FE Power Forums
FE Power Forums => FE Technical Forum => Topic started by: winr1 on August 05, 2019, 09:49:36 PM
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I see where folks say to shot peen rods on the side after grinding the ridge off
How much does it help, any wet mag or x ray before an after ??
Just curious....
A few Friends have done their beams on FE's an 385's with no shot peening
One 385 is a 521 with factory truck rods, big roller cam, aluminum CJ heads, dominator
Ricky.
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Ford's own now ancient O.H.O (Off Highway Operation, circa 1972) series of how-to build everything from Boss 302's-FE's-Boss 429's says that rods should be magnafluxed, beams polished and and shot-peened, in that order. Shot to be small enough to get into the fillet of .060R and must induce approximately 20,000 psi compressive surface stress.
That all said, in today's world, to do all that work plus new ARP bolts, would cost as much, if not more, than a good set of aftermarket rods.
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The shot peen is a stress reliever. Factory rods were done at Ford. The forging line can be a stress point. I have a set of C7AE-B's that are completely done. They were NOS rods still sealed in the Ford boxes. I put less than 400 miles on them after the two cylinders cracking so I went a different route with the new build.
I'll pass you the link via PM.
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Invest in new rods like a SCAT or better. Lighter and stronger!
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There is a difference in true shot peening versus "steel abrating" them. If the work is done incorrectly , it can actually INDUCE stress back into the rod. Companies that do shot peening use specific size media and pressure in their process to produce measurable results. As Keith mentioned , all Ford rods were shot peened , it was part of the manufacturing specifications on the blueprints used to make them. Polishing the beams is OK to do but rods rarely break there "on their own". Rod failures are "usually" caused by bearing failure ( welding the rod to the crank) or bolt failure. Breaking in the beam is most often a secondary effect of the initial problem.
Randy
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Per GT350hr - it has to be correctly done. Blasting with buckshot in a Harbor Freight blast cabinet won't do. There are only a couple of places left around here that have the equipment and know how to perform that operation.
>Invest in new rods like a SCAT or better. Lighter and stronger!
I just captured a 69 429 from a barn. The rods are the base engine broached unit. Re-size the rods runs about $250, plus bolts at $67. So we're at $317 plus some "disposal fee" that the shop has to charge to pay the city, no peening or grinding labor included. I can call RPM and have a set of H-beams sent over for $400. Scat are in the $500 range, so same. Not hardly worth spending time and $ on stock parts.
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Decades ago when I was finishing up my degree in Automotive Technology, part of my exams were to balance an engine rotating assembly, bore a block, hand hone final finish, and of course assembly blueprinting. I was taught that the beams on the rods were ground to remove any possible cracks from starting, and polishing the beams afterwards would be better than peening. The polishing removed any surface imperfections, and helped shed oil quicker. Removing the forging parting line did not weaken the rods if done properly. If the grinding was done without generating heat, and with a fine grit belt, the polishing was accomplished much easier, and less metal needed to be removed, making balancing easier. I polished the balance areas on the beams after balancing, and then rechecked balance. Nitpicking, but the Professor liked my thoroughness. Joe-JDC
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Chris is right about the cost of reworking original rods. As long as the aftermarket H beam rod doesn't need work ( some of the really cheap ones DO) it is very cost effective. The improvement in strength goes without question.
Randy
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Yep, and RPM is one of the brands that need work.
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I have only broken one fe rod about one inch below the pin in a 427 put a window in each side of the block i still have it.
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Wayne ,
It would be interesting to look at the broken end to see if there is an "early fracture mark" or "tear point". These would be important for determining crack origination and resulting failure. I realize it's water under the bridge but since only one failed out of eight something was odd there.
Randy
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I have a set of shot peened Lemans rods in my 428cj I run in my pickup. I have a small fortune tied up in them back when I did it(like 25 yrs ago). The motor had a full set of copper Fomoco "rejects" in it and I wanted to upgrade since I was "racing" it back then. The set I bought had a strange, non Lemans rod beam in it so I had to buy one more rod, shot peen it and then add it to the bunch. I had new bolts and bushings installed on all eight. Oh, the money I spent back then I could have bought two sets of good aftermarket rods today and be a TON lighter.
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FE rods will sometimes break about an inch or so below the pin from accumulated fatigue. Nothing will show up on a magnaflux or x-ray because the failure initiation is not from a crack or inclusion. Often on breaks like this you can still spin the big end freely on the crank and the bearings will look perfectly fine - as will the pin end.
The OEM shot peen process introduced surface compaction into the rod - a hardened non-directional "pebbled" exterior surface that prevented cracks from forming or traveling along any surface architecture. Polishing the beams removes the rough surface where cracks could conceivably begin, but also removes the hardened and textured layer that prevented them from expanding/growing. Shot peening a polished rod is too expensive these days in comparison to other options, but it does give you a superior product. It still does not address accumulated fatigue, nor the thin cross section of steel found at that "inch below the pin" area. If you ever take an OEM FE rod to a band saw at that spot you will be terrified to see just how thin they really are...
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I do not have the rod any more it was like Barry has seen free on the big end and the pin.
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Agreed . That 1" below area seems to be a focal point for rod flex under cylinder pressure. Rods don't stay perfectly straight under extreme combustion pressures and flex at the weakest point. The tapered design causes the 1" below to be the weak point. H beams are not immune to fatigue breaks , but they are usually "half way" down due to their lack of taper. Of note is "early" Carrillo rods had tapered beams and would eventually fail at ( guess what) 1" down from the pin. Their beams have been straight for well over 40 years.
Randy
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The rods that came out of my tunnel port were from the Mickey Thompson Bonneville car with the H/M engine. The beams were finished in a polished surface not shot peened.
They were heavy 956 grams and I eventually switch them out for aftermarket H beams.
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Two of the comments above speak of shot-peening as 'stress-relieving'. Actually the reverse is true. Proper shot peening, as Barry said, compacts the surface of the rod. Think of it as the equivalent of putting a sleeve of harder and stronger material over the surface of the rod. This process actually induces stress in the surface, but in a good way. Of the total of five years I spent at T&C Livonia, the two after I graduated were spent as a metallurgical process engineer in Quality Control.
The aftermarket rods available now are far superior to anything we could produce by re-working production pieces. And they're NEW, not something that's had many years to accumulate difficulties.
KS
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Re-working race/use rods, perhaps. I have less than 400 miles on a set of NOS rods that were given the treatment.
-Keith