At what point, be it horsepower or RPM limit, does the stock small block harmonic balancer need to be upgraded to one of the more expensive "Race" types? I'm not interested in which kind or brand is better at this point, but rather when the move has to be made. I hear terms like "mild street build", "street/strip", etc but I really have no frame of reference for what that means regarding engine performance. I'm sure five different people would have five different interpretations as well. I have seen where the stock-ish ones have a 6500rpm limit. What about horsepower? 400, 450, 500???

I think an aftermarket dampener should be used always. They are inexpensive enough to use one every time.

The damper doesn't know horsepower, it sees rpm. I use nothing but the best damper available. Why not put the best parts on an engine? Lots of dollars invested.

Old factory dampers are two piece with rubber in between. The halves can slip and move out of alignment. I've had it happen and it created a noticeable vibration. Over the years I've seen it more than once. That was the selling point for me.

If you decide to use the original balancer make sure you verify the timing mark is really on top dead center. I check it on new balancers too

Rulebook says anything quicker than 10.99. I would say anything spinning over 5k or so. Or if it's a dry rotted 50 year old OE piece. Common sense should guide the decision.

The /6, like all L6 engines, has a torsional twist problem due to crank length (unlike V6, V8) and should use a quality damper.
Please note that when the ring separates from the hub it's toast, as on all dampers.
The SEMA damper standard (S.F.I. 18-1) does not rate a damper’s effectiveness, or certify that it works at all (let alone on a specific engine) - only that it fit the designated engine, and didn’t explode during the test. Their interest is limited to safety and qualify control, not specific engineering results.

IMO anytime someone is going through the expense of rebuild an engine should upgrade better than stock.Then the quality of the replacement is up for debate.

The aftermarket damper rule was put into effect because of high winding CHEVY dampers flying off and hitting people. The stock mopar damper is BETTER than a lot of the cheaper aftermarket dampers that are out there. My Son and I both spun Summit brand Dampers and they both went on the scrap pile. All my engines except one now have ATI dampers on them. Todd at Compitition Wedge recomended the Powerbond damper and I have on on my Sons engine he is using now. So far, so good.

The original balancer on my 340 is pretty much toast as far as the rubber goes so it will be replaced soon. The options range from $90-$120 for a copy of the original cast iron type, ~$180-250 for a steel unit that uses the same rubber system and has a SFI stamp, then you get into the $350 ones that advertise "special" damping rings or the fluid filled type. My original question was pointed at the latter two. It's a street car and won't be drag racing but want to do some road course stuff. I don't plan on spinning it much more than 6000-6500 rpm and it will be limited to 5k until I have an opportunity to freshen the lower end. I like to buy once, cry once so if there is a advantage to the expensive ones over the mid-range, I'll do it. I've searched but really haven't seen any supporting data that points to when you need to go top of the line like ATI, TCI, or Fluidamper. That probably means that one of the decent middle of the road ones would suffice. Some of the expensive ones also pose pulley spacing problems that I'd like to avoid.

There are only a few RPM levels in which torsional forces are dangerous, largely based on the dimensions of the crankshaft. Power has nothing to do with it, except that it may push the RPM to a level beyond which the OEM damper doesn't work. Poster child: 289 Windsor low perf upgraded with 271 hp parts (especially cam and springs) but using the original (low RPM) damper: loosened bolts, damper shifted, crank breakage at front MB, etc.
An OEM (bonded rubber) damper is almost always specific to not only a specific engine but specific stroke length and journal size. Aftermarket silicone, friction etc. can work on more frequency range and are more generic.
Read more http://harmonicdampers.com/index.php?main_page=page&id=4&chapter=0

I've seen the results of stock Chevy stuff coming apart in the old days. The amount of damage they could do was impressive. Buddy had one come apart in a first gen Duece, sever a brake line and about lose the whole car. Personally I wouldn't use an OE type piece on anything but a stock/resto type engine that I want to look original and uses original front accessories.

I've used a bunch of different balancers on both BB and SB Mopar V8 from cheap to all out race.
I have a pair of used after market race SB balancer in my shop now, a ATI and a Fischer Racing fluid type, I'm hoping to use the ATI on a Hi Po pump gas 360 stroker motor converted to internal balanced No plans for the other one
On your deal the Power Bond will probably meet all your needs

I'd have to advise against using the 440Source one. Less than 4 years old and never seen over 6400 rpm.

What style of dampener is that? I can't tell if it's an elastomer or fluid style.

Elastomer/Rubber. Outer ripped away from inner for some reason. Crickets from 440Source.

Thanks for the input, ive seen stock ones that lasted better then that.

The Powerbond Race looks like a good option. Something doesn't jive with the application data on the Summit site though. I select the 340 motor but they say it only goes back to 72, which is externally balanced. I have a 70 340 motor so I need the internally balanced one. But, the description of the part says it is internal balance. Something is not right here? There is no mention of external weights to add or if the pics are correct, holes to mount them. If I search by 1970 340, Powerbond is not an option that comes up. Same thing on the Powerbond website. Only for 1972 or newer PB1004SS, but shows as neutral weighted....
https://www.summitracing.com/parts/pbb-pb1004ss/overview/

These are the only dampeners on the market with an alloy inner and a heavy steel outer, which to me makes them the best on paper (think a undercut crank counterweight) Anything else on the market has a steel hub and alloy outer or is all alloy... $467 is out of my budget a tad though
http://harmonicdampers.com/index.php?main_page=product_info&cPath=7_61&products_id=121

The Powerbond Race looks like a good option. Something doesn't jive with the application data on the Summit site though. I select the 340 motor but they say it only goes back to 72, which is externally balanced. I have a 70 340 motor so I need the internally balanced one. But, the description of the part says it is internal balance. Something is not right here? There is no mention of external weights to add or if the pics are correct, holes to mount them. If I search by 1970 340, Powerbond is not an option that comes up. Same thing on the Powerbond website. Only for 1972 or newer PB1004SS, but shows as neutral weighted....
https://www.summitracing.com/parts/pbb-pb1004ss/overview/[/quote]


Could this be because of the symmetrical/ non symmetrical pulley bolt holes? Not sure what year they changed that.