Need some advice on S52 rod clearances

[jph]

Ok, so the new .001" oversize bearings showed up Friday evening and I got around to getting them in the rods and all torquing the caps down tonight. And wouldn't you know it all six checked out GREAT! I'm at .0020" on four rods and .0019" on two rods. This is perfect and right where I wanted to be. I didn't even bother trying to mix shells before measuring. I just popped out all the STD bearings and used all 12 of the oversized shells on a hunch and bingo. Thanks to all who contributed to this thread.

Lesson learned here for me (and hopefully others reading this in the future) is that if you're on the low side of standard spec on the crank journals just start with the .001" oversize bearings and go from there. I could have saved myself about a month of downtime and around $300 doing it this way. Live and learn I guess.

[jeffnhiscars]

Didn't help with the bearings or your sanity :)

[jph]

Oh, right, then- if you're measuring a clamped rod with shell IN it, that's about
it. I thought you were going by the rod ID without shell, then adding the shell mathematically.


You can have the rods resized- the M10 rods seldom need it, but it's standard practice
for most 'real' builds.


And the 'mix and match' trick is an old one...

t

I did use the method of simple addition to see if the advertised shell thickness would bring me to the correct oil clearance, but would never use this method to determine the final clearance. It was just a sanity check to TRY to help me avoid wasting money on the wrong bearings but in this instance it didn't help me much!

[TobyB]

Oh, right, then- if you're measuring a clamped rod with shell IN it, that's about
it. I thought you were going by the rod ID without shell, then adding the shell mathematically.

You can have the rods resized- the M10 rods seldom need it, but it's standard practice
for most 'real' builds.

And the 'mix and match' trick is an old one...

t

[jph]

Yeah, something's not adding up.

seems to cover it all, though, unless something really really weird is going on with your tools.

I too would plastigauge, then try the larger shells. Have you tried measuring a shell
clamped inside a rod? It's hard to do without damaging the shell, but it might tell you something...

Keep us updated.

t

Not sure what you mean by a shell clamped inside a rod? If you mean installed in the rods and the caps torqued to spec and then the inner bore with bearings installed measured then that's what I have been doing all along.

I ordered a set of King .001" oversize rod bearings to match the set I have here that are standard size. I am going to mix and match the STD and .001" bearings to get to the exact clearance I want. Each bearing shell is .0005" thicker so I should be able to get right down to where I want +/- .0002". My goal is to be at .0018-.0020".

EDIT: I have to assume I am getting loose clearances because the crank journals have been polished down to the extreme low end of the STD spectrum. My smallest rod journal is 1.7707" and low side of spec is 1.7707". Largest journal on my crank is 1.7708".

[TobyB]

Yeah, something's not adding up.

Set the micrometer to the journal measurement and zeroed the gauge to the micrometer

seems to cover it all, though, unless something really really weird is going on with your tools.

I too would plastigauge, then try the larger shells. Have you tried measuring a shell
clamped inside a rod? It's hard to do without damaging the shell, but it might tell you something...

Keep us updated.

t

[AndrewBird]

I would plastiguage them and see with you come up with. I having a feeling something is wrong with your measurements, either with your method or the gauges themselves.

[jph]

You would think with the hard parts bang on spec that the clearances would fall in line and if you are using tty's I would think all that torquing wI'll one a problem no ?

The bolts were supplied with the rods and they are manufactured by ARP. They are not TTY like the factory rod bolts. I actually contacted Tom Molnar the rod manufacturer to buy a complete new set and he talked me out of it saying the bolts would be fine for many torque cycles as long as they were torqued using the specified lubricant and 25 ft/lbs and then 55 degrees. A bolt stretch gauge is relatively inexpensive and truly is the right way to ensure proper bolt loading and in this case I get the benefit of monitoring bolt health as I see this process leading me to go through X number of torque cycles to find a bearing that provides the oil clearance I need.

EDIT: Looks like the ARP stretch gauge will set me back another $175 or so. Might have to put this on hold for now. The cheaper brands will less resolution are about $60.

[jeffnhiscars]

You would think with the hard parts bang on spec that the clearances would fall in line and if you are using tty's I would think all that torquing will cause a problem no ?

[jph]

Since VAC did all your machine work and sold you at least one set of bearings, what do they have to say about this ?

Hi Jeff! Since VAC didn't check oil clearances as this was not part of my work request I cannot rightfully ask them to remedy the issue. I asked them to measure the parts I supplied (rods and crank) for sizing and i ordered bearings accordingly. The crank specs out to the lower end of STD and the rod big ends measure out to dead in the middle of spec. So when VAC tells me everything is STD that is in fact correct based on my findings. I'm at the point now where I'm leaning more toward ordering the .001" oversize ACL bearings and giving it another go. I have torqued and removed the rod bolts now a total of three times plus what I am assuming was one time when VAC measured. I'm looking into now adding a bolt stretch gauge to my growing collection of engine assembly tools. I don't know whether that's a good thing or not

[jeffnhiscars]

Since VAC did all your machine work and sold you at least one set of bearings, what do they have to say about this ?

[jph]

i get a stock bearing from KS or whoever and measure it

I have been tossing that idea around too. I can get a complete set of KS rod bearings for about $55 shipped from ECS tuning. I also found that ACL makes a .025mm (.001") oversized bearing which would bring my clearances from where they are now to pretty much right where I want them to be (~.0018"). The ACL's are about $100 for the set.

At this point I'm already $300+ into rod bearings that are out of spec for me and obviously non-returnable. If my crank was on the higher side of "standard" these sets would likely be fine.

[digger]

i get a stock bearing from KS or whoever and measure it, double check with plasti gauge?

[jph]

Do you have a calibration ring for your bore mic? Usually they come with a precision ground ring to set your zero with. Setting it off a micrometer might work, but you could get some variation.

Also, what type of bore gauge? I've found that this style of gauge is a lot more accurate to use than a dial gauge that is a little more subjective in how it sits in the bore.

Thanks for the feedback. The dial bore gauge didn't come with a zeroing ring. Don't think it would be much help in this situation since I'm basically measuring the difference from one value (crank's rod journal) to another (rod's big end with bearings installed and caps torqued to spec). That difference is my oil clearance. I zero the dial bore gauge to the micrometer set up to the exact measurement of the crank's rod journal. I then transfer the "zero'd" gauge to the rod and measure the difference.

As far as the alternate tool you mentioned I'm not sure it would be right for this application since the bearings are manufactured with a small amount of eccentricity making them their tightest at the 12 and 6 positions and opening up a very small amount as you get closer to the parting line where the cap meets the rod.

EDIT: This is the exact bore gauge I'm using: http://images.nationaltoolwarehouse....72-646-400.jpg

[AndrewBird]

Do you have a calibration ring for your bore mic? Usually they come with a precision ground ring to set your zero with. Setting it off a micrometer might work, but you could get some variation.

Also, what type of bore gauge? I've found that this style of gauge is a lot more accurate to use than a dial gauge that is a little more subjective in how it sits in the bore.