Did you know your timing mark can MOVE on Olds engines? I didn't.

[Jim Hupy]

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

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.

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] On Behalf Of James
Hupy
Sent: Friday, November 24, 2017 11:11 AM
To: gmclist
Subject: Re: [GMCnet] Did you know your timing mark can MOVE on Olds
engines? I didn't.

MOST OF the harmonic balancers that I have encountered on Olds engines that
have not been tampered with, do not exist any evidence of lightening drill
holes on the outer ring. That tells me that the purpose is to cancel
harmonics, not engine balance. The engines that have been overhauled and
rebalanced frequently DO HAVE drill spots on the balancers as well as the
flex plates, as is common in good overhaul shops.
Don't know all the specifics of engine harmonics on multi-cylinder
engines, but it is a complex mix of crank pin location, firing order,
stroke length, rpm range, etc, etc. But I do know this much. If a
compensating balancer is separated and no longer aligned like the factory
did it, it possibly is not a good thing for engine longevity.
Jim Hupy
Salem, Or

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[Ken H.]

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.
>

 

[Jim Hupy]

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

> 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

>
> > 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.
> >
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
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>

 

[robert mueller]

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] On Behalf Of James Hupy
Sent: Friday, November 24, 2017 7:11 PM
To: gmclist
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

 

[Matt Colie]

> 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 - '73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan
OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Twixt A2 and Detroit

 

[Ernest Dankert]

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

 

[Jim Hupy]

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

> 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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