Custom Pistons feedback - PeachParts Mercedes-Benz Forum

Tony H · #1 02-13-2019, 07:02 PM

Any one here had custom pistons made and what was your experience? The more I think about it I am considering having pistons made for my iron bock 5.6 project instead of using the 5.6 pistons with unknown properties. I think the $1000 or so is worth the peace of mind.

Frank Reiner · #2 02-14-2019, 10:52 PM

Quote:

Originally Posted by Tony H

Any one here had custom pistons made and what was your experience? The more I think about it I am considering having pistons made for my iron bock 5.6 project instead of using the 5.6 pistons with unknown properties. I think the $1000 or so is worth the peace of mind.

Tony,

After a bit of discussion of this with a shop I frequently work with, the starting point is to find rings in the diameter and widths that you want and which will be readily available. Total Seal and Nippon Piston Ring (NPR) may be able to satisfy your requirement. Once the ring package is specified the piston maker can proceed. If the rods are bushed with Ampco 45 the wrist pin diameter can be reduced to a common US pin size such as .927", which in this case would yield a .048" wall thickness pin bushing.

Generally custom forged pistons will be made in 2618 alloy which has very good strength, but which must be run with increased clearance. A few forging blanks are available in 4032 alloy, which is a high silicon content alloy and runs at smaller clearances. Possible piston makers are CP, JE, Wiseco, and Diamond.

Roncallo · #3 02-23-2019, 12:35 AM

I did a Ferrari 275 about 40 years ago with custom pistons. I forgot who made them. I believe it was a company called Aries or something like that. I used rings from a Ford Courier. It worked very well. The job was much simper back then as you didn't have as many choices. Today your specifications can run wiled with coatings and ring configurations. I wouldn't doubt you can get a set of custom made pistons cheaper than genuine OE pistons from MB.

Tony H · #4 02-23-2019, 03:01 AM

Thanks-New OE pistons are not an option-I still would not know if they are compatible with Iron cylinders-I need a custom solution or pistons that were used in a iron block engine. I am giving the Turbo Buick V6 pistons a fresh look. They would work with little modification and are the correct diameter-std size is 3.800" which is right where my finished cylinders are. Compression height is just slightly higher that what I need at 1.8". Pins are slightly smaller(.940") so I could have the pistons machined for the MB pins and retaining clips. They have a dish of similar shape and volume as the MB pistons. I ordered 1 piston to check out.

Tony H · #5 03-01-2019, 01:01 AM

The Buick pistons will be too much trouble-not enough left on top of the compression ring after machining for squish and other issues trying to adapt the rod to the piston. At least it only cost $5.00 to send it back. I guess I will be going with customs when the time comes.

rwd4evr · #6 03-02-2019, 12:16 PM

Have you considered using a stock piston with a custom rod instead?

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Tony H · #7 03-03-2019, 01:11 AM

Yea but that's deviating a little too much from what I had in mind. I already had my rods rebuilt so I would like to use them. Good idea though.

rwd4evr · #8 03-03-2019, 01:54 AM

So is it a worry about the cast iron spray coating in a cast iron block? I've never seen one out of the block so I've got no idea what it's like.

I've been thinking about putting the m119.960 bottom end and flat top pistons in a bored 4.5 block with 560 heads. High compression short stroke, good(or better at least) head flow. But then as soon as I nuke it I'm out a bunch of money. Lack of a great trans option too. Sadly I'm. Really considering just going LS. IM NOT recommending that for your coupe, but my drift car gets thrashed and run hot overrevved. The stock m117 does take a beating though. I will give it that. Maybe just throw the 3.5 heads on for a bit more punch. Sorry. Rambling.

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Roncallo · #9 03-03-2019, 08:41 AM

Quote:

Originally Posted by Tony H

Thanks-New OE pistons are not an option-I still would not know if they are compatible with Iron cylinders-I need a custom solution or pistons that were used in a iron block engine. I am giving the Turbo Buick V6 pistons a fresh look. They would work with little modification and are the correct diameter-std size is 3.800" which is right where my finished cylinders are. Compression height is just slightly higher that what I need at 1.8". Pins are slightly smaller(.940") so I could have the pistons machined for the MB pins and retaining clips. They have a dish of similar shape and volume as the MB pistons. I ordered 1 piston to check out.

I'm not sure if the OE pistons are compatible with the iron block. But if you speak to the piston makers they may be able to recommend the necessary changes to the piston required just as they do with ring grooves. You would probably want to give them piston to cylinder wall clearance for both an iron block and alloy block engine.

Tony H · #10 03-05-2019, 01:22 AM

The 5.6 pistons have some type of ceramic? coating so they will not scuff the aluminum cylinders and the pistons were designed to run in aluminum cylinders that expand twice as much as cast iron. So too many unknowns to risk it. When I started this project it was a low dollar upgrade to more displacement but I have put too much effort into it at this point to cheap out on the pistons. If I have pistons made the mfr will spec the bore size with the proper clearance built in, also my machine shop want's the pistons when they size the cylinders. I had the block bored for the 5.6 pistons but I will have to have it bored/honed again for the new pistons.

rwd4evr · #11 03-05-2019, 01:50 AM

From what I understand it is actually an iron coating of some kind, sprayed on. I'll see if I can figure out where I did see that.

Tony H · #12 03-06-2019, 12:42 AM

It is non ferrous. A rare earth magnet will not stick. I think it is some kind of ceramic composite coating. I have given up on the idea of using the 560 pistons-I have been uncomfortable with them from the beginning.
Some pistons had a tin coating that was a sacrificial break in coating-maybe that's what you saw.

rwd4evr · #13 03-06-2019, 12:50 AM

Is the alloy block or iron block required piston clearance larger? I know you've made up your mind, but isn't the alloy harder and would remove/damage the coating easier than the iron block? If it's non ferrous it won't gall either. How about a test on the coating? Maybe it's the best thing you can use��

Tony H · #14 03-06-2019, 01:42 AM

I'm sure the coating would be a benefit as it has a slippery feel to it and it is used in industrial engines. But uncoated pistons will run hundreds of thou mi. Mainly I am unsure of the running clearance. These engines run very tight piston/cylinder clearance and the alu block piston may have different expansion characteristics than pistons intended for iron blocks. In other words the pistons may expand enough to scuff the cylinders in an iron block-I don't want to take that chance. I had the block honed for .0015" clearance and even that is large but I was concerned at that time also.

Tony H · #15 07-03-2019, 03:32 PM

I finally decided to go with customs-too much to go wrong with the 5.6 pistons. I got a quote for less than $1000 for 2618 made to my specs. I will have to have my block honed but that is a given. (only a few thou for the customs). They come with new pins to my specs-I could have the pins made slightly oversize so the rods could be fit to them. They will design the dish based on the sample I send them. They can also design to the 5.6 piston weight so I don't need to get the engine balanced.