| swmddo | -- 02-17-2011 @ 5:37 AM |
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Thanks to all regarding my valves. I have all of the pistons out, ready for new rings. The carbon build-up does not come off easily, even after soaking them in carb cleaner overnite. I am reluctant to use a knife to scr*pe it off, as it is not very efficient. I want to know if I could use a Dremel with a soft abrasive head to basically "buff" the head clean? Thanks Steve
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| supereal | -- 02-17-2011 @ 7:57 AM |
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Just scr*ping off the carbon deposits is OK, just be careful not to damage the top ring groove. If you haven't already, remove the ridge around the top of the cylinders with the proper tool. Installing new rings takes some steps, including measuring the ring gap by placing the piston rings in a cylinder and measuring the gap with a feeler gauge. A gap that is wider than the specs is OK, but don't install rings with less than the spec, which should be at least .012 to .017, but not larger than .035. Side clearance of the top ring, .0015. to .0030, the rest .0010 to .0025. You will also have to hone the cylinder walls enough to at least break the glaze, and preferably produce some "cross hatch". Otherwise, without a "plateau", the rings will take a long time to seat, if ever. This may be more than you want to know, but is essential to a successful job.
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| swmddo | -- 02-17-2011 @ 9:15 AM |
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Thanks. Not sure what ridge you refer to...I am being very careful with the pistons. I am going to replace all of the rings, as when I placed one of them by itself in the cylinder, the gap looked to be at least 3/8". If using the dremel with the mild abrasive end won't hurt the pistons, it sure makes getting the carbon off easier. Steve
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| 37RAGTOPMAN | -- 02-17-2011 @ 12:02 PM |
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also try moving the rings up in down in the ring glands, if they move to much the ring glands in the pistons are probably wore out, and replace the pistons, just my 3 cents worth, 37RAGTOPMAN is the carb cleaner the one you soak the carb in,when you overhaul the carb, and still does not remove the carbon,?
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| swmddo | -- 02-17-2011 @ 12:57 PM |
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Yes, regular carb clean spray. Doesn't seem to do much at all. The dremel works great...as long as I know what I'm doing. The pistons look like they are in great shape. The pin bushings are smooth, no problems with the ring glands (the width of them?), and the rods look almost new. Steve
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| supereal | -- 02-17-2011 @ 4:38 PM |
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The "ridge" I referred to is the band of carbon around the top of each cylinder. It is also unworn by the piston rings because the top ring doesn't come up that high. If the ridge is considerable, you run the risk of breaking new rings when you drive the pistons into place. The ridge is removed by a tool called a "ridge reamer". They are not expensive, and can often be borrowed or rented for one job. If you measured the ring gap at 3/8", that is way too much, and would compromise compression, as well as allow loss of oil. Review the specs I posted earlier. You may have the wrong rings. In any case, stagger the ring gaps on the piston before you insert them.
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| swmddo | -- 02-17-2011 @ 5:14 PM |
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Yes, thanks! The compression is 85 or so, and should be 120. This is on each cylinder. one of the rings I removed snapped and broke very easily, indicating that they were old. I understand the ridge now. Other than the rings being old, everything else looks pretty good. Steve
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| supereal | -- 02-18-2011 @ 10:58 AM |
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Steve: If the rings were that badly worn, it can be expected that the cylinder bores are also affected and shold be checked for taper and size. Otherwise reringing pistons will not provide much improvement, and piston "slap" can be expected. Years ago, we used to have pistons "knurled" to, in effect, increase their skirt size. I don't know if anyone is doing that now. We don't at our shop. Also, have the rod assemblies checked to be sure they are straight, and that the wrist pins are within tolerance. There aren't many things more disappointing than to spend time and money on an engine, only to end up with a noisy, smoking mess. I'm certainly not against anyone doing their own work, but there is more to engine work than just bolts and nuts.
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| swmddo | -- 02-18-2011 @ 2:48 PM |
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Hmmmm...I checked the ridge and there is almost no lip. Certainly no carbon. With the rings off of one of the pistons, I can put the piston in the cylinder (very carefully). The pistons are "STD" and the inside diameter of the cylinders is 3.184, so that all seems to be within tolerance. I will certainly have the machine shop true up the heads and the block, as well as check the rods and wrist pins. Appreciate all of the heads up! Steve
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