Engine Balancing question

[aklb43]

When you have an engine built buy the local shop, do you usually supply them with the flex plate and harmonic balancer to balance the rotating assembly?

Something weird happened here. I had to pull off my harmonic balancer and it has a 28oz weight when it’s suppeosed to be a 50oz being that the block is from a 86 mustang. The flex plate is a 50oz. The engine didn’t have any noticeable vibration to it when I rev’d it up.

I’m thinking I supplied the wrong imbalance weight harmonic balancer to the shop and they balanced out the normally 50oz imbalance rotating assembly to be in balance with the 28oz imbalance harmonic balancer that I supplied them.

Should I throw a 50oz on there and see how it runs? Or just put the 28 oz back on?

 

[Broncobowsher]

It was common a long time ago to balance the old 3-bolt damper as part of the engine build so you would have a 3-bolt damper with the engine.
The issue today is you have no idea how that was done. Did they do something inside the engine so the old damper would work? Did they modify the damper to work with the engine? Did they do a little of both?

Sounds like someone had this built as a package in the past. It works, I would put the known good parts back on and call it a day.

 

[rjrobin2002]

There are companies that change the balance of harmonic balancers. So it could be marked 28 amd be a 50.

I had my explorer harmonic balancers changed to work on my 351.

 

[aklb43]

I had the engine made quite some time ago and I don't recall anything about what the machine shop did. It harmonic balancer doesn't appear to be modified. However, the balancer does have a detachable weight. I think I'll pull of the weight and inspect the back side of it. Maybe they drilled a few holes and added a heavier metal to increase its weight. The imbalance weight model currently specs that its a 28 oz version and not the 50 oz though. I guess I could also weigh the weight to make sure. I can always source a cheap 50 oz, attached it, and fire it up so see out it runs.

 

[aklb43]

It was common a long time ago to balance the old 3-bolt damper as part of the engine build so you would have a 3-bolt damper with the engine.
The issue today is you have no idea how that was done. Did they do something inside the engine so the old damper would work? Did they modify the damper to work with the engine? Did they do a little of both?

Sounds like someone had this built as a package in the past. It works, I would put the known good parts back on and call it a day.

Yea, I think your right. Only problem I have with the balancer it uses, is that it has multiple timing marks and I don't know which one to use. I'll have to go figure that out.

 

[Broncobowsher]

Removable counterweight is an aftermarket thing. They just bolt in the counterweight that is needed for the build. There should have been 2 different counterweights in the box with the damper.

Don't have to go so far as to remove the damper, just the bolt holding it on. Once it is off you should be able to see a keyway. Point that straight up and it is at TDC. The timing marks will be at 10,11 or 2 O'clock position.

 

[DirtDonk]

And once you've done that, clearly mark which grouping matches your timing pointer. You may not have a stock Bronco version of that either.
If none of them match (it happens) then line up things at TDC and get some timing tape to fine-tune he markings with your existing pointer.
Or make a better pointer if needed.

paul

 

[aklb43]

Removable counterweight is an aftermarket thing. They just bolt in the counterweight that is needed for the build. There should have been 2 different counterweights in the box with the damper.

Don't have to go so far as to remove the damper, just the bolt holding it on. Once it is off you should be able to see a keyway. Point that straight up and it is at TDC. The timing marks will be at 10,11 or 2 O'clock position.

This particular damper came with the 28oz, but you can purchase the 50oz for it. Thanks for the timing info, the correct markings are at 2'0clock. I'm pretty sure this solves another problem I was having. My engine would backfire with distributor vacuum advance connected, meaning I was using the incorrect timing marks!

 

[aklb43]

And once you've done that, clearly mark which grouping matches your timing pointer. You may not have a stock Bronco version of that either.
If none of them match (it happens) then line up things at TDC and get some timing tape to fine-tune he markings with your existing pointer.
Or make a better pointer if needed.

paul

I didn't even know timing tape was a thing. I was considering painting the balancer since its looking a bit rough and I was looking for a way to put the marks back on. Thanks!