Today on my way to work my harmonic balancer split apart and now I'm stuck at work with no belt running my alternator. I have called around to the local scrapyards to see if I can get a replacement but none have any in stock and it's over $300 from the dealership.

I have a b18c5 motor at home with a recently replaced harmonic balancer and as a last resort I'm contemplating using the b18c5 pulley on b20b.
i know it will fit but will this throw off the balancing frequency and possibly cause damage to my motor?

 

It'll be fine.

They're just crank pullys anyway, there's no dampening.

 

If it's split apart then it is obviously a dampener and the dampener itself came apart. It's likely not going to be an issue since it's going to be around the same size. Hopefully the ribs are the same.

 

It's my understanding that Honda 4 bangers are internally balanced. So the Harmonic Balancer (dampened or not) doesn't affect the crank balance.

The only issue is replacing a dampened pulley with a non dampened pulley.

The vibrations will eventually tear the motor apart.

I would think the B18C5 is also a dampened pulley as I thought the C5 was the USDM Type R which would be a high performance motor and would likely need extra harmonic dampening for the extra oomph it has.

I've not seen the pulley's so I don't know if it has the compressed rubber ring in the middle of it. But what I've observed on the Single cam motors, the performance motors always have the dampening pulleys.

 

The purpose of the crank pulley is to help dampen the vibrations through the rubber inside the pulley. This means since his crank pulley came apart that means it has the rubber material specifically designed to dampen the vibrations. This means his is a dampener.

 

The first statement isn't true of all honda pulleys. The non vtec SOHC 1.5L's don't use a dampened pulley.

I wasn't contradicting your second statement. If anything I was supporting it and questioning whether the B18C5 is a dampened pulley. If it is, then it's perfectly safe to use. If it's not, it will cause damage over time being the B20 pulley is dampened as was proven by you noting of it separating.

 

I've run CTR N1 pullys for years.

 

I suppose it probably depends on the motor and how much ***** to the walls driving one does.

I went to pull a crank from a D16Z6 (dampened pulley) that they put a D15B7 (non dampened pulley) on and it had a spun bearing so I left it even though I fought to get that rod cap off and loose. Whole area was black it got so hot.

I am pretty sure the bearing spun on the Z6 to the point of seizing the motor due to the motor not being dampened and being pushed to red line a lot.

Never saw a bearing melted like that before, was a sad sight to see the only dual oil hole crank of the 92-95 area toasted.

 

It's extremely rare for a crank pulley not to have a dampener. It's normal across all manufacterers. You must know this. This is why they are also called harmonic balancers. Again, this is true across all makes and models. I guess I could have said most but given I was talking specifically about this particular case it should be obvious I was specifically referencing this particular case.

 

You won't have any issues in terms of balance. You may want to confirm that the alternator belt will be the correct size though.