Inliners International Forums General Discussion Engines Question on GMC 302 harmonic balancer

I am replacing the bad GMC 228 in my 51 1-ton with a GMC 302. I need a single pulley harmonic balancer as the double pulley on the motor would hit the radiator. I haven't pulled my 228 harmonic balancer yet but I assume it will fit, although it apparently presses on while the 302 HB bolts on. Does anyone know if the 228 HB will fit the 302?

I've also been told that the harmonic balancer must be balanced to the crank and flywheel and that a machine shop can balance my replacement HB the same as my original. Is this necessary and recommended?

Thanks for your help.

Sidehill
Grand Junction, CO

Sidehill,

Assuming you have a GMC (not Chevy) truck, the 302 will fit just fine with the double pulley. Just remove the radiator and slide it back in with the mounting points just outside of the core support channel. Use some longer bolts with spacers to tilt the bottom of the radiator forward an inch or so. You may have to patch in a piece of copper pipe in the lower hose, but otherwise it's an easy fit.

While you're at it, replace the fan with a 6-blade rigid Flex-O-Lite. It will cool better and prevent launching an old, metal-fatigued blade through the hood.

Jack

I'm installing it into a 51 GMC 1-ton. I'm not really certain that the pulley would hit the radiator, but the fan would. This is because the heavier 5 blade fan has blades so long it must clear the wider pulley, this required a spacer between the water pump and the fan. I figured I could take out the spacer so the fan would clear the radiator but then the fan would hit the pulley. I thought the simples solution might be a thinner pulley. Your suggestion of a different fan might be the ticket if the blades aren't real long and if my 2 groove pulley wont hit the radiator. Then my balance problems will be solved.

Thanks for the help

Sidehill

Have You changed to a 12 volt system yet ? If You have install a electric fan that is made to mount on the outside of the radiator.I perfer to use late model GM car ones. I had one on my 1950 chevy 1/2 pickup.I used a toggle switch to turn mine on. Most of the time I did not even need to use it unless I was stopped in traffic for a few minutes.You can also buy a automatic switch to do it for You.It is also a good reason to get rid of that rid of that factory exploding fan blade.
EvilDr235

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Two types of people drive old cars.Rich people because they want to and poor people because they have to.
Remember EvilDr235 has a cure for Your sixness.

I'm not sure the fan was actually a Flex-o-lite, it came from Pep Boys, 17" dia, 6 rigid aluminum blades and the center hole is 5/8" diameter. The spacer has to be there to keep the blades from hitting the damper pulley.

I don't like the fans with flexible SS blades, they always slice up my hands when trying to do any work near the front of the motor.

As to the second part of your question, the answer is "Probably not". An inline six is inherently balanced, so minor variations in the weight of flywheels and dampers rarely cause a noticeable vibration. Each component is balanced separately so unless your 302 has a heavy rod or other flawed internal part, a balanced flywheel, clutch or damper is not going to change that situation. Not to say that balancing a six isn't a good idea, but it isn't critical for normal usage.

Not so with a V8, which has a "rocking couple" effect with rods and counterweights flying around in different directions. So what you were told does apply to a V8, but in general, not to a line six.

Jack

Now that you bring it up I remember seeing the same discussion on another board on inline Toyota 4 vs v-6, where the 4 just had a pulley, not really a harmonic balancer. The heavy 302 harmonic balancer has been balanced though(probably factory.

A poster on the SB forum mentioned that since the 228 HB is so much lighter (guessing 3-4 lbs vs 8 lbs) that it might not need balancing anyway.

I should have time within the next few days to get this figured out so will let you know what I came up with.

Thanks again

Sidehill