Steel-on-steel unbushed rod small ends

General engine tech -- Drag Racing to Circle Track

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PackardV8
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Steel-on-steel unbushed rod small ends

Post by PackardV8 »

Happy Thanksgiving!

I remember a couple of discussions about running steel-on-steel and there were several who've done it successfully. I did a search, but must not have had the correct terminology. Anyone point to the link(s)?

Second question - in a road race 7,500 RPM build, hour-long races, if you had the choice of pressed pins or fitted steel-on-steel, which would you choose and why?
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Re: Steel-on-steel unbushed rod small ends

Post by Krooser »

The NASCAR Pankl rods I have are pressed fit w/ o bushings.
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Re: Steel-on-steel unbushed rod small ends

Post by Stan Weiss »

Jack,
If you asking about floating the pin in the rod without a bushing. Many years ago I ran that setup in a SBC that I shifted between 7500 and 8000 RPM but it was a drag race engine

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Re: Steel-on-steel unbushed rod small ends

Post by jcisworthy »

My friend ran a 351C engine floating and no bushing for years. I was going to try it on a different engine but I chickened out

What I was told to do for safety is have the pins DLC coated if not using bronze bushings. Never tired that either.
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Re: Steel-on-steel unbushed rod small ends

Post by billet »

I did it all the time, right or wrong never had an issue.

This was for a limited Late model with a 311 SBC, I had 2 with 5.565 rods and 283 off the self aftermarket pistons and tool steal pins in a 3.25 stroke engine that turned 8300 and both ran for 3 years with only yearly freshens and replacing the stock cranks every year.

Then had 2 more 311 engines with 5.7 rods and custom pistons doing the same thing, again no issues what so ever.

We ran 20 lap features and ran about 25 races a year, if that helps you out Jack
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Re: Steel-on-steel unbushed rod small ends

Post by jed »

I wouldent hesitate to run steel on steel. Just drill a 3/32 hole centered on the pin end along
With a small chamfer. We would put .0008/.001 in sbc and olds rods.
Used them in dirt and asphalt circle track engines turning 7000/8000 rpm.
Tracks were 1/2 mi to 1 mi tracks. Those engines would get 5/7K laps per season.
Never had a problem.
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Re: Steel-on-steel unbushed rod small ends

Post by cjperformance »

I have done a lot , in particular on factory 351 Cleveland rods as floating pin with no rod bushing and no coating back when aftermarket rods were an expensive luxury here in australia! These were not road race or endurance but ranged from hot street/strip to drag and drag nitrous max rpms 7000/7300. No problems at all following .0008/.001" max clearance per inch pin diameter in this application. These days i would err on the tighter side given the typically lighter vis oil used.
The Cleveland rod is fairly thick up around the pin which i think really helps, i would be sceptical doing this on a thinner factory type rod. But if its an aftermarket quality steel rod then no problem. These days if i were to do it i would go for a DLC pin for sure. Thay said my own 351 still has a set in it, they have done probably around 80/100 n2o passes and 15,000 miles of street thrashing years back in one block, still looked perfect and now in in this block around another 10,000 miles, no strip work but had about 6 or 7 10lb n2o bottles thru it at 175hp added n2o. Its only a weekend car so when it get used it gets a hiding. Same old set of Boss rod bolts fitted in 1991 too! I like Clevo rods! [-o<
What rod will you be using.
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Re: Steel-on-steel unbushed rod small ends

Post by Brian P »

Every motorcycle engine that I've ever had apart has steel-on-steel con-rod to (floating) wrist pin, with the wristpin directly in the aluminum piston. No bushings.
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Re: Steel-on-steel unbushed rod small ends

Post by cjperformance »

Brian P wrote: Thu Nov 23, 2017 6:40 pm Every motorcycle engine that I've ever had apart has steel-on-steel con-rod to (floating) wrist pin, with the wristpin directly in the aluminum piston. No bushings.
Yes a good point there!
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Re: Steel-on-steel unbushed rod small ends

Post by modok »

Main reason to run a floating pins is so you can run the piston tight as possible on the pin.
This isn't said often enough, but it's true.

For a lot of applications it is FINE to run steel on steel, and ultimately it's lighter. There is a small chance the pin will seize solid from galling, but if it does.....so what? If the answer is it won't make any difference if it does, then DO IT. If the answer is if that happens it will break the skirt next time you start it up in the middle of winter then don't do it, OR get DLC coated pins and do it :D

There are some exceptions where a floating pin is good idea to make wear even and/or to allow more accommodation for crank flex, but that would be mostly OLD archaic designs.
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Re: Steel-on-steel unbushed rod small ends

Post by pamotorman »

jed wrote: Thu Nov 23, 2017 6:35 pm I wouldent hesitate to run steel on steel. Just drill a 3/32 hole centered on the pin end along
With a small chamfer. We would put .0008/.001 in sbc and olds rods.
Used them in dirt and asphalt circle track engines turning 7000/8000 rpm.
Tracks were 1/2 mi to 1 mi tracks. Those engines would get 5/7K laps per season.
Never had a problem.
I did the same with circle track engines with no problem. some of these engines were rum on 1 mile tracks and longer I always used moly kote on the assy.so there were no dry starts
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Re: Steel-on-steel unbushed rod small ends

Post by geraldtson »

Answer to your second question. Pressed,because fitted steel on steel will wear to much in that application. I ran fitted steel on steel in drag engines(seemed to be a trend at one time) several years and upon teardown there was always a big wear issue. You could get away with it on a drag race engine and regular maintenance but i wouldn't try it on anything else.
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Re: Steel-on-steel unbushed rod small ends

Post by SupStk »

Ran them on drag engines with H-11 pins and no issues. Trying the same thing with OEM style pins, not so good.

In my case no coatings.
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Re: Steel-on-steel unbushed rod small ends

Post by cjperformance »

geraldtson wrote: Thu Nov 23, 2017 10:05 pm Answer to your second question. Pressed,because fitted steel on steel will wear to much in that application. I ran fitted steel on steel in drag engines(seemed to be a trend at one time) several years and upon teardown there was always a big wear issue. You could get away with it on a drag race engine and regular maintenance but i wouldn't try it on anything else.
Did you have any oiling hole/s drilled in the small end?
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Re: Steel-on-steel unbushed rod small ends

Post by integrale Evo »

modok wrote: Thu Nov 23, 2017 7:33 pm

For a lot of applications it is FINE to run steel on steel, and ultimately it's lighter.
I'm struggling to see how it can be lighter?

I guess the idea of a bush goes back to times when items were serviced, repaired, sent out to run again, tolerances maybe not what they are now and neither was the quality of oil. Now some rods are so cheap, they are almost a throwaway item.
I have noticed on some engines there is an advantage in that they become sacrificial, when tuners get it wrong and detonation occurs it hammers the bush elongating it and saving some other components, you can then either bin the rod or put a new bush in.
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