M42club.com - Home of the BMW E30/E36 318i/iS

DISCUSSION => Engine + Driveline => Topic started by: Darky on March 25, 2014, 07:54:59 PM

Title: M42 conrod selection
Post by: Darky on March 25, 2014, 07:54:59 PM

Hi
I planed on using a m47 crank 88 mm and s50 euro pistons 86 mm with m44 conrods, but I received a m47n crankshaft 89.6 mm.
So my initial conrod selection is not suitable any more.
The conrod specifications I need are
Be width 22 mm
Be diameter 48 mm
Pe diameter 21 mm
Length 138 mm
Any ideas?

The honda b18c conrod is close but it's width is wrong at 21.8 mm

Have already tried MM, but they can't seem to reply to emails and I fall asleep about an hour before they answer phones at 3 am my time.

Title: Re: M42 conrod selection
Post by: Warsteiner on March 25, 2014, 09:48:22 PM

Quote from: Darky on March 25, 2014, 07:54:59 PM

Hi
I planed on using a m47 crank 88 mm and s50 euro pistons 86 mm with m44 conrods, but I received a m47n crankshaft 89.6 mm.
So my initial conrod selection is not suitable any more.
The conrod specifications I need are
Be width 22 mm
Be diameter 48 mm
Pe diameter 21 mm
Length 138 mm
Any ideas?

The honda b18c conrod is close but it's width is wrong at 21.8 mm

Have already tried MM, but they can't seem to reply to emails and I fall asleep about an hour before they answer phones at 3 am my time.

Hey Darky,
You can definitely use the S50 Euro piston but will need to modify it to fit obviously. The GSR and M42 have the same dimension on the BE and you have a win with the pin diameter being 21mm for your piston so no modification needed there. Both rods are 21.79mm or .858" I am running them in my motor:-)

As far as your crank....I think that you have to have an extension piece made up for the M47N crank. Using that stroke with the 138mm rod you will really have to modify your piston. You'll need a compression height of 29.35mm which is acceptable. So you'll need to shave off 2.25mm of your piston and then dish it and make sure valve reliefs are good for whatever cams you're running and compression you want.

That's it...LOL

Cheers,
~Ralph

Title: Re: M42 conrod selection
Post by: Darky on March 26, 2014, 03:54:07 AM

Hi Ralph
But the be with m42 is 21.97 mm
And for the Honda it's 21.8 mm.
I realized we are only talking .17 mm but for something moving at 6-8 thousand rpm. :-\
Will it be all right?

Cheers
Darky

Title: Re: M42 conrod selection
Post by: Warsteiner on March 26, 2014, 05:32:51 AM

Darky,

Here is Pauter's and other website to confirm for you the 21.79mm BE width. I'm sure there are other websites as well.

http://pauter.com/shop/rods/bmw/

http://pauter.com/shop/rods/acura-honda/b18c-rods/

I did however find 2 other sites that state the BE width to be 21.89mm and 21.97mm.

http://www.fastwayracer.com/p3635/91-99-BMW-318IS-E30/E36-M40/M42/M44-4-Pieces-H-Beam-Connecting-Rods-with-Bolts/product_info.html?osCsid=faee6325fa9f914ecd7f1ebd024545c0

http://www.cambridgemotorsport.com/BMW-M40M42M43---M44-4Cyl---Pro-H-Beam-SPS-Carrillo-Con-Rod-Set

I went with Pauter's site since they actually manufacture the rods as opposed to other sites that just sell the rods. Maybe you can call one of the manufacturers and ask them directly to get a definitive answer?

HTH...
Cheers,
~Ralph

Title: Re: M42 conrod selection
Post by: Darky on March 26, 2014, 05:58:40 AM

Thanks Ralph
That is just weird isn't it.
But your right there all over the place like brides nighty!
Yet I measure the rods in the garage from the m42 I pulled apart and get 21.97-22 mm area.
What where the exact rods that you used?
Cheers rohan

Title: Re: M42 conrod selection
Post by: Warsteiner on March 26, 2014, 07:50:21 AM

Rohan,

They're completely all over the place...LOL

I got my rods from Nick Arias III. Have you heard of Arias pistons?  Great guy...has been around the car world for a long time. Family business. Remember that you're looking for a specific numbers for measurements and not what the application is intended for. IF you can get any of the manufacturers to agree on measurements, then you're good to go.

Nick gave me the inside scoop on rods....There are only a couple of rod manufacturers and they're all based in China more or less. Aside from the big names like Carillo, Arrow,and Pankl...I'm sure there are more, the others are all basically the same ::)

So I just checked the Arias website and found they list the big end as....are you ready?.....   .935" or 23.749mm .. ::)LOL
SO....I went with Pauter's numbers and used the Honda B18C GSR rods at 138mm or 137.92mm or ?? depending on your website and manufacturer or person typing the wrong information onto the website or.... Hahahahha

Isn't this fun?

Cheers,
~Ralph

Title: Re: M42 conrod selection
Post by: Darky on March 26, 2014, 07:15:31 PM

Ralph

Fun, yea right try annoying.

But your right because pauter is the bible as far as I'm concerned when it comes to these things!

Thanks for clearing this up, sort of! Maybe making it more confusing not sure yet.

Cheers rohan