Exekiel69

Is there a way to tell if it is bad? any good source, I know there is a thread about an upgrade, is it worth doing or the stock one good enough?

Thanks.

maybe368

usually when they go bad, the rubber bonding between the inner and outer parts fails and it is pretty obvious. What are your symptoms?...Mark

Exekiel69

Well honestly I tried asking this question on a 4bt forum and could not get an answer , I feel this little engine vibrates a bit more than the 6bt and the ribs on the pulley look a little worn. It does not vibrate too much but I can tell it more than other engines and the engine mounts are fine as well as the fuel system.

Thanks.

maybe368

Maybe use a mirror and flashlight to try and get a look at it. Sometimes you can see that the rubber is real dry and cracked. They really don't fail often, but then again how many engines run a half million or more miles?...Mark

Exekiel69

Thank You I'll try that or maybe just pull the pulley and inspect it, any cracks are sign that a new one is needed then?

maybe368

Not so sure about any cracks, but if it is causing a vibration, I would think that it would be obviously separated. But, cracks are never good in rubber...Mark

thrashingcows

I didn't think 4BT motor came stock with a front harmonic balancer? Don't they run a crazy gear driven balancer with weights and such that mounts down under the rotating assembly? Or non at all?

I have seen a couple 4BT build where guys have used front accessories from a 6BT motor...balancer and all.

93-12Smoke

The 4bt has a 90 degree firing rotation which causes a bad vibration. A fluid dampner will help some but not much. Mine shakes the whole truck.

jimbo486

4BT motors just have a pulley with no damper of any kind. At least according to pictures in my Cummins B-Series Shop Manual anyway.

On 6BT dampers/balancers there are 2 indexing marks on the inner and outer ring that the rubber is sandwiched between. If the marks don't line up, it's on it's way out. The Cummins B-Series Shop Manual confirms this and states as such:

"Verify that the index lines are aligned. If the lines are more than 1.59mm (1/16") out of alignment, replace the damper. Inspect the rubber member for deterioration and missing pieces. If pieces of rubber are missing or the member is more than 3.18mm (1/8") below the metal surface, replace the damper."

Here's a picture I have of my stocker. You can see the index marks near the 5 o'clock position.

sootnsmoke

Thanks for posting that info. I did not know those 2 alignment marks were there to check. I wonder how easy they are to see from under the truck.

jimbo486

Well I can tell you that there's a crossmember directly below the damper . You could slip a mirror in front of it from the driver's side. A flashlight will aid in finding the index marks, I'm sure.

Exekiel69

Well, You are right, the 4bt I have does NOT have a vibration damper. Now My question is, should I have one? I'm asking this from a longevity point of view.
I read a 6bt harmonic balancer will not work on a 4bt engine.

Any advice? Thanks.

jimbo486

Well, if Cummins didn't build them with dampers, they must do fine without them.

I don't understand why a damper from a 6BT wouldn't work. Nor, do I see any disadvantage to using one either. I suppose as long as the pulley diameters are identical, it should be fine. If you have access to and/or can borrow a damper from a 6BT, it would be worth a shot to bolt it on and find out.

maybe368

Google 4bt damper and a few good forums come up. Apparently they only put dampers on some marine applications and they are rare and pricey. They did not use them because they are 90 degree firers and used primarily in equipment and generators.There are threads that talk about fitting a 6bt one, but it requires the machining of a keyway. I am a bit rushed, but if you cannot find them I'll post them in a while...Mark

j_martin

The reason for a tortional damper is to damp out twisting in the long 6 cylinder crankshaft. 4BT's don't have them because with the shorter crank, they are not needed. The few that exist probably got there by way of some over educated, under experienced, probably guvmint "engineer" demanding that they be there for a particular purchase.

I guess you'll have to find out some other reason why your engine shakes.