Piston Pins, Pressed...Full Floating..Trying New Technology!

[slownrusty]

Guys - As my build is coming together its time to address the piston pin which I received with my new custom JE Pistons.

 

I spoke at length today with Greg Whitehead of Whitehead Performance (http://www.whiteheadperformance.com) to chit chat about options of running the 240Z 9mm steel rods and the JE Pistons.

 

I decided that the best option is to go full floating rods, so

The options are:

1) Pressed Pin (steel rod on steel pin with oil holes drilled) - not really an option

2) Pressed Pin with brass bushing

 

-or- try something new and innovative

 

3) Coat the pin with DLC, making the brass bushing not needed.

 

DLC stands for Diamond Like Coating and the ONLY car that uses this from the factory right now is the Honda S2000 (I confirmed this with the rep from JE). Formula 1 and Nascar also use this technology right now as well as the Motorcycle industry.

 

Benefits:

1) Relatively cheap - $40 per pin (cheaper than buying Carillo Rods with the bushing already installed...LOL!)

2) Is applied in 3 layers and will not wear-out or "gall"

3) Provides full floating and lubriation

4) Means you do not have to run a Brass bushing, so no honing out the small end of the rod (sacrificng strength). Plus bushings do wear out and are a real precise install, if you are off even 1/2 degree it translates to trouble down the road. Also no chance of the bushing moving as the engine is subjected to loads over time etc etc

5) Have been tested to stand up to extremely high hp levels

 

Very few places in the US offer this service, but I am VERY excited to try it. I will post pics when I get the pins back.

 

Thought I would share.

 

Yasin

[Tony D]

Why is a full floating pin running without a bushing 'not an option'? Plenty of people do that, looking at it one way the bushing is nothing more than insurance, looking at it another way, the bushing is just something else to fail.

[SUNMASTER]

My engine builder also did not use the brass bushing .He cut oil grooves in the small end. Only time will tell if it was the right thing to do . my 2c

[BRAAP]

Yasin,

Sounds like your engine build is coming along nicely. Can’t wait to read your post when it is built, running, and dialed in… YEE HAAA….

 

 

For the newbie’s that will inevitably read this thread, for clarification sake, the term “Pressed pin” is just that, a press fit piston pin, i.e. an interference fit between the piston pin and the small end of the con rod. When it is a “Floating pin” it is no longer referred to as a “pressed pin”., i.e. there is a clearance between the piston pin and the rod small end and most of time a bushing is used, but not always.

 

As Tony D. stated, you don’t have to use a bushing. The bushing is merely a replaceable “consumable” as it WILL wear over time. Even if you don’t use a bronze bushing but still utilize a floating piston pin, the small end of the rod will still wear over time and during its subsequent overhaul, will then need to be bushed at that time, i.e. just like sleeving a worn piston bore.

 

Personally, if I have the choice between pressed pins or floating pins with a set of pistons, for a street engine, even hot street engines that will hopefully run 100,000 miles before its next overhaul, I much prefer to press fit the pins. For a race engine that will get regular overhauls like every season due to the high demands and stresses imposed during a season of full tilt racing in a high output race engine, floating piston pins definitely have their place. For you guys with mega boost Turbo street engines, I feel the use of floating piston pins is a matter of personal preference as those mega boost turbo engines are in essence, street driven race engines. i.e. they tend to get rebuilt frequently, (more frequently than the owners originally intended), due to the extremely high demands, heat/forces placed on/in that little engine.

 

For those interested, here is BRAAP’s not so complete “pros and cons” list for pressed pins vs Floating pins…

 

 

Cons for Floating piston pins…

 

1) Bushed pistons pins require some sort of “pin lock”, whether it be cir-clips, snap rings, etc. to keep the pisot0n pin from walking over to the cylinder bore and tearing it to shreds. These removable pin locks are just another part attached to an already stressed component that is being yanked an yarded at very high velocity and G-forces and those “pin locks” are not fail safe, they do on occasion come loose which, even when installed properly, will allow the piston pin to “walk, and when that happens, SEVERE cylinder scoring does take place. Proper pin lock installation is also VERY critical. Pin Buttons are nice, but they do add wear to that portion of the cylinder wall that they come in contact with over time and buttons are pretty much an aviation engine thing any way…

 

2) I already covered the small end wear.

 

 

Pros for Floating piston pins…

 

1) Ease of overhaul for engines that are to be frequently overhauled, i.e. full tilt hard core VERY high output race engines, (very high output boosted street engines do fall into this category… ).

 

2) Pistons are not destroyed when they are separated from the rod, i.e. they don’t need to be pressed off, so they can be reused if they were not damaged while in operation.

 

 

Con’s for pressed piston pins…

 

1) Pistons usually are damaged/destroyed when pressed off the rod. Though the pistons are typically not reusable if they need to be removed the rods any how, so for a street engine, this doesn’t really apply.

 

 

Pro’s for pressed piston pins…

 

1) The interference fit of the piston pint to small end of the rod, HOLDS the piston pin from ever walking over to the cylinder bore and scoring it…

 

2) Small end of the rod don’t “wear” so they don’t need constant attention during subsequent rebuilds.

 

3) Once the pistons are on the rod, getting the pistons “clocked” on the rod in the correct orientation is one less thing you have to deal with during assembly.

 

4) No cir-clips, snap rings, etc to loose or improperly install….

 

 

Ok, that’s my basic $.02 on the pressed vs Floating pin debate…

[Phred]

I built Trans Am Chev engines in the late 70's, early 80's. Cosworth and Ford based race engines in the 90's. Porsche engines at present. On the old trans-am engines we did a lot of experimenting with rods with and without bushings. All the results are directly tranferable, since then I have used this info when deciding which type to run in many different brands of race engines. Really, it just depends on the customers budget. A non bushed rod with non coated pin @ .0008 clr worked well for about 5 hours before very slight metal transfer occured. This happened with a single top oil hole, or two underside holes. More initial clr. was tried, extending the life a couple hours. (engines were min. 530 hp, dry sumped, 8500 rpm.) Then we tried oil grooves, with the same results. Then we tried something unique. We first honed the rod to .0007 clr. Then shot peened the pin bore. Then did a final plateau hone over the top of the shotpeened bore with a final clr. of .001. This left a fine dimpled surface that retained oil, and the life of the pin bore was then as long as the rest of the engine. Note: the only reason we went to such lengths was to make the small end of the rod as light as possible. The small end was turned on a rotary table on a mill so the wall thickness was a consistent .120. For one race only engines (9000rpm) we could reduce that to .100. But, for all the effort expelled, a bushed Carrillo rod was only slightly heavier, and could be rebuilt (rebushed) easily. Casidiam (DLC) had yet to be invented. But I have built USAC Midget engines that have Titainium pins coated with DLC. Those engines take a severe beating and live long lives. Upon disassembly, the coated pins look perfect. They run in bushed Carrillo, or Titainium rods. For the ultimate life expectancy, a bushed rod is superior, no mater what type of pin/coating is used. FWIW.

Phred

[Tony D]

"1) The interference fit of the piston pint to small end of the rod, HOLDS the piston pin from ever walking over to the cylinder bore and scoring it…"

 

I will say you may need to revise that portion of the statement.

 

Until our overhaul of the Bonneville engine two years ago, I thought the exact same thing.

 

Matter of fact, so did everyone else who we showed our block to after the pins walked out to the wall and put an 0.080" score down each bore.

 

Pressed pin setup, done at a competent machinist facility in L.A. well known for Nissan Engine Work (not their fault, so I'm not naming names, everything else they did was pristine, and we did final assemlby of subcomponents ourselves)

 

Still made 300+ to the rear wheels at 8300rpm, blowing by like a mother. And took two more records at Bonneville (final was 173.325mph) that year before retirement and building of the current L20A.

 

Granted that was after four seasons of running at redline, but it CAN happen.

 

That information posted by Phred is VERY interesting to me. Very interesting approach to the problem. BTW our rods were race prepped Nissan units, and you know how thick those ends are with a 22mm pin in them.

[slownrusty]

All great discussions guys and thanks all for chiming in. This will make for great archived material down the road for any member pursuing engine building.

 

I feel that the wrist pin is usually overlooked, I say that loosely. I am still not a big fan of the pressed-in (bronze) bushed small end as I have seen one move 14" when tearing down a motor. I would hate to see the soup if it had come loose all the way. Plus they wear out...all be it after quite a long time.

 

I am anxious to pursue the DLC coatings and will post the pics of what the pins look like after I get them back.

 

Yasin

[NZeder]

Who does the DLC coating process? Anyone have any DLC coatings done who did you use to do this and would you recommend them to others? I would like to know who does this processing I am happy to send stuff to the US to get it done.

[TheNeedForZ]

DLC = diamond-like carbon(coating)

 

http://en.wikipedia.org/wiki/Diamond-like_carbon

[slownrusty]

Who does the DLC coating process? Anyone have any DLC coatings done who did you use to do this and would you recommend them to others? I would like to know who does this processing I am happy to send stuff to the US to get it done.

 

There are only a few places in the US that does DLC coatings. It is the latest technology being used in Nascar, Formula 1 and most high performing motorcycles come with this from the factory due to the sustained higher rpms that bike engines see. The only car that comes with DLC from the factory is the Honda S2000.

JE offers this as an optional coating on their wrist pins.

 

If you want to read more check:

http://www.oerlikon.com/coatingservices/

 

I have more info if you would like.

 

Regards - Yasin

[1 fast z]

Ill put my two cents in.

 

The MAIN purpose to the performance advantage to a full floating pin, is that if you get the frictions somewhat equal when the engine is warmed up, ie. the piston pin bores as well as the rod end bushing, you dont have to accelerate that wrist pin between rotating cycles. Basicly the pin "CAN" just stay neutral and not move at all, and let the piston and connecting rod do the moving, as they have to. Also, as for piston pin bushings walking, that is a problem with the machinest who installed them. They NEED to have a .003" interference fit between the rod end and the od of the bushing. They need to be loctited with Green loctite sleeve retainer. I have seen a few rods that were just run on the forged rod end, bare metal, and have seen them fail by different machine shops.

 

I just got done doing the rods for my L31dett motor, and yes it time consuming, but worth it. You also cant just use any old bushing material, I use alluminum bronze, which is VERY tough at resisting "squish" force, basicly its a very high PSI rated material. Here is a picture of my bushings I installed on one of my stroker engines

 

 

I only install ONE oiling hole for strength reasons, and works great.

 

ALso about pins, on a NA engine and some boosted engines, I always use a .090" wall A-2 tool steel pin for strength and lighteness.

 

Also, I always use double true arc retaining rings, as I have never had a system like that fail.

 

 

Thats just my two cents.

[TheNeedForZ]

I have heard using teflon buttons to keep the pins from scratching the cylinder walls. Anyone else heard about that? I saw that in the "how to modify your datsun engine..." book...of all places.

[Doug71zt]

You don't want teflon buttons in your street engine. They can and will score up the bores as they pick up debris and grind them into the cylinder walls. Leave them to the 30's technology aircraft engines that run at 2500 rpm.

 

Doug

[Phred]

To correct a slight inaccuracy, pin plugs as Continental refered to them, were/are made from aluminum. Most aircraft engines use these, and are either a slip fit in the pin, or are pressed in. Teflon style butons were offered by Datsun Comp. as far back as 25 years ago, and I used these on many L motors. It is required to maintain tight clearence in the pin, and end clr. in the bore for proper operation.

Don't forget another type of pin retainer which has even a better record of staying put under extreme use. The round wire lock is nearly bullet proof. It is designed to be used with a pin which has a a precision outside chamfer. In use, the pin will exert longitudinal force, and will push the round lock down into the lock groove, instead of out. These are being used by more manufactures than in the past, and I prefer them to all other types which I have used for many years. The last set of JE pistons I ordered for my LD28 have these round wire locks. Porsche has used these locks exclusivly in all their engines for years.

Phred