Piston Ring Gaps

[GTX]

Folks,

I have been told that the gaps should be:

1st ring: 0.016-0.018
2nd ring: 0.018-0.022

However, the set I have got already has 0.022 in the first. I measured the old, original Mitsubishi ring, and it gave me 0.018

What are the typical gaps you make in your racing engines?

I have read, you need to make it a bit loose: piston clearance about 0.020 and ring gaps 0.020-24

Thanks
Alex

 

[toybreaker]

Many folks run piston ring gaps in those ranges.

fwiw I've had good luck at .018 top and .021 bottom.

... but I build for modest power levels and a long service history




In order to give you accurate advice, we are going to need some more information.


Whose pistons?

The expansion rate of the various alloys will change the recommendation


What are your power goals?

High cylinder pressures will require significant adjustment in the end gap


What fuel are you going to run?




Quoting GTX:
I have read, you need to make it a bit loose: piston clearance about 0.020



damn, that's gonna rattle some /ubbthreads/images/graemlins/wink.gif

 

[GTX]

The power levels will be below 300. We have a restriction in effect. Pistons are Mizumo/Evergreen. I suspect it is a no name aftermarket stuff, nothing fancy, aluminum alloy. Same applies to rings, which I have to replace now, as at least one is defective and has a gap of 0.024 from the get go. Manufacturing defect.
The car will not run high mileages at all, but need to sustain runs at high (5k-6k) RPMs for 10-20 minutes (your stage times), then 20-30 min at your normal street speeds. Reliability is more important than power. The engine block (6-bolt) I got had near perfect nominal bore sizes with run out just about 0.02mm. all we did is de-glazed it. Same applies to the crank. So, new pistons (the old stock is almost the same size), new rings, old 6 bolt rods(1990), new King main and journal bearings. The rest is new.

 

[tektic]

I did .021/ .024 as per Manley and total seals tech department.

 

[mitsuturbo]

I ran what the Mahle engineer suggested, but this was for 4032 low expansion evo stroker pistons.

Top: .017" (3.3855" x .005")
2nd: .014" (3.3855" x .004")