Author Topic: Help required 2.1 stroker (Read 13646 times)

bigdogcb · « **on:** August 25, 2012, 05:01:21 AM »

Hi all,
OK, I have several components ready to start the build of an M42 stroker, but I need some advise, and I hope someone out there can assist.
I have STD M42 block and head, the correct M47 long nose crank, 3.2 M3 pistons and rods. The questions I have are as follows:

1. what main bearings should I use for the M47 crankshaft?
2. What con rods should I be using with the 86mm 3.2 M3 pistons and the M47 crankshaft?
3. What height should the pistons be reduced by to obtain a near STD compression ratio?
4. What should the block be bored to in order to accept the 86mm 3.2 M3 pistons?

If anyone has this info then I would apreciate a little assistance.
Thanks in advance.

Warsteiner · « **Reply #1 on:** August 26, 2012, 08:48:48 AM »

There are so many thing that have to be thought about before you take on this project.

Are you doing all of the work yourself? Who is doing the math for the compression ratio? It's not as simple as cut the deck of the piston X and you'll have Y compression. Other factors are very important.
Where are you located? Are there shops in your area familiar with the M42?
Is this a complete rebuild? Are you rebuilding the head as well? Maybe even porting it? If you don't have a friend in the business this can get very expensive.

I can answer all the questions you listed but are they euro pistons?
1. Stock M47 mains or your choice of some special ones.
2. Best length to not have to deck the piston much is a 138mm rod, and the 3.2 piston is 86.4
3. This is where your math comes in. I wouldn't do stock compression. You're leaving horsepower on the table. Lots of variables from head gasket to dishing the piston to piston compression height etc.
4. Usually it's stamped right on the piston. Clearance I believe is around .04mm

This is an awesome project but you need people involved that are familiar with building engines. There is a lot of thought that goes into an engine like this.
For instance.... Cams? Exhaust? Inj's? Valves 6 or 7mm? Engine Management? All the machine work you need, decking pistons , block and head, cutting keyweys and turning down the nose on the crank....etc..
It's a lot to think about. You want a good team and have everything sorted out before you even start doing any work.

Hope you get this up and running soon cuz it will be fun going though the process of building it!

Cheers,
~Ralph

bigdogcb · « **Reply #2 on:** August 27, 2012, 09:45:37 AM »

Hi Ralph, thanks for your reply.
I work in the motorsport idustry and we use several engine builders for our work projects. On my programe we use a very reputable company that builds many WRC, Touring car and rallycross engines, and the guy that does our engine support at the circuits is being kind enough to assist me in my project. At my work we have full machine shop, CNC mill and lathe etc etc so I am lucky enough to have good skilled guys around me.
In response to your questions, I am doing the head work myself, using 7mm valves, using stock cams as im looking for the engine to be nice and driveable as its for fun road use although would like the capability in the build to house more aggresive cams in the future should I feel that it would be the route to go.
I will be using OMEX for the engine management as we also do alot of work with them on R&D projects. They have been really interested in my project and if succesful may put a kit together for retail if the kit is of interest, so watch this space!
I will be using standard exhaust headers at the moment but when the engine is in and run-in I will look at options regarding exhaust primary lengths and collector options.
I am using Euro S50B32 pistons for the project which I do have. Any idea what engine has the 138mm rods as mine are 140mm I believe.
Thanks again for your input on this project, I may do a wright up but fear that its been done many times, maybe I will focus more on the ITB set up as this could be a different option to Dbilas as an off the shelf fitment.
Regards,
Chris

Warsteiner · « **Reply #3 on:** August 27, 2012, 09:24:04 PM »

Awesome Dude!! You're in good hands then.
I'm not sure what the compression height is on a Euro piston but the better option is the US 3.2L 86.4mm You would have to shave a minimal amount off.
IF you really plan on building a motor then plan it out from intake to muffler.
I'm not sure if the 138mm is the best for you with the Euro pistons. However, they are from a B18C Honda GSR engine. They are perfect in every way but have a small pin diameter of 21mm which is perfect for you if you use the Euro pistons. Now I got mine from Nick Arias III and they are aftermarket which means lighter and less expensive. I would do the 6mm valves if you're not porting the head. I would port the head:-) The power is in the head! You can do S14 or S50 ITB's.
When I get my computer up and running again I can list all the parts that I used in my build.

Cheers,
~Ralph

bigdogcb · « **Reply #4 on:** August 28, 2012, 02:00:38 PM »

Great info on the rods Ralph! Had a look into them and sourced some here in the UK and ordered today, no messin here!
Pin diam is perfect as you say. Just need to work out what big end bearings to source. Im having the boring carried out tomorrow so when thats done and the rods arrive, i can do a dummy build to see how the pistons sit on the block deck etc. Head is stripped and now setting aside a day or 2 to look at head porting etc.
Would be great if you could let me know what components you used, looking forward to that.
Currently sat in my garage, music on, organising nuts, bolts etc etc, need to knuckle down and focus on this now!
Ta buddy
Chris

Warsteiner · « **Reply #5 on:** September 01, 2012, 07:32:22 AM »

You definitely don't mess around!! Tell me what rods you got exactly.I think I used an Acura bearing.
You don't need to dummy a build if you do your math correctly:-) But you can do it anyway to see how much actually protrudes out of the block. It'll probably be scary for you.
If you have the team you say you do........get the head ported!! You won't regret it.
I hope you have some good music...hahahha, there is a lot of planning involved. My hard drive crashed so it may be a few days for the info but I can go from memory so just ask away!!

I did the Dbilas 45mm ITB's but do have a set of S42 44mm Slide Throttles. I have pics of the S14 46mm or 48mm ITB's that someone did. You have to cut a section out of the airbox to work around the brake booster but it should work.
It has an E30M3 exhaust with SuperSprint.
I did the E36 318Ti puller fan instead of our engine fan.
I have S50/52 cam trays with the lighter 33mm buckets, valve springs and 6mm valves.
Custom 250* cams that are more aggressive than the Schrick 256*'s. I wanted to pull hard through 7500rpm but not fall on my face with torque for a street car even with the 2.1L
I had the keywey cut for the crank, lightened the crank, and had a custom spacer made for the new crank bolt which you will also have to cut because it's too long. I'll get you the part number.
It'll be running MSII v3.57
TechEdge WBO2

Probably lots more.........just ask if you think of something!

Cheers,
~Ralph

BenjaminAS · « **Reply #6 on:** September 02, 2012, 02:42:57 AM »

Hi Guys !
my name is Benjamin and I am from Bavaris owning my 318is since 8 years now.
I want to build a 2.1 stroker too so I will read along and ask a few things if you don't mind. Why don t you take a m43 block which is windowed (i hope it is called like that ?)
cheers
Benjamin

Warsteiner · « **Reply #7 on:** September 02, 2012, 07:12:39 AM »

Read along....:-)
Not sure what "windowed" means but we can't get the M43 in the US.

Cheers,
~Ralph

BenjaminAS · « **Reply #8 on:** September 02, 2012, 09:22:34 AM »

it means that you got less pumping looses because of connections between the cylinders.
Sorry my english got a bit rusty...

Warsteiner · « **Reply #9 on:** September 02, 2012, 10:38:12 AM »

Not sure what you mean... but the M43 has a Bore of 85mm and Stroke of 83.5mm. So yes the bore is larger than the M42 and the block may have thicker cylinder walls to start with. I'm not sure about that but for the M42 we can easily bore for a 86.4mm piston and some have even bored for 87mm piston but that's about as far as it can go due to the water jackets in the block.

Cheers,
~Ralph

PS Everyone should have a stroker motor in the near future! More power and just as efficient:-)

colin86325 · « **Reply #10 on:** September 02, 2012, 11:36:51 AM »

Windowed means that the adjacent piston bores are connected with a passageway. So if a piston is decending, it does not have to fight as much friction (pumping losses), as the air has a place to escape (into bore of the rising piston to which it's joined through the window).

Warsteiner · « **Reply #11 on:** September 02, 2012, 01:04:06 PM »

Thanks for the explanation!
~R

MLM · « **Reply #12 on:** September 03, 2012, 05:55:06 PM »

This sounds like an impressive project with an impressive ammount of expertise available. Please post your progress and any pictures if you can. Its rare that a good project gets documented or completed!

bigdogcb · « **Reply #13 on:** September 12, 2012, 12:48:18 PM »

Hi, only a small update as I have been working away. Ok, the block is bored now, picking it up tomorrow. I have been struggling with the keyway in the crank. Have been advised to have it spark erroded rather than machined as doing that can put stress points in the crank nose. So thats being done next week. Once all the parts are together i will do a photo shoot.
Thanks for all your help and interest in my project.

timothymcn · « **Reply #14 on:** December 17, 2012, 10:03:05 PM »

Well this a cool build that's way over my head. Bump for updates?