FE Power Forums
FE Power Forums => FE Technical Forum => Topic started by: gregaba on January 19, 2021, 11:13:35 AM
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I don't know if this is something to worry about but I was assembling my pistons and rods this morning and one is a little tighter then all the others. Racetec forged pistons, with Scat h beam rods.
There is no catch or rough places in the piston movement but it is just a little bit tighter then the others.
I was reading Barry R's book on this and he said they should all be free but didn't give a cure for a tight one. In a normal build I wouldn't worry about it but really don't want to have to pull the motor after it is running and fix it.
Any reason for worry or am I just a willy nilly?
Greg
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Is it tight in the piston or tight in the rod? Can you push it in or does it fight you?
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Tight in the rod and it was a little harder to push in then the other pins. Wasn't real hard to install just a little bit harder.
Greg
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I think I solved the problem.
I disassembled the piston and removed the pin.
I took the pin and ran it back and forth [left to right] in the rod for about 15 minutes and it seemed to free up.
Re assembled the piston and now it moves like the others.
All I can figure out is it must have had a small burr on the bushing that I could not see.
Greg
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Greg,
I too have had the same thing happen and did the same thing to fix it. I shortened up the process by finding a small shiny spot on the end of the rod bushing and scrapped it a bit off of the high spot and problem solved.
Randy
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I didn't see or feel anything on the bushing but it must have been there.
I did have to rock the rod back and forth a bit to get the pin to go in but it turns freely now so I guess it is OK.
Greg
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Sounds like it.
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I have a home made mandrel with a flap strip of 400 grit on it for such things. Soak in WD-40, flap the hole a short bit, clean and re-fit. Like a poor boy hone. You'd have to really get on it a while to remove very much material.
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Sounds good
The reason I didn't use my brake hone is because I wasn't sure how much it would take off.
Just pushing it in and out for a while seemed to work.
Greg
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The reason I didn't use my brake hone is because I wasn't sure how much it would take off.
No! Don't do it, for a number of reasons, but basically: to much material removed in a somewhat less than idea process.
With the completion of the process of pin-fit honing of the rod pin bushings, I will utilize a section of the "red" Scotch-Brite folded in one hand between the thumb and fore finger clamping the connecting rod small-end across the pin bore and rotating the rod in the circular plane of it's motion in relation to the pin, this burnishing down the otherwise unseparated swarf material clinging to the edge of the bushing and often creating the issue. This often proves sufficient and will only clean the inside edge at the termination of the bushing and not effect the diameter. If this doesn't "fix-it", take your stuff to a machine shop for proper inspection and determination of what is required. ;)
Note that in my experience generally the "import" rod bushing pin bores will be of insufficient oil clearance value nor of consistent dimension, at least of what many might think things should be anyway. :o
Scott.