I checked my boresize with the appropriate tool today and cam up with 3.365 inches which is 85.47100 mm I think. does that sound low or high for ross .020 overbore pistons to ya'll???

 

Well using some math, stock 4G63 bore size is 85 mm, adding .020" to that gives you:

.020" * 25.4 = .508 mm + 85mm = 85.508 mm

Now you measured your bore to be: 85.471 mm

Which means the piston is larger than the bore, so that is not working out righy. Contact Ross and ask them the actual size of their 20 thou over pistons are. Or ideally measure the ones you have.

How did you measure the bore?

 

I measured them with a dial bore gauge.

 

I'm not sure but I think you might need to calibrate it with an outside micrometer. Someone else who knows more than me can chime in.

 

Where are you measuring the bore? You will get different readings at the top, bottom and middle of the cylinders. Measurements will also vary if you measure across the bore or from top to bottom. This is because of how the piston rocks in the bore and wears different spots more or less.

 

under WOT no, under part throttle GOD YEAH.

Eric

 

oh well, I guess I'll figure it out someday if it was wearing out prematurely or not, because I just put the head and timing belt on. hopefully it'll be ok. I didnt see any scuffs or anything that the side skirt of the pistons would've made. I actually had a friend that works in a machine shop come out and measure the bore. yeah he set the dial bore gauge first with a micrometer.

 

I'm pretty sure I saw him measuring near the top of the cylinder.

 

at 6 spots, top, middle, bottom, pin side and skirt side.

 

what afr do ya'll aim for on idle???

 

i would assume stoich, 14.7