350 Pontiac undersized harmonic balancer

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350 Pontiac undersized harmonic balancer

Post by Kev7s »

I just finished a Pontiac 350 build and crankshaft is aftermarket. The crank snout diameter measuring 1.3710” the balancer bore is 1.3745. Does any one make a undersized balancer for Pontiac, or what have any of you guys done in past to resolve an issue like this. Thanks for everyone’s time.
Last edited by Kev7s on Tue Feb 20, 2018 9:09 pm, edited 2 times in total.
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Re: 350 Pontiac undersized harmonic balance

Post by ProPower engines »

What balancer are you using??
I have done several stroker builds but the last one I had issues with even getting a new balancer.
I had to send the OE balancer to be rebuilt as Power-Bond was out of the better balancers and they were about 4 months back ordered at this time last year.
But I did find that there are several different styles and if you are using the stock pointer you may have issues if the crank is undersized as the balancers are a very tight fit and need honing most times to get the correct press fit but that is an item that needs to be checked prior to any work proceeding.

The only recourse you may have is to bore and sleeve the balancer you have to correct the press fit if the crank is sized that far off.I have done this on many balancers that the crank was worn in the balancer mounting area.
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Re: 350 Pontiac undersized harmonic balance

Post by MadBill »

According to Professional Products http://www.crankshaftcoalition.com/wiki ... _Instr.pdf your snout is three thous undersize and the damper is five tenths beyond the upper limit. They list the crank at 1.374" to 1.3735" and the damper ID at 1.373" to 1.374".

It would be just moving the issue down the road, but Loctite could be an option. Retaining compound 638 is good for ~ 4,000# shear strength, so a damper bore of 1.374" x say 2" would be over 30,000#. Something rather weaker would likely suffice...
Last edited by MadBill on Tue Feb 20, 2018 9:12 pm, edited 1 time in total.
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Re: 350 Pontiac undersized harmonic balance

Post by Kev7s »

PowerBond Street Performance Balancer
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Re: 350 Pontiac undersized harmonic balancer

Post by Kev7s »

Bill you right on the numbers, I’am getting a knocking noise at idle I believe it is do to balancer movement.
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Re: 350 Pontiac undersized harmonic balancer

Post by tjs44 »

looks like a bad crank,I have done tons of pontiacs and have never had a loose one.One of the aftermarket balancers is tight.On that one I need a puller to remove.FWIW,Tom
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Re: 350 Pontiac undersized harmonic balancer

Post by tresi »

Long ago before aftermarket dampeners existed for Pontiacs my friend bracket raced a ventura. One odd thing that I noticed was neither engine he had for it required a puller to remove the dampener. They weren't sloppy loose but with a bit of work you could pull them off by hand.
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Re: 350 Pontiac undersized harmonic balancer

Post by MadBill »

The torsional forces are very high. I have often seen it written that a heavy press fit is necessary to prevent fretting in most apps and that the key should be regarded as just an alignment device. I guess Pontiac and others didn't read the same books... :-k
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Re: 350 Pontiac undersized harmonic balancer

Post by Geoff2 »

Bill,

The dampener bolt is torqued to 160 ft/lbs [ minimum ], factory spec. If properly torqued, there is no problem with the design.
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Re: 350 Pontiac undersized harmonic balancer

Post by mag2555 »

Pontiac V8 Balancers are not, nor never have been the press fit type!
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Re: 350 Pontiac undersized harmonic balancer

Post by tenxal »

mag2555 wrote: Wed Feb 21, 2018 6:05 amPontiac V8 Balancers are not, nor never have been the press fit type!
This ^^^^^^^! =D>
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Re: 350 Pontiac undersized harmonic balancer

Post by MadBill »

Glad I slipped the '...most apps...' escape clause into my post!
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Re: 350 Pontiac undersized harmonic balancer

Post by tresi »

mag2555 wrote: Wed Feb 21, 2018 6:05 am Pontiac V8 Balancers are not, nor never have been the press fit type!
And I believe it.
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Re: 350 Pontiac undersized harmonic balancer

Post by amc fan »

I have found that all the Pontiac's I ever did were all slip fit. They were 400 cubic inch GTO motors 68-70's
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Re: 350 Pontiac undersized harmonic balancer

Post by jsgarage »

Romac says they started making undersized balancers as catalogue items for some strokers 'cause the crank snouts were so often undersized. Might call one of their U.S. dealers & get the current skinny. Maybe your engine is one they have a part for. Mine has been on the motor (not a Poncho) for 15 yrs and I have no complaints. Mechanically restrained and rebuildable, too.
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