M20 Autowelt Pistons + .50mm oversized. Who has used this

[Motorsport1207]

Considering these EBay Autowelt pistons for my M20 build that is not $600 + What do you guys think. Compression 9.4:1 Any other suggestions for oversize that won’t break the $600 mark https://www.ebay.com/itm/193054916799 Thanks in advance Sent from my iPhone using Tapatalk

[digger]

Toftt

[Motorsport1207]

Toftt

Hi Is that a brand of Pistons Thanks Sent from my iPhone using Tapatalk

[digger]

Hi Is that a brand of Pistons Thanks Sent from my iPhone using Tapatalk

Nah, google it

[Motorsport1207]

Nah, google it

Not sure I am quite up to doing that. Thanks for the offer Sent from my iPhone using Tapatalk

[digger]

Not sure I am quite up to doing that. Thanks for the offer Sent from my iPhone using Tapatalk

Wwhat i mean is you are going to have to take one for the team and test them out. there are few members from that part of the world so they are not common and hence unlikely to find a user here. It is certainly an interesting find.

There was thread here not that long ago (within the last year) where someone said there were sets of OE for like $500 with rings so that sounds like a better option if the prices are still cheap and pistons are sre still available

https://www.ecstuning.com/b-mahle-pa...251735758~mah/

cheap price but these are 8.8:1 and need a couple mates to help you get 6

[D.Martijn]

A friend of mine went with these, he did a trip over 2500km long after just braking in the rebuild engine. so far so good..

[Motorsport1207]

Thanks. Best price in finding now for Mahle + .5mm oversized is $550 w rings. I have 5 M20 blocks and it seems that all these blocks bores are way out factory spec. +.0009 to + .0032. ( not surprised) Still have to measure pistons, I think I may still be within piston clearance limit of .0047” let me finish up all measurements and then I will decide. Ultimately I want build the first one with a set of oversized pistons +.5mm and get back to that factory spec of piston clearance limit of .0004” to .0016” i know this only applies to OEM pistons. Non OEM may have different clearances Thanks Sent from my iPhone using Tapatalk

[Motorsport1207]

What is the difference between these 2 M20 pistons. The one without the curved skirt is a Mahle, what is the other Sent from my iPhone using Tapatalk

[digger]

Could be a Mahle as well or a KS (Kolbensmidt).
Difference is the mass optimisation and clearance to counterweight. Neither will be a big deal on a M20b25 as long as all 6 are the same. On a stroker 2.7/2.8 the bottom style is preferred less likely need to grind skirts away

[Motorsport1207]

Thanks for the good information Sent from my iPhone using Tapatalk

[ForcedFirebird]

Toftt

LOL Seems like I'm the Guinea Pig.

Aside from that punny, Digger is correct. There are a few different part numbers for the b25 pistons. The real early ones have very long/even skirts, then you got the curved skirts, finally they all had short skirts.

I got a set of those pistons after a PM about them. They are currently in the spare race motor that had to get swapped in the car a few weeks ago during a 14hr. They have done about 9hrs of racing so far with no ill effect, but time will tell. We break the motors often for preventative maintenance.

While the pistons seem like a good deal, they don't come with rings. Decent rings are about $30 per hole, plus the $250 puts you ate $430. Not a huge savings over Mahle with the ECS sale (they are usually about $90/ea). Honestly, if you are rebuilding an engine properly, $200 in the grand scheme of things is a drop in the bucket. The only nice thing, is these are available in the 9.4:1.

[Motorsport1207]

LOL Seems like I'm the Guinea Pig. Aside from that punny, Digger is correct. There are a few different part numbers for the b25 pistons. The real early ones have very long/even skirts, then you got the curved skirts, finally they all had short skirts. I got a set of those pistons after a PM about them. They are currently in the spare race motor that had to get swapped in the car a few weeks ago during a 14hr. They have done about 9hrs of racing so far with no ill effect, but time will tell. We break the motors often for preventative maintenance. While the pistons seem like a good deal, they don't come with rings. Decent rings are about $30 per hole, plus the $250 puts you ate $430. Not a huge savings over Mahle with the ECS sale (they are usually about $90/ea). Honestly, if you are rebuilding an engine properly, $200 in the grand scheme of things is a drop in the bucket. The only nice thing, is these are available in the 9.4:1.

Thanks for the feedback. For the Autowelt. What piston to wall clearance did you go with. BMW design .0004 to .0016” No one has been able to tell me if these pistons comes with a tech sheet that calls out a different clearance other than OEM. Sent from my iPhone using Tapatalk

[Tinkerer007]

ForcedFirebird any update on your experience with these pistons?
I am buying some...
Any recommendation on rings for these?

[Tinkerer007]

My pistons showed up today. I didn't order rings because I thought that was a generic part. But it has been more difficult than I thought, and they are more expensive than I thought.

Any advice on how to measure the dimensions of where the rings go? The top two lands(?) are narrower than the pin end of my digital caliper (~2.1MM), so not sure how to measure the depth.
I think I can stack feeler gauges to measure the height.

Do you think the rings would be same as used on a stock BMW piston?

Any recommendations on what rings to get?