[1BADS72]

I'm looking for opinions on fluid based harmonics. My Malibu has a built 400 small block running approximately 400 horse. My problem is that I have been through two factory balancers already. I am trying to find a permanent solution to a reoccuring problem. My original balancer had a bad rubber liner when I got the car and started to go out of balance. When I rebuilt the motor I replaced it with a used one that appeared great when I got it but now is about 17-20 degrees ahead of where it should be. I don't want to have to buy another factory style and wait until it goes out. Is a fluid type unit available for an externally balanced 400 small, or is there a better way to go?
Thanks ahead of time for the help...
Rob
1BADS72

 

[Tom Mobley]

1BADS72

Yes, there is a FluiDamper for a 400. Essentially, their product is set up as a hub/ring assembly with some countersunk Torx bolts holding it together from the front. The fluid part must be removable so the assembly can be balanced. Apparently the inner ring settles off center in the fluid when the engine is off. This throws the balance operation off as there's not enough time or RPM to let it find it's centered position. The 400 part has an unbalanced hub.

For the money I'd suggest buying a new 400 balancer, they're well under $100. If it slips the ring again you'll be needing to Magnaflux the crank. Have you had any trouble keeping belts on it?

Tom

 

[BillK]

Bad,
If you are having problems with stock balancers on a motor that is 400hp or so, I would have to say there may be a problem with the balance of the entire assembly. Was the motor balanced when it was built ? It is amazing how much difference there is in the weight of aftermarket parts compared to stock ones and they almost always require balancing. The harmonic dampner (correct name) is there to absorb harmonics but can only do so much. If the motor is badly out of balance, you will continue to have problems, no matter what dampner you use.
Bill Koustenis
Advanced Automotive Machine
Waldorf Md

 

[1BADS72]

I can't verify that the motor was balanced after it was assembled. I do know that it had factory style pistons before and has Hypereutectic pistons now. I am using the original connecting rods. Everything was machined to match at the time it was rebuilt. I am using the original flywheel. The only reason I went with a stock style dampener this time is I didn't know if the Fluid style was worth the money and didn't really know what kind of hp I would be getting out of it. I didn't change the compression or the cam timing from what it was. I had to rebuild it because of piston failure in the #1. I am not a motor expert. I feel the problem lies in the harmonic because it purred like a very large kitten when I put it together and now, knowing that the outer ring of the harm has shifted by way of marks I put on it, it can't stand still at idle.

How would you balance an externally balanced engine?
Is there another option between stock and fluid style?
If I have to go to another stock unit how do I keep the outer ring from slipping?
Your help is greatly appreciated!
Rob

 

[BillK]

Rob,
There is only a couple of reasons a stock harmonic dampner will seperate. 1. Inproper installation such as using a hammer instead of pulling it on with an installation tool. 2. Old age. 3. Something else out of balance in the motor. When the motor is running, the rubber part of the dampner sort of acts like a spring, allowing the outer ring to move back and forth slightly and absorb harmonic vibrations. If the basic motor is way out of balance, the ring will be moving so much that eventually the bond with the rubber will fail and the ring will move, as yours has. A fluid type dampner will not fail in this way because there is no rubber to fail, BUT, if there is an imbalance problem, it will show up in other ways, usually main bearing failure. You may or may not actually feel a vibration. You mentioned that you used Hypereutectic pistons ? What brand were they ? I know that the Keith Black ones are usually a lot lighter than the stock pistons and always require re-balancing the entire assembly. The only way this can be done in your case is to completely disassemble the motor. Have the balance job done, and reassemble it. Let me know which pistons you have and I should be able to find out what they weigh. In your application, the stock dampner from GM should work fine. We use them all the time with no problems.

------------------
Bill Koustenis
Advanced Automotive Machine
Waldorf Md

 

[1BADS72]

Bill-
Pistons are Federal Mogul 040 over.
Also found sparatic spark in the #5 cylinder this afternoon. I know for a fact that the new harmonic was hammered on. I watched the builder do it.
Tommob asked if I have had problems with belts. Until recently, no. Now I have a random squeak under light acceleration. I replaced the alternator after its bearings gave out and put on the old belt, its only got about 750 miles on it. I tried a new belt and it squeaks, too. I lit the car up with the belt off and no squeak. I tried the alt in a buddys truck and no squeak.
Duh?
I only have 750 miles since my rebuild and trying to budget in another rebuild is not gonna happen without a miracle. Will replacing this dampener with a NEW one get me back online? Dropping the pan to inspect the mains is not a possibilty in a 72, and pulling the motor robs me of my only daily driver.
Help...
Rob
(Bill-ATI?)

[This message has been edited by 1BADS72 (edited 12-01-98).]

 

[Tom Mobley]

1BADS72

If the guy hammered it on, he's not an engine builder, he's a hack. Even the magazine guys know better than this.

Buy a new damper and the tool for installing it. Put it on yourself, don't let that doof touch your stuff anymore. You'll need a puller with a 3 bolt pattern to get the old one off. The bolt in the center torques to 85 lbs. Make it easy on yourself, pull the water pump first.

The reason I asked about belt trouble is that a cracked crank will sometimes toss belts off regularly, along with balancer rings.

Chances are both your dampers were OK until they were hammered on.

Engines are normally balanced at the machine shop while they are in pieces. The pistons are weighed and matched, the rods ditto, weights are built up according to a formula and attached to the crank, which is then spun on a machine that senses the imbalance and points to an area to add or remove weight from the crank to achieve balance. Usually about $125. It'll be on you ticket if it was done.

Tom

 

[1BADS72]

I checked the build sheet for the motor and balancing was not checked off under work performed, however there was an extra charge for "matching" the pistons and connecting rods. I checked with the builder and he explained that he normally hammers on harmonic with a mallet and centering slug that spreads out the force to ensure that the threads in the crank end aren't stripped out. I checked the threads and I can understand why. Mine are pretty nasty and I don't know if they will hold up to pulling on a new harmonic.
**I am still confused as to how an externally balanced motor can be balanced by a shop without having the weighted flywheel or weighted harmonic. I theorize that if the shop had somehow managed to balance the motor, adding a weighted flywheel and harmonic would screw it up. If not for the added and possibly incorrecly positioned weights, then for the inconsistency in the amount of weight itself.
This makes sense to me, but like I said, I am not the expert here.**
Summit has a stock style unit for $70 and I can borrow a pull off tool from a local speed shop(read-dad's garage). That is probably the way to go. I can't get a better price locally on the harmonic.
I plan on marking the new harmonic like I did this one to see if it spins. What kind of tolerance should there be, if any? Also, on a different note, does anyone know what kind of ohms resistance level I should get off my Accel 8 mm wires.
Thank you!
Rob

 

[1BADS72]

New problem- I noticed that the oil psi at loaded idle(500-700rpm) is down to 10 pounds. It has been as low as 20 pounds before in the same situation. The oil pressure change has been in the last week, same time frame of the motor starting to idle rough. Is this indicative of bearing failure? I broke the motor in on non-synthetic 10W-30. Changed it after about fifteen minutes of run time. New oil and filter, same type oil. Changed it again at about 125 miles, and used synthetic and a K&N oil filter. Changed it at 650 miles, back to non-syn oil and a new K&N filter. Have I shot myself in the foot by doing this? I have no clue as to why I went with the syn, other than I know it was on sale.
Rob

 

[BillK]

Rob,
The reason for not hammering the damper on has nothing to do with the front of the crank. When you hammer on the center part of the damper, each time you hit it, the outer ring tries to stay where it is at and ends up separating the rubber. Just imagine taking two ten pound barbell weights and gluing them together with som real weak rubber cement, then laying them on the floor and smacking the bottom one with a large hammer. The bottom one would move, but more than likely, the rubber cement would give it up and the top weight would stay put. This is the same as the two pieces of the damper. The other reason is each time you wack the damper, you are shoving the crank back against the thrust bearing surface on the rear main bearing ! This does it no good at all. As far as the oil pressure problem goes, a fresh small block with a stock pump and 10w30 oil should have around 50lbs oil pressure cold and at least 35lbs hot idleing. Was the crank turned or just polished ?? The synthetic oil should have nothing to do with it. We use it from the start on new motors and so does GM in the Corvettes. We have never had a problem with rings seating or anything else. How is your oil pressure at 1500 rpm or so ? If it goes up ok, you may have a stuck relief valve in the oil pump.
Next, you cannot balance a 400 or any other externally balanced motor without the damper and flywheel being on the crank when you spin it.
My suggestion would also be to get a new factory damper, install it properly and see what happens. Let us know the results.
P.S. Try an A.C. filter. Dont ask me why but I have seen some filters cause lower oil pressure readings.

------------------
Bill Koustenis
Advanced Automotive Machine
Waldorf Md

 

[1BADS72]

Oil psi hits a steady 62 pounds at anything above 1500. The crank was turned .010. Is it a possibilty that I have too much resistance in the K&N filter? I tore into the one I used during the break-in and it was like having 30 "orange" filters in there. I was impressed by the claim on the box that it could withstand an outrageous psi load and not bypass, and trap smaller particles than my fiance's precision jewelry equipment, so I tried it.

** Will order new harmonic from summit as soon as I get offline.

I appreciate your help.

Rob

 

[Tom Mobley]

1BADS72,

Bill is right about the balancing. The shop must have your crank, rods, pistons, wrist pins, flywheel, damper, 1 rod bearing and 1 cylinder set of rings to balance your 400. If you weren't charged for balancing, it wasn't done.

If you repair the threads in the crank nose properly, it will be good enough to hold an installation tool. Find one of the long helicoils and put it in. Have at least 2 guys with good eyes handy when you drill, one will look from the side and one from the top so as to avoid drilling the hole crooked.

When you order the balancer from Summit, order the tool also. If they don't have, Performance Chevy here in Phoenix has them, they have an ad in all the main mags.

The tolerance for ring slippage is zero. They don't slip unless something is wrong. Verify that the balancer and the timing tab you have are compatible, there's several different ways to get mismatched parts here.

Let us know how things go.

Tom