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Old 10-17-2010, 05:27 PM   #1
Bad Noodle
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Member#: 174442
Join Date: Mar 2008
Chapter/Region: Tri-State
Location: NNJ
2007 SuperWagon
I don't spell well

Default DIY Piston Ring End Gap - No funny tools

Thought I'd share what I've learned here.

So here goes.

- First, figure out what your ring end gap should be. Ring end gap is usually based on bore diameter so do your math. Your top and second ring gap will be different based on what pistons your get. For my manley 100mm pistons my end gaps are:

End gap in In = bore diameter in mm / 25.4 * factor from instructions

Top Ring = 100/25.4*0.0055 = 0.0216"
Second Ring = 100/25.4*0.0035 = 0.0137"

So first thing's first, check what you have:

I keep my bores coated with white lithium grease to prevent them from rusting. Works great. Anyway, wipe off about 2 inches. Don't need to clean it with carb choke cleaner since a little oil film is ok:

Put the ring into the bore at the top and use the piston to push the ring into place about an inch down or whatever your instructions say. You want the ring to be square in the hole. Using this piston I lines up the flat underside with the deck of the block ensuring the rings is square.

Next, insert feeler gauges into the gap at the end of the ring until you have one that just barely holds itself up. This is your starting end gap:

Next, you need to practice grinding rings. So after measuring your top and second ring gap, you will work with the ring that needs the most work. For example, my top ring starting gap was .0175" and I need .0215" so I need to grind off .0030". Since this is the first ring I'm going to be doing, need to do some experimenting first. Set before I try to go for .0215" I'm going to see if I can set .0190" properly and if that works out, then go for .0215".

The file setup look like:

When grinding the rings, grind one side only. Hold them so the flat side rides along the vice and when looking down at the ring, the edge is square to the file. This will insure the end gaps stay square. Also, only grind the ring pulling towards you or file from the outer edge towards the inner edge. Do NOT rub it back and fourth.

Use your left had to push the ring against the file and the right hand to keep the edge square. Keeping the edge square takes a little practice which is why you shouldn't grind off too much at first.

If you do really bad, when you hold the ground end of the ring into the light you will see that you're grinding only part of the face. It will looks something like:

If you're grinding the entire face, but not square, when you check your end gap as you should be doing frequently, you will see that the feeler gauge will slip easily into the inner edge but won't move all the way to the outer edge/bore wall. The error looks like:

If you're doing everything correctly, meaning your end gap is set and your faces are square, the feeler gauge should be inserted so that it touches the bore wall, should be a little snug, enough to hold itself up, and the ground faces should be even on the feeler.

Also, be sure you deburr your edges. You're not going to grind off any extra material, you just want to pull off any shards sticking out. I used a bigger dremel grinding wheel and just pulled it lightly against the edges. You can feel it catch the burrs as it moves, so once you can pull it over the edges smoothly, you're good to go.

This will take a while, so take your time. Just for reference, it took me 4 hours to do my rings working at a even pace. Took me about 2 hours to get the setup right and learn to grind them properly, then another 2 hours to do all the rings.
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