Harmonic balancer balance

[Ryan Stout]

If I had an internal balancer on an externally balanced engine, how bad would it vibrate? (I'm positive flywheel is correct, just curious about balancer)

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[Fastbird]

Explain further.......

If this is LTx related, the LT1 as stock is balanced via the flywheel/flexplate. The "balancer" up front is just a pulley, it does nothing for balancing the motor. So if you're asking what I think you are (can a run a stock balancer on an internally balanced engine) the answer is yes.

[Ryan Stout]

My engine is externally balanced. I run an external balance flywheel. LT1 internal balance balancer. Always had a vibration at 4000-7000+. Its not horrible, none of my friends notice it, just me. Got thinking about it and wondering if I need to switch to an externally balanced balancer or if its just these solid motor mounts.

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[firebird_1995]

No you definitely don't want to do that. I recall you saying it was a long story about the reason it was externally balanced when it was built but can you give us an abridged version?

[Ryan Stout]

Its external because the machine shop wouldve had to add heavy metal to my crank and it woulda been expensive. He just did it externally to save me some coin.

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[Ryan Stout]

Old guy remembers the story to the T, off the top of his head, 4 years later, and all I gave him was my name and its a 383

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[Fastbird]

Honestly, it's probably the solid mounts. You just running a stock balancer? If so, try an ATI balancer......ben and I both run those and neither of us has vibration problems, though granted we're both on poly mounts too, not solids.

[firebird_1995]

Its external because the machine shop wouldve had to add heavy metal to my crank and it woulda been expensive. He just did it externally to save me some coin.

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OK. Something i just thought of (and you probably though of too) this was balanced when you were running the 6 speed, right? If the imbalance on the flywheel was not the same weight as stock, before you install the new flexplate it will need to be matched to what was removed. .....Or at least I would think so anyway.

[Ryan Stout]

Yea I thought sbout that, machine shop said go external but a couple oz is no big deal. Yea it was all balanced to the 6spd. He only balanced the flywheel, it had a twin disc. Wonder if the pp was slightly off or something.

No its an ATI balancer.

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[BALLSS]

Ryan

your solid mounts may the the problem.

assumeing you still have the FW on that the machine shop used to balance with rotating assembly the motor should still be "balanced". The damper should be neutral in balance.

If you replaced clutches since the motor was balanced the new PP may not have been balanced the way the old one was. would be better to have PP neutral balanced since FW was balanced to motor.

I have internal balance 383 so run a neutral balance FW (McLeod Twin) but sent my FW & flater plate & PP to machine shop to confirm...it was 25 grms out of balance

[shownomercy]

Yea I thought sbout that, machine shop said go external but a couple oz is no big deal. Yea it was all balanced to the 6spd. He only balanced the flywheel, it had a twin disc. Wonder if the pp was slightly off or something.

No its an ATI balancer.

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ATI is neutral balanced, so it does not care if your motor is external/internal.

I run solid mounts and the ATI dampener (its NOT a balancer) without issue, I am external balanced as well.

[Ryan Stout]

So neutral is not the same as internal or external? Balancer, dampener?

Might've been the clutch.

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[Fastbird]

If it was the clutch I'd think you'd feel that all over the place. Hell, any reciprocating mass unbalance you should feel throughout, not just in a 4-7K RPM band. I think it's probably just your solid mounts.

[shownomercy]

So neutral is not the same as internal or external? Balancer, dampener?

Might've been the clutch.

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Neutral as in it should not affect any sort of rotating assembly once bolted on.

[Ryan Stout]

Sounds like its my mounts then. Kinda wondered but I worry about dumb stuff all the time lol.

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[shownomercy]

Sounds like its my mounts then. Kinda wondered but I worry about dumb stuff all the time lol.

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IDK, like I said, I have solid mounts, external balanced and an auto... sooo think of what changes you have made, then evaluate.

[Ryan Stout]

Its been like this since the solids. Wondered if they causes it or if my rubbers just hid it. With the new tq converter, I wonder if it'll absorb it (or fix it if it was the pp)

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[shownomercy]

How radical is your cam?

[Ryan Stout]

Its a baby.

224*/224* @.050
.575"/.575"
114lsa

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[shownomercy]

You know. Other than turbo, we have the same setups.

[BALLSS]

if you are going from M6 to A4 just have the flexplate =balance your FW that was used to balance rotating assembly. If it was a stock LT1 FW than a stock or replacement Flexplate made for LT1 will be the same. If your FW was a aftermatket with a "screw on" weight you might want to get the flexplate compared for balance.

your vibe at 4k-7k rpm more likely is because of the solid mounts. If your flexplate was off balance it would vibe at all rpm.

if data log says motor is pulling timing from knock sensor you could just run poly mounts...

Another area to check would be brive line angle

[Ryan Stout]

True. Its not pulling any timing at all. Angle is -2*.

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