Spinning harmonic balancer - really HEI problem

Vragor · Oct 15, 2010

Since my recent rebuild, I've been chasing my timing a bit.

Truck runs fine and then suddenly seems to be miss-timed. Things like missing a lot, a loud chug as I'm trying to accelerate from a stop, or even a real backfire on decelerate.

Timing light usually shows the timing out. Generally retarded a bit.

I'm running a Duraspark II which can only move 20 or 30 degrees before hitting something, so I can tell by physical proximity whether the distributor has actually changed position or not, and it doesn't seem to be.

I mentioned this to someone at a recent meet and greet and he asked what kind of shape my harmonic balancer was in, and its in bad shape. Lots of cracks in the rubber ring, and even bits protruding. When its idling I can see a slight wobble to the outer ring.

Yesterday I pulled the distributor out to see if the gear was wearing or any other obvious problem, but all looked fine. The gear is on with pins all the way through the shaft, so no possibility of a loose set screw and a slipping gear.

When I put it all back together and re-timed it, it was running terrible. I advanced the distributor until it was running smooth and checked the timing again and it looks like I'm way advanced. I can't see the TDC mark at all, and the mark for normal timing barely visible under the water pump.

Is this conclusive proof that I need a new harmonic balancer? How would the balancer shifting make my truck run worse if the distributor hasn't changed?

Nightstick · Oct 15, 2010

Stupid question... are you sure you have the correct balance on it (28 vs 50oz)?

blubuckaroo · Oct 15, 2010

It can't make it run worse. Sounds like the distributor came loose or the timing chain jumped. You better replace the balancer anyway. I had the ring come off one while on a trip. The pully kept it from coming all the way off and causing any damage but it made a lot of noise.

Viperwolf1 · Oct 15, 2010

The wobble and bits of rubber sticking out are reason enough to replace the balancer. If it fixes the timing problem also then it's two fixes for the price of one.

Vragor · Oct 15, 2010

Nightstick said:
Stupid question... are you sure you have the correct balance on it (28 vs 50oz)?

Not a stupid question. I am more than capable of screwing it up if it's possible. But in this case, I only have one balancer, the one that came on the 302 originally.

It sounds like I'll be buying and changing a balancer tomorrow. Found one in town at O'Reilly's for $89

Nightstick · Oct 15, 2010

I have an extra in the shop from an explorer motor which I'm pretty confident is the 28oz. Is your 302 an HO or older motor with the 50oz? ( I may have that backwards but you get the point)

Vragor · Oct 15, 2010

Nightstick said:
I have an extra in the shop from an explorer motor which I'm pretty confident is the 28oz. Is your 302 an HO or older motor with the 50oz? ( I may have that backwards but you get the point)

From what I've read, 50 oz is for 80's or newer 302/5.0L.

I have a '68 block in my truck which takes a 28oz balancer. Further, I have a v-belt setup so I need the 3 bolt configuration. I've already ruled out most of what I've found locally from one or the other of those 2 requirements.

Luckily I have Bronco Hut just 30 miles up the road where I'm sure I can get what I need.

blubuckaroo · Oct 15, 2010

Before pulling the balancer, time it by ear and see if it runs ok. I'd hate to see you go to the trouble of replacing the balancer just to take it apart again to replace a sloppy timing chain.

Broncobowsher · Oct 15, 2010

Loosing timing and the distributer isn't moving is one of 2 things. Distributer gears or timing chain. the ring on the balancer can more all it wants, that won't affect the crankshaft to distributer timing. the timing marks will be pointless, but no change in the timing.

Do the timing chain test. remove the distributer cap and by hand rock the crank back and forth. See how play there is. I know you stated "recent rebuild" but that doesn't mean that new parts are always good or that they will last.

broncnaz · Oct 15, 2010

I'm going to say its your balancer. Due to the fact you you said this was a recent rebuild(you did install a new timing chain/gears right?) and see the balancer wobble and are using the timing marks to time the engine. Few people replace balancers during rebuilds even though a lot of them should be replaced.
If the timing chain did jump a gear you would really have to move the dist to get it timed and since you stated its in the same lcoation then its not a timing chain issue.

bblue · Oct 15, 2010

Yes do the chain test.... I just pulled apart my 302 that had under 5000 miles and there was alot of play in the chain.

Vragor · Oct 15, 2010

If the timing chain jumped, wouldn't I be having much more trouble than just timing? Wouldn't the cam be opening and closing the valves out of coordination with the piston and probably bust a valve?

If I time it by sound or vacuum, the engine runs really well and delivers allot of power.

What I'm hoping is that the spinning outer ring of the balancer was causing me to set the distributor timing bad, but not so bad it wouldn't run. And then something like the electric choke was keeping the engine running and when it finally kicked off I would notice the bad timing. . . .

First step, do the timing chain test (I bought a long block from a local shop).

Second step, pull the plugs and passenger side valve cover, then rotate the engine to #1 top dead center and see for sure if my balancer is spinning. I did this check when I installed the harmonic balancer.

Third, come back here and ask for more opinions if those both look good.

broncnaz · Oct 15, 2010

I've never heard of and SBF's having issues with the valves hitting the pistons. If your timing chain jumped then you would have probably needed to pull the dist and turned it a tooth or two to get enough adjustment or at the very least you would have to turn it quite far to one side to get it to run.
I'd just pull #1 spark plug no need to remove the valve cover you can pull the dist cap to see if its on #1 as well that will tell you its at TDC. The compare the timing marks.

blubuckaroo · Oct 15, 2010

I'm so confused. I thought you said it had been runnung great then started running crappy. Even if the harmonic balancer were missing, it wouldn't cause that. I'd look for something that changed on its own loke maybe a vacuum leak, bad plug wire, or loose distributor bolt. Get the balancer replaced though. You need it to document where the timing is set.

markperry · Oct 15, 2010

I partially sheared off the pin that holds the distributor gear on! Did the same thing!

Bronco_69 · Oct 15, 2010

blubuckaroo said:
I'm so confused. I thought you said it had been runnung great then started running crappy. Even if the harmonic balancer were missing, it wouldn't cause that. I'd look for something that changed on its own loke maybe a vacuum leak, bad plug wire, or loose distributor bolt. Get the balancer replaced though. You need it to document where the timing is set.

this guy knows what he is talking about. if the truck runs worse it is because something changed and not the balance.

however you do need a new balancer from the sound of it.

Vragor · Oct 15, 2010

I've been confused too, that's why I was asking whether the balancer would cause the engine to run rough, and the answer seems to be no.

UNLESS I kept chasing the wandering balancer and setting the timing wrong.

I checked the balancer against #1 top dead center and the balancer was way off so I need to change it. Once I have that fixed I'll try to figure out if something else is going wrong.

Zillacon · Oct 15, 2010

If its the balancer is spinning it will throw the balance of the motor off causing you to feel harbonic vibes in the floorboard/gas pedal/seat of your pants but will not cause your actual timing to slip. It still sounds like your balancer is in need of being changed though. The timing light will physically be off on the line on the balancer when checking if the balancer is spinning but thats it. You can also mark your inner and outer part of your balancer to see if you are getting and rotation/spinning. If you are occasionally having to adjust your distributor something else is causing it! (Timing chain, cam gear or dist gear wear,bolt loose, tiny leprechan etc.) I could be wrong and have seen weird things happen before but that is my take on it. Are you timing it by sound and it still moves?
Are you doing anything goofy with your fuel? Buying different grades or stations? How are your plugs, cap rotor? Do you have the points to put back in ans see how it runs with out the EI? Just digging a little.

broncnaz · Oct 15, 2010

Vragor said:
I've been confused too, that's why I was asking whether the balancer would cause the engine to run rough, and the answer seems to be no.

UNLESS I kept chasing the wandering balancer and setting the timing wrong.

I checked the balancer against #1 top dead center and the balancer was way off so I need to change it. Once I have that fixed I'll try to figure out if something else is going wrong.

As was said you might get some vibrations but it wouldnt really cause the symptoms you've described. Unless you keep chasing the wandering outer ring as you said.

The only other thing to make sure its a slipped balancer is to check the position of the key way on the crank when the #1 is at TDC the keyway should be straight up at the 12 oclock position. of course you would have to remove the pulley and balancer bolt to see this. but if the key way is stright up and the timing marks dont line up with the pointer then you know for certain the ourter ring has slipped.
I had a buddy come to work one day as tell me his engine was making a strange noise when he shut it off. Well I go out and listen to it and I pretty much knew it was his balancer his outer ring would just spin as all the rubber had come out. $100 and a few hours later he was good to go again.

Bronco_69 · Oct 15, 2010

i bet your pin is sheared. it is very hard to tell by looking at it. pull the distributor and try to press the pin out. if it will start to press out then it is ok. just press it back in.

the rotor could also some how be turning on the shaft.

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