Lets Start a Custom Pistons Specs thread for Different Stroker Combos

[Overlord475]

Hey guys,

Lets try to get a thread going that contains all the specs needed for custom forged pistons for various crank / rods combos for our M20 stroker projects.

Lets state the following:

Top design (Flat, Dome, Crown)
Piston Bore Diameter
Skirt Length
Pin Height Position
CR For Given Specs

We all know the 2.7I combo

Crank: ETA / 324td (81mm Stroke)
Rods: ETA (130mm)
Bore: 84mm (Stock)
Pistons: 1988 SETA



Now for the Crank / Rod Combos

2.8L

Crank: ETA / 324td (81mm Stroke)
Rods: ETA (130mm)
Bore: 86mm

Crank: M52 (84mm Stroke)
Rods: ETA (130mm)
Bore: 84mm (Stock)
Pistons: Can use stock 325i pistons

Crank: M51D25 (82.8 Stroke)
Rods: m20b20 (130mm)
Pistons: Can use stock 325i pistons (machine skirts down ~14mm)

2.9L

Crank: M52 (84mm Stroke)
Rods: ETA (130mm)
Bore: 86mm

3.0L

Crank: S50 (85.6mm Stroke)
Rods: S50 (135mm)
Bore: 86mm

Crank: S52 (89.6mm Stroke)
Rods: S50 (135mm)
Bore: 84mm (Stock)

3.15L

Crank: S52 (89.6mm Stroke)
Rods: S50 (135mm)
Bore: 86mm



This way we don't each have to call MM and get stuck on the phone for 3 hours at a time, ha ;)

This should be a great help when ordering custom pistons


**** Let me know if I got something wrong or more info needs to be added / requested

Thanks guys!

[MonkeyMadness]

3.0L

Crank: S50 (85.6mm Stroke)
Rods: S50 (135mm)
Bore: 86mm

Crank: S52 (89.6mm Stroke)
Rods: S50 (135mm)
Bore: 84mm (Stoke)

Oh so Sexy.... CR?
this is all on M20B25 block and head?

3.15L

Crank: S52 (89.6mm Stroke)
Rods: S50 (135mm)
Bore: 86mm

Interested in more info on these PLease....
Are these N/A motors...?

Makes me Wish I was into N/A and not Boost...:-(

[Larsinnj]

For 2,8

Crank: M51D25. Forged aswell. Don't know if it is forged on petrol M50.
Rods: m20b20 130mm
Pistons: Stock late model m20b25 with cat. Need to machine of the skirts.

I'm running this setup. I took off 14mm from the underside of the pistons.
Runs well. :)

[tinkerputzer]

Page 4 of the MM PDF gives you a lot of good info for the different combination's available.

http://www.metricmechanic.com/pdfs/metric-mechanic-m20-engine-booklet.pdf

[Overlord475]

For 2,8

Crank: M51D25. Forged aswell. Don't know if it is forged on petrol M50.
Rods: m20b20 130mm
Pistons: Stock late model m20b25 with cat. Need to machine of the skirts.

I'm running this setup. I took off 14mm from the underside of the pistons.
Runs well. :)

Nice! What is the stroke of that crank; 84mm?

[Overlord475]

Oh so Sexy.... CR?
this is all on M20B25 block and head?



Interested in more info on these PLease....
Are these N/A motors...?

Makes me Wish I was into N/A and not Boost...:-(

Yes, all of these NA stroker set ups are on the stock b25/b27 M20 blocks.

Everything above the 2.8L M52 crank set up requires custom pistons however in order to move the pin position high enough that there is no piston/valve clearance issues.

[XvillainousX]

Crank: M51D25 (82.8mm stroke Stroke)

[Overlord475]

Crank: M51D25 (82.8mm stroke Stroke)

Thanks. List updated....

[Larsinnj]

14mm sounds like a lot to machine of the pistons, but it works great. They are a little lighter aswell, but don't know if that matters.

Here is a pic of my pistons after they were machined. There is a little ring running around the inside of the skirts. I just took off the goods to that ring. :)
They got a real clean before going into the engine again. :)

[MonkeyMadness]

Question:
Ok so if I'm doing my math right and reading this here and at MM correctly..
The block M20B25 "I" and "E" that's stock at 84mm or 3.428" bore
can tack a hoging out or boring out to 86mm or 3.510" bore
If i'm not wrong that's a cut of .082 on the cylinder walls?

Now I must let you all know I have never built an M20 motor
so I'm not privy to this info...

thanks..

[MonkeyMadness]

Crank: M52 (84mm Stroke)
Rods: ETA (130mm)
Bore: 84mm (Stock)
Pistons: Can use stock 325i pistons

Need more info on this build setup..
I just happen to have a buddy sitting on an m52 crank
So i getting it tomorrow from him..
Any info would be helpfull

[Overlord475]

Crank: M52 (84mm Stroke)
Rods: ETA (130mm)
Bore: 84mm (Stock)
Pistons: Can use stock 325i pistons

Need more info on this build setup..
I just happen to have a buddy sitting on an m52 crank
So i getting it tomorrow from him..
Any info would be helpfull

Using the M52 84mm crank you will need a crank spacer for the front of the crank so that oil doesn't poor out. One can be bought from IE for $60.

Here is a guy on e30tech selling a good set of ETA rods at a great price:

http://www.e30tech.com/forum/showthread.php?t=101320

This crank and rod combo will set your pistons 0.5mm lower than stock.

If you're going to rebuild your motor I would do it right and not re-use used b25 pistons. I would at very least go with a set of MaxSil 84.5mm bore pistons. They're brand new and should give a nice ~9.8:1 CR when the block is planed down the needed 0.5mm.

Even better would be to go with a set of custom forged pistons provided by JE, Metric Mechanic, or IE. This will allow you to use longer rods (example: S50 135mm) for a better rod to stroke ratio and will be much lighter. The rods will also be lighter (~100g less).

This 135mm rod and 84mm crank combo will set your stock piston 4.5mm higher then stock so at this point custom pistons are a must.

With custom pistons you can also go with a larger bore and whatever CR you'd like.

Here is a great engine displacement calculator:

http://www.nightrider.com/biketech/calc_displacement.htm

You could go with 86mm pistons which would give you ~2928.84cc (a true 2.9L)


FYI: this is the set up I'm using. M52 crank, JE pistons, and S50 rods. Though I am going with 85.5mm pistons to help with motor longevity

[Justin B]

Buy the metric mechanic oil spacer, its more expensive but is actually a nice piece, not a chinese made piece of garbage. There was a thread around somewhere, maybe on the 'tech, and they tried to use that IE spacer, and gave up on it. Machining marks were terrible and it actually got stuck on the crank trying to remove it because of them. Steer clear.

[MonkeyMadness]

3.0L

Crank: S52 (89.6mm Stroke)
Rods: S50 (135mm)
Bore: 84mm (Stock)

3.15L

Crank: S52 (89.6mm Stroke)
Rods: S50 (135mm)
Bore: 86mm

Old a dead thread but I have a question hopfully some one can answer it for me....?

Can I sub the crank for the above builds with a M54B30 Crank
it has the same stroke 89.6mm??

I've also heard they are one in the same? Is this also true...?


thanks

[The Humjet]

I'm pretty sure you can. Actually I've heard the s52b32 and m54b30 cranks have the same part numbers. Obviously you'll need to do some machining on the counterweights and piston skirts to fit this sort of crankshaft.