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The Terminator
Engine/Tuning
Looking for opinions on piston ring gap
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<blockquote data-quote="MalcolmV8" data-source="post: 15258376" data-attributes="member: 8854"><p>I thought I'd come back and update with my experience with gapless rings for others that may be searching on the subject. I went with a gapless top ring. </p><p></p><p>Pros - It seals so well. I quite literally get 0% leak down.</p><p></p><p>Cons - It seals so well. Since day 1 of firing up this motor it's burnt oil, lots of it. I'm talking about 1 quart every 250 miles or so. Piston tops are black, exhaust looks like diesel soot, O2 sensors get trashed to non working in about 800 miles, plugs look oily, wet on threads even on a few of them. </p><p></p><p>I pulled the blower / intake (No PCV system, only breathers on valve covers) and the intake runners were covered in oil. The intake valves have had so much oil on them that in approximately 800 miles there's oil caked on them like an old oil burning engine would. I called Total Seal and they said the vacuum produced the the gapless rings is so strong it will pull the oil right past the valve guide seals if they're not in impeccable condition. My heads were just serviced and worked on at the engine build. Valve job, new exhaust seats, ported and of course new seals. None the less I began stripping things down and painstakingly changed all 32 valve seals in the engine bay. I cleaned the head thoroughly with brake cleaner and compressed air and installed each new FelPro seal with a dab of silicon to seal the base and prevent oil from been sucked between the guide and the head. </p><p></p><p>The results? Not much changed. Did an oil change, topped up to full on dipstick and did approximately 260 miles and oil is just barely marking the bottom of the dipstick. I called Total Seal again and they now feel its my lack of PCV system. They say the 4.6 has a very small crank case area and the cavitation caused by the pistons suspends a great quantity of oil vapors in the air that will land on the cylinder walls and is more than the oil rings can handle. This causes it to go into the combustion chamber and burn. Total Seal feels that if I re-install the PCV system the oil burning problems will go away. I considered purchasing an electric vacuum pump and attaching to my valve covers but I'm not convinced this will do much of anything. The reason I deleted the PCV is because of the recirculated oil that gets into my blower's intercooler reducing heat transfer efficiency. </p><p></p><p>So I started searching google for gapless rings and oil burning and loan behold there's no shortage of links or complaints. So I started reading the many forum threads and info I could find. In the process I learned a lot more about how piston rings work than I previously knew and about how the combustion pressure actually pushes the ring outwards against the cylinder providing the pressure or seal for that ring. I also read up links and info on how into today's engines the 2nd compression ring is only 5 to 10% compression control and 85 to 90% oil control. Interestingly enough I found information that says the gapless top ring seals so well no pressure gets by it and the 2nd ring has no pressure to expand it out and press against the cylinder. Thereby rendering that 2nd ring's oil control useless and making you burn oil. </p><p></p><p>I found some theories and suggestions of using a Napier 2nd ring due to the cut design (looks like a claw with a reservoir) to aid in the oil control when the gapless top ring is not providing any pressure to the 2nd ring. It was just a theory though and could not find anyone who had tested it and confirmed success. </p><p></p><p>So at this point I'm pretty disappointed in my gapless top ring experience and will probably need to tear this motor back down and hone the block and re-ring it with conventional rings to fix this oil issue.</p></blockquote><p></p>
[QUOTE="MalcolmV8, post: 15258376, member: 8854"] I thought I'd come back and update with my experience with gapless rings for others that may be searching on the subject. I went with a gapless top ring. Pros - It seals so well. I quite literally get 0% leak down. Cons - It seals so well. Since day 1 of firing up this motor it's burnt oil, lots of it. I'm talking about 1 quart every 250 miles or so. Piston tops are black, exhaust looks like diesel soot, O2 sensors get trashed to non working in about 800 miles, plugs look oily, wet on threads even on a few of them. I pulled the blower / intake (No PCV system, only breathers on valve covers) and the intake runners were covered in oil. The intake valves have had so much oil on them that in approximately 800 miles there's oil caked on them like an old oil burning engine would. I called Total Seal and they said the vacuum produced the the gapless rings is so strong it will pull the oil right past the valve guide seals if they're not in impeccable condition. My heads were just serviced and worked on at the engine build. Valve job, new exhaust seats, ported and of course new seals. None the less I began stripping things down and painstakingly changed all 32 valve seals in the engine bay. I cleaned the head thoroughly with brake cleaner and compressed air and installed each new FelPro seal with a dab of silicon to seal the base and prevent oil from been sucked between the guide and the head. The results? Not much changed. Did an oil change, topped up to full on dipstick and did approximately 260 miles and oil is just barely marking the bottom of the dipstick. I called Total Seal again and they now feel its my lack of PCV system. They say the 4.6 has a very small crank case area and the cavitation caused by the pistons suspends a great quantity of oil vapors in the air that will land on the cylinder walls and is more than the oil rings can handle. This causes it to go into the combustion chamber and burn. Total Seal feels that if I re-install the PCV system the oil burning problems will go away. I considered purchasing an electric vacuum pump and attaching to my valve covers but I'm not convinced this will do much of anything. The reason I deleted the PCV is because of the recirculated oil that gets into my blower's intercooler reducing heat transfer efficiency. So I started searching google for gapless rings and oil burning and loan behold there's no shortage of links or complaints. So I started reading the many forum threads and info I could find. In the process I learned a lot more about how piston rings work than I previously knew and about how the combustion pressure actually pushes the ring outwards against the cylinder providing the pressure or seal for that ring. I also read up links and info on how into today's engines the 2nd compression ring is only 5 to 10% compression control and 85 to 90% oil control. Interestingly enough I found information that says the gapless top ring seals so well no pressure gets by it and the 2nd ring has no pressure to expand it out and press against the cylinder. Thereby rendering that 2nd ring's oil control useless and making you burn oil. I found some theories and suggestions of using a Napier 2nd ring due to the cut design (looks like a claw with a reservoir) to aid in the oil control when the gapless top ring is not providing any pressure to the 2nd ring. It was just a theory though and could not find anyone who had tested it and confirmed success. So at this point I'm pretty disappointed in my gapless top ring experience and will probably need to tear this motor back down and hone the block and re-ring it with conventional rings to fix this oil issue. [/QUOTE]
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