Rod side clearance

[Brandon Sinclair]

What do you guys use for rod side clearance on a daily driver?  I know the specs in the Bently manual are a pretty large range from .006 to .028 with an upper limit of .016 for new parts.  Well my new crank and rods spec out at .018 on two journals and .020 on the other two.

[Germanlkmanx]

I like to have around .018" on a hipo motor so I would run it with what you have. No issues doing that.

tom.

[stealth67vw]

I've got .020 side clearance on my Bugpack 78 using CB H beams. I've been told by a few people (including Pat Downs, DRD Darren and  Jim Ratto) that although .020 is big, it is just fine.

[Brandon Sinclair]

John,

Have you run your current set up and did you notice anything happening with the oil pressure as a result?

I am trying to build this thing with some tight tolerances, but I am having difficulty.  This is a CB crank and their Unitech rods.

My last cranks was a DMS and I used CB H beams and the side clearance was .015" all the way around.

Thanks for the info.

[stealth67vw]

It's still on the stand, so feedback yet.

[Jim Ratto]

I would be careful about getting that side clearance too tight (like under .012"). Not only will the rod bearings not like it, but the cam and lifters won't either.
I think if your radial clearances (rod journals) are correct, you do not overheat the motor, lifter bores are tight, and you use a good oil pump, along with the correct viscosity oil, then .020" will be acceptable. I'd worry more about bypass valves seating correctly in bores.
Or tight side clearances.