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73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: jaysons on November 03, 2010, 04:04:50 pm

Title: harmonic balancer size ??
Post by: jaysons 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.
Title: Re: harmonic balancer size ??
Post by: motion427 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.
Title: Re: harmonic balancer size ??
Post by: reallyrusty on November 03, 2010, 07:00:36 pm
In general... The smaller (lighter) the balancer, the higher rpm/performance, the application.
Title: Re: harmonic balancer size ??
Post by: VileZambonie on November 03, 2010, 08:53:35 pm
For your 4x4 run the 8" balancer
Title: Re: harmonic balancer size ??
Post by: jaysons 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?
Title: Re: harmonic balancer size ??
Post by: VileZambonie 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"
Title: Re: harmonic balancer size ??
Post by: reallyrusty 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.
Title: Re: harmonic balancer size ??
Post by: jaysons 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.