Chris, did you had problems with spun bearings when using the smaller bearing shells on the crank pins? Do I need to use sputter bearing shells due to the reduced bearing areas?

I'm planning now to build 2 engines over the winter (1 Turbo and 1 N/A) and want to try the MAHLE Gold pistons and K24 Carrillo rods. I thought of customized big ends of the K24 rods.

 

The engine that ran narrow rods on wide journals was an Spiess Opel engine out of my Dallara Formula 3. Spiess build engines for DTM and other race series so they know what they are doing.

The rods were centred in the pistons with < 0.1mm clearance, and had +3mm exposed pin either side of the rod at the crank end. Interesting the bearings had no retaining notch and relied completely on the crush to hold the shells in place. The bearings were only 10mm wide and were pristine when replaced for rebuilds.

I've run K24 bearings in a F24C build on the narrow K24 crank journals, and also K24 2.5L race engines without any problems of bearing wear. These engines were running dry sump lubrication so had no problems with oil pressure.

 

Yes Spiess - I know them. They're good...
But I need to build daily drive engines. I'm concerned about the smaller areas when using the smaller crank bearings with standard K24 rods. Not because of the higher bearing pressures, but I'm more sceptical because of the missing center fixation of the rods.

BTW, I had an older version of the CARRILLO part catalogue. In this catalogue the K24 rods had the same dimensions as the F20C rods - just 1mm shorter lenght.


OK, for my winter project I'm thinking about:

a) use MAHLE Gold pistons with customized K24 rods from CARRILLO (bigger width on the crank end);
b) use customized MAHLE pistons (23mm pin diameter, 30mm compression height) with standard CARRILLO F20C rods
c) use MAHLE Gold pistons (22mm pins, 31mm compression height) and standard F20C CARRILLO rods and install some selfmade bearings on the upper part of the rods to reduced the diameter for 22mm pins and also put the bearing center 1mm lower.

At the moment I prefer solution c)...

 

is there any reason why you have gone off the Woesser pistons?

 

Yes, they are more expensive than the Mahle's.
It's weird but true...

The Woessner piston set is 756,- Euro (1,120 US$)