Question(s): Is it really necessary to heat con rods/wrist pins for press-fit pistons prior to assembly? Or, would a press ram with proper anvils/installers, minus the oven process, work just as well? Thanks, Eric
Hey Eric, Back when I used to do this, we did them cold. But that was almost 30 years ago now. And even then we didn't have the best equipment in our shop. So, to do it right...I'd take it in and let an expert do it. That was of no help at all, was it???
I agree...one tiny mistake and you can ruin an engine. It doesn't cost much at a machine shop just to press the pistons on.
well you can press them cold. Sometimes what happens is that the pins will "seize" a little while pressing them in. When that happens it usually releases with a bang...and if you have hyperutectic or cast pistons, they'll sometimes (usually) break. Especially hyperucraptic pistons. They're pretty brittle. Pressing them cold just doesn't give you a feel for what is going on. I use a propane camp stove. Put all 8 rods on the stove (small ends resting directly on the burner), heat 'em for about 5 minutes, flip them over, heat 'em for another 5 minutes and then just slip the pins through by hand. Super simple. The propane usually won't heat them enough to turn them red or discolor them unlike a regular rod heater that most machine shops use. Even then, I doubt that it's any problem if they do discolor...I've never seen one break at the small end. Usually they'll break at the big end or rod bolts first.
Just one more thing on the heating and pin fit process. Be sure and check each pin in the matching piston, to make sure it fits without binding or such. Should slide in easily and turn smoothly. Have had to polish some a bit to achieve correct fit, or even do a little buffing on the piston pin holes themselves. Just a tiny bit though with some fine emery cloth, when assembled and the rod is cooled, grab the big end and lift it up. The piston should flop from one side to the other very easily. Be sure and lube the pin when assembling them into the block.
god i love my floating assembly..... double spiral locks, although a pain the first few get so easy to install.
Wow! Lots of great info. guys. Thanks! Not to worry, Tony, any advice/opinions/stories are appreciated; and you nailed all three categories! However, the "propane camping stove wrist pin-to-connecting rod installation method" wins my Backyard Institute of Automotive Whatevers tech article of the month award. Seriously though, that idea addressed both my concerns for monetary effeciencyand "did it myself" bragging rights. Thank you mavman! I think I have a project lined up for this weekend, now. This is great, I don't even have to marinate them first. Thanks all, Eric
A camp stove is too fancy for me. The george forman grill has been used for many a rod journal and bearing race. 300 F is normally good enough for most press fits. You can get that with your wife's oven too, but she might not like having engine parts where she cooks the food. Most shops I've seen will cool the pins in liquid Nitrogen before they heat the rods. I've also seen them press in pins using a ram. They have a min force required for press. This just makes sure the pin won't come loose. If the pin goes in too easy it's normally swapped out for a slightly larger one. Or you go to full floaters.
