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Piston Lapping
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Piston Lapping
I read about piston lapping the cox engines to loosen the piston to cylinder fit and get better performance. I used a piece of clear vinyl tubing,3M white rubbing compound and CRC 6-56 oil. I placed the piston conrod inside the vinyl tubing and saw where the hole of the rod was. using an awl I punched a hole about 1/16 inch lower so the tubing would hold the piston firmly. Put a mixture of oil and rubbing compound in the cylinder and worked the piston back and forth giving it a small twist every so often. I did that for a while then I cleaned the piston and cylinder it was still tight so I did a little more,I cleaned and tried again. the idea is to go slowly and check often to avoid damaging your P/L set. here are some pics.
Juan
Juan
F4D Phantom II- Gold Member
- Posts : 159
Join date : 2019-04-08
Re: Piston Lapping
Not seeing your technique...a HINT
Lap in the piston cylinder with the piston skirt UP.... checking often that the Piston Top stops at TDC and takes a slight tap to fall free into the bore
IOW never reduce the top of the cylinder or top of the piston
Lap in the piston cylinder with the piston skirt UP.... checking often that the Piston Top stops at TDC and takes a slight tap to fall free into the bore
IOW never reduce the top of the cylinder or top of the piston
fredvon4- Top Poster
-
Posts : 4000
Join date : 2011-08-26
Age : 68
Location : Lampasas Texas
Re: Piston Lapping
Hello Fred
Thanks for the advice. I was doing it with the piston facing the top but I haven`t worn the P/L set. I`m experimenting and learning. Yesterday I had the engine running good and have been going up in rpm. it started at 19381 rpm and in the last run it hit 20,320rpm using an APC 4.75 x 4 and 25% nitro. I hope to get some more R`s from a timing change I`m doing. Thanks again.
Juan
Thanks for the advice. I was doing it with the piston facing the top but I haven`t worn the P/L set. I`m experimenting and learning. Yesterday I had the engine running good and have been going up in rpm. it started at 19381 rpm and in the last run it hit 20,320rpm using an APC 4.75 x 4 and 25% nitro. I hope to get some more R`s from a timing change I`m doing. Thanks again.
Juan
F4D Phantom II- Gold Member
- Posts : 159
Join date : 2019-04-08
Re: Piston Lapping
Good job. Sounds like you are on the right track. I cannot comment, as I tried doing this once, and ruined a piston/cylinder set. Before I knew how to do it properly, I assembled my engine, removed the head, put in some polish, then chucked the prop screw in my drill and ran it for a few minutes..... It was sort of like throwing a hotdog down a hallway when I was finished. It does run still, but very poorly. I am working on something to tighten it back up now, but it is still being looked into, so will not say how just yet.
NEW222- Top Poster
- Posts : 3885
Join date : 2011-08-13
Age : 45
Location : oakbank, mb
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