Hi, I want to replace stock piston 440 '76, with kB 236. I removed wrist pins with help of press, now I'm going to press in new ones. It seems that pins are quite loose in the rods, i can insert them almost manuały. The old pins are the same. Stock pins are press fit style like the new that came with pistons. I'm concerned that after i will heat rod and insert pin it will be still loose. Am I right? Shall i proceed any how?.
Wrist pin stock rods issue, too loose?
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What makes you say they are loose when you had to press them out? Measure the pin and bore and check the specs!
Challenger340
Well-Known Member
Stop what you are doing, because to install New Pistons on OEM Rods you do NOT "press" the Pins in.
and,
especially not with a KN236 Pistons which are an extremely brittle alloy(moreso than even a stock Piston), and which are prone to cracking around the Pin Bosses even when pressing them off after service for any reason.
to re-iterate:
"Pressing" new Pins into new Pistons onto an oem Rod is NOT an accepted method of installation. Removal = Yes, Installation = NO !
If the new Pins are loose in the old Rods you have a problem, because the interference fit should be around -.001". meaning either your Pins are small or the Rod Small ends are too big.
IMO,
You are best to take your Pistons/Pins and Rods to a professional Machine Shop with a Sunnen AG300 Gauge to check both, then if satisfactory interference is present in the Rod small ends they can Install the Rods on the Pistons thermally using a Rod Heater.
Rod heater for sure !!
Lefty71
Well-Known Member
Not necessarily "shot", but would need bushed to be useable correct??
(Not necessarily cost effective without knowing particulars)
Thanks guys for quick reply. I,m going to do it for the first time.Curently preparing stuff and myself to insert new pin and pistons. I've been watching YouTube instruction: heating device for rods, fixing plate for pistons etc.
Month ago I pressed pin out, i did it with hydraulic press, no problemem. Lately I took this pin and inserted manuały into rod. It suprised me, without force. Therefore i'm a little bit worried what will happen with new pins. Certainly i will make precise measurement. Is that tipical after press out pins become loose? Press out went very easy, no issue.
Month ago I pressed pin out, i did it with hydraulic press, no problemem. Lately I took this pin and inserted manuały into rod. It suprised me, without force. Therefore i'm a little bit worried what will happen with new pins. Certainly i will make precise measurement. Is that tipical after press out pins become loose? Press out went very easy, no issue.
Your best bet.....get the wrist pins floated by a machinist and circlips used in the piston to hold the rods in place. The pistons should have come with the clips. The machinist can bush the small end or bore them plus add a oil hole to float them.
I did hot heat up rod before press out, is that necessary?
jamie
Well-Known Member
Not sure his pistons have circlip groove's. Might be cheaper to work with a different set of used rods.
jamie
Well-Known Member
Did you only press out one pin so far?
Oh I see the KB236 does come with clips.That is an option.
wyrmrider
Well-Known Member
yep first thing is to check for circlip grooves and rebuild the rods- use DC bolts for value
oversze pins? (with rods resized) and hone the piston pin bores
have the pins chromed? (just kidding)
oversze pins? (with rods resized) and hone the piston pin bores
have the pins chromed? (just kidding)
Two pins pressed out, the same situation for both, manualy I can put it in rods. I would prefer to press in new ones rather floating, last option. Can you support me in press out good practise?
Below piston picture with cirlclip on 236, am I right?
Below piston picture with cirlclip on 236, am I right?
Pressing the wrist pins out is fine. Problem is the pins no longer friction fit the rod. Will they all end up the same? Who knows. But I wouldn't chance it with them. You either have press fit pins or circlips. Not both or they will bind. The 236 is set up for press fit or float.
Are you using the wrist pin that came with the pistons? Can you measure one and one you pressed out?
Are you using the wrist pin that came with the pistons? Can you measure one and one you pressed out?
Not sure if this is a typo, but are you saying you heat the rod pin ends (red hot?) to get the pins out. If you heated the ends cherry hot, or past the straw color, the rods are junk now. I showed (or told) a customer how I install pistons, and he ruined a set of new eagle rods by heating the pin end of the rods too hot. They were stretched too far, and I could press a pin in by hand on one rod.
Lefty71
Well-Known Member
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