Author Topic: Using old rings to get idea about bore  (Read 1619 times)

Adnoh

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Using old rings to get idea about bore
« on: April 10, 2009, 06:10:53 PM »
I went ahead and did some pic taken to show how yu could use your old or new rings to get idea on how you bore is before rering. It's important to take note as you go. If you did take notes on you first rebuild of the motor you would numbers for comparison. An hour meter not a bad idea either. This is using limited tools under $40.00. I have two sets of filler guages,one set of calipes and a set of telescoping guages. These all came from harbor freight.

Adnoh

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Using old rings to get idea about bore
« Reply #1 on: April 10, 2009, 06:25:55 PM »
Now what i did was get data from oringal rebuild on ring cap. The gap at new bore was .021 in. The ring cap at top of cylinder wore was .024. Thats .003 difference. This tells me the ring end cap is at its max standard limit. The ring has wore .003 in the bore. I could take it to .028 if I was crazy but I,am not. So it would reguire new rings if this was all I considered. I used the top of the bore beacuse the rings never ride there and is the most accurate place to measure. see pic. I used the skiirt of the piston upside down in bore to get levle at top.

Now we have a base line for cylinder ware lets find out how the bore is with out a bore gauge.

Adnoh

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Using old rings to get idea about bore
« Reply #2 on: April 10, 2009, 06:43:13 PM »
Know I have a base line to work with I will now check out the ret of the cylinder to get data. I check it in four other places to get idea of where its at. see pic

Adnoh

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Using old rings to get idea about bore
« Reply #3 on: April 10, 2009, 06:53:14 PM »
The first place I chaeck is wher the piston rotates over and is under the most pressure keeping rings tight against the round cylinder all thing being equall. As well as the ring being slamed form the bottom of the piston ring gap to the top of the gap under cranking pressure and crank pin rollover. The ring gap here measure .025. This tells me the squish band is effecive keeping the top coll and the crown swell down so far so good see pics.

Adnoh

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Using old rings to get idea about bore
« Reply #4 on: April 10, 2009, 07:11:50 PM »
Now that we have .001 in of cylinder ware not bad for an engine with almost 100 hours on it. Now lets go to line #2 this one I added because it located right above the exhaust port. This location get full exhaust gas temp and the this is where the ring get a work out, the ring is under combustion pressure as it expandes out into the port and the gap is opened up. and the pressure is released toward the exhaust flange and the ring surface is exposed the heat and pressure entering the piston ring cap lessing the pressure on the cylinder wall. Now you know why a good oil is a must. #2 ring end gap is .027. WOW. .003 inchs of wear.

One other thing to mention is the piston walls are tight againgt the cylinder walls at this point and the olny thing between them is the oil film left behind from the evaporated fuel keeping from sticking. This is were the camp and barrell and the piston to wall clearenc is important to keep the crown from swelling shut on the rings forcing them into the wall and causing stuck ring or excessive ring ware.

Adnoh

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Using old rings to get idea about bore
« Reply #5 on: April 10, 2009, 07:16:08 PM »
I'll finish up after I get back from LS I got to go eat desert the Wife fixed and get to bed. I hope your stating to get the idea of what happing here and why.