3.4 turbo ring end gap

[gpitts714]

I am rebuilding my 88 930 and am installing 3.2 cylinders that have been bored to 98mm and replated through LN Engineering. I am installing JE pistons also supplied by LN Engineering and have been advised by Charles Navarro to use Porshe's recommended end gap but there is no listing in Wayne's book for a 3.4 turbo engine. Can anyone assist with this? I would also like to know where it is recommended to measure the end gap. Wayne's book says close to the bottom of the cylinder but I have read on this forum that you measure near the top of the cylinder. Any help will be greatly appreciated.

Thanks
Greg

[sjf911]

Chris at TurboKraft gave me 0.017" for the top and 0.019" for the middle ring with a similar build but I don't know if the ring types are exactly the same. I actually ended up about 10% larger.

[AlfonsoR]

I would try to confirm through a couple of sources, your ring mfr, JE's website, and an engine builder on this website.

On where to measure, I believe Wayne says bottom, but that's only if you're reusing cylinders that haven't been refinished. Cylinders that have been in use, usually receive the least amount of wear at the bottom. So if you're gapping rings to a used cylinder, obviously you want to gap the rings at the cylinders smallest diameter.

Since you're cylinders have been refinished, you may want to confirm roundness and taper. The best way to do this is with a bore gage or bore comparator. Once you confirm that cylinders are round and taperless (measure within specs) then it doesn't matter where you take your measurements for determining ring gap. You do want to make sure the ring is square to the bore though. There are ring squaring tools, although I haven't seen one on Pelican.

[gpitts714]

I contacted Chris Carroll at Turbokraft and he gave me the information I needed. As was posted earlier, he told me .017 on top and .019 for the 2nd. ring. Thanks for your input and thanks to Chris for his help.