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Re: Pile of junk connecting rods. [Re: John Healy] #666179 09/02/16 6:32 am
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Originally Posted by John Healy
Quote
I know Chevrolet found that the rods pinch in at
the parting line and wipe oil off the crank so they had more
clearance at the parting line either on rod or bearing


All rods are torqued and finished honed perfectly ROUND during production. Rod bearing shells are NOT manufactured perfectly round. They have more clearance designed in at the split.


Let me clarify my statement...Many years ago Smokey Yunick was digging into what was causing spun bearing failures in stock car engines. He discovered that when the rods and mains were stressed from HP and or detonation the big end "stretched" caused the parting line of the bearing bore and insert to be drawn in..The bearing insert split acted like a squeeze wiping oil from the crank surface... Yunick claimed he had TRW/Clevite 77 bearing company taper the bearing shell at the split to eliminate the problem...


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Re: Pile of junk connecting rods. [Re: Hillbilly bike] #666180 09/02/16 6:36 am
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All bearing shells have a relief area next to the parting line to offset the effect of the inbuilt crush to stop the bearing rotating in the housing. So maybe he asked this to be increased rather than added as it was already there.

Re: Pile of junk connecting rods. [Re: kommando] #666184 09/02/16 7:12 am
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Originally Posted by kommando
All bearing shells have a relief area next to the parting line to offset the effect of the inbuilt crush to stop the bearing rotating in the housing. So maybe he asked this to be increased rather than added as it was already there.


He asked the bearing manufacturer to decrease the insert thickness near the parting line which gave more leeway to prevent the squeeze effect. This was a problem on US production engines modified for racing in the mid 1950's.


79 T140D, 96 900M Ducati ....On a bike you can out run the demons..
Re: Pile of junk connecting rods. [Re: Hillbilly bike] #666192 09/02/16 9:04 am
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When I said increase I meant increase the depth of the relief, so same as decreasing the thickness.

Re: Pile of junk connecting rods. [Re: Hillbilly bike] #666193 09/02/16 9:06 am
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HB as Kommando said the thinned area of the shell insert, adjacent to the rod split, has always been there. As Kommando said, it is there to offset any distortion created by the inbuilt crush. With a replaceable rod shell the crush is necessary to keep it from spinning in the rod.

Those bent out tangs are not there to keep the shell from spinning, but to insure the shell is aligned with the center line of the rod. The amount the seated shell sticks up above the rod parting line is there by design. It is called the crush. The thinning of the shell, or as you said it the decrease of shell thickness, is there to compensate for the slight distortion caused by the crush.

It can, and should be checked, during any engine build. It should be checked especially if you suspect, or know the rod has been re-sized. IMHO it must be checked, or at least visually verified, if you plan to use the engine "in anger." It's presence can be checked with a feeler gauge.

Kommando is Glacier Scotland still sending rolls of shell stock to Atlantic?


Re: Pile of junk connecting rods. [Re: Hillbilly bike] #666194 09/02/16 9:18 am
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Kilmarnock is hanging on and still making Al/Sn strip and sintered Cu/Pb, Atlantic takes the Al/Sn, bearing production is close to ceasing but they currently have nowhere else to go for the Al/Sn strip until the Slovakian plant is upgraded so a few more years to go. The Cast Cu/Pb strip line factory closed some years ago, roof was taken off the building last week to stop the requirement to pay local rent tax.

Re: Pile of junk connecting rods. [Re: Hillbilly bike] #666197 09/02/16 9:44 am
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Originally Posted by Hillbilly bike
Originally Posted by kommando
All bearing shells have a relief area next to the parting line to offset the effect of the inbuilt crush to stop the bearing rotating in the housing. So maybe he asked this to be increased rather than added as it was already there.


He asked the bearing manufacturer to decrease the insert thickness near the parting line which gave more leeway to prevent the squeeze effect. This was a problem on US production engines modified for racing in the mid 1950's.

yeah i'm aware of Smokey Yunick and David Vizard research and
development for Chevrolet

Re: Pile of junk connecting rods. [Re: Hillbilly bike] #666209 09/02/16 12:41 pm
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Quote
when I've checked rods on engines i've built, verticle
measurement then 45 degrees each side of verticle to get
correct out of round


Inquisitive minds would like to know how you routinely machine a rod big end eye oval. That's a bit of clever engineering or you have access to a CNC machine.


Re: Pile of junk connecting rods. [Re: John Healy] #666219 09/02/16 1:36 pm
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Originally Posted by John Healy
HB as Kommando said the thinned area of the shell insert, adjacent to the rod split, has always been there. As Kommando said, it is there to offset any distortion created by the inbuilt crush. With a replaceable rod shell the crush is necessary to keep it from spinning in the rod.

Those bent out tangs are not there to keep the shell from spinning, but to insure the shell is aligned with the center line of the rod. The amount the seated shell sticks up above the rod parting line is there by design. It is called the crush. The thinning of the shell, or as you said it the decrease of shell thickness, is there to compensate for the slight distortion caused by the crush.


The story is in Yunick's book Power Secrets. He presents the story as if he was instrumental in having the bearing thinned more than it had been...Yunick is gone and the story was from about 1955 so ......


79 T140D, 96 900M Ducati ....On a bike you can out run the demons..
Re: Pile of junk connecting rods. [Re: Hillbilly bike] #666223 09/02/16 1:58 pm
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In my day the reduction in thickness of the shell to give the relief area was derived from the amount of crush which was itself derived from the diameter of the bearing and the thickness of the steel, all set down in formula. If an application needed more relief clearance then that could have been accommodated on the drawing and the angle of the taper modified so the bearing was thinner near the joint with the metal machined from the bearing material side. What would not have been allowed would be the extension of the relief area to cover more of the diameter, this would reduce the bearing surface area and cause premature bearing failure.

So the story is perfectly possible, the std relief that was fine in a production engine, in competition it was a problem and all production changed to increase the amount of relief at the joint with no effect on production engines.

Re: Pile of junk connecting rods. [Re: kommando] #666241 09/02/16 5:04 pm
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HB
Enough technology and physics, I'll take 5 of them to make a coat rack.


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Re: Pile of junk connecting rods. [Re: desco] #666252 09/02/16 8:29 pm
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Originally Posted by desco
HB
Enough technology and physics, I'll take 5 of them to make a coat rack.


Oh, the junk rods? They have left the building

Kommando, Yunick was arguably the most innovative American race engine and car builder. He was also a great story teller and perhaps he may have seen only his version of the facts...


79 T140D, 96 900M Ducati ....On a bike you can out run the demons..
Re: Pile of junk connecting rods. [Re: Hillbilly bike] #666253 09/02/16 9:48 pm
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My favourite Smokey Yunick story is the one where ( one of his Chevelles, I think ) completed a long race without a fueling stop. This being impossible if the fuel tank capacity was within the rules.
Anyway,Smokey's car won and the first thing the officials did was to check ( then, of course, bone dry!) the fuel tank capacity.This was legal !
Then Smokey got into the car, started it up and drove off.
Yes, the fuel tank was legal.......... I think the miles of large diameter fuel line coiled out of sight around the car may have been a bit borderline, though !!

Re: Pile of junk connecting rods. [Re: Triless] #666386 09/03/16 9:24 pm
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And, Smokey's reply to the judges was "If the rules don't specify it's 'illegal' to do it, I must assume IT'S LEGAL!"

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