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Pistion ring end gaps

Engine Building Fundamentals

Discussion and questions related to the course Engine Building Fundamentals


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I am working on doing end gap on my rb25 that I just had rehoned to fit 86.5mm wisceo pistons. The first ring by the manufactures spec need to be .017 which I can achieve but the second ring end gap calls for a .018 ring end gap but I have around .020 before the ring even gets touched. I am going to call the manufacture on Monday to see if I am doing anything wrong or where I went wrong but was wondering if you guys could shed some light from a different

Unfortunately this isn't an uncommon situation where you find the rings gaps are excessive right out of the box. 0.020" isn't crazy large so it becomes your discretion whether you run it like that or source rings that are tighter to start with. While obviously we'd like to have everything perfect, the top ring is the one that's really much more important.

Is that something u would let go or would u get tighter rings?

For a basic street motor I wouldn't be worried about running with it.

First thing would be to double check the gap requirements - that seems a little on the tight side, especially the difference between top and second.

If you are having trouble getting rings to gap, pick up a next-size bore set.

[edit]Yup, every turbo' guide for rings works out at more than that - a thou or three too loose will not be a problem except a slight increase in blowby that may not even be noticed, but a thou' too tight and the rings butt up and you will be looking at an instant failure that, in extremis, could break pistons and send rods out the side.