Gettin ready to install the piston and was looking over my old instructions from HPR just to refresh my memory. I came across something. "Ring and gaps should be opposite of each other once installed on the piston. On naturally aspirated engines- The top ringend gap should be positioned toward the intake side (call for nitrous applications)

I have a nitrous application so what is different with the ring placement?

 

Scatter, I dont know if any different placement for the rings. But you need to give yourself more end gap. Like 3-5 more thou than standard. It lets the rings swell a little with the added heat.

 

I had Eric gap the rings for me. They know Im on the funny stuff hopefully they adjusted for it. Whats the procedure for checking the gap width. The install sheet specs a minimum of .022 so it should be more around where?

 

I put mine at 25. Take the rings off your piston, and stick them in your cylinder. Use a feeler gauge to check the gap. Use a small fine file to open them up if needed.

 

Thanks Jed, Do I need to check all the rings including the the oil rings?

 

No, he will have that set for you. Gap the top two.

 

Jed is exactly right about what is going on here. The 730 wants .023 of ring gap and I recommend calling.......even though they are not open right now and you want to proceed......the reason is there is no standard in this regard. If a stock bore piston requires 3 -5 thousands more gap, the 105.5 bore will have about 17% more circumference meaning you will have more ring length to expand. If you give it to much you might get excess smoking and blow by until you get a fair amount of heat built up in the engine. If you don't do enough, you might on a hot nitrous pass have those rings butt ends which will most likely ruin your nikasil liner. You might get it right so you avoid either extreme but......

I have to re-gap my rings now that I have decided to go Noss. What were you gapped before?

 

Check your ring gap near the top of your cylinder. I don't know about stock bores but our 730's are slightly larger diameter at the bottom of the cylinder than they are at the top.

 

Im not sure I didnt check them on the first build. Simply put it together per instructions from HPR. Im going to check the old ones when I get to the shop. I will give HPR a call I know there closed but Im sure there there getting ready for planet sand. Maybe get an answer.

 

If your ring gap checks in at .020 to .023, you are not gapped for Noss. If they are .025 to .028 I would say Eric planned for you being heavy on the bottle, lol