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Re: [GMCnet] Did you know your timing mark can MOVE on Olds engines? I didn't. [message #326316 is a reply to message #326314] Fri, 24 November 2017 19:19 Go to previous messageGo to next message
Ken Henderson is currently offline  Ken Henderson   United States
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
Senior Member
I can't imagine anyone balancing a crankshaft with an external engine
component, like a flex plate or harmonic balancer, or hub, attached. What
if one of those requires replacement on an assembled engine? Disassemble
the engine to re-balance? Seems much more logical to me to balance each
component individually. One might, in an especially critical application,
then test their balance while assembled, but even then, if a system
imbalance appeared, I'd want to find and correct the out-of-balance
component.

JMHO,

Ken H.


On Fri, Nov 24, 2017 at 8:05 PM, Rob Mueller
wrote:

> Jim,
>
> My experience with "good overhaul shops" is that they balance the crank by
> drilling holes in the counterweights to lighten them or
> filling the holes with lead to increase the weight.
>
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Ken Henderson
Americus, GA
www.gmcwipersetc.com
Large Wiring Diagrams
76 X-Birchaven
76 X-Palm Beach
Re: [GMCnet] Did you know your timing mark can MOVE on Olds engines? I didn't. [message #326317 is a reply to message #326316] Fri, 24 November 2017 19:28 Go to previous messageGo to next message
James Hupy is currently offline  James Hupy   United States
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Registered: May 2010
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Senior Member
Some engines are "internally balanced" like a 327 chev from the 60's.
Others, like the small block 400 2 bolt main chev engines are "externally
balanced". If you really want an engine to shake, bolt a 327 balancer and
flex plate on to a 400. Been there, done that, still got the broken crank
somewhere in my junk pile. Broke the block too.
Jim Hupy

On Nov 24, 2017 5:21 PM, "Ken Henderson" wrote:

> I can't imagine anyone balancing a crankshaft with an external engine
> component, like a flex plate or harmonic balancer, or hub, attached. What
> if one of those requires replacement on an assembled engine? Disassemble
> the engine to re-balance? Seems much more logical to me to balance each
> component individually. One might, in an especially critical application,
> then test their balance while assembled, but even then, if a system
> imbalance appeared, I'd want to find and correct the out-of-balance
> component.
>
> JMHO,
>
> Ken H.
>
>
> On Fri, Nov 24, 2017 at 8:05 PM, Rob Mueller
> wrote:
>
>> Jim,
>>
>> My experience with "good overhaul shops" is that they balance the crank
> by
>> drilling holes in the counterweights to lighten them or
>> filling the holes with lead to increase the weight.
>>
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Re: [GMCnet] Did you know your timing mark can MOVE on Olds engines? I didn't. [message #326318 is a reply to message #326315] Fri, 24 November 2017 19:59 Go to previous messageGo to next message
USAussie is currently offline  USAussie   United States
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Registered: July 2007
Location: Sydney, Australia
Karma: 6
Senior Member
Jim,

I misunderstood; I thought you meant the good engine shops used the flexplate and harmonic balancer to balance the rotating
assembly.

I agree good engine shops balance the crank on it's own (taking into consideration the reciprocating weight), the flexplate on it's
own; and the harmonic blancer on it's own.

Regards,
Rob M.
The Pedantic Mechanic
Sydney, Australia
AUS '75 Avion - The Blue Streak TZE365V100428
USA '75 Avion - Double Trouble TZE365V100426
USA '77 Kingsley - TZE 267V100808



-----Original Message-----
From: Gmclist [mailto:gmclist-bounces@list.gmcnet.org] On Behalf Of James Hupy
Sent: Friday, November 24, 2017 7:11 PM
To: gmclist@list.gmcnet.org
Subject: Re: [GMCnet] Did you know your timing mark can MOVE on Olds engines? I didn't.

That is correct, Rob. But the "fussy duck" engine balancers do the steps I
mentioned, in addition to the crank, rod, and piston work. Nothing is left
unbalanced except the owners checkbook. (Grin)
Jim Hupy


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Regards, Rob M. (USAussie) The Pedantic Mechanic Sydney, Australia '75 Avion - AUS - The Blue Streak TZE365V100428 '75 Avion - USA - Double Trouble TZE365V100426
Re: [GMCnet] Did you know your timing mark can MOVE on Olds engines? I didn't. [message #326319 is a reply to message #326316] Fri, 24 November 2017 20:19 Go to previous messageGo to next message
Matt Colie is currently offline  Matt Colie   United States
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
Senior Member
Ken Henderson wrote on Fri, 24 November 2017 20:19
I can't imagine anyone balancing a crankshaft with an external engine component, like a flex plate or harmonic balancer, or hub, attached. What if one of those requires replacement on an assembled engine? Disassemble
the engine to re-balance? Seems much more logical to me to balance each component individually. One might, in an especially critical application, then test their balance while assembled, but even then, if a system imbalance appeared, I'd want to find and correct the out-of-balance component.

JMHO,

Ken H.

Ken,

While it may be your opinion, can you imagine trying to balance the assembly and then disassemble it and build it back into an engine every 83 seconds? (That was speed of the line at Mound Road Engine when they were building the LA5.9 (360) there.

The fact is that they have balancing equipment that accommodates the external components and the bob weights that should be on the crank and do it all as a dynamic balance. If you have to replace a damper or a ring gear, you just have to hope that it was made with the correct imbalance.

Just a side note. Virtually all of the V-6s built in the US are externally balanced along with those the JimH just mentioned.

What a hoot? Get some jamoke to static balance a V-8 crank on knife edges and see if the engine stays under the hood when it get started. Balancing these parts is not a blacksmith job, it is much closer to rocket surgery.

Matt


Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
Re: [GMCnet] Did you know your timing mark can MOVE on Olds engines? I didn't. [message #326320 is a reply to message #326271] Fri, 24 November 2017 20:32 Go to previous messageGo to next message
Ernest Dankert is currently offline  Ernest Dankert   United States
Messages: 133
Registered: May 2007
Location: Ogden, New York
Karma: 1
Senior Member
Drilling the harmonic balancer to balance the engine will shift the rpm band the balancer is to operate. The crank will
have rpm ranges where it will wind and unwind (resonate) due to the firing order. The rotational mass is bonded in rubber
at the opposite end of the crank to counteract the effect. [On my 1977 Chev 350 the timing mark is aligned with the key
way.]

I will go so far as to say if your harmonic balancer is drilled to balance the rotating assembly it will shift the operating
rpm band to actually be detrimental.

Running the power unit on cruise control to the tuned region would hasten the point to where the timing alignment would shift.

I seem to recall some classroom discussion in my Dynamics class regarding crankshaft loading; unfortunately my notes are gone.


1977 Eleganza II
Ogden NY
Re: [GMCnet] Did you know your timing mark can MOVE on Olds engines? I didn't. [message #326322 is a reply to message #326320] Fri, 24 November 2017 20:38 Go to previous message
James Hupy is currently offline  James Hupy   United States
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Registered: May 2010
Karma: -62
Senior Member
I, on purpose, did not want to get too in depth into the art of engine
balancing, particularly in the area of "odd-fire" v-6 engines vs "even
fire" v-6's. Suffice it to say that there is considerable room for
discussion there.
Jim Hupy

On Nov 24, 2017 6:33 PM, "Ernest Dankert" wrote:

> Drilling the harmonic balancer to balance the engine will shift the rpm
> band the balancer is to operate. The crank will
> have rpm ranges where it will wind and unwind (resonate) due to the firing
> order. The rotational mass is bonded in rubber
> at the opposite end of the crank to counteract the effect. [On my 1977
> Chev 350 the timing mark is aligned with the key
> way.]
>
> I will go so far as to say if your harmonic balancer is drilled to balance
> the rotating assembly it will shift the operating
> rpm band to actually be detrimental.
>
> Running the power unit on cruise control to the tuned region would hasten
> the point to where the timing alignment would shift.
>
> I seem to recall some classroom discussion in my Dynamics class regarding
> crankshaft loading; unfortunately my notes are gone.
> --
> 1977 Eleganza II
> Ogden NY
>
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