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Rod Bushing service for 390...asap

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Traveller View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Traveller Quote  Post ReplyReply Direct Link To This Post Posted: Feb/05/2013 at 9:36pm
Originally posted by 69 ambassador 390 69 ambassador 390 wrote:

 
 
I was only stating that Factory Fords ran unbushed rods on the FE motors and they are always full floating with factory lock rings.  ALL full floating pistons MUST run lock rings whether factory or aftermarket.  A factory rod would rquire material to be removed for the bushing installation unless the custom piston was ordered with a smaller pin size.  That is not the case here.  The OPs' pin size seems to be undersize for a correct 2000lbd press fit and the correct option here for expedience is to hone the rods for a good full float and install as is with clips.  A better option would be to drill a small hole at the top of the rod also and chamfer for oil supply also.  No need to bush these rods at all, just hone.  What is the resistance to running full float on just the rod casting itself?  does everyone think the aluminum at the other end of the pin is harder and more wear resistant????  If you have an aversion to running stock style circle clips then you could use teflon buttons as well.  My Ford 390s and 428s all were happy with this non-bushed as factory supplied setup on cast rods.  Proven system and as Tony stated, works on our AMCs also.  Bush only as a last resort or for a race engine that will see multiple taredowns.  After bushing once, they are easily replaced and honed to size in the race trailer with hand tools and a press.  Heck, it used to be standard practice to purchas pistons and pins as seperate items and the hand fit the pins  individually.  Every mechanic had a piston pin hone set and it was a part of every rebuild or piston service.  In the early 1960s "PIN FITTED PISTON SETS" became the rage as manufacterers heaped out to press fit assemblies that eliminated a manufactering step.  They are cheaper to make but not better.   
 
All the factory FE rods I've seen in the shop have bushed small ends.  We've done a couple 352's, 390's and a 428 this last couple years, and they all came apart with bushed rods that I've changed the bushings out on during the rebuilding process.   They simply get cut out and a new set gets pressed in and sized.  The co-owner of the shop has a 406, we have a couple 428's and some 427 stuff in the shop.   Even the rebuilding books on Ford FE's say that since the FE uses full floating rods, that all the rods were bushed from the factory.  All the FE's I've taken apart had bushed rods, and at least 3 of them were first runs (and TIRED).   The bushings are thin wall, but they are bushings.   The stock spec for the small end is 1.028-1.038 without the bushing, .9752-.9755 with the bushing installed.
 
The pictures I've seen of Ford FE rods all show a bushed rod and the rebuilding books all show a bushed rod, and replacing the bushing during rebuild.  So where does the info come from that FE Fords use steel on steel?  That's a recipe for disaster.
 


Edited by Traveller - Feb/05/2013 at 9:39pm
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69 ambassador 390 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 69 ambassador 390 Quote  Post ReplyReply Direct Link To This Post Posted: Feb/05/2013 at 10:28pm
I guess I stand corrected.  It's been 25 years since I worked with the FE's.  But why would steel on steel be a recipe for disaster when steel on aluminum is not.  Tony ran steel on steel for many many thousands of miles and many drag passes.  If clearances are correct and there is ample oiling.  Why a problem.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote SKeown Quote  Post ReplyReply Direct Link To This Post Posted: Feb/05/2013 at 10:58pm
 
 Steel on steel is not good, no matter if some have gotten away with it. NASCAR runs rods with no bushings, but the wristpins are casidiam coated and EDM pressure fed oiling. Even with those precautions the rod's small ends are turned blue from the heat.
 
 SKeown 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 69 ambassador 390 Quote  Post ReplyReply Direct Link To This Post Posted: Feb/05/2013 at 11:42pm
And up to 9000+ RPM.  Mant stock rods are not accurate enough in the small end to accept a bushing.  Off center holes are very common. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Traveller Quote  Post ReplyReply Direct Link To This Post Posted: Feb/06/2013 at 12:22am
Originally posted by 69 ambassador 390 69 ambassador 390 wrote:

I guess I stand corrected.  It's been 25 years since I worked with the FE's.  But why would steel on steel be a recipe for disaster when steel on aluminum is not.  Tony ran steel on steel for many many thousands of miles and many drag passes.  If clearances are correct and there is ample oiling.  Why a problem.
 
The reason is dissimilar metals.  You can run steel against bronze, steel against aluminum, etc.   You can't run some metals that are similar metallurgically against each other, because they tend to gall themselves together.  If the metals in sliding contact have a similar surface hardness, then high spots (all surfaces have high and low spots) can rub against each other, create heat and then microweld.   With steel against steel this happens to the point that the surfaces gall quickly and sieze.  You can run bronze against bronze, and brass against brass.   You can run very hard surface finished steels against other steels, which is why transmissions work.   Constant lubrication is key, as is proper surface finish. 
 
NASCAR steel rods and pins are finished to a very high level, as are pretty much all the parts in those cars.  They still don't last forever, and you wouldn't do what they do in a passenger car engine.  They definitely DLC coat the pins, which is like running dissimilar metals because of the hardness and polish of the coating.
 
Titanium is especially bad at galling, which is why we DLC or PVD coat titanium valvetrain components.   Running titanium locks against titanium retainers or especially titanium valves usually causes them to stick to each other at disassembly time.  Putting a PVD (usually ceramic) or better yet a DLC coating on the locks stops the microwelding.   Running DLC coating on steel wrist pins stops galling of the pins in the pistons AND the rods.   Even though they run fine in a street performance engine, some of the race stuff uses quite a bit of vacuum in the crankcase, which cuts down on oil windage.   Windage is what typically lubricates the wrist pins, so they tend to chew into the pistons if you don't lubricate them.   If you DLC coat the pins, they lubricate with much less oil.  Putting oil holes on the rods doesn't help there because there isn't windage for the hole to pick up.   
 
Steel against cast iron can work, because the metallurgy is different.   Cast iron self lubricates to a degree because of the graphite in the matrix, which is why it's a good block material. 
 
In engine building, it's all about the package.   You build for specific goals and intended use.   We call it the 90% rule at our shop.  What the engine will be used for 90% of the time dictates the build.  
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 69 ambassador 390 Quote  Post ReplyReply Direct Link To This Post Posted: Feb/06/2013 at 12:59am
So tool steel pins on cast iron rods is fine.  No bushings needed.
 
"
Steel against cast iron can work, because the metallurgy is different.   Cast iron self lubricates to a degree because of the graphite in the matrix, which is why it's a good block material.  "
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Plan B Quote  Post ReplyReply Direct Link To This Post Posted: Feb/06/2013 at 7:20am
My builder did make mention of the strong possibility of galling during our conversation. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote tsanchez Quote  Post ReplyReply Direct Link To This Post Posted: Feb/06/2013 at 9:22am
I stand beside my statement, it has been done for many yrs with success and for a engine that will not rpm much it would be a non issue, worst that could happen is the pins tighten up in the rod and then its where you wanted in the first place.

We used to do small chevies with stock rods to 8000 rpm for hrs and just the drilled hole at top was enough oil for it, remember the pin and rod are not the same hardness. 


In the end its what your machinist is comfortable with, my guy in Albuquerque was an aircraft machinist and his stuff was spot on. 

I personally would not bush a stock rod, for one the small end strength is compromised and the cost just does not make sense for the aftermarket you can get.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Peter Marano Quote  Post ReplyReply Direct Link To This Post Posted: Feb/06/2013 at 9:49am
 "  You can run very hard surface finished steels against other steels, which is why transmisions work"

Please excuse this small point of correction.


The contact on a gear tooth face should be rolling not sliding.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote tsanchez Quote  Post ReplyReply Direct Link To This Post Posted: Feb/06/2013 at 10:00am
Except diffs lol
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