mahatma Posted February 6, 2004 Share Posted February 6, 2004 Just building up my engine, crank and main bearing ladder installed and I've beeen putting the spring clips and piston rings on the pistons and noticed something that concerns me slightly. The rod does not appear to be central on the piston and I just wanted to ask what people though about this, I've got a couple of pictures one large, one small; Small picture Large picture The image isn't quite square on, but you can clearly see the rod is not in the centre of the 'piston gap' that houses the little end. I tried checking one of of the big end caps on the crank and there isn't any tolerance of to speak of, which I thought may be the case. The pistons were installed on the rods for me by a company but I couldn't see this effect until the spring clips were put in the pistons at the ends of the gudgeon pins. Any opinions appreciated. Andy Link to comment Share on other sites More sharing options...
Rob Walker Posted February 6, 2004 Share Posted February 6, 2004 If the gudeon pins are interference fit then you should not be fitting circlips. The gudgeon pin is suposed to be slightly offset and will find its own center IF its been correctly positioned on the rod end. Link to comment Share on other sites More sharing options...
mahatma Posted February 6, 2004 Author Share Posted February 6, 2004 The gudgeon pin is floating in the piston but an interference fit on the little end. Since the spring clips were installed, there is no lateral movement of the gudgeon. Should have mentioned in the first post, the rods are standard and the pistons are accralite. Thanks Andy Link to comment Share on other sites More sharing options...
Paul McKenzie Posted February 6, 2004 Share Posted February 6, 2004 Oily will be along in a moment with the definitive answer, but I seem to remember something about the rods needing to be fitted a particular way round 😳, but I may just be confused Paul Link to comment Share on other sites More sharing options...
Roger King Posted February 6, 2004 Share Posted February 6, 2004 You absolutely must NOT fit circlips with an interference fit rod. Unless you get the rod in exactly the correct position (and I mean exactly) on the pin, you will be forcing the rod to bend and the piston to tilt in the bore when you fit them in the bore. The piston circlips are to be used when the rod is bushed and therefore is able to float on the gudgeon pin. Link to comment Share on other sites More sharing options...
mahatma Posted February 6, 2004 Author Share Posted February 6, 2004 Thanks Roger, So the solution is to just remove the circlips then, right ? Cheers Andy Edit ... Rob, along with the post from Roger, I think understand your reply. This is all still quite new to me. The advice is appreciated. Edited by - mahatma on 6 Feb 2004 20:27:26 Link to comment Share on other sites More sharing options...
oilyhands Posted February 6, 2004 Share Posted February 6, 2004 Second Roger's advice, circlips should only be fitted when the pin is fully floating in both rod and piston. If the pin isnt exactly central this is not normally a problem, provided that difference isnt greater than 1mm, there will be a degree of movement required when the rods are fitted and you may find that the rod eye is not completely central between the pistons bosses. FWIW I would always fit forged pistons fully floating, it is possible to hone the small end of the rods to size to allow run the pin directly in the rod material, provided that an oil delivery hole is drilled in the top of the rod. Oily Link to comment Share on other sites More sharing options...
mahatma Posted February 7, 2004 Author Share Posted February 7, 2004 Excellent, thanks all. Andy Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now