1600 crank suggestions

[MichaelP]

Hi all. It's been a few years since I've posted, but it's good to be back!

I've gotten serious about getting our 3/'71 1600's motor rebuilt and I need to get to back to Korman this week with final decisions, so I'm looking for some input before I jump.

The rebuild recipe involves bumping the motor up to street 1600ti spec plus some (40mm DCOE, 292 cam, etc), but what has me confused is what to do about the crank. As a late 1600, it has the 8-bolt crank, and I'd like to maintain the 1600's uniquely cheery willingness to spin up to and live at high rpm.

My guy at Korman is recommending a 2 liter crank, but searches through this forum suggest that the added weight of the 8 weight, 2 liter crank (vs 4 on the 1.6 crank), combined with the added stoke length would compromise it's rev-happy nature. The archives say that go-fast 2 liters sometimes substitute a 1.6 crank for this very reason.

Am I reading this right? Suggestions?

[aa/fd]

Put the big arm in, the jump displacement is significant, plus it will still rev up.

[jdm1602]

Usually just lurk here but this question I can answer. I had the 1.6L in my 1602 rebuilt with 1800ti pistons and a 2L crank.

Original bore / stroke was 84 x 71

New bore / stroke is 84 x 80 which is identical to the 1800 motor.

I have 292 cam and DCOE 40s, it still revs like crazy but has better low end power. You'll love it.

[Slavs]

If you want to use a 2002 crank in a 1600 block, you will have to use the 1800 or 1800ti pistons from the early 1800 New Klasse 1800s (up to about 68) where they had the 84mm bore and 80mm stroke. You can't use your 84mm pistons from the 1600 with the 2002 crank because the pin to deck height if way off. There were some New Old Stock oversize 1800 and 1800ti pistons listed on e-bay for a very good price, but there are only a few of us out here who still run the small bore engines. 1600 pistons are also getting hard to find, and the 1600ti pistons are most difficult to locate. If you get a hold of at least one, you can use it as a model to get them made. There are places that manufacture pistons. Be carwful when mixing and matching cranks. You can't always mix and match parts. The 1600 and 1600ti is the reviest of the 02's and not the most practical to rebuild since parts are getting sparse.

Slavs

[Highgrade]

Hi Slavs you're not alone ;-) I still run the old block of my 1967 NK 1800 and snatched a set of over sized 85mm NOS Mahle pistons few months back from eBay.

Michael try finding this seller : (Linea_Veloce) he is the one who got few sets of those, but I'm not sure if he has any in store or could find you some, send him a message.

Cheers,

Omar

[MichaelP]

Thanks for the replies. Slavs, I have a set of 1600ti, high compression pistons that are somewhat used, but useable. I'm not sure of their provenance, but the stamps read "MAHLE 34/39 0021." The PO of the car sourced them from Schimmer Tuning some years ago.

I don't suppose using those pistons would help the deck height issue if using a 2 liter crank?

Originally, I had no intention of using a 2 liter crank - it was the mechanic who suggested it. I'm just looking for logical reasons to go with one crank or the other, and the deck height might be the clincher. I'd be perfectly happy with the 1.6 arm.

Thanks again.

[TobyB]

If you're happy with the 1.6l motor, then just rebuild it!

Boring out to 1800 displacement would be nice... but as Slavs says,

pin height is the issue.

And look at it this way- if you ever get torque envy, you can build a 2l

motor, put your 1600 on a stand, and be happy...

t

[schwartzerritter]

thanx all

my 1600 gets the 32/36 and after that a 2 litre or the M 42

[Slavs]

Michael,

You can't use the 2002 crank with the 1600 pistons because the pin on the 1600 pistons is positioned for the short stroke of the 1600 crank. If you have the 1600ti pistons, consider yourself very lucky. Just rebuild the original motor to 1600ti specs with the stock cam because all ti's had the same cam as the standard non-ti cars. A higher duration cam will give you more lumpy idles. And that gets pretty irritating unless you're just going to use the car for high speed joy rides on the weekends.

All M10 cranks are built to be mated with either the 71mm stroke motors or the 80mm stroke motors.

The 71mm stroke motors include the 1600, the later post 68 1800, the 1802 and 1.8L 320i's and 3181.

The 80mm stroke motors include all 2000cc BMW 4 cylinder motors and the early 1800 (1963-68)

BMW made 2 versions of the 1800cc motor. The first version had a 84mm bore and a 80mm stroke. The second version from about 1968 and on has the 89mm bore and the 71mm stroke.