[68WarDog]

How much more if any harmful harmonics do solid roller assemblies put into the block over hydraulics? Back in the early 90s, a lot of us sort out better balancers, which was Fluiddampers for me. Yes I'm aware of the controversy about the weight on the end of the crank. But >25 years it has served me well. I also have used Romac. Although I believe in balancing and blueprinting the assemblies, I believe that harmonics takes away power. What are some of the better Pontiac balancers on the market today?

[mgarblik]

IMO, ATI makes the best harmonic balancer on the market. They are expensive and they DO NOT make a hub that works with stock Pontiac pulleys. So that is a detraction for some applications.

[steve25]

You might be surprised to hear that a steel cam unlike a cast iron cam will twist in response to cam lobes being loaded and unloaded by the springs.

It’s been seen to make anywhere from a 4 to 6 degree change in the timing for what might be needed to fire the cylinder.

In a SBC motor for example that was set to 40 degrees total at 3000 rpm the timing was seen to drop to 36 at 5500 and then went up to 44 at 8500.

The power loss was so great that some engine builders like Jenkins started to have cams ground as in this photo to help stiffen up the cam.

So back to your question, if your cam is flexing ( which it is to some level or another) how do you know if the harmonics are not countering some of the twisting action and helping power production or not at certain rpms?

[68WarDog]

Originally Posted by mgarblik

IMO, ATI makes the best harmonic balancer on the market. They are expensive and they DO NOT make a hub that works with stock Pontiac pulleys. So that is a detraction for some applications.

Thanks for the information. Same holds true for Fluiddampers.

[Dragncar]

The best 4 bolt Pontiac balancer is the BHJ and they are not cheap. 535 $ but are 100% USA made and these balancers require you to get a snout measurement with a micrometer, not a caliper so Darrin can get you one with the correct .001-.0015 press fit.
I run one and even have a factory lower pulley with a V pump mandrel on it.
But, there is more money you would have to spend with a press fit balancer. You need the Moroso installation-removal tool.

http://nitemareperformance.com/bhjbalancers.html

And these are 312 $
https://www.summitracing.com/parts/mor-61745

[68WarDog]

"It’s been seen to make anywhere from a 4 to 6 degree change in the timing for what might be needed to fire the cylinder."

Definitely never heard or considered that. My thinking has been that solid roller cams exert better control over valve train timing events than any hydraulic. Or am I missing something?

So back to your question, if your cam is flexing ( which it is to some level or another) how do you know if the harmonics are not countering some of the twisting action and helping power production or not at certain rpms?

( Cam flexing/ a form of harmonics)?One of the reasons I don't put much faith in engine dynos, other than leak checks. Chassis tuning involves any and all harmonics that may be transferred to the engine. But that's jmo.

[Dragncar]

There are reasons folks run 55mm cams. Camshaft flexing is one of them.
How much flexing is going on in a street engine ? Might not be enough to worry about.

[Gach]

My vote ATI makes the best harmonic balancer on the Market. Definitely! Press fit is definitely the way to go. I run BBC deep grove pulley. Because I run alternator its no big deal lining them up. I use 1970 gto alternator bracket, think you can still by them from Ames.

[Sirrotica]

FWIW, the 6.5/6.2 GM Detroit Diesel designed engine that came in the chevy trucks beginning in the early 80s, to roughly 2000, and the military Humvees, has a cast crankshaft, The balancers tend to slip the ring off of the hub. If not caught soon after the balancer slips, the crank will break in half. There is an aftermarket chinesium forged crank available for them, but as long as you keep a good balancer on them, they live with the cast cranks.

Diesels are tougher on cranks due to the built in torsional twist they are subject to, the compression ratio on these engines is usually around 22 to 1 so the crank is always accelerating, and slowing down, as the engine is running. Considering how much torsional twist the diesel cranks are under, and considering Pontiac also uses cast cranks they're more durable than people give them credit for. The harmonic balancer is of major importance to keep the harmonics from destroying the cranks in short order.

The idea of using a nylon toothed cam timing gear was also used to absorb the crank harmonics on some engines. I believe Grumpy was also using one of those gears on his race engines for that reason.

[Dragncar]

The IA2 engine of mine is getting a ATI balancer. 4.5 crank and steel Power Adder rods so it will get the best race balancer.
And its cheaper than the BHJ.
My V pump mandrel also has a 3 bolt pattern as well as 4 bolt.

[Half-Inch Stud]

So, just to get all on the same page:

The Front damper is first-needed because the long crank is loaded at the back end, allowing the front-end to attain an ADVANCED twist during the 2&1 Power Stroke the rear flange is RETARDED. Then the Front-end unloads that twist before the 1+2 Exhaust Open event.
Same goes for Compression stroke, yet in the opposite twist direction.

Raise compression, or TQ curve (hp) or likely both and I'm swaggered to insist the front damper weight (inertia) need be increased, the Mains dia too. The early 60s SD & 69 OHC-6 Sprint had impressive front Dampers. Didn't they.

Repeat the crank-twist effect for the remaining CYLs, but figure the integrated crank-twist may not be as localized as the 2-1 event. Well the Front Damper allows the front-end to appear inertially loaded during the 1&2 Peak CYL Pressure that causes a peak crank-acceleration (not peak Piston velocity but close, before peak velocity). Those peaks are effectively blunted by a properly sized front damper.

Those peaks are more effectively dampened by the 2-piece (elastomed-coupled) Stock Damper design. Those peaks are moreso dampened by the Rattler configuration, when properly designed with several different-sized (brass) bobb weights to tune for the many peaks occurring in a rotation.

Far as i know, it is difficult to hand-calc the design. Maybe CAD today has a neatly developed model to design and optimize dampers of 1-piece, elastomer, and Rattler configs.

As for Fluid-damper, ahhh i dunno about the dampening capabilities for twist-untwist vs rpm. I can get technically-scared think about how a fluid damper might not work as well. Maybe some believers here (posted above) can crow about HOW the damper works.

In contrast, the lack of a front damper will produce a 2-piece crank right away upon driving the engine into peak-TQ.

PMD knew what they were doing with the dyno-testing for engine life duration, as they went to 3.25" Mains. What Main dia did the 1st Stratostreak have?

Many thoughts, conclusions can be supported with Race results for Forged Cranks vs Cast cranks, recipro-weight, and Blocks that hold together.

[Half-Inch Stud]

So, just to get all on the same page:

The Front damper is first-needed because the long crank is loaded at the back end, allowing the front-end to attain an ADVANCED twist during the 2&1 Power Stroke the rear flange is RETARDED. Then the Front-end unloads that twist before the 1+2 Exhaust Open event.
Same goes for Compression stroke, yet in the opposite twist direction.

Raise compression, or TQ curve (hp) or likely both and I'm swaggered to insist the front damper weight (inertia) need be increased, the Mains dia too. The early 60s SD & 69 OHC-6 Sprint had impressive front Dampers. Didn't they.

Repeat the crank-twist effect for the remaining CYLs, but figure the integrated crank-twist may not be as localized as the 2-1 event. Well the Front Damper allows the front-end to appear inertially loaded during the 1&2 Peak CYL Pressure that causes a peak crank-acceleration (not peak Piston velocity but close, before peak velocity). Those peaks are effectively blunted by a properly sized front damper.

Those peaks are more effectively dampened by the 2-piece (elastomed-coupled) Stock Damper design. Those peaks are moreso dampened by the Rattler configuration, when properly designed with several different-sized (brass) bobb weights to tune for the many peaks occurring in a rotation.

Far as i know, it is difficult to hand-calc the design. Maybe CAD today has a neatly developed model to design and optimize dampers of 1-piece, elastomer, and Rattler configs.

As for Fluid-damper, ahhh i dunno about the dampening capabilities for twist-untwist vs rpm. I can get technically-scared think about how a fluid damper might not work as well. Maybe some believers here (posted above) can crow about HOW the damper works.

In contrast, the lack of a front damper will produce a 2-piece crank right away upon driving the engine into peak-TQ.

PMD knew what they were doing with the dyno-testing for engine life duration, as they went to 3.25" Mains. What Main dia did the 1st Stratostreak have?

Many thoughts, conclusions can be supported with Race results for Forged Cranks vs Cast cranks, recipro-weight, and Blocks that hold together.

Yea, I don't mistake me as an expert, but do know enough to know that a fella has to be a specialized expert to be manufacturing good dampers.

[Half-Inch Stud]

Oh, and manufacturing good front dampers based on Race results is sufficient expertise, and likely more effective than driving a CAD model in a CAD program.

Either way, it stinks to be the development test engine(s).

[mgarblik]

I agree HIS !. The 1955 287 Pontiac had 2.5" mains. Great for heat and bearing speed, not so much for flex and strength as power and displacement increased. As you mentioned, Pontiac engineers were smart and frugal. There was obviously a reliability issue as the displacement went above 400 Cu. In. in the Pontiac design. They had 2 choices, really. Put an expensive forged crankshaft in every large displacement V-8 or simply bite the bullet once, change the molds and make the existing block 3.25" for a stronger low cost cast crankshaft. For purely racing, that was the wrong move, IMO. The huge size mains needed lots more oil and the surface speed at high RPM's killed the bearings, blocks and crankshafts. But with a 60 lb. oil pump, running at designed engine speeds, this worked just fine and saved Pontiac a ton of money.

[tom s]

Just a FYI,the engineers chose 2.5 mains for the 303 short deck SCCA RA V engine.They also did a very unusual balancer.Larger diameter and bonded like the later styles.Tom

[Shiny]

Originally Posted by Half-Inch Stud

So, just to get all on the same page:
......

Yea, I don't mistake me as an expert, but do know enough to know that a fella has to be a specialized expert to be manufacturing good dampers.

Good explanation, thanks HIS.

Pls forgive my rambling but the thread dragged me into the weeds.

I agree damper design would take specialized expertise and the complexity of the application, as you point out, is non-trivial so may not be easy to optimize by modeling. Especially if an aftermarket damper is selling into a wide and random range of applications.

But I'm fuzzy on a lot of the discussion in this thread.

In my limited understanding the need for a damper is mostly about the effects of undampened vibration on risk for crankshaft fatigue failure. To me, this is about crankshaft stress increasing if there is undamped torsional resonance.

What other bad things happen if the vibration is undamped? For example, do the dynamics in the valvetrain change? Do the loads on bearings change?

I am also confused by statements of damper designs needing to be tailored to crankshaft materials. For example, cast iron vs cast steel vs billet steel, etc.

To me, the fatigue strength can obviously be higher for steel but the basic elastic modulus and therefore, resonance, is basically the same for cast iron, forged steel, billet steel, etc. I do know cast iron will dampen vibration better than steel but not sure that difference is enough to change a damper design. If cast iron dampened itself well enough, Pontiac wouldn't have needed a damper....

If the crankshaft dimensions are totally identical (which they won't be) and the application is totally identical (which it could be), why does a damper for a cast crank need to be different than one for a forged steel crank?

Now, back to your regularly scheduled programming...

Mike

[steve25]

Even with 3” mains if your peak hp is coming in above 7K and your also running only a 6 counter weight crank you need a very effective balancer.

Yes as mentioned in post 9, Jenkins preferred ( at least for his drag motors and there short duration runs) the nylon covered tooth cam gear and chain set up.