Top guided vs. bottom guided rods

[skialot2]

Wow!!! 5 hours total at 7K or less! And with bottom guided rods. You have convinced me. I will never ever be using Wiseco pistons in any motor I build.

[NZ Sidewinder]

I haven't got to that stage yet with wiseco pistons.
This motor is running .009 clearance and it runs in cold water.
The pistons show zero scuffing that would indicate that the piston ever good anywhere near either hot or cold sieze.
On this basis I'd say that the Bore diameters could be pulled back at least a thou, maybe 1.5 thou.
I'd never use them top guided with big clearance though.
It's all about learning also.
For example, based on what I've seen, I've changed my view on cooling.
My view is now to run the cylinders with racing clearances cold,
Pour that water in, use diverters of course.
Keep water pressure under 20psi but increase flow.
This will be how I run this season.
Just my plan and not advice.

[skialot2]

Just curious, did you mic the Wiseco pistons before installing them? Or just after racing them for a season? Are you sure that the pistons are not ball shaped when brand new?

[NZ Sidewinder]

Always measure pistons first.
The plus 20 piston started life at 3.514 across.the widest skirt.
The recommended bore for that piston is 3.521
7 thou total clearence.
I have just now measured a new std wiseco same part number red box
Widest skirt is 3.493
Bore for that piston is 3.501
8 thou total clearence but the piston is very cold so might gain half thou and have 7.5 thou clearance.
Point of this is to show that the plus 20 piston was within manufacurers spec.
After the seasons use that 3.514 measurement was less than 3.510 with no visible wear.
I've now knurled them back out to 3.513.
May be ok in a fishing motor