Exotic-metal55

I found my weights on the Mahle forged pistons Vs stock and some other specs as well.

We custom machined to size a lot thicker wrist pin (pin that goes through piston), to add more strenght but still keep the rotating assembly light.. The stock pin is a lot longer than the Mahle pin and pretty thick but not up to the new HP levels of these engines. Threw out the Mahle supplied pins and clips, as not thick enough and better clips out there than thier off he shelf stuff. Stock pistons are also made by Mahle but of the mass produced quality. from. .

Mahle piston on right and Stock left. Mahle also has a thinner secondary and oil rings and a added anti-detontaion groove. Extra oil ports as well, shorter coated skirt and lot of other race features.



Stock piston and wrist pin weight 557 grams



Mahle piston without pin . 395 grams and depending on pin used, can be up to two ounces lighter per piston. So depending on wrist pin used, balancing is a must.

e55amgrocket

After talking with Mahle i was told the dish of the SLR piston is smaller. Did you CC it by chance? Wondering if i was given the correct CC's or not.

Sir-Boost-a-Lot

iTrader: (1)

Nice! 395 grams is a light piston for that diameter. Are those factory SLR pistons or something made as an aftermarket upgrade?
I personally wouldn't bother with the wrist pin on that application because if the power levels were to get high enough to tweak a wrist pin, the high silicon alloy the pistons are made from will shatter first. Neither scenario is likely however for this use, and the thicker wrist pin definitely won't hurt anything except for adding a little weight.
It's just pointless weight IMO like putting super heavy duty drive axles in a car running street tires. The car would blow the radials up in smoke way before it hurt the stock axles

Exotic-metal55

Factory pin wall was like 5mm and we went a little more to 6.5 mm per side as I recall, since they had to be changed anyway. You can save about 2 ounces per piston, depending on what your level of wrist pin wall thickness level is. The pistons in the picture are SLR "style" or as you say, factory upgraded for stock Alusil wall bores. The pistons in the darton sleeve blocks are a little different. Notice the heavy webbing under the piston and assume that allowed the shorter wrist pin.


Steve, did not CC those pistons in the picture but have also seen some specs with wrist pin center`s being higher than stock and top rings can also be lower.

layzie12g

I'm assuming these are a 4032 forging.

How much will a set run?

When will someone get a hold of Scat to get a set of rods to them so they can work their magic and give us an affordable forged rod?

Sir-Boost-a-Lot

iTrader: (1)

For the extremely low volume, I'd be surprised if they were interested.

A better choice might be using an off the shelf Honda rod, since the crank shares the same 1.888 journal size, and have custom pistons made to work with the compression height dictated by the length of the available rod. The factory AMG rod is 5.85 inches IIRC and theres a little room to go longer with the rod if the ring pack is squeezed tighter, and room to go shorter at the expense of a little rod/stroke ratio(no biggie at these RPMs)

The stock AMG rod with bolts and upper pin bushing, but no lower bearing shells weighs 547g. Being forged and of a cracked cap design, I think these are stronger than you might assume. The bolts are a joke however, but would be less of a joke with those 395g pistons Brooke pictured above swinging on the top of them as opposed to that stock anvil.

e55amgrocket

Yea the rod itself is strong but the bolts like you said are a joke. I tossed around the idea of swapping the bolts but figured I just get better rods made and not worry about it. There's .041" of material left between the bearing and the bolt hole so that crossed the idea of going bigger off also. We Didnt want to squeeze the ring package any tighter and added some height to the piston on mine. Also went with a steel top ring and a ductile Napier 2nd ring so that should work well with the darton sleeves. Hopefully I will have them tomorrow to take some close up shots and and measurements.

Brooke- any idea what ring package they come with?

Exotic-metal55

It seems we both come from LSX roots. Yes, we have measured and looks like we can turn these darton blocks into a LSX bottom driven engine with honda bearings. Few small hurdles but is doable.

I totally agree on the rod stenght and cold cracked /fitted rods can take a lot and it is rare to see an AMG rod bent , even with all the engines that have detonated. We had custom rod bolts made to add a little more strenght but was not to worried wither way, at under 7K rpm engines. We are hitting the rod cap seat with a 90 deg , to allow a little more space for new bolts.


Steve, I have check again on the ring specs for the new piston but they are the top of the line Total seal rings. I checked at ordering and recall top being steel and then napier set up as well. Ours will be in soon as well.

e55amgrocket

Still going to stay under 7k? If I was going with a stroker I would but I really want to zing it some. We spent a lot of time on the heads and valvetrain so I think rpm will help a lot with my build. As soon as we measured the crank last April and found out it had 1.888 journals I was in heaven . As for the bottom end we didn't worry about weight at all kinda just let things fall where they did without trying to go as light as possible. Can't wait to see what everyone does with these engine builds now.

Exotic-metal55

Plan to stay right at 7K range with the power curve the engine will have but things can change. Want the tranny and other parts to live for a while and feel that is a good RPM to keep the shifts at and not tax the tranny to hard. Will be nice to see all the new builds and eventually, we will all be building super strong custom tranny`s as well. Someone may even do a powerglide at some point.

Sir-Boost-a-Lot

iTrader: (1)

That's disgusting.

GT-ER

That is serious webbing...love it.

BC928

Alex L

You can order the pistons via Ultimate Performance. I believe they were the original customer that ordered them from Mahle Motorsport.

Those pistons do have a little issue though. It is to do with size of the oil ring so personally I'd just send a stock piston to any of the many manufacturers and get them to make you a set.

BC928

Thanks Alex. What is the issue with the Oil Ring?