Full floating wrist pin Qs- Steel on steel? options?
#2436801
01/18/18 01:03 PM
01/18/18 01:03 PM
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Joined: Jan 2003
Posts: 9,670 Lima, Peru
domingo
OP
EL Master
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OP
EL Master
Joined: Jan 2003
Posts: 9,670
Lima, Peru
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Hi!
I am currently building an engine that will use 1.090" full floating pins.
1. If I bush the small end of the rods, after I hone for the desired 0.001" clearance w the pin, I'd end up with bushings that have a wall thickness of 0.031". I fear the wall thickness wont be enough to hold the interference fit over time and might come loose? Whats the minimum wrist pin bronze bushing wall thickness allowed? These are all bronze bushings with no steel backing. I have seen the Eagle H beams or similar do have very thin bushings aroung 0,030" but I wonder if they are press fitted or if they are actually brazed on? My machinist told me a non steel backed bushing thats press fitted and final honed to a final wall thickness of 0,030" doesnt make him too conffortable. He advised against it. 2. In order to install the wrist pin bushings I have, I would also have to open up the small end of the rod to accept the bushing. Thing is the wall thickness of the small end of the rod right now its at 0.168" (see attached pic). If I open it up for the bushing the wall will end up at 0.125". Again, I might fear this might weaken the rod and lead to a majour failure? These are stock reconditioned rods.
DUE TO THE ABOVE REASONS, THAT DONT GIVE ME MUCH PEACE OF MIND.....I WAS THINKING ABOUT OPTING FOR A 2ND OPTION: Would it be OK just to run a full floating pin steel on steel. No bushing. Is this OK to do? And what pin to rod clearance should I run?
I have to use the parts I have on hand as this is a budget build. I just want to choose the best route so I can have peace of mind about not having an engine that will come apart.
Last edited by domingo; 01/18/18 01:10 PM.
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Re: Full floating wrist pin Qs- Steel on steel? options?
[Re: domingo]
#2436809
01/18/18 01:17 PM
01/18/18 01:17 PM
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Joined: Mar 2005
Posts: 1,406 New Jersey, USA
yella71
pro stock
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pro stock
Joined: Mar 2005
Posts: 1,406
New Jersey, USA
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If its a budget build just press the pin and be done with it No money spent at all. the rods you have were not designed to be bushed full floating rods leave the as they are
71 challenger convertable, 64 sport fury 383 ci with factory air
99 sebring convertable
89 CTD pup
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Re: Full floating wrist pin Qs- Steel on steel? options?
[Re: domingo]
#2436866
01/18/18 03:00 PM
01/18/18 03:00 PM
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Joined: Jan 2003
Posts: 16,376
dogdays
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 16,376
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Not enough meat for a press fit? Do you mean the hole is too large? That would explain your problem.
1. I have never seen a wristpin bushing with steel backing. Ever.
2. There's no way in heck that Eagle or any other high performance rod manufacturer BRAZES a bushing into a connecting rod. Again, I have never seen it done in any application. Ever.
3. If Eagle uses a 0.0030" thick bushing there's no reason why you can't.
At 5000rpm, a stock dimension 440 piston exerts 5000lb of pull on the pin end of the rod. That's assuming an 1100gram piston and pin. If the wall thickness is 0.125 and the length is 1.1", the cross-sectional area of the pin end is 0.275 square inches. That computes to 18,182psi tensile stress.
Using Young's Modulus for 1541 steel of 28x10^6, the deformation of a 1.09" length stressed at 18,182psi is 0.0007". The press fit has to be greater than that. Steel elasticity is not dependent on its tensile or yield strength.
If you wish to float steel on steel, you will need an oiling hole on top of the pin end about 1/8" diameter with a small chamfer. I would suggest 0.001" clearance as a starting point, although others who know much more than I should be consulted first before setting that as ideal. The racing community started out with this as pin oiler, moved to two holes coming up from the bottom sides at an angle, but then moved back to the single hole on top of the rod. That is the latest configuration I have seen.
R.
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Re: Full floating wrist pin Qs- Steel on steel? options?
[Re: domingo]
#2436896
01/18/18 03:47 PM
01/18/18 03:47 PM
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Joined: Jan 2003
Posts: 25,942 Rio Linda, CA
John_Kunkel
Too Many Posts
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Too Many Posts
Joined: Jan 2003
Posts: 25,942
Rio Linda, CA
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My machinist told me a non steel backed bushing thats press fitted and final honed to a final wall thickness of 0,030" doesnt make him too conffortable. He advised against it.
He's being too cautious, it's common practice to bore the small end to 1.160" to bush for a 1.094 pin which makes the bushing wall thickness .033". I've run lots of them on the street that way. Some people run floating pins without a bushing, when doing this it's best to dip the small end in molten tin and then hone to size.
The INTERNET, the MISinformation superhighway
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Re: Full floating wrist pin Qs- Steel on steel? options?
[Re: domingo]
#2436972
01/18/18 06:09 PM
01/18/18 06:09 PM
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Joined: Mar 2010
Posts: 625 Indianapolis In. usa
Quickrunner
mopar
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mopar
Joined: Mar 2010
Posts: 625
Indianapolis In. usa
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I did it in a small block many years ago with no issue at all. Drilled and chamfered a small oil hole in top of the rod and ran it at .001
05 Ram 1500 Daytona package 71 Demon Gen3 hemi drag radial project
Missin' my 9 second 70 runner!
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Re: Full floating wrist pin Qs- Steel on steel? options?
[Re: domingo]
#2436973
01/18/18 06:12 PM
01/18/18 06:12 PM
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Joined: Jan 2003
Posts: 13,382 Marion, South Carolina [><]
an8sec70cuda
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 13,382
Marion, South Carolina [><]
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Used to do a lot of sb roundtrack motors that way. Hone the rods out for about .001" clearance w/ no bushing and drill the oil hole at the top. Worked good, but these weren't exactly real powerful engines either.
CHIP '70 hemicuda, 575" Hemi, 727, Dana 60 '69 road runner, 440-6, 18 spline 4 speed, Dana 60 '71 Demon, 340, low gear 904, 8.75 '73 Chrysler New Yorker, 440, 727, 8.75 '90 Chevy 454SS Silverado, 476" BBC, TH400, 14 bolt '06 GMC 2500HD LBZ Duramax
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Re: Full floating wrist pin Qs- Steel on steel? options?
[Re: an8sec70cuda]
#2436993
01/18/18 06:39 PM
01/18/18 06:39 PM
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Joined: Mar 2006
Posts: 2,675 Mt. Eden Ky.
Hemi Allstate
master
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master
Joined: Mar 2006
Posts: 2,675
Mt. Eden Ky.
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GM did it from the factory on the 1969 Z/28 302 . I also had an L-88 427 that came with the floating pins and no bushings. As said above adding an 1/8" hole with a chamfer was a popular mod. My $.02
Mark
1996 Ram 1500 Sport 1968 road runner 1952 Sears Allstate licensed, pump gas, Hemi 5.98 @ 115.73 1.33 60 ft. The best is yet to come. Painless Performance / Street RODDER magazine Top 100 for 2019
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Re: Full floating wrist pin Qs- Steel on steel? options?
[Re: domingo]
#2437003
01/18/18 06:51 PM
01/18/18 06:51 PM
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Joined: Jan 2003
Posts: 4,287 Morrow, OH
markz528
master
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master
Joined: Jan 2003
Posts: 4,287
Morrow, OH
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All I can tell you is mine are steel on steel - older build and not sure where along the line this happened as I don't believe that they were floating originally.
Just found major galling on most of the pins and rods. Both are junk. Buying new bushed rods and new pins from Todd Marsh to fix the problem.
67 Coronet 500 9.610 @ 139.20 mph 67 Coronet 500 (street car) 14.82 @ 94 mph 69 GTX (clone) - build in progress......
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Re: Full floating wrist pin Qs- Steel on steel? options?
[Re: domingo]
#2437040
01/18/18 08:10 PM
01/18/18 08:10 PM
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Joined: Nov 2004
Posts: 3,544 Syracuse,NY
CompWedgeEngines
master
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master
Joined: Nov 2004
Posts: 3,544
Syracuse,NY
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Steel on steel will work fine with an oil hole for what your doing, BUT, .001 isnt enough clearance when doing that on a 1.094 pin
RIP Monte Smith
Your work is a reflection of yourself, autograph it with quality.
WD for Diamond Pistons,Sidewinder cylinder heads, Wiseco, K1 rods and cranks,BAM lifters, Morel lifters, Molnar Technologies, Harland Sharp, Pro Gear, Cometic, King Engine Bearings and many others.
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Re: Full floating wrist pin Qs- Steel on steel? options?
[Re: CompWedgeEngines]
#2437047
01/18/18 08:25 PM
01/18/18 08:25 PM
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Joined: Feb 2005
Posts: 20,197 PA.
pittsburghracer
"Little"John
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"Little"John
Joined: Feb 2005
Posts: 20,197
PA.
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35-40 years ago most of us ran steel on steel with the 1/8 mod. Most of us also ran that heavy azz Speed Pro or TRW pistons. On rebuilds we had to take our flapper wheels and get the pins cleaned up so we could throw it back together.
1970 Duster Edelbrock headed 408 5.984@112.52 422 Indy headed small block 5.982@112.56 mph 9.42@138.27
Livin and lovin life one day at a time
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Re: Full floating wrist pin Qs- Steel on steel? options?
[Re: domingo]
#2437260
01/19/18 01:34 AM
01/19/18 01:34 AM
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Joined: Jan 2003
Posts: 20,204 Park Forest, IL
slantzilla
Too Many Posts
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Too Many Posts
Joined: Jan 2003
Posts: 20,204
Park Forest, IL
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My first good Slant had the pins steel on steel. They had the pins coated with something. (Can't remember what) It lasted over 50K on the street and about a bazillion passes. They were beat up when we took it apart, but it had suffered an oil pump failure.
"Everybody funny, now you funny too."
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Re: Full floating wrist pin Qs- Steel on steel? options?
[Re: Medlock51]
#2437334
01/19/18 05:46 AM
01/19/18 05:46 AM
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Joined: Aug 2003
Posts: 43,277 Bend,OR USA
Cab_Burge
I Win
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I Win
Joined: Aug 2003
Posts: 43,277
Bend,OR USA
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I took one motor apart that had the wrist pins floated with the small end of the BB rods steel on steel, can't remember now if they where six pack or LY rods, knurled for oil retention and clearances I'm assuming/. I'm sure the piston where the old heavy forged TRW small dome "race" 440 pistons I've never saw or heard of anyone else using that type of set up since
Last edited by Cab_Burge; 01/19/18 05:47 AM.
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: Full floating wrist pin Qs- Steel on steel? options?
[Re: domingo]
#2437593
01/19/18 06:46 PM
01/19/18 06:46 PM
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Joined: Jan 2003
Posts: 9,670 Lima, Peru
domingo
OP
EL Master
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OP
EL Master
Joined: Jan 2003
Posts: 9,670
Lima, Peru
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Thanks for all the replies.-
At this point I think that bushing the rods is the way to go.
Good thing is the machine shop I use listens to what I ask them and they always do a good job. If I have oddball requests they also go the extra mile to do procedures as I ask them to. Remember I live in LIMA, PERU so race engine machining is not what they do, they just do regular rebuild jobs. I have to walk them through certain procedures like using honing plates, multi angle valve jobs, etc.
Now I have 2 questions:
#1
Now....the machine shop I use would generally just press in the bushings with their interference spec. Lets say 0,002"
But, Since these bushings will end up being about 0,03" thick once proper clearancing is completed, I was thiknig that maybe not just press fitting them, but freezing the bushings and heating the rods would be the best option? Will installing them like this guarantee a better grip than just pressing them? If its the better way to do it, what would be the intereference to shoot for prior to install? Also, would freezing the bushings in dry ice or just throwing them in the fridge would do the trick??? What about the rods? dipping them in boiling water???
#2
Is it an absolute necessity to use a burnishing tool to achieve clearance once the bushings are pressed in? I see that they just press in the bushings and they they just hone them to size, but they do not have burnishing tools- I hear burnishing will help achieve a better hold with a thin walled bushing as opposed to just honing to size. Are burnishing tools expensive? how much would it cost one to do a 1.09" bushing? Does anybody have a link to the appropiate one to do the small end bushings?
Thanks!!!
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