_)--o--)_)

74 GMC, 75 K5, 84 GMC, 85 K20, 86 k20, 79 K10

Offline reallyrusty

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Re: harmonic balancer size ??
« Reply #6 on: November 08, 2010, 09:19:39 pm »
i agree, run the 8 inch.


just because you can run the 6 3/4 doesn't necessarily you should.
I had a friend years ago that ran an aluminum flywheel because he could..... until he bent all his rods.
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Offline jaysons

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  • Posts: 20
Re: harmonic balancer size ??
« Reply #7 on: November 08, 2010, 11:04:45 pm »
Ok. Thanx for all the input guy's! The 8" is on it.

 Next question..... got a brand new distributor with a rev limiter replacing the module in it. What is a good rpm to set it at, until I get the rings seated? And then Imma guessin I'll be able to set it according to what I feel the engine is comfortable with.
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'87 4x4 ~10 inches of lift on 35" General Grabber MT's ~ 350 -.060 over ~ T.H.400 ~ N.P.203 ~ Dana 44 front ~ 12 bolt rear ~ 3:73's ~ Future upgrades ~Dana 60 rear ~ N.P.205 ~ 5:13's or 5:88's ~ etc.etc.etc. ~ The list seems to get longer every week or so
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