Polishing side beams
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Re: Polishing side beams
Only if you can’t buy an aftermarket rod. I you an any work an OE rod is just maximum work near zero gain.
Re: Polishing side beams
Yes, but it can get a bit messyrocketracer380 wrote: ....... and do they need to be shit peened afterwards
'Shot' works much better .........
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Re: Polishing side beams
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
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.
Re: Polishing side beams
Speaking just to the processes: polish first then peen; the latter produces a compressed surface that resists fatigue cracks.
Felix, qui potuit rerum cognscere causas.
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Happy is he who can discover the cause of things.
Re: Polishing side beams
All joking aside ……
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
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
Re: Polishing side beams
^^^^ This^^^^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.
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.
Re: Polishing side beams
Agree.
Disagree. Eyeballs will often lead you wrong. Always weigh first and write it down.
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.
Agree, grinding one back heavier is really time consuming.
Of course, you meant to say, "Check for straightness, correct center-to-center length, peen, fit good bolts, resize.
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
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.rocketracer380 wrote: ↑Sat Nov 27, 2021 2:54 am Is it worthwhile and do they need to be shit peened afterwards
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
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?
Cheers
Steve
Cheers
Steve
Re: Polishing side beams
the engine will be able to accelerate faster.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?
Cheers
Steve
Re: Polishing side beams
BCjohnny wrote:Obviously looking at the balancing pads will show you where to start ….
The assumption being you'd weigh them first and then visually assess where to remove the material subsequentlyDisagree. Eyeballs will often lead you wrong. Always weigh first and write it down.
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.
I think you're missing the specific process I'm referring to ..... not achievable with a 'belt grinder'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.
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.
BCjohnny wrote:Peen, resize, fit good bolts, check for straightness and final balance.
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 wiseOf course, you meant to say, "Check for straightness, correct center-to-center length, peen, fit good bolts, resize.
BCjohnny wrote:All the above is why it’s mostly uneconomic to do it properly, and you still might have a marginal piece.
The example given now makes over 100 bhp per litre NA, and can live, at least race distance, with properly prepared factory rodsAgree 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.
BCjohhny wrote:So concisely
Maybe should have put this in ...... BIG LETTERS ...... lolThere’s more but that’s the bones of it ……
Re: Polishing side beams
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
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.
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.