up to date stroker info

[mountaineerjeff]

Just reread the RPM thread. I've read it before, but it's been years.
So it seems to be universally excepted that the harmonics issue is crank related, but is passed to the cam/distributor/oil pump until it finds the weakest link.
So do to the harmonic being crank related, those numbers change with the crank/stroke. So despite piston speed and internal stresses on the bottom end a stroker actually has a higher harmonic rpm threshold.

Solution 258 crank. Now there still seems to be inconsistent opinions on 12w vs 4w. But from my understanding Scat makes a forged crank? If this is the case I'll just run Scat forged crank and rods. Possibly just their full rotating assembly. I'd assume the scat crank wouldn't need any machine work, notably the known issue of the cranks being 1-3 degrees out and the balancer mounting issues.

As for wrapping up the bottom end, no acl race bearing option? So I'm just stuck with king? What's the defined answer on using 258 main caps? Can they be used with the 96+ girdle? Any ring set that is above and beyond the rest?

I'm hoping to compile a post with all the final conclusions to keep the research easier and the community advanced.

[SilverXJ]

Just reread the RPM thread. I've read it before, but it's been years.
So it seems to be universally excepted that the harmonics issue is crank related, but is passed to the cam/distributor/oil pump until it finds the weakest link.

If we believe the data in the thread, then the crank is most likely the source, especially from this quote:

Peter,

Don't waste your money on moving the thrust. I have moved it to read an make
steel caps, still no help at 5375rpm. The problem seems to be more related
to the 4.0L and the elder 232 (close to the same stroke). I have not seen
the same res at 5375 when using the 258 crank. This crank has 12 counter
weights. I believe that the crank is more of the problem than the cam. The
cam is just the results of the harmonics. I have used a test damper from
Fluid Dampers that did make a change in the range (raised to 6600rpm) but
still had the harmonics.

The thin spots can be as thin as .085 as long as they are below the ring
travel and 90 degrees from thrust.

I would suggest trying to stay below 5300rpm.

The problem is that the only good source of info on this is Hesco, and I don't believe they are letting the whole truth out. Aside from that we have anecdotal evidence that there is a problem some where. Cracked cranks, spit our distributors, worn & broken chains. As Lee said the gear drive is a bandaid, and a poor one at that. A better solution would be a belt drive setup, which is much better at isolating the cam and crank and takes less power to turn. Combine that with a good harmonic balancer (not fluid damper) performance crank (258) work and all the nitty gritty work and it may be alleviated or reduced.

Solution 258 crank. Now there still seems to be inconsistent opinions on 12w vs 4w. But from my understanding Scat makes a forged crank?

Scat's crank is not forged.

I'd assume the scat crank wouldn't need any machine work, notably the known issue of the cranks being 1-3 degrees out and the balancer mounting issues.

Don't assume that. There have been a few people that reported tight bearing clearances on the Scats, but that problem may have been fixed. As far as balance I would never use any crank without a good machine shop checking the balance along w/ the balancer and the flex plate/ fly wheel.

As for wrapping up the bottom end, no acl race bearing option? So I'm just stuck with king? What's the defined answer on using 258 main caps? Can they be used with the 96+ girdle? Any ring set that is above and beyond the rest?

I believe it is TurboTom that was running 258 caps/late girdle combo or at least investigated it. Besides the bearings there is much you need to attend to in the bottom end if you are going this route.

Would having a dizzy vs. cps stick be any improvement - vs. a billet piece here?

What would that do? The distributor or cam sensor has very little drag.

And was there any evidence showing that the cam retainer plate in the NVH 99+ blocks did any good with higher

I've never seen any and I don't see why it would be.

[jsawduste]

Everyone is throwing out some information here.

The links are providing some interesting information but at the same time leaving out a tremendous amount.

The info from Leee leaves out a lot of build detail. What crank, what stroke, how many counter weights, what B/S ratio, rod length, piston weight are a few pieces missing

While the cam only has 4 journals is runs at half speed.

Chrysler did significant changes to the block for NVH. If there wasn`t an issue then why did they go to the considerable expense of changing the casting and adding the girdle ? It would seem logical that the purpose was to control harmonics. That is what NVH is. Noise, Vibration and Harshness.

The crank if properly indexed and balanced simply spins along within it`s bearings with little in the way of harmonics at the speeds we are considering.

[Cheromaniac]

One thing I do know is that my stroker (12cwt crank in '00 block) is smoother at higher rpm than my old 4.0 ever was.

As far as balance I would never use any crank without a good machine shop checking the balance along w/ the balancer and the flex plate/ fly wheel.

Agree about the need for the crank to be balanced but, unlike a crossplane V8 that has uneven firing pulses on each cylinder bank, an I6 crank doesn't need to be balanced with the HB and flywheel/flexplate in place.

I don't know if running 258 main caps makes any real difference but if you did, you'd need to have the main bearings line bored to ensure perfect alignment of the caps.

[jsawduste]

One thing I do know is that my stroker (12cwt crank in '00 block) is smoother at higher rpm than my old 4.0 ever was.

Agree about the need for the crank to be balanced but, unlike a crossplane V8 that has uneven firing pulses on each cylinder bank, an I6 crank doesn't need to be balanced with the HB and flywheel/flexplate in place. Despite the design parameters of the I-6.

I don't know if running 258 main caps makes any real difference but if you did, you'd need to have the main bearings line bored to ensure perfect alignment of the caps.

Dino, when I have an engine balanced it is done dynamically. That is with all the parts in place and moving. Including the flywheel and pressure plate if it is a manual transmission. Simply making sure the parts all weigh the same is not dynamic but static balance. You already know that and I am sure you understand the benefits of such.

The I-6 is a long engine and the factory machining is somewhat "loose" in tolerances. Line bore/hone is a given on both the mains and the cam journals.

I cannot concisely say the "solid" caps are stronger then the "hollow" as I do not know the metallurgical properties of each. Taken at face value it would seem the solid caps would be stronger. That may not be true due to the outside radius the hollow caps have on the outer dimension and the effect of that rib. This is a subject that I will need to further investigate.

[Cheromaniac]

Dino, when I have an engine balanced it is done dynamically. That is with all the parts in place and moving. Including the flywheel and pressure plate if it is a manual transmission. Simply making sure the parts all weigh the same is not dynamic but static balance. You already know that and I am sure you understand the benefits of such.

Indeed. I may not have made myself clear enough in my previous post. What I meant was that the balancing (dynamic obviously) can be done without the harmonic balancer and flywheel/flexplate in place i.e internal rather than external.

[jsawduste]

Thanks Dino !!