Resizing big end??

[novafornow]

Thank you Modoc. That is what my gut was saying but I don’t machine engines every day so had no baseline to go by. These are quality rods and have been used a long time. I just put new bolts in when I freshen.

[Metrobilly]

Doesn't changing the rod bolts distort the big end enough that resizing often becomes necessary?

[Dan Timberlake]

It's been decades since I resized con rod big ends (All Sunnen and tobin-Arp equipment, and a skilled and experienced mentor).
Thus my remembered examples are out of date, but I still find the principles useful.

The knurled body bolt and nut design typical of Gen 1 SBC and many others could be counted on to cause a certain amount of cap shift . Page 11 here -
https://www.mahle-aftermarket.com/media ... ochure.pdf

Rods with locating dowels of various types were better, but generally used cap screws and threaded holes in the con rod body, so the bolts had no centering/alignment responsibilities anyhow.

Porsche 911 rods and some others used real fancy bolts with an enlarged ground body diameter at the parting line to serve as "dowels" shared by the cap and rod).
https://www.partsklassik.com/images/Pro ... e/3311.jpg

British iron seemed fond of such bolts from very early on.
https://cdn.shopify.com/s/files/1/0717/ ... 1506619570

Or, When there was not enough beef on the (angled, to fit down the smallish cylinder bore) big end to include a stepped locating register at the parting line.
https://mossmotors.com/media/catalog/pr ... -300_1.jpg

[NXBOY]

Well these are Brand new rods. All the big ends are out of tolerance on the big side. One is .0005 measuring above or below the parting line. I ordered Hbeams with 2000 ARP bolts but got regular rods with a 2000 bolt upgrade and a rehone. NEW bolts distort the big end of the rod making it bigger at the parting line. I might HAVE to buy just one rod to sleep at night since my BEARING manufacturers TECH Manager said not to run them Big do to little crush. HE said no accurate way to measure crush do to the way it distorts to rod? Unless I bend the big end in press there no way to make round when resizing the New rods im told.I suppose if i'm lucky the 7 rods out of spec only .0002 will be fine but at 800 HP plus , I WANTED to atleast be in the middle of spec. IS bending .0005 and reworking to outer tolerance of big end ok in performance? Or should I JUST buy one rod thats worse and pray the KINGS HP have plenty of crush? never had a very high compression big motor and the cranking before oil pressure thing bugs me if it like kicks back once:( Just hate not doing my best on this build. If you guys have ran looser with this power with good luck would love to know.

[jed]

This might help with parting line dimensions http://www.wallaceracing.com/line-hone-calc.php

[lance flake]

Well these are Brand new rods. All the big ends are out of tolerance on the big side. One is .0005 measuring above or below the parting line. I ordered Hbeams with 2000 ARP bolts but got regular rods with a 2000 bolt upgrade and a rehone. NEW bolts distort the big end of the rod making it bigger at the parting line. I might HAVE to buy just one rod to sleep at night since my BEARING manufacturers TECH Manager said not to run them Big do to little crush. HE said no accurate way to measure crush do to the way it distorts to rod? Unless I bend the big end in press there no way to make round when resizing the New rods im told.I suppose if i'm lucky the 7 rods out of spec only .0002 will be fine but at 800 HP plus , I WANTED to atleast be in the middle of spec. IS bending .0005 and reworking to outer tolerance of big end ok in performance? Or should I JUST buy one rod thats worse and pray the KINGS HP have plenty of crush? never had a very high compression big motor and the cranking before oil pressure thing bugs me if it like kicks back once:( Just hate not doing my best on this build. If you guys have ran looser with this power with good luck would love to know.

If your vertical measurement is in spec and the horizontal (parting line) is a half thou big (.0005) you are good. Now if you are worried about that heat a rod up to about 150-175 degrees and remeasure it.

[modok]

The bearing crush relates to the average diameter of the big end.
It is not possible IMO that the new bolts made the average size of the big end larger, unless you have gone to a lower torque.
So, the rod must have been oversize before, or something is OFF.

If the rod is .00025 oversize, I think it can be resized no problem.
Although there are limits to what can be done, this should be easy.

[NXBOY]

No, none are in the tolerance aloud, one around .0005 both measurements. I researched tell im blue in the face. Pinning bearings might be a possibility since vendor not offering much.

[modok]

pinning the bearings.... Is it an aluminum rod?
can be Re-sized NO problem I think
I'm in colorado springs, colorado. maybe 20$ a rod, roughly. I make the holes not the prices.

[lance flake]

Are you measuring the rods right out of the box or have you taken them apart cleaned reassembled with fresh lube?

[NXBOY]

I measured them before took apart or loosened fasteners, had a machine shop measure them because its been a while since i used a dial bore gauge and mt dial didn't have a plus or minus and one was off more then others. He said not to get them honed because 7 was already big and one was .0005 too big. That relates too the difference I measured on that one out of box. Took to my buddy with a partial private shop and he measured and got the same as I remeasured. All 7 are perfect round at .0002 out of the reconmended tolerance for a BBC 2.20 big end. I can remeasure one if ya need the measurement. My buddy agreed to with my math also. Yes been apart and ends cleaned always got the same. I SHould of bought directly from manufacturer I Think.

[NXBOY]

I'm going to go to buddy shops and get the sheet where their all wrote down on. My memory not that great anymore, been a couple months since been there, he's in busy season at his main job. I just measured two in my house and now i KNOW THE BIG DEAL. There .002 over 2.3252 (HIGH side) at the parting line. Thats 2.3272 I Remember one builder saying thats how they used to do rods and its already done. ALeast now I realized my crush isnt acceptable if it the average of clearances. THe straight up side is .0002 or 2.3254 on the two I just measured. i WAS TOLD NOT TO MEASURE OR WORRY ABOUT PARTING LINE MEASUREMENT at FIRST. One rod was.0005 over or 2.3257. IF I could find a race bearing with less eccentric built in then I would be better off. .002 oval with the already .003 oval or so built in the bearings oil film strength won't be very good says KINGS Bearings. I understand the pumping action the eccentric has and Kings did test and too much hurts.. Sound like I'm getting new RODS.

[lance flake]

I would say if you have a reputable shop near by take them in for resizing. I like the vertical measurement to be at the top side of spec. If the parting line is a little big no worries.