BEST CRANKSHAFT FOR 131

[miro-1980]

Dear Guy,

It took me some time but I have finally decided to build a real sports engine.

Have a stock 131 2,0 liter engine as donor (with all auxiliaries in perfect shape - practically no wear and no previous mechanical changes or modifications).

Will be trying to get 180 bhp (if we decide to go with carbs WEBER IDF 45) or as much as 200 bhp (if we decide to go for mechanical f.i.)

I have just done a very thorough research of this site and found a lot of useful information.

At this stage I am starting collecting the parts:

As the plans are very ambitious there is a lot of parts we need. Obviously the engine will be based on forged pistons and cranks, large cams, full rally head preparation.

At this stage I have two questions:

1/ What crankshaft to use ?

The one I have is in very good condition and your posts on crankshaft preparations are very informative and interesting. But ... do I have any options : i.e can I use a non 131 crankshaft? I understand the one from Fiat Croma will fit, but is there any reason why I should use the one from Croma and not from 131 ( assuming the same very good condition)? Do I have an option of using a crankshaft from Lancia Delta ? Will this fir ? Will any other crankshaft fit? Is there any other reason to go for something else than the original 131?

2/ What do you think about modern "mechanical" f.i. - which I understand to be electronically controlled development of the Original Kugel-Fischer?

Miroslaw

[Guy Croft]

You should definitely use the 131 crank because;

1. It has a better array of oil holes - fully crossdrilled and twice the number of main journal holes compared with the others.
2. It has the correct nose - the others use a front mounted oil pump with different block front end - not interchangeable, same applies to the cambelt drive pulley
3. It has the correct counterbore for input shaft support bearing at the FW end

It is exactly the same material/heat treatment as the later ones and if good std size should have oilway mods, tap/plug with assoc cleaning, light polish opposite direction to rotation and balance with reground/lightened fw. Double dowelling is not a bad idea for a comp engine too.

I will just mention that the oilway mods must be carried out with great care (and precision) and the finished shapes must be fully radiused with 500 grade carborundun and oil and then fine Scotchbrite - sharp edges will rip the bearings to pieces. However, if done well, the oil supply to the rods will be greatly improved and add hugely to the survivabilty of the engine. Naturally a well-made big wing sump is a must, along with cooler etc.

Hope this helps,

GC

GC

[miro-1980]

Thank you Guy ,

As usual very helpful and informative reply .

Miroslaw

PS : Any ideas about the MECHANICAL FUEL INJECTION ?

[Guy Croft]

Hi Miro

the best mech inj is probably the old Kugelfischer - as used on the 124 16v and also the prod BMW 2000ti.

I have worked with it and properly calibrated it is a very robust and accurate metering device. The pump is essentially a diesel type injector pump with 4 little pistons to compress the fuel in the inj line, the device is driven off the crank. The BMW one may well be still aval. Calibration however would require a very competent diesel injection system workshop to adjust the stroke of the pistons to suit your engine. Usually this means running it as-is and using Lambda to see how rich or lean and then, really, guessing how much to adjust. All very fiddly and time consuming, nay, costly and hardly worth the trouble.The Bosch K Jetronic was also a good mech system but figuring out how to recalibrate it for your engine, well, I couldn't tell you how to do it!

There have been numerous aftermarket mech inj systems over the years. The Lucas shuttle-pump inj used on Triumph 2.5Pi and adapted for the Hart 420R and other race engines was, well, OK I guess in its day but by modern (and even carburettor) standards the metering was pretty inaccurate ie: running over-rich or over-lean here and there..

The famous Hillborn (USA) website is great fun and it's clear there is a terrific variety of bits and pieces availalbe for their mech systems but I could not tell you how easy it is to get product support for your application. I've always fancied running it but never had the time.

http://www.hilborninjection.com/about.asp

Electronic fuel injection is a much better bet than mech in terms of how well the mixture is matched to demand. However, despite all the words written on EFI most folk go to the 'wrong' place for the hardware or calibration and get disappointing results. The whole issue has become a 'fixation'. The number of true experts is pretty small in my book. And I have to stress that for the DIYer Weber carbs are by FAR the best solution. Why? Because they don't depend on thousands of presets of ignition and injection settings and NEVER break down due to faulty sensors et alia. If there is airflow - the carb will provide a prefectly adequate (indeed very accurate) fuel supply every time.

GC