3.1 stroker? on boost?? ..anyone?

[4evere30]

hey everybody i was hoping i could get some clarification of what combination of pistons ill need to build a 3.1 l stroker m20 , also wondering how it will do with boost? im tired of the 2.5 in my car now , although the turbo is fun , i want more power down low
i already have
- Super eta head
- o-ringed "eta" block
- o-ringed "i" block
- m54 3.0 crank
- "eta" crank
- "i" pistons
- "eta" pistons
- 25lb ford injectors
- Holset he351cw
- ebay turdblo manifold
i really dont want to buy any more pistons if i dont have to , or do i ? ;D

[DesertBMW]

im tired of the 2.5 in my car now

I probably want to say tired of M20. With 24v engines being cheap now, I would not even think about M20 3.1L. Even non vanos M50 is better than M20 3.1L.

[digger]

I probably want to say tired of M20. With 24v engines being cheap now, I would not even think about M20 3.1L. Even non vanos M50 is better than M20 3.1L.

lol,

[einstein57]

25# injectors aint gonnah cut it. There is a local with a 3.1L turbo vert. I've been helping him sort it out. Its a high CR FTL but it has torque everywhere. Your gonnah need custom pistons to not have a high CR

I probably want to say tired of M20. With 24v engines being cheap now, I would not even think about M20 3.1L. Even non vanos M50 is better than M20 3.1L.

I'd rather have a freshly built m20 then a used tired s52.

[MR 325]

hey everybody i was hoping i could get some clarification of what combination of pistons ill need to build a 3.1 l stroker m20 , also wondering how it will do with boost? im tired of the 2.5 in my car now , although the turbo is fun , i want more power down low
i already have
- Super eta head
- o-ringed "eta" block
- o-ringed "i" block
- m54 3.0 crank
- "eta" crank
- "i" pistons
- "eta" pistons
- 25lb ford injectors
- Holset he351cw
- ebay turdblo manifold
i really dont want to buy any more pistons if i dont have to , or do i ? ;D

To build a 3.1L you need go go 1mm bigger with custom pistons along with a S52 crank. You can still boost a 3.1L if you go with something along the lines of 8.5:1 up to 9:1 compression. If you want a potent NA engine go with 10:1. A good affordable and robust set of rods to use would be S52. As far as your head, if it's a Super Eta head it is the 885 casting which is good BUT you need to get either dual i valve springs or performance springs in there along with a nice cam to wake things up.

I probably want to say tired of M20. With 24v engines being cheap now, I would not even think about M20 3.1L. Even non vanos M50 is better than M20 3.1L.

Do you ever post advice that makes sense?

[JCarp90]

^ lol matt

[4evere30]

Thanks for the replies so far ..So do I need to bore 1mm over and get new pistons to build this? Or is that just if I want a suitable cr for boost? What are some good cheaper options for pistons if I need em?

[downforce22]

you can get 84mm custom pistons and and m54b30/ s52 crank / spacer and its a drop in fit. I've heard 85mm bore leaves too thin of walls but can't confirm.

If you are going cheapo use the m20b27 crank with eta pistons and make a 2.7 stroker with the 885 'i' head. That is the cheapest option.

[4evere30]

I'm aware of the 2.7 stroker combo but that doesn't really appeal to me for effort of a bottom end rebuild , so to use the 3L crank I HAVE to bore the block and get custom pistons then?
Suggestions on good pistons for this?

[einstein57]

No effort. You go to the yard and grab a super eta block and just replace the rod bearings. Slap on your head and your done. $200 build that can be completed in 1 day. Either that or spend $2k on a proper bottom end build. Your choice.

[acolella76]

I'm aware of the 2.7 stroker combo but that doesn't really appeal to me for effort of a bottom end rebuild , so to use the 3L crank I HAVE to bore the block and get custom pistons then?
Suggestions on good pistons for this?

You don't HAVE to bore the block anymore, you will still be at 3.0L (2979cc) with 84mm bore, but you will still need custom pistons because of the change in stroke. Since you have to use custom pistons anyways it would be pointless to not go to a bigger bore, IMO. 85mm will yield you a 3.1L M20 and 86mm will yield you 3.2L, although I hear the cylinder walls are dangerously thin for boost at 86mm.

[SkiFree]

You don't HAVE to bore the block anymore, you will still be at 3.0L (2979cc) with 84mm bore, but you will still need custom pistons because of the change in stroke. Since you have to use custom pistons anyways it would be pointless to not go to a bigger bore, IMO. 85mm will yield you a 3.1L M20 and 86mm will yield you 3.2L, although I hear the cylinder walls are dangerously thin for boost at 86mm.

Well put, saved me 5min. typing the same thing.

[digger]

its probably possible to find pistons from another engine and machine the crown down but seems like a pita.

i think alot of the swedes use 86mm for boost so it cant be that "dangerous" but with boost there is no need to push the envelope as far as bore goes

[SkiFree]

i think alot of the swedes use 86mm for boost so it cant be that "dangerous" but with boost there is no need to push the envelope as far as bore goes

I've had a number of sweds who have regretted going that big on an non-inspected block. Basically, due diligence is necessary when going over 85mm.

[4evere30]

well then maybe ide rather just go will a 3.0l then and save myself the $$ for bore/bigger pistons ,one more question.... anyone know of another car that would have pistons that will work for a 3.0 M20? m54/s54 pistons work right?
but anything else?

(DAMN I WISH I TOOK THE PISTONS WHEN I GRABBED THAT M54 CRANK!!)