My Pete rebuild

[Nostalgic]

Had a little bit of time today and since the replacement crank showed up, I was able to get it in.



.010" of end clearance checks out, rear seal area runout has one high spot @.003", front seal area .002" Crank turns nice and smooth. Since there's the chance that it may be 2-3 months before this is finished, I chose to assemble with Lubriplate 105.


Got it flipped over and did a quick check of the liners. Kind of frustrated with with the Central Tools sled. It's not perfectly flat and it doesn't take much of a pressure change to affect reading by .0015". I clamped down #1 and #4 with readings of .0115-.012" Pulled #1 liner, removed the shim and clamped down I get -.021" So, depending on how 2-6 check out, I'll either order .036" or .0365" shims to put me at .015" I know my stacked brass shims "settled" about .002" when I pulled the IPD parts out 2 years ago. S/S shouldn't have the crush brass does, so .015" should hold true.

One big observation was how tight the liners fit in the new block at the deck. In hindsight, I should have shopped for another buildable block back in the beginning...

[Nostalgic]

This is becoming a very aggravating experience in getting usable parts.

Warning, long winded, lotsa words rambling ahead.

Visual check of pistons show a half moon area in the center of the bowl (or whatever the little raised spot in the middle is called) of bare metal. I thought I saw this brought up by another member, but couldn't find the thread/post?

So far, all 8 pistons I've received look like this. Yeah, I had to buy 8 pistons to get 6 damage free ones. One, AND it's first replacement both had heavy marks on the outside of the crown in the APR area. Looked like it was dropped or dragged across concrete before they packaged it up.

Since I'm putting together what's ultimately going to end up being a pretty big chunk of $$$ and quality so far has been so bad, I decided to start checking things in a little more detail. Using my old postage scale, I weighed my pistons. Between the 6, theres a 1.4 ounce spread between the lightest and heaviest. Rods are even worse, with a 2.4 ounce spread. Even on a big clunky diesel, if the heavy piston was put on the heavy rod without checking, that's a huge imbalance in my eyes. I understand that dead weight on rods is only half the story, so I purchased a more accurate scale that reads to .1 grams and I'll dig into reciprocating/rotating weights later once I get a jig setup since I'm going down this rabbit hole.

I have 5 left over rod "cores" that I could possibly use, but the wrist pin bushing specs were tighter than my tools capabilities, so, I bought a new Mitutoyo dial bore gauge. I'm no machinist and now find myself trying to zero a .0001" bore gauge with .001" calipers is a little frustrating lol. The rabbit holes I find my head stuck in...

At least I can kind of sort of determine a go/no go for pin bushings? Cummins specs are 2.502" min -2.503" max. By my shaky hands, I'm reading 2.5025" on one of the recon rods. Even if I'm off by .0005", at least I can know not to consider using one of my used rods if it reads 2.5035" on the vertical measurement (horizontal was same reading as the new recon sample).

Not sure if I should just order 4-5 more rods and try to put together 6 with a closer range of weights or...? The return process with Hunter's is a pain, and it sucks having thousands tied up in returns. I know, I'm probably preaching to the choir here.

All of that said, I really am hesitant to remove material from the pistons. There's no real "good place" I can see, not to mention, what affect does removing the underside coating have? Even though it's very thin and I can already see some shiny metal on the edges of the valve recesses just from rubbing against the bubble wrap, doing so intentionally feels wrong lol. I'm tempted to match heavy pistons to light small ends of rods, and then try to balance the rotating weights of the rods...

You may be asking why I'm doing this. Best I can come up with is 'cause. I want an engine that doesn't shake my mirrors, produces moderate power and is happy and content to spin at higher rpms while doing both.

[tree98]

Won't the balancer take care of any vibration from that little bit of weight difference?

[Nostalgic]

Problem is, several ounces of imbalance @ 2500 rpm can be upwards of 100 lbs. There's no viscous dampener or balancer that can resolve that. Viscous dampeners are great at absorbing torsional vibrations, but they don't really do any balancing.

[tree98]

I don't remember seeing Rawze weigh all his parts when he did his rebuild. What am I missing?

[Rawze]

(12-25-2021 )tree98 Wrote:  I don't remember seeing Rawze weigh all his parts when he did his rebuild. What am I missing?

not trying to be a meanie, just my thoughts...

I am starting to think that he's ... yet again ... going to make it worse, rather than better. - The engine, from the factory, if it is simply built 100% right with all oem internals, and then cared for properly, will already last a million miles on its own.

I have also yet to open an overhaul kit and find defective components, aside from maybe the replacement head gasket shifting in the box it comes in and getting glue on it or marred a bit, or something dumb like that due to rough handling during shipping. Its pretty rare for there to be factory defect parts, right out of the boxes... and buying things individually is not only far more expensive, but you can get different year/style of components, depending on the supply chain and local stocks, that may not match up 100% together.

- Even if a person does improve the quality above what is discussed on here with precision balancing the reciprocating assemblies, and all things else.. It is not going to last any longer than normal, for the typical truck application. If the engine is simply built 100% correctly, and cared for properly, it is almost never any of the lubricated components that lead to an inframe 10+ years down the road any ways.

I had offered to let him build it again over here with some guidance (as long as he used all OEM internals) a while back when it first needed it, but I guess he was not able to take me up on it.

[Nostalgic]

(12-25-2021 )tree98 Wrote:  I don't remember seeing Rawze weigh all his parts when he did his rebuild. What am I missing?

I think Rawze reused his rods. I've never had a set of original assembled rods to use, they are not available new through Cummins, and buying RX's get you rebuilt rods that could have been manufactured over a 20+ year span.

The new block kit - the only way I could find to get a virgin block, comes with liners pre-installed, oil cooling nozzles & bolts, and dowels. The only advantage of buying a kit is that pistons would most likely all have the same date code and possibly vary a little less in weights. It would cost more because I would be buying new liners that I don't need.

And - I would still be faced with wide ranging rod weights.

Cummins is still producing new CM570's for export, but aside from snagging one of those on it's way out of the country, it's been pretty challenging to source all of the parts needed to make a brand new 14 year old model engine without going aftermarket.

[Rawze]

When a new complete engine is needed, I think hag typically buys a short-block and head.. tears it down and re-cuts counter-bores, etc... and then builds it up again.

[Nostalgic]

Of the 6 RX saw cut rods I received, 1 wrist pin bushing measured 2.5032", and another was right on the outside edge of 2.5030". Quickserve lists Min of 2.5020" and Max 2.5030" and my old cores all measured between 2.5025 and 2.5029"

Got 2 replacements, and they match the other new remans range of 2.5023"-2.5025"

If there's any takeaway that would apply to most people reading this, it's make sure to check your Covid-era produced parts, regardless of brand. From batteries to chips to hard parts, it's all pretty much looking like a disaster and crap shoot.

Rod weights varied 48.8 grams, and pistons by 49 grams. I picked up an extra inframe kit and the pistons actually had 2 date codes, one of which matched some of the pistons I already had, but none in the kit weighed the same. Go figure.

I wanted to know how the rods were balanced, and spent the better part of the weekend figuring out how to get consistent, repeatable results haha.



I watched a lot of videos and had to laugh at guys measuring to .05 grams. Some rods would have required me to remove 60 grams of weight if I wanted to make all 6 balanced and equal, and there just isn't that much material to work with. So, short of buying an extra dozen rods to sort through, I weight matched as close as I could get.



I got static weights within 6 grams, reciprocating within 59, and rotating within 40. Seems like a lot, but when grouped on the 3 crank throws, the groups are pretty tight in my opinion.

There's some variance of rotating and reciprocating that may cause some crank oscillation? but I tried to stagger them from hole to hole if it makes sense. Either way, it's a hell of a lot closer than it was. All wrist pins weighed pretty much exactly the same, and I can't see rings or snap rings varying enough to matter, so I left them out of my adventure.