Polishing side beams

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rocketracer380
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Polishing side beams

Post by rocketracer380 »

Is it worthwhile and do they need to be shit peened afterwards
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Re: Polishing side beams

Post by ClassAct »

Only if you can’t buy an aftermarket rod. I you an any work an OE rod is just maximum work near zero gain.
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Re: Polishing side beams

Post by BCjohnny »

rocketracer380 wrote: ....... and do they need to be shit peened afterwards
Yes, but it can get a bit messy

'Shot' works much better .........
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Re: Polishing side beams

Post by Alaskaracer »

With the availability of aftermarket rods, no reason to use stock rods unless it's a stock build....Even then it's questionable because some aftermarket rods are less expensive than a reconditioned stock rod, yet stronger.......
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Re: Polishing side beams

Post by Ks Fats »

I spent a great deal of my time reworking stock components due to restrictive rule requirements that did nothing to reduce the cost of racing. If you are not required to do it, go aftermarket. Time saved,better Q.c.,stronger components = less cost in the long run.
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Re: Polishing side beams

Post by MadBill »

Speaking just to the processes: polish first then peen; the latter produces a compressed surface that resists fatigue cracks.
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Re: Polishing side beams

Post by BCjohnny »

All joking aside ……
Is it worthwhile and do they need to be sh(o)t peened afterwards

As with most things it depends what you start out with, and whether you’ve the ability yourself to competently complete the work ….. most pros won’t touch such labour intensive tasks

So concisely :

Modern PM ‘net forged’ rods are mostly best left as is

Older SBC & SBF type rods can benefit slightly, but your time would be best spent on disassembly, re-shot peen the halves in pairs, resize with upgraded bolts etc …. or if possible buy an off the shelf upgraded rod

Now with lots of older stuff, especially where there is no readily available upgrade, there’s more wriggle room

Take, say, an ‘A’ Series 1275 rod …… if you’ve the inclination it would go something like this :


Separate the rods into halves, find the lightest of each and work down to that

Obviously looking at the balancing pads will show you where to start …. in the above example the first task would be to set up the caps in the Bridgeport and mill out the centre of the solid balancing pad, but don’t go mad

Resist the temptation to remove anything other than the extraneous from the parting line

You can reduce the balancing pad on the little end also, but don’t make the lightest too light otherwise you’ll might be running out of final balance stock

Linish the forging line mostly out of the beams but don’t go mad and ‘thin’ them

No need to be anal about it but keep an eye on the ballpark balance as you go along

If you know the material, though not critical, and have the equipment, stress relieve ….. depending on what you’ve already taken off they’ll have likely moved slightly anyway

Peen, resize, fit good bolts, check for straightness and final balance


All the above is why it’s mostly uneconomic to do it properly, and you still might have a marginal piece

Polishing is not needed, or wanted …...on a few occasions I’ve seen rods, even new aftermarket ones ….. where the peening hasn’t obliterated the machining / reworking

This isn’t what’s required, a reasonably homogenous surface is

At the end of the day you’re not usually going to make massive improvements, it sometimes falls into the ‘if it makes you feel better’ category, and there’s always the chance an idiot could make it worse

There’s more but that’s the bones of it …… feel free to disagree
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Re: Polishing side beams

Post by dannobee »

Ks Fats wrote: Sat Nov 27, 2021 12:38 pm I spent a great deal of my time reworking stock components due to restrictive rule requirements that did nothing to reduce the cost of racing. If you are not required to do it, go aftermarket. Time saved,better Q.c.,stronger components = less cost in the long run.
^^^^ This^^^^

I've been in the same boat with some circle track classes and even with NHRA Super Stockers. By the time you factor in the labor to clean up the parting line, send out for shop peening, install new bolts and bushings, then resize, you're into them more than a brand new set of aftermarket I-beam rods.
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Re: Polishing side beams

Post by PackardV8 »

BCjohnny wrote: Sun Nov 28, 2021 4:08 amSeparate the rods into halves, find the lightest of each and work down to that.
Agree.
BCjohnny wrote: Sun Nov 28, 2021 4:08 amObviously looking at the balancing pads will show you where to start ….
Disagree. Eyeballs will often lead you wrong. Always weigh first and write it down.
BCjohnny wrote: Sun Nov 28, 2021 4:08 am in the above example the first task would be to set up the caps in the Bridgeport and mill out the centre of the solid balancing pad, but don’t go mad.
With a good belt grinder, I can do a set of rods before I can make up the jig to clamp them in a mill.
BCjohnny wrote: Sun Nov 28, 2021 4:08 amNo need to be anal about it but keep an eye on the ballpark balance as you go along.
Agree, grinding one back heavier is really time consuming.
BCjohnny wrote: Sun Nov 28, 2021 4:08 amPeen, resize, fit good bolts, check for straightness and final balance.
Of course, you meant to say, "Check for straightness, correct center-to-center length, peen, fit good bolts, resize.
BCjohnny wrote: Sun Nov 28, 2021 4:08 amAll the above is why it’s mostly uneconomic to do it properly, and you still might have a marginal piece.
Agree with uneconomical, but having custom rods made up for an obsolete engine is even more uneconomical. That most of this old shite won't make enough horsepower to hurt a precision resized rod is the saving grace.
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Re: Polishing side beams

Post by Walter R. Malik »

rocketracer380 wrote: Sat Nov 27, 2021 2:54 am Is it worthwhile and do they need to be shit peened afterwards
If you are using production type rods, you merely are removing any surface imperfections which would become a stress riser which could cause a crack or breakage. It doesn't make that rod any stronger.
Shot-peening ... compacts the surface and does make it a little stronger. It was common before better rods became available.

When RULES require stock production rods it can cdertainly be a benefit.
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Re: Polishing side beams

Post by chimpvalet »

Pardon this slight hijack but, since we're in the thick of discussing optimal approach on rods: If aftermarket rods are found with ample strength but significantly less weight than heavy OEM, ( eg: 250 grams off a stock 900 or so, inline 4 banger ) what benefits are confidently expected?

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Re: Polishing side beams

Post by lefty o »

chimpvalet wrote: Sun Nov 28, 2021 1:50 pm Pardon this slight hijack but, since we're in the thick of discussing optimal approach on rods: If aftermarket rods are found with ample strength but significantly less weight than heavy OEM, ( eg: 250 grams off a stock 900 or so, inline 4 banger ) what benefits are confidently expected?

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Re: Polishing side beams

Post by BCjohnny »

PackardV8 wrote:
BCjohnny wrote: Sun Nov 28, 2021 4:08 amSeparate the rods into halves, find the lightest of each and work down to that.
Agree.
:wink:
BCjohnny wrote:Obviously looking at the balancing pads will show you where to start ….
Disagree. Eyeballs will often lead you wrong. Always weigh first and write it down.
The assumption being you'd weigh them first and then visually assess where to remove the material subsequently
BCjohnny wrote: in the above example the first task would be to set up the caps in the Bridgeport and mill out the centre of the solid balancing pad, but don’t go mad.
With a good belt grinder, I can do a set of rods before I can make up the jig to clamp them in a mill.
I think you're missing the specific process I'm referring to ..... not achievable with a 'belt grinder'

Regardless no 'jig' is needed
BCjohnny wrote:No need to be anal about it but keep an eye on the ballpark balance as you go along.
Agree, grinding one back heavier is really time consuming.
:roll:
BCjohnny wrote:Peen, resize, fit good bolts, check for straightness and final balance.
Of course, you meant to say, "Check for straightness, correct center-to-center length, peen, fit good bolts, resize.
Slight correction if needed could be attempted when shaving the rods, another assumption, other than that you're stuck with what you've got core wise
BCjohnny wrote:All the above is why it’s mostly uneconomic to do it properly, and you still might have a marginal piece.
Agree with uneconomical, but having custom rods made up for an obsolete engine is even more uneconomical. That most of this old shite won't make enough horsepower to hurt a precision resized rod is the saving grace.
The example given now makes over 100 bhp per litre NA, and can live, at least race distance, with properly prepared factory rods


BCjohhny wrote:So concisely
There’s more but that’s the bones of it ……
Maybe should have put this in ...... BIG LETTERS ...... lol
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Re: Polishing side beams

Post by amc fan »

I would consider how many miles/cycles are on the rods also. I would feel a lot more confident polishing and doing the rod recon from rods out of a lower mile mom and pop type car then rods out of a car that was beat the snot out of. Mild steel bending /deflecting then straightening again for 100,000 miles or more is a time bomb ticking.
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Re: Polishing side beams

Post by Dan Timberlake »

Stock Gen 1 SBC rods have a gruesome notch broached straight across the rod for the bolt heads.
The geometry makes that a pretty high stress location.
The terrible broach finish on some years jaxxks the stress concentration factors up even higher (= bad).
I bet way over 50% of those rods I wet mag particle inspected had "indications" in the bolt notch. Some were small and easily ground out. Some had grown until they extended around the corner and even across the side clearance face.

Leaving the rod bolts in hid that vulnerable area from view, and good quality surface and geometry improvement and proper shot-peening too.

Grinding I-beams does not improve that trouble spot.

Rods wit fancier shapes and thru bolts instead of nuts-n-bolts likely are way less vulnerable to fatigue and cracking.
Easier to grind the i-beams nicely too.
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