Heckeng Posted February 7, 2007 Share Posted February 7, 2007 Does anybody know if changing press-fit rods to bushed rods would reduce the strength of the rod due to the decrease in material on the small end? Link to comment Share on other sites More sharing options...
Sam (Bones) Posted February 7, 2007 Share Posted February 7, 2007 how often do you ever see the small end fail? Link to comment Share on other sites More sharing options...
Heckeng Posted February 7, 2007 Author Share Posted February 7, 2007 That's kind of my question Sam! I know bushed rods are better as far as rpm potential and friction, but most rods that are bushed are bought that way, so the manufacturer could make the small end a little larger to accomodate the bushings and retain their strength. If a person has some decent stock rods that are not bushed, is it beneficial to bush them? Link to comment Share on other sites More sharing options...
Sam (Bones) Posted February 7, 2007 Share Posted February 7, 2007 send a email to Don, he'll set you straight Link to comment Share on other sites More sharing options...
alex's72fgmc Posted February 8, 2007 Share Posted February 8, 2007 bushed rods dont exist.... Â bushed wrist pin piston holes are what you are refering to where the piston is made to where the pin slides in verses being pressed in and uses spirolocs/ inside spring clips to hold them in the piston. the rod end is the same size either way and slides on. If the connecting rod was made loose the rod would break and destroy the engine. "i dont think a manufacturer would want to pay for a motor that blew because of that design would you?" Â Alex Link to comment Share on other sites More sharing options...
Heckeng Posted February 8, 2007 Author Share Posted February 8, 2007 I don't think that's correct Alex, If you want a free floating wrist pin, I believe the pistons you order are the same, but the small end of the rod will be machined and have the wrist pin hole enlarged so that a bronze bushing can be pressed into the rod itself. The bushing and the pin are not an interferance fit, so the pin is free to slide back and forth. If you do that, then the spirolocks will be used to retain the pin instead of the interferance fit between the rod small end and the wrist pin. With aftermarket rods, you can order bushed or press fit and the rod is designed to be a certain strength with each, but with stock rods, you have to have them machined and remove material to allow the installation of the bronze bushing. Link to comment Share on other sites More sharing options...
Guest Posted February 8, 2007 Share Posted February 8, 2007 bushed rods don't exist....  bushed wrist pin piston holes are what you are referring to where the piston is made to where the pin slides in verses being pressed in and uses spirolocs/ inside spring clips to hold them in the piston. the rod end is the same size either way and slides on. If the connecting rod was made loose the rod would break and destroy the engine. "i don't think a manufacturer would want to pay for a motor that blew because of that design would you?"  Alex Incorrect the pin presses into the rod not the piston. Alex, most aftermarket rods do have an ampco bronze bushing in the pin end that is honed to give .001"/.0015" of clearance on the stock diameter wrist pin, .990" on BB's and .927" on SB's. Chevrolet did run floating pins in a few Special HIPO engines from the factory. 302's in the Z\28's,the ZL1 427,The LS7 454,The L88 427 come to mind. You are correct about the spirolocs/round wire retainers. There are pin buttons of aluminum and teflon that center the pin by taking up the space between the pin and the cly wall, this is done in top fuel hemi's. A piston with the lock grooves on the outboard ends of the pin can be used as floaters or pressed pin. The pin for a floater piston has the ends ground and micro finished so the pin can't grab the locks or push unevenly against the locks. With a pressed pin set up the rods small end is heated to expand it so the pin can be pushed in, when it cools the rod shrinks around the pin locking it tightly in the rod so it can't walk out into the cly wall. Back when,1900's to 1940's, there were some engines that had a pin that slipped in like a floater and had bolts that locked the piston to the pin on each end. The advantage to full floating wrist pins is that even if the pin locks up in the piston the pin still turns in the rod. If you freeze a wrist pin in a std pressed pin set up the piston gets torn off the rod and wrist pin, then the rod attempts to cut into the block like an axe. Scott is correct in his thinking 100% The wrist pin hole is bigger in a floater rod than a stock pressed pin rod. Strength wise would be the same on a given rod, the floater is more durable and less likely to cause problems. Don Link to comment Share on other sites More sharing options...
alex's72fgmc Posted February 8, 2007 Share Posted February 8, 2007 err i stand corrected. I forgot about the baking of the rod and piston and freezing of the connecting rod. my appologies Link to comment Share on other sites More sharing options...
Sam (Bones) Posted February 8, 2007 Share Posted February 8, 2007 I knew Don would straighten us out Link to comment Share on other sites More sharing options...
wallaby Posted February 9, 2007 Share Posted February 9, 2007 Did we get to the part about which design is the stronger rod? Link to comment Share on other sites More sharing options...
Guest Posted February 9, 2007 Share Posted February 9, 2007 I was going to say then my SIR bushed rods are missing, call the cops!!! I better go home and fire her up and see if there is any compression if bushed rods do not exist. Link to comment Share on other sites More sharing options...
Guest Posted February 9, 2007 Share Posted February 9, 2007 Did we get to the part about which design is the stronger rod? Did this part help Wallaby? "The advantage to full floating wrist pins is that even if the pin locks up in the piston the pin still turns in the rod. If you freeze a wrist pin in a std presses pin set up the piston gets torn off the rod and wrist pin then the rod attempts to cut the block into like an axe. Scott is correct in his thinking 100% The wrist pin hole is bigger in a floater rod than a stock pressed pin rod. Don" Link to comment Share on other sites More sharing options...
Heckeng Posted February 11, 2007 Author Share Posted February 11, 2007 Don had e-mailed me, and said that stock rods are usually honed if they are wanted to be made "floating". The metal is not hard enough to hurt either the pin or the rod. If you actually bush the small end of a rod that was originally not bushed, you will reduce the strength because you remove material, that just makes common sense. BUT, most of the time, the transition area where the large end of the rod is machined for the head of the rod bolt is where a rod breaks. With stock rods, acording to Don, there is normally plenty of extra metal on the small end and the small end is not where you need to worry about. Link to comment Share on other sites More sharing options...
Sam (Bones) Posted February 11, 2007 Share Posted February 11, 2007 so...in a way, we were correct Link to comment Share on other sites More sharing options...
Heckeng Posted February 12, 2007 Author Share Posted February 12, 2007 Yup, Everybody is correct! Link to comment Share on other sites More sharing options...
wallaby Posted February 12, 2007 Share Posted February 12, 2007 It's one of those chicken/egg deals. If the small end of the rod is not the end to worry about, why bush it? From the sound of it, the process doesn't make the rod stronger, doesn't reduce friction, and doesn't increase horsepower. I always thought full-floating wrist pins were the way to go because all the high-muscle chevy stuff had 'em. Is the only advantage a less catastrophic rod throwing...if it were to happen? Or is it just a miniscule bit of insurance so it doesn't? Link to comment Share on other sites More sharing options...
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