Harmonic Balancer

Use the stock balancer. You can find them used for under $100. You are describing keeping the engine within stock specs. That's fine. That's how Ford originally set the car up. You should be fine with that.

Any damper over 20 years old should be replaced. There are 3 reasons for this:

(1) The rubber sleeve has hardened, and the harder the rubber becomes, the less the ring is capable of moving independently of the hub; the three piece damper behaves more like a one piece "weight" hanging on the nose of the crankshaft. Thus the damper is not dampening the crankshaft (absorbing twisting) as it was designed to do. 

(2) The 3 pieces of the stock damper (hub, rubber sleeve, and the ring) are unbonded, they rely upon the "stiction" of the rubber sleeve to hold the damper together. As the rubber sleeve hardens (resulting from age and heat cycling) it no longer grips the hub and ring as tightly as it should. That loss of "stiction" means the positioning of the crankshaft damper’s outer ring has most likely shifted on the hub to some degree, and will continue to shift over time. Thus the timing marks are not reliable. I've witnessed this on many older cars.

(3) The OEM H code (351 2V) and R code (Boss 351) dampers are counter-weighted via the hub. But the OEM Q code (351 cobra jet) damper is partially counter-weighted via the ring; thus as the ring shifts the Q code reciprocating assembly shall no longer be balanced properly.

Turns out the Romac damper I used to recommend is not fully bonded, an Australian member made me aware of this. You had to read the small print. Thus I no longer recommend it. A quality replacement damper, made in Australia, that is fully bonded, made of steel rather than iron or aluminum, is the PowerBond p.n. PB1082SS. It is far better quality than OEM. It is SFI approved. And it costs only $215 at Summit Racing.

Choice quality stuff.

Simpler. Send your stock balancer out for a rebuild.

The original post links to a balancer at Summit Racing. I noticed it has a 50oz weight.  28oz should be stock for the Cleveland and there should be another 28oz on the flywheel.  Just nit picking. 

George is giving good advice. I replaced mine with the PowerBond unit. While you’re in there I recommend changing your timing chain and gear set. Mine (original) was surprisingly stretched for the 23,000 miles on it. Then engine actually feels tighter as a result. 

Mark yes I'm also doing the timing chain and gears. My engine was rebuilt and only has about 200 miles on it. There were things that were and were not replaced and probably not the best part (good enuf!) was put back on.

Tom, what are your goals here? OEM M-code 351-C in Panteras were redlined at 5900/6000; that's about all the cam, stock hydraulic lifters and OEM valves could reliably deliver under load. For under 6K max revs, about any balancer will work. It's when we push the revs to 6500, 7000 or beyond, that Plan A needs modification.  

The near-stock 351-C needs a 28.2 inch-ounce balance factor on both the harmonic balancer and flywheel to work correctly. 50 inch-oz balance factors were used starting in the '80s after Clevelands were out of production. If used, 50 inch-oz on either end of a crank will quickly tear a near-stock engine apart, sometimes breaking the crank or motor mounts.

Some references say OEM Ford balancers were bonded, some say they were only press-fitted and some say the Boss & HO series was both. The outer ring on old assemblies has been known to get so loose that it spins off and hits the pavement or walks back and wears a hole in the oil pan. A few balancer rebuilders use RTV to glue the two iron parts together and I doubt anyone knows what the real vibration-absorbtion effect is with that technique.

I believe the most important thing for you is, your balancer of choice should be new since rubber deterioration with age (and oil leaks) is the killer here. Not expensive at all. 

Thanks Jack! I plan on limiting my RPM to 6,000-6,500, and will put a decent spring on the valves, but don't expect to exceed lift by .550".  I will run a flat hydraulic lifter (not sure which one) with a good rocker arm and push rods. I doubt I need to go to the expense of an SFI balancer. The balancer below would seem to meet my needs, with medium duty design.

 https://www.summitracing.com/p...amily/ford-cleveland

 One more question, my motor was balanced during a rebuild by the previous owner with the OEM balancer. If I changed out the balancer do I need to have it rebalanced?

tomsealbeach posted:

Thanks Jack! I plan on limiting my RPM to 6,000-6,500, and will put a decent spring on the valves, but don't expect to exceed lift by .550".  I will run a flat hydraulic lifter (not sure which one) with a good rocker arm and push rods. I doubt I need to go to the expense of an SFI balancer. The balancer below would seem to meet my needs, with medium duty design.

 https://www.summitracing.com/p...amily/ford-cleveland

 One more question, my motor was balanced during a rebuild by the previous owner with the OEM balancer. If I changed out the balancer do I need to have it rebalanced?

They aren't supposed to touch the balancer or fywheel. The balancing is done internally on the reciprocating assembly. You generally will see weight taken off of the throws (counter balances on the crankshaft)

6,000 to 6,500 rpm is not a medium service engine. 5,000 to 5,500 is. That is what the stock balancer is good up to. 6,000 to 6,500 is a Boss balancer territory.

A 351cj is a 5,500 rpm engine. That's it.

Interestingly enough, the 289hp engine requires weight added to the reciprocating assembly and they did that with an add on hatchet looking counterweight. This enables you to change components without rebalancing th entire assembly.

I was fortunate enough to find a NOS D2ZX ('72 HO and 71 Boss service balancer). It may be my imagination but it seems to have even smoothed out the idle a little. Like it took some of the cam duration out of it.

The thing is huge. I think it weighs seven pounds.

It does make sense to use a forged steel aftermarket flywheel with it.

The combination then limits the rpm's to you and how fast you want to go.

Ford built those heavy "Boss" balancers for a reason and it wasn't because they were being cheap. I'm skeptical therefore of any aftermarket balancer that is smaller or lighter.

No worries on rebalancing the rest of the engine with a new 28.2 inch-oz harmonic balancer. An SFI rating is only insurance so may not be necessary if you feel lucky.... I personally use a Romac balancer since it has the following advantages: it is constructed such that it CANNOT come apart or mis-index while running, it is fully degreed around its pheriphery which makes setting valves & timing easier, and it is fully rebuildable (by Romac-USA). I do spin the engine above 6000 now 'n then; note that most ANY 351-C will go to 7000+ under light load if you hit neutral or grab 2nd instead of 4th when downshifting. I'd worry more about a stock iron flywheel breaking at high rpms than a stock-type balancer. Good luck- JD