R3VLimited Forums

Go Back   R3VLimited Forums > E30 Technical Forums > Engine & Drivetrain > M20

Reply
 
Thread Tools
Old 01-10-2017, 05:46 PM   #16
digger
No R3VLimiter
 
Join Date: Nov 2005
Location: Sydney, Oz
Posts: 3,655
in that case with MS and possibly ITB then yes that is the direction id be looking. , otherwise a 284/272 is still a good all round street cam but it gives up some topend due to the smaller exhaust duration (not much use bringing in air and fuel if you cant get it out efficiently)

i ran a catcams 298/285 as a daily driver inc A/C with OEM intake for a few years in bigger engine (bigger engine keeps things a little tamer compared to a smaller engine), and with standalone it was perfectly fine, drives better on ITB though .
__________________
89 E30 325is Lachs Silber - currently M20B31, M20B33 in the works...

new build thread http://www.r3vlimited.com/board/showthread.php?t=317505

digger is offline   Reply With Quote
Old 01-10-2017, 06:16 PM   #17
zaq123
Grease Monkey
 
Join Date: Jul 2016
Location: NE
Posts: 317
Quote:
Originally Posted by ForcedFirebird View Post
I wouldn't turn the crank, I have always stayed away from under sizing them - specially on a 2.8, IMO when stroking an m20, you are creating a horrible R/S ratio and don't need any more of a failure point. I have always just had the journals polished, and scrap the ones that need a .010" under - I wouldn't even consider a .025" under.

The m52 crank does not need a lot of meat removed with the flat bottom short skirt pistons. The two center throws are larger than the rest. They will need about 5-6mm (guessing) and the outer ones will only need a 1-2mm. $450 to cut and balance the crank isn't overly expensive if you don't have it ground. I have actually notched the piston skirts just enough to clear the throws and left the m52 crank full circle, so that's an option too (this was with Mahle +.5mm stock replacement pistons)

BMW has extremely tight piston to wall clearances with a 83.98mm piston and 84mm bore (.01mm per side ~.0004", 4 tenths of a thousand of an inch - 1/10 the thickness of human hair). I have rarely have seen a decently kept m20 go out of round, and usually show sign of almost no wear. If you can see the cross hatches still, you will probably get away with a deglaze, we tend to go over size more for the added compression and small bump in displacement. Have your machinist measure to confirm.

Since you already have the crank, $450 for them to prep it up, spend $600 on +5mm OEM pistons, have the rotating assy balanced (~$250 here locally), and whatever your bore/hone is going to cost ($250 here), and take .010" off the block deck ($120 here). This will give you a very strong m20 for not a lot of money. I prefer to recondition the stock rods as they are seasoned and really strong already. If you use aftermarket rods, make sureyou have them checked for round and use the ARP 2000 stamped bolts. A lot of rod companies use the cheapest ARP, so you may need bolts and a big end resize even if they are aftermarket.

I wouldn't trust used stock springs unless they are tested for stiffness, never mind for a cam with extra lift. New OEM springs may be suitable for the 288, but if that's the minimum suggested, that's too close for my comfort.

Finally, shoot for a .045" head to piston clearance. The m20 really likes this number for some reason.
Thanks for your take on it, sounds like a pretty solid logic. I've seen +.5 pistons and was considering them as a replacement for my possibly tired 160k pistons. All in all...do you think extra 0.5mm (85mm total with IE/Mahle), deeper valve pockets (no interference with the larger crank) and an opportunity to leave pistons as is ( no notching etc) is worth extra $600? ..... $600 looks like $0 cam + a head gasket.... Hmm My biggest concern is ...in order to leave the crank alone, I have to mess with the pistons and that $600 margin can shrink to $400-300-200 very quick.
zaq123 is offline   Reply With Quote
Old 01-11-2017, 03:49 PM   #18
digger
No R3VLimiter
 
Join Date: Nov 2005
Location: Sydney, Oz
Posts: 3,655
Quote:
Originally Posted by zaq123 View Post
Thanks for your take on it, sounds like a pretty solid logic. I've seen +.5 pistons and was considering them as a replacement for my possibly tired 160k pistons. All in all...do you think extra 0.5mm (85mm total with IE/Mahle), deeper valve pockets (no interference with the larger crank) and an opportunity to leave pistons as is ( no notching etc) is worth extra $600? ..... $600 looks like $0 cam + a head gasket.... Hmm My biggest concern is ...in order to leave the crank alone, I have to mess with the pistons and that $600 margin can shrink to $400-300-200 very quick.
A good 84mm OE set and good block will also be fine
__________________
89 E30 325is Lachs Silber - currently M20B31, M20B33 in the works...

new build thread http://www.r3vlimited.com/board/showthread.php?t=317505

digger is offline   Reply With Quote
Old 01-12-2017, 10:52 AM   #19
ForcedFirebird
R3V Elite
 
ForcedFirebird's Avatar
 
Join Date: Feb 2007
Location: WOT-Tech, Florida
Posts: 4,882
Quote:
Originally Posted by digger View Post
A good 84mm OE set and good block will also be fine

Yup. As I said earlier, the extremely thigh OEM tolerance of the m20 has proven to me to hold for a long time. I would just have the machinist measure before doing anything.
__________________
-john "If you can't afford to do it proper the first time, what makes you think you can afford to do it again?"


WideOpenThrottleTech@gmail.com

Facebook
Instagram
YouTube
ForcedFirebird is offline   Reply With Quote
Old 01-12-2017, 11:58 AM   #20
zaq123
Grease Monkey
 
Join Date: Jul 2016
Location: NE
Posts: 317
I think I'm going with new 85mm pistons and 135mm rods. Better R/S ratio than 130mm and no 160k mile pistons. After all....this is supposed to be a project

Any reason to go IE/Mahle vs custom JE for $200 more? Also looks like schrick and dbilas cam is about the same price.. The head has new OEM springs: should I go with dbilas 284/284 or schrick 284/272? I trust schrick but do not know much about dbilas cam.
zaq123 is offline   Reply With Quote
Old 01-12-2017, 04:00 PM   #21
digger
No R3VLimiter
 
Join Date: Nov 2005
Location: Sydney, Oz
Posts: 3,655
Quote:
Originally Posted by zaq123 View Post
I think I'm going with new 85mm pistons and 135mm rods. Better R/S ratio than 130mm and no 160k mile pistons. After all....this is supposed to be a project

Any reason to go IE/Mahle vs custom JE for $200 more? Also looks like schrick and dbilas cam is about the same price.. The head has new OEM springs: should I go with dbilas 284/284 or schrick 284/272? I trust schrick but do not know much about dbilas cam.
The mahle are coated for protection against galling during run in, and for lower friction. They also have a nicer design particularly the skirts so they should be a bit lighter and stiffer.

JE can do the OEM dome shape (if you use the right dealer) but canít do equivalent skirts as the Mahle with 4032 alloy, they donít have the forgings for it. They give you the full skirt when you order a 4032 alloy. This in itself is not a big deal but the direction the industry is heading more and more is a non full skirt so there are advantages with this.

If you order 2618 JE can do the FSR skirt but it costs more anyway, especially if you get their skirt coating. The different alloy that comes with FSR skirt is better suited for FI or race applications and less ideal for a street engine that you want to cover a lot of miles and do lots of cold starts like something that gets driven multiple times a week experiences.

The rings from Mahle will probably be better, if I was to order a set of rings for a set of JE id be looking for total seal conventional sets not the standard JE ones that come with it, this will also cost moreÖ.

The advantage of the JE is they are a true custom piston as opposed to an off the shelf design, this means you could spec them in larger bore like 86mm, or for even bigger crank, higher CR, deeper pockets for big overlap cams for negligible extra cost. This might not be an advantage for you since you are using a specific crank and for a mild build, and the Mahle are basically ideally matched for this exact build anyway.


Quote:
Originally Posted by zaq123 View Post
The head has new OEM springs: should I go with dbilas 284/284 or schrick 284/272? I trust schrick but do not know much about dbilas cam.
i know a guy who used dbilas 276, works well and quality seems on par with schrick
__________________
89 E30 325is Lachs Silber - currently M20B31, M20B33 in the works...

new build thread http://www.r3vlimited.com/board/showthread.php?t=317505

digger is offline   Reply With Quote
Old 01-12-2017, 04:55 PM   #22
ForcedFirebird
R3V Elite
 
ForcedFirebird's Avatar
 
Join Date: Feb 2007
Location: WOT-Tech, Florida
Posts: 4,882
Don't forget forged pistons usually require .003"-.004" (.0762-.1016mm) clearance for expansion, so they are slapping until warmed up. This is 5x that of a stock m20 piston. They will also be heavier.

The Mahle pistons are very high quality. I have abused them pretty decently, even in turbo builds and haven't had any more issue that with forgings. I have yet to break a ring land, but have burned/broke holes though them when losing a valve under boost :/
__________________
-john "If you can't afford to do it proper the first time, what makes you think you can afford to do it again?"


WideOpenThrottleTech@gmail.com

Facebook
Instagram
YouTube
ForcedFirebird is offline   Reply With Quote
Old 01-12-2017, 06:12 PM   #23
digger
No R3VLimiter
 
Join Date: Nov 2005
Location: Sydney, Oz
Posts: 3,655
its more clearance but 4032 alloy JE (SRP) "only" require (0.0020-0.0025") clearance for NA (same as what MM spec on the wiseco slugs they sell dependent on application e.g. street, rally, race, FI a) its the 2618 alloys are normally 0.0030-0.0035" or more for FI

For the IE Mahle MS its going to be much the same as the 4032 alloy because that is basically what it is from a thermal point of view, these are the kind of alloys almost all OEM use when they use forged slugs on mass production. OEM like to run them tight to keep emissions low during warmup and reduced noise as the more the piston rocks the worse it seals, at operating temp there isnt any practical difference worth worrying too much about. also you can ask for pin offset to make them run quieter, the mahle MS will have offset most likely.

the stock pistons can and are usually run tighter, they have metal bands brazed into them to help control expansion despite having similar silicon content and thermal expansion coefficient as the forged 4032 plus i gather more R&D was done during development to work out how the piston behaves in terms of temperature profile in the engine and adjusting the ovality and taper of the barrel to suit. Still The more likely you are to put heat into them the more clearance you should run to avoid scuffing. From memory OEM s50B32 euro cast slugs are quite loose 0.0014" or there abouts as they see much more heat than the average engine

so yes aftermarket forged pistons will be run looser when cold and warmup but its not a huge issue with the right alloy (high silicon) 4032 as its minimized somewhat,

As for weight (exc pin, rings, locks) stock are ~370-410g ish depending on version, forged should be around mid to low 300 grams depending on bore and comp height i dont have a set of pistons for a 2.8L to weigh, the light stuff (long stroke engine, stroker pistons) can be into the high 200's so forged should be alot lighter.

anyone technically minded interested in piston tech should read this, probably the best source of information you will find

https://www.fsb.unizg.hr/miv/MSUI/Ko...ubner-2012.pdf
__________________
89 E30 325is Lachs Silber - currently M20B31, M20B33 in the works...

new build thread http://www.r3vlimited.com/board/showthread.php?t=317505


Last edited by digger; 01-13-2017 at 03:01 PM.
digger is offline   Reply With Quote
Old 01-12-2017, 07:44 PM   #24
zaq123
Grease Monkey
 
Join Date: Jul 2016
Location: NE
Posts: 317
Quote:
Originally Posted by ForcedFirebird View Post
Don't forget forged pistons usually require .003"-.004" (.0762-.1016mm) clearance for expansion, so they are slapping until warmed up. This is 5x that of a stock m20 piston. They will also be heavier.

The Mahle pistons are very high quality. I have abused them pretty decently, even in turbo builds and haven't had any more issue that with forgings. I have yet to break a ring land, but have burned/broke holes though them when losing a valve under boost :/
FF, thank you for your crank seal spacer, got it today. Haven't tried to install it yet. Was it designed as an interfearance fit? Any tips on the installation?

I ordered 135mm rods today so I'm pretty much committed to the aftermarket pistons at this point.

Gents,

I think I'll go with DBilas cam.

Street car that will be used with the wide rpm range (not daily driver):
2.8L with pretty much stock head with new oem springs(except Supertech valves and HD rockers)
Megasquirt
Stock exhaust for now and stock intake (for a while)

What is the consensus on the cam: 276, 282/270, 284 ?

Last edited by zaq123; 01-12-2017 at 07:50 PM.
zaq123 is offline   Reply With Quote
Old 01-13-2017, 01:51 AM   #25
digger
No R3VLimiter
 
Join Date: Nov 2005
Location: Sydney, Oz
Posts: 3,655
284/284 should be pretty good IMO, 276 works well, i was very impressed how it performed, it wont have the same topend so its more of a torquey beast but its usually a tradeoff
__________________
89 E30 325is Lachs Silber - currently M20B31, M20B33 in the works...

new build thread http://www.r3vlimited.com/board/showthread.php?t=317505

digger is offline   Reply With Quote
Old 01-13-2017, 05:51 AM   #26
nando
Moderator
 
nando's Avatar
 
Join Date: Nov 2003
Location: bellingham, wa
Posts: 32,670
I don't know that the stock springs were ever considered suitable for the 288 - the 284/272, yes (if new!), but Schrick specifically states in their catalog that you need upgraded springs with the 288.

FWIW I put almost 100,000 miles on my 284/272 with new OEM springs and never had an issue.

Also in 10 years of my M20 stroker, I never had any piston slap or rattle or burned any oil (leaking is another issue lol). It has about 85,000 miles on it now. I ran clearances similar to what Digger posted above with the 4032 alloy MM pistons.
nando is offline   Reply With Quote
Old 01-13-2017, 07:30 AM   #27
zaq123
Grease Monkey
 
Join Date: Jul 2016
Location: NE
Posts: 317
Quote:
Originally Posted by nando View Post
I don't know that the stock springs were ever considered suitable for the 288 - the 284/272, yes (if new!), but Schrick specifically states in their catalog that you need upgraded springs with the 288.

FWIW I put almost 100,000 miles on my 284/272 with new OEM springs and never had an issue.

Also in 10 years of my M20 stroker, I never had any piston slap or rattle or burned any oil (leaking is another issue lol). It has about 85,000 miles on it now. I ran clearances similar to what Digger posted above with the 4032 alloy MM pistons.
I think we are talking 284/284 with new springs.....
Do you run ITB on your strocker or stock intake?
zaq123 is offline   Reply With Quote
Old 01-13-2017, 07:39 AM   #28
nando
Moderator
 
nando's Avatar
 
Join Date: Nov 2003
Location: bellingham, wa
Posts: 32,670
ITBs weren't really a thing when I built this - running the stock IM.
nando is offline   Reply With Quote
Old 01-13-2017, 08:45 AM   #29
whitebulat22
Grease Monkey
 
whitebulat22's Avatar
 
Join Date: Apr 2014
Location: Long Beach, CA
Posts: 305
Some weights from my maybe accurate home scale-

Mahle MS pistons- 310 g, 96 g per pin
M52 rods- 540 g
IE forged rods- 467 g

The cost was high for the pistons but I don't regret it. The 135 mm rods are a huge benefit imo because they're also a lot lighter than the shorter eta rods. Then the pistons are basically genuine BMW without the normal markup.

I vote for the 284 cam personally because I'm not seeing any complaints about drivability or loping from anybody running these cams. But with stock intake manifold it will be peaking just over 6000 rpm so the choice isn't going to make or break the powerband. With ITBs I bet there would be a noticeable difference.
whitebulat22 is offline   Reply With Quote
Old 01-13-2017, 09:51 AM   #30
SkiFree
R3VLimited
 
SkiFree's Avatar
 
Join Date: Jun 2011
Location: Fullerton, CA
Posts: 2,563
I weighed a 130mm oem "e" rod once and it came out to something like 633g. Heavy little sucker.
__________________
ADAMS Autosport

Last edited by SkiFree; 01-13-2017 at 10:12 AM.
SkiFree is offline   Reply With Quote
Reply

Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -7. The time now is 02:35 AM.


Powered by vBulletin® Version 3.8.10
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Copyright 2004 - 2020 R3VLimited LLC