Using my old Harmonic balancer

Friscoboater

Friscoboater

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I just upgraded from a 305 to a 350. Should I get a new HB? If i need to replace it, does getting a really good one make any difference?
 
gbeltran

gbeltran

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Re: Using my old Harmonic balancer

Yes, I would get a new balancer, I don't know if the 305 and 350 use the same one, even though I know the 305 balancer will physically fit the 350 I thought the 350's used a bigger unit, and no, for a stock engine, even a mild performance one a high dollar piece isn't going to be any better than the stock unit.
 
Bondo

Bondo

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Re: Using my old Harmonic balancer

Ayuh,... Their both neutral balance motors, so it Should be fine...
No need for a Hi-performance balancer, unless your spinnin' up around 7,000rpms...
 
glennwolf

glennwolf

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Re: Using my old Harmonic balancer

You should definitely replace the balancer and CHECK TOP DEAD CENTER! This is a must for ensuring acurate timing. You can get a cheap but good balancer for about $50. With the amount of time a boat spends at WOT an older balancer could spin off and damage your boat as well. The TDC marks between the 2 different cranks could be different as well. GM keyed thier cranks/balancers 2 different ways thoughout the years.
 
Friscoboater

Friscoboater

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Re: Using my old Harmonic balancer

Thanks for the info guys. I am going to oder one from Napa.
 
mkast

mkast

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Re: Using my old Harmonic balancer

According to the Mercruiser parts manual, part number 75420 is the same balancer used on all 305 and 350 engines used from 1977 through 1987.
 
PitchFork

PitchFork

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Re: Using my old Harmonic balancer

mkast said:
According to the Mercruiser parts manual, part number 75420 is the same balancer used on all 305 and 350 engines used from 1977 through 1987.
Click to expand...

That is the part number I found as well for my GM 305, but I have found two different HB on the Dorman Website for 305s. The difference is the timing mark location. The Dorman Part Numbers are 594-009 timing mark farther away from Key-way than 594-012. So what I am going to do is find TDC on my motor and mark it on the old HB before I pull it so hopefully I get the right one.

594-009 -1993-77 5.0L (305), 5.7L (350) Buick, Cadillac, Chevrolet, Oldsmobile, Pontiac, GMC Truck.

594-012 - 1995-69 5.0L (305), 5.4L (327), 5.7L (350) Chevrolet, GMC Truck, Oldsmobile, Pontiac.
 
mkast

mkast

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Re: Using my old Harmonic balancer

What is wrong with the old balancer?
 
R

RicardoMarine

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Re: Using my old Harmonic balancer

Jay, Suggestion:
Whether re-using or replacing the balancer, consider marking it off in degrees, and in the correct direction for YOUR engine rotation, for use in setting/checking ignition TAT (total advance timing).
Zero to 30* will do!
Many of today's engines are coming with markings in place.
Degree tape/decals are ok, but mechanical markings are more permanent!

Something similar to this.

images
 
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