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Off The Shelf (OTS) Custom ModMotor Pistons

60K views 171 replies 41 participants last post by  Stangman105 
#1 ·
OK guys, for those of you who are looking for pistons or have looked for pistons, you will be familiar with the problem of finding a manufacturer and then getting the specs correctly communicated and finally getting the piston you wanted. Usually things do not go the way you anticipated at first or the process is painfully long with something always just a little bit different than what you hoped for when you finally get the pistons.

I may have a fix for everyone in the next week or thereabouts.

If things work out as currently anticipated (always a challenge) I'll have a piston manufacturer that will be willing to build the piston, the way we all have wanted them built, and all you have to do is specify bore size and compression ratio. The rest will be already done for you, i.e. heavy wall H-13 pins, supercharged ring land placement, proper radial clearance for the rings, a TotalSeal AP Steel ring package, two country miles of PTV clearance, 0.200" skirts and any bore size your heart desires. All you will have to do is identify the piston by name for example XXXX, bore size and compression ratio - that's it!

The pistons will be individually replaceable if you do have a whoops (lets hope not) and the replacement will not require you to rebalance your crank - it will come within +/- a gram of what the original was. If this comes together the way I am hoping, ordering custom pistons will be sort of like ordering lunch in the old days when you could walk in and just say, "I'll have a cheeseburger, fries and a Coke", and you end up with the exact meal you wanted, the way you wanted it.

In a week or so I hope to have a 3D Acrobat image of the piston I can post up on the site here that will allow you to rotate, turn around and see the piston from every perspective. Stay tuned ...
 
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#7 ·
Thanks for the vote Joe but I suspect they will use a pretty numeric looking identifier for these pistons. Although "Ed Special" does sort of have an interesting ring to it. :)

Regarding the pins.

Is there any point in specifying "super finished" on the pins? I have seen that term used by several manufacturers but none of them specified any performance differences.
In years past Drew the pins would sometimes come with a lets say a somewhat less finished surface and then the manufacturer might offer the super finished surface which was just a smoother surface finish probably down in the ~10 Ra area. With todays machinery and finishing capabilities the surface finish, especially on stuff like tool steel pins, is down in the 1 Ra area or less which visually looks like a mirror. This is a pic of a Winberg billet crank for one of our engines and it has been finished with their oil shedding WinFinish. This is a close up of the flywheel flange;

Rim Bicycle part Nickel Font Auto part


And this is a close up of #1 counterweight on the same crank;

Bicycle part Rim Liquid Metal Auto part


This surface finish is less than 1 Ra which is essentially the equivalent of a mirror as you can see from the reflected image of the snout.

The wrist pins that will come with these pistons are like the finish on that crank although they are one notch down strength-wise from the absolute best money can buy. The reason for that is because when you see the price of the best money can buy it would bring tears to your eyes and no measurable improvement for our application.

BTW I am a very big Winberg fan. After I committed to a custom billet, Randy Winberg was the only guy that would make a custom 4.6 crank for me and do it in Timken 4330V steel which is the same super steel the Top Fuel cranks from Bryant and Winberg are made from now.

Awesome to hear! Look forward to seeing them and comparing them to mine to make sure I did ok!
You have an excellent set of forged pistons there Cody. Yours and Cobraracer46's below are kissing cousins, at least from the underside, but from different manufacturers. Your tough luck in the specifying process and the ordering / manufacturing process was what finally pushed me over the edge to make this piston generally available without all the pain and suffering you and a number of other guys have had to go through to get your pistons.

I would like to buy the strongest flat top pistons ( tool steel pins, thick skirts, etc) with super charger specific ring lands for my 4.6 that maintains the OEM pin offset ( no noise!). In other words, I want diesel like durability.

Something like this would be nice as long it does not make any noise:
You have a great piston there Cobraracer. Whoever spec'd that piston out knew what he was doing and he did your stuff very well. If it was you, congratulations, you belong to a pretty small group of very smart guys.

There are a lot of details that would be nonsensical and boring for most about this piston however there is one other aspect of it that is unavailable anywhere else other then OEM. That is the special pin boss treatment for offset pins. In aftermarket pistons the pin boss is always on center and if you offset the pin you make the pillars that comprise the pin boss thinner in the thrust direction of the piston because of the offset. When OEM's use offset pins on hi performance engines and sometimes just grocery getters they will offset the pin bosses to match the pin offset.

These pistons will come with the pin bosses offset in the piston to exactly match the pin offset so both sides of the pin boss are identical. The upshot of all this geometric calisthenics is a pin boss that is equally strong on both sides. There are a number of other reliability considerations designed into the piston that are pure boring.

Usually (not always) only the special line or hand built engines in Detroit get this sort of treatment. For a hi-performance engine like our own the benefits can be very real. The thin side of the pin boss usually doesn't, but can fail and when it does you have a forged 4340 connecting rod swinging around on a rod journal like a weed whacker in your back yard. The damage it will do inside your engine is impressive in the extreme. It will surpass even your wildest imagination.

Hang tight guys this thing is winding up pretty quick now. I think you will really like these 'off the shelf custom pistons'.

BTW Cobraracer, these pistons will easily meet the requirements you specified in your opening sentence.
 
#5 ·
I would like to buy the strongest flat top pistons ( tool steel pins, thick skirts, etc) with super charger specific ring lands for my 4.6 that maintains the OEM pin offset ( no noise!). In other words, I want diesel like durability.

Something like this would be nice as long it does not make any noise:
 
#14 ·
According to John Tymensky, there are other benefits to running some offset in pistons:

"forgings with a quiet-running 0.050-inch pin offset are John's choice. The pin offset reduces "flop over" at top dead center, allowing a better ring seal with modern, narrow rings. John specifies a little more barrel to piston skirts going into forced-induction engines such as this one for the same reason. The pin is 22mm in diameter with 0.155-inch-thick H13 material-hard stuff. Because of the nitrous, the piston dome is also thicker at 0.250-inch."



Source: http://www.mustangandfords.com/how-to/engine/m5lp-0809-big-bore-modular-build/
 
#11 ·
Ed, the finish on your custom crankshaft is just incredible!
Was that done to promote oil shedding? Or just so it makes it obvious that there are absolutely no machining flaws?
Was that finish included 9n the price you mentioned a while ago?

But if I ever got a crank like that made I bet it would get me in a lot of trouble. It might go something like this.......

DREW! You love than crankshaft more than you love me. I bet you would rather have it in bed than me!

WELL?

"I'm thinking, I'm thinking."
 
#12 ·
My name suggestions from back in April in the "custom pistons thread" when I suggested this very thing!

Can we just get one of the piston manufacturers to make these heretofore custom pistons a standard catalog part for boosted 4.6 engines? Just call it the "Ed". How about the "Mini Pro Mod"? I believe that's what one of the pistons companies said they thought it sounded like when Ed spec'ed it out to them.
It's too bad my stock motor is so durable... or wait.. nevermind.
 
#13 ·
My name suggestions from back in April in the "custom pistons thread" when I suggested this very thing!

It's too bad my stock motor is so durable... or wait.. nevermind.
Your post was the genesis of the idea Drew. A telephone call with another site member and then Cody's (among other people's) trials and tribulations jelled the idea. The challenge was finding the right forging blanks - not impossible but also not your everyday forging. The other problem was maintaining the forging supply.

That particular 4.6 crank in the pics is not mine. For a race only application I would have done it. For a primarily street application I elected not to. The cost was not that expensive ~$300 or $400 if I recall. The issue is the maintenance of the crank when it is not in an engine. The unprotected but highly polished surface is very susceptible to rusting from moisture in the air. That first rust dot is a stress riser that did not exist before. The finish is a race use preparation that belongs on a race crank not necessarily a street crank - but it sure does look pretty.
 
#19 ·
OK guys. Below are two pdf views from a SolidWorks model of pistons for our engines. There are subtle finishing touches still required like intake valve reliefs but you are looking at the essence of the piston. The skirts are 0.200" the piston uses a full slipper skirt and despite it's hefty dimensions comes in at 394 grams without pin.

This project will allow you to specify a bore size and a c/r and all the PITA design issues will already be covered correctly for you. Here are the images and attached are the files.

Bottom View

Automotive tire Automotive design Automotive lighting Automotive exterior Automotive wheel system


Top View

Automotive tire Headgear Font Auto part Tire


Enjoy,


Forgot the pdf's

View attachment Top.pdf

View attachment Bottom.pdf
 
#22 ·
Yea :) I thought so too, Bob.

Great looking piston, Ed! From a glance, I thought it had a resemblance to the JE 314631 (shown below), but the skirt here is definitely beefier. Since this is still an early sketch, did they - or you - see an advantage or disadvantage to an asymmetric skirt? Probably one of many questions on the way.

The JE's were ones I looked at seriously, but they came it at over a 9.5:1 C/R - definitely a bit on the high side. It will be nice to give the "new guys" (I won't give it away) the exact specs now, and if this package is going to be complete with the tool steel pins and good rings, it should be a real score. Thanks again for your efforts!

View attachment 128833
It is going to be a soup to nuts package for us Joe. It will literally be a bore size and c/r. The rings, pins, locks etc will all come pre-packaged. If someone wants to go ala carte that is equally possible. Gibtec will make anything, for anybody, any way they want it. Whatever your heart desires (practically) their CNC manufacturing process can provide. Remember these guys roots are in ProStock, ProMod, Blown Alcohol and Top Fuel. They build the very best stuff available for the toughest pro classes.

The reason for the slipper skirt instead of the asymmetrical skirt is part cylinder wall loading. The asymmetrical skirts are plenty strong. The asymmetric design is geometrically quite rigid and produces high localized cylinder wall loadings. The slipper skirt has some flexibility or spring and spreads the load over a wider area of cylinder wall. It is going to be easier on pieces. The additional surface contact area also provides opportunities for additional heat xfer to the cylinder walls.
 
#21 ·
Great looking piston, Ed! From a glance, I thought it had a resemblance to the JE 314631 (shown below), but the skirt here is definitely beefier. Since this is still an early sketch, did they - or you - see an advantage or disadvantage to an asymmetric skirt? Probably one of many questions on the way.

The JE's were ones I looked at seriously, but they came it at over a 9.5:1 C/R - definitely a bit on the high side. It will be nice to give the "new guys" (I won't give it away) the exact specs now, and if this package is going to be complete with the tool steel pins and good rings, it should be a real score. Thanks again for your efforts!

Hand Automotive tire Hood Wheel Automotive lighting
 
#23 ·
I had a sneaky suspicion that you were going to use Gibtec for these pieces, excellent quality stuff. I like the .200 thick full slipper skirt design. I've never spec'd a piston with that thick of a skirt trying to keep weight down, but if they come in at 394 grams, that's not bad at all. What material are they going to use, 2618 I would imagine? Looking forward to the final details.
 
#24 ·
I figured you and a couple of other guys on the site had already figured it out Jim. You didn't let me down.:) You are correct about the material it is 2618. 2618 just makes more sense for a maximum effort piston like this. No reason to shortcut a premium piece material-wise.

My own forged versions of this piston came in right around 420g w/o pins - I want to say they were right between 419g to 421g with the heaviest less than 423. Not bad for a forging but heavier and not anywhere near the precision available with a billet piston. These pistons were designed in Solidworks so as to leave no wasted material in the finished piston while maintaining maximum strength in all the areas we most highly stress the piston. They will be much more consistent weight-wise. My expectation is right around a gram perhaps less weight difference per piston. I am quite pleased with the final design. Like I observed earlier there are little items like the intake valve reliefs that have to be added but other than that sort of window dressing it is a complete design.

Next step is to get the package pricing put together and we should be ready to go.
 
#25 ·
Looks great Ed.

But a question. I know that given the best of all possible worlds you want the rings as far down as possible. But is there a longevity trade off to having the oil ring unsupported where it crosses the pin gap?

Or is there a secondary support ring below the lower oil ring?

And will they be supplying the ring pack? Tool steel top, total seal second (gapless), high tension oil? And is the gapless total seal second a modified napier? Or is that face profile not available in a gapless?
 
#31 ·
Apologies for the delay Joe. The day job has been demanding this week. I'll get something going with them by email this weekend and I suspect we can have a package part# within a week or hopefully less.

You, Jim (Helomech74) and a couple other guys figured it out right out of the box and set my PMs on fire :) with your suspicions about who the manufacturer was. As you guys already noodled out, Gibtec is the company! BTW thanks for posting the Gibtec link, it is a great look at who these guys are and what they are about. Most guys outside of the Pro classes do not know of them.

Gibtec specializes in extreme service supercharged engine pistons for ProMod, Blown Alcohol and Top Fuel. They also have a cutting edge n/a piston for the ProStock cars. The pistons they make (IMO) the very best available for supercharged applications. While I do not have any ProStock engine experience with them I would expect the n/a versions of their pistons to have a comparable level of attention to detail and application specific design innovation.

The company and their custom piston manufacturing mission fit our application needs like a glove. The best part of this is it will give end users, like many of the guys on the site here, the ability to order an optimized, finely tuned piston design for a blown Modmotor without all the hassle of hoping they properly learned custom piston design, ring packaging, selection and the myriad of other considerations that go into the design and design preparation prior to production.

As the end user all you will have to know is what bore size you want to use and what compression ratio you want. All the structural design and engineering for sinking heat out of the piston, optimizing ring packaging, pin boss strength and pin offsets (when requested) has already been done for you. The piston will look like a piece of fine jewelry everywhere, have an unprecedented weight consistency from piston to piston and be physically as strong a piston and as light (at that strength threshold) a piston as is physically possible to be made.

We often look at F1 engines and their componentry as sitting at the top of the high performance design and engineering pyramid. These pistons are kissing cousins — except for use in a supercharged Modmotor.
 
#34 ·
Awesome!

I'll soon start on my bottom end build and will completely trust in this Piston and its design choice.

Thanks For working on this Ed.. Thanks all who supported.

Neil
Glad you like them Neil and thanks for the good words.

This piston was long overdue. The number of "custom" piston choices out there that are merely warmed over n/a designs and or are missing important design considerations is disappointingly high. Our engines cost two boat loads of money to build and there is no reason why we should have to settle for anything other than the best when it comes to our pistons.

This initiative will give anyone access to a premium quality, blown Modmotor specific, piston design they can have confidence in. We should have the last pieces of the package together this coming week. I will be traveling Wednesday through Saturday but checking mail as I go. As the last pieces come together i will post them up.
 
#35 ·
Looks Awesome! Are you going to have a version for the stroker guys?
 
#38 ·
Ed,

Will the pricing for the initial buy be lower than if we need a set down the road?

Is there any coating options?

I'm not need a set at the moment but don't mind having them sit on the shelf for future needs if there's a initial discount.

Thanks
 
#39 ·
Ed,

Will the pricing for the initial buy be lower than if we need a set down the road?

Is there any coating options?

I'm not need a set at the moment but don't mind having them sit on the shelf for future needs if there's a initial discount.

Thanks
The run up to the holiday has been challenging Keith so I am a little behind in driving this project but the answer to your pricing question is no.

In fact there are coating options but I have not included them in the basic piston package. The general market awareness of surface coatings is driven by magazine articles and some piston manufacturers. The coatings add considerably to the price of a set of pistons and have a very narrow target market - they are not needed by more than 99% of the buyers. If you decide you want the coatings however, they are readily available for both crown and skirts.
 
#40 ·
OK, guys, the deal is done, and the numbers are in. Here are a few PDF views of the piston from different perspectives;

Angled Top View,
Automotive tire Automotive exterior Plastic Auto part Circle


Angled Bottom/Side View,

Automotive design Automotive tire Peripheral Automotive wheel system Automotive exterior


Bottom View,

Sports gear Automotive tire Camera accessory Automotive design Peripheral


Angled Top and Side View,

Watch Automotive tire Automotive design Wheel Font


Thrust Face View,

Rectangle Gas Plastic Auto part Metal


To allow you to look to your heart's content, I have also attached a 3D PDF file of the piston to the bottom of this post. The file is named Gibtec.pdf. Download it, and you can spin the piston around to your heart's content looking at it from all sides.

What you see is basically 99% finished. Little elements still need to be added, like the double pin oilers, but the design is essentially complete.

I can tell you with virtual certainty this is the finest Modmotor piston you can buy anywhere at any price. It just doesn't get any better than this. The best pistons I could build using forgings fall decidedly short of this design. These pistons fall into the F1 class of piston. You do not have to order in standard, 0.010, or 0.020 oversize. These pistons can be available in any bore size you want in 0.001" increments!

The Complete Package Will Include the Following;
  • Eight billet 2618 aluminum pistons with pin fitting,
  • TotalSeal Ring set 1.5 x 1.5 x 3.0 mm
    • Ductile Iron Top Ring
    • Standard (non-gapless second ring)
    • Standard tension oil rings
  • Eight 0.866 x 2.500 x 0.180 wall H-13 Tool Steel Pins (if you want a heavier wall, it is also available)
  • Sixteen 0.866 wire locks (If you prefer Spirolocs, specify at ordering time)
  • Eight oil support rails.
That is the entire ModFords Terminator Piston Package. The actual part number is not yet established in the Gibtec computer system but will be very shortly. All you need to know to order is the bore size you want and the compression ratio you want; Gibtec handles the rest for you. You do not have to know about skirt cam, skirt thickness, ring package design or placement, valve reliefs, etc. The work has already been done for you.

The Price for The Entire Package is $1,138!

Remember, these are custom billet pistons explicitly engineered for our supercharged engines. These are not warmed over n/a forgings masquerading as blower pistons.

If you ever hurt one, you can order an exact replacement or an exact replacement 0.001 or 0.002, or 0.003 bigger and not have to step up for a whole new set of pistons. The shirts on these pistons are 0.200" thick; the rings are 0.280" down from the crown, the ring land depth, clearance, and finish have been optimized for the TotalSeal ring set. The piston you see with the (essentially) flat top will produce a 9:1 c/r with two country miles of PTV clearance on cams as big as 0.525" lift.

For those who would like a Moly coated dry lubricant on the skirts, you can add it for $160!

OK, guys, you finally have the ultimate blower motor piston expressly designed for our engines. :)

Say some words at me.
 

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