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  #11  
Old 07-18-2018, 05:06 PM
lr172 lr172 is offline
 
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Originally Posted by maniago View Post
Please...go build some motors before you talk. As for turbo and supercharged motors, anyone who knows how to build uses gapless rings for those applications.
I have built more than 10 engines in the last several years. Yes, my memory failed me and the SBC is closer to 016 - 028 in gap, based upon a minimum .004" of gap per inch of piston diameter. However, that general rule of thumb translates to about .021 on our larger bore lycomings, which is what they spec. In fact, they spec only a minimu gap of .007 when measured in the full TDC position of a choke barrel. I fail to see how you conclude that these engines have WAY bigger gaps then auto engines unless you consider a couple of thou to be significant in ring gap and create a tornado of air in a leak down test. I would happily debate that one.

Larry
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Last edited by lr172 : 07-18-2018 at 05:13 PM.
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  #12  
Old 07-19-2018, 10:26 AM
Lars Lars is offline
 
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Location: Davis, CA
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Originally Posted by maniago View Post
Drop the valve into the cylinder and youve just turned a minor mx issue into a major.
That was the whole point of the exercise. To drop the valve into the cylinder so the guide could be reamed.
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  #13  
Old 07-19-2018, 10:36 AM
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JonJay JonJay is offline
 
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He is just doing a wobble test.
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  #14  
Old 07-19-2018, 11:14 PM
riobison riobison is offline
 
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Location: Oliver BC & Red Deer Alberta Canada
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For me the air is simpler. The valves are laying horizontal so not likely to fall in. They need to come out anyway (in a controlled manor of course) to ream the guides.

I've got the cracked jug out and on the bench so it will make a good piece to practice on as far as the reaming, fishing the valves back in and messing around installing the keepers without losing them.

Tim
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  #15  
Old 07-19-2018, 11:34 PM
lr172 lr172 is offline
 
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Originally Posted by riobison View Post
For me the air is simpler. The valves are laying horizontal so not likely to fall in. They need to come out anyway (in a controlled manor of course) to ream the guides.

I've got the cracked jug out and on the bench so it will make a good piece to practice on as far as the reaming, fishing the valves back in and messing around installing the keepers without losing them.

Tim
Be sure to search this site. Someone did a really good right up with a few good pointers, if I remember correctly. I think he used a 3 jaw grabber through the exhaust port to hold and manuever the vavle while reaming. Seemed like a good idea when I ready it, though I haven't had to do this (knock wood) on my Lycoming yet.

Larry
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  #16  
Old 07-20-2018, 12:13 AM
Lars Lars is offline
 
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Quote:
Originally Posted by lr172 View Post
Be sure to search this site. Someone did a really good right up with a few good pointers, if I remember correctly. I think he used a 3 jaw grabber through the exhaust port to hold and manuever the vavle while reaming. Seemed like a good idea when I ready it, though I haven't had to do this (knock wood) on my Lycoming yet.

Larry
Special incantations are useful. The 3 jaw grabbers need a shot of LPS-1 or 2 to help them operate smoothly, and a good headlight (the kind you strap to your noggin, not the ones on your car) helps. Throw a little salt over your left shoulder somewhere in the process. Open a bottle of your favorite IPA to celebrate after you get everything back together.
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  #17  
Old 07-20-2018, 09:54 AM
Pat Falley Pat Falley is offline
 
Join Date: Jun 2013
Location: Encinitas, CA
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I did the guide reaming thing a few years ago. There is a really good post on this site with step by step pictures I followed. Also, get a copy of Lycoming service bulletin 1425A, which is the official instructions. Overall, it's not too hard to do, but here are a few lessons learned that might save time.

1. Air pressure worked great for removing the valve keys. Hard to imagine messing with rope.

2. I made the valve key tool from Home depot pry bars, but it barely worked. If I had to do it again I would buy or borrow a real one.

3. When the spring is off, check wobble, and check if the valve slides in and out and rotates easily by hand. If all checks good, put it back together and go on to the next cylinder. No point in risking going further.

4. Get a good gripper. It's stressful trying to regain control of the valve if you drop it in the cylinder.

5. When putting the rocker back on, I used the wood dowel trick to compress the lifter. A short piece of 1/2 inch wood dowel can be can be slid in with having to compress the spring. Once it's in, turn the engine over a few times to compress the lifter. Then remove the dowel and slide in the pin.
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