Narrowing rods

[ProPower engines]

What is the best method to narrow the big end of rods.
I want to adapt for longer rods to a different engine and they need to be narrowed.

[PackardV8]

What is the best method to narrow the big end of rods.
I want to adapt for longer rods to a different engine and they need to be narrowed.

How long is longer? If you have a lathe which will swing them, that's how we narrow them.

If they are too long to swing in the lathe, then use the Tobin-Arp rod boring machine.

jack vines

[modok]

Lathe would be my first choice, but I could do it with pretty much any machine that cuts metal. Grinders, millingmachine, even the brake lathe

[frnkeore]

How much has to be removed and how much has to be removed from the tang notch side? Remember that if you remove any from the chamfer side, it will have to have the chamfer re-cut, to match the crank radius.

If you have more than .020 to remove, a lathe is the fastest way. I re-cut SBC 400 rods, to fit SBF and use a spud, in the lathe, that is .0005 - .001, larger than the big end, then torque the rod and cap on it. I have it setup in one of my lathes, right now. I started to do a set a few months ago and got involved in other things and haven't got back to it. I'll take a picture of it tomorrow.

[ProPower engines]

As it turns out there is no off the shelf rods for the build and the rods that were shipped are not correct for the crank.
This is a mopar stroker and I want to use a better rod length to stroke ratio then the current 1.464 in a small block mopar that is being used with the big stroke cranks available.
Custom rods are just too far out there in cost and wait time but there is a few options for a std. sm. blk GM rod in both I and H beam configurations.

I want to use a 6.250 long for use with a 1.889 rod pin. The bearing is a narrowed Quad 4 bearing in an H series like what the cup guys were using which is still available readily.
That will still keep the compression height reasonable and not end up with no skirt support and a decent ring pak.

I really only need about .015" narrower on the big end but I have to wait till the bearings get here to confirm tang location before I can machine anyway

[benno318]

im lucky, at my shop i have a surface grinder with magnetic chuck - line them all up on the bed, grind all 8 at once, demagnetise and done.
maybe there is a shop near you that has such a machine, it is such a quick process its not worth much $$.

[jed]

If it's only .015 I would and have used a mill vise and some kind of flat surface plate to set the side of the rod on and clamp the rod in the vice. Take .007/.008 at a time and be done in 10 minutes.

[MotionMachine]

I do it in the lathe, then finish on the mag base surface grinder for a nicer finish. Not everyone is aware that on many lathes the first section of ways are bolted in. You can gain another couple of inches of swing by removing them.

[PackardV8]

I really only need about .015" narrower on the big end but I have to wait till the bearings get here to confirm tang location before I can machine anyway

Don't sweat the tang location. Many years ago, I was at a seminar with a Clevite engineer. He said tangs are only so blind guys can assemble engines. Their recent OEM bearings don't have tangs at all. If the tangs aren't where they need to be on modified rods, just grind them off. I've done several builds like that with no issues.

[BlitzA64]

Mine were done with a lathe

[frnkeore]

This is the simple setup, I use to narrow rods as I described above.

Note the square tool, it both faces and chamfers. This lathe swings 18 1/2 inches and the rod is 5.565 CC. It will take at least a 12" lathe, with a gap that will swing 15" to safely do a 6"/6 1/4" rod.

[modok]

Yes, nice setup it's very foolproof way to go. If you had many to do, soft jaws trimmed to the right size would save SO much time.

I'm thinking a lathe chuck with soft jaws is the best way to hold the rod, no matter if you use a lathe, milling machine, surface grinder or flywheel grinder.

[ProPower engines]

I really only need about .015" narrower on the big end but I have to wait till the bearings get here to confirm tang location before I can machine anyway

Don't sweat the tang location. Many years ago, I was at a seminar with a Clevite engineer. He said tangs are only so blind guys can assemble engines. Their recent OEM bearings don't have tangs at all. If the tangs aren't where they need to be on modified rods, just grind them off. I've done several builds like that with no issues.

I realize that is a non issue. Most all newer engines like Ford and Chrysler do not use tangs on the bearings.
My concern was the bearings where the tangs are get real thin there from what I see here now so reducing the steel
back any more may be an issue. I have several jigs to modify the bearing shells but the need to remove the tang has me concerned since there will be a few freshen ups in the next few race seasons depending on how the bearing coating goes and how long it will last on the half's of the bearings.

[mt-engines]

I really only need about .015" narrower on the big end but I have to wait till the bearings get here to confirm tang location before I can machine anyway

Don't sweat the tang location. Many years ago, I was at a seminar with a Clevite engineer. He said tangs are only so blind guys can assemble engines. Their recent OEM bearings don't have tangs at all. If the tangs aren't where they need to be on modified rods, just grind them off. I've done several builds like that with no issues.

I realize that is a non issue. Most all newer engines like Ford and Chrysler do not use tangs on the bearings.
My concern was the bearings where the tangs are get real thin there from what I see here now so reducing the steel
back any more may be an issue. I have several jigs to modify the bearing shells but the need to remove the tang has me concerned since there will be a few freshen ups in the next few race seasons depending on how the bearing coating goes and how long it will last on the half's of the bearings.

A piece of Delrin round stock cut to just larger than the journal size and a hose clamp does the trick for milling or even just hand grinding off those pesky tangs. I have had to narrow bearings into the tang before. Some sizes you can get with or without tang depending on application. Unfortunately calling manufacturers gets you nowhere now days, you are sometimes lucky to get an email weeks later.

If you anticipate the freshen ups you may as well see if you can order a tray, or just cut a few sets at the same time. No sense in charging twice for the setup if you can get the owner to oblige.