OT - shrink fit piston wrist pin - connecting rod

i suppose its like anything. Once you've done it, piece of cake. If you want to give yourself a bit more margin, put the pin in the freezer. if you do go to the auto shop, they'll just use a torch.

Karl

No- Take it to a shop. The piston needs to go into a Sunnen heater that is a heating unit designed exactly for this. Any other attempt could be a very expensive mistake. Trust me...

Rob Fraser

Fraser Competition Engines Chicago, IL.

"Rob Fraser" wrote: (clip) The piston needs to go into a Sunnen heater that is a

^^^^^^^^^^^^^^^^^^^^^^^^ From your business name, I assume you know something about engines. So my question is not a challenge, but a request for an explanation. The OP says he pressed the wrist pin out of the rod end, and now needs to reinsert it. You certainly can't have an interference fit in both the piston and the rod. So why would you have to heat the piston?

He meant the rod, I bet. Sunnen makes a small heater for rods

No need to heat the rod if you use a good lubricant and properly support the piston while pressing.

I use Goodson's lubricant when pressing pins:

A bit of lube on an interferance fit can save one from disaster.

It is amazing how quick, the hot / cold thing seems to equalize and grip like a gorilla. DAMHIKT.

Wes

-- "Additionally as a security officer, I carry a gun to protect government officials but my life isn't worth protecting at home in their eyes." Dick Anthony Heller

Boiling water on a rag wrapped round the rod (to provide a resevoir of heat), and plumbers pipe freezing spray for the pin (better still if its hollow and you can stuff some rag down it to provide a resevoir of freezing spray and you've got a fair chance it will just drop in. If not, check how tight it feels and either apply more boiling water and freezer spray and procede as advised above or farm it out to a pro if it is not even starting to fit. At 100 deg C, there is no risk of de-tempering anything. Just make sure its absolutely square ...

On Wed, 1 Oct 2008 12:14:20 -0500, the infamous "Rob Fraser" scrawled the following:

Is this one of those DAMHIKT things, Rob?

- If the gods had meant us to vote, they'd have given us candidates. --------------

Correct- it is a rod heater. I sometimes toss the wrist pins in the freezer for a while too on a known tight fit. Like any Carrillo or Manley Hbeam rod. I would never, ever, do it any other way. It's a lesson in disaster and I have had engines with 2-3 passes from other assemblers shops who cheated it and blew the top of the rod clear off. 15k engines destroyed because someone took a shortcut. It takes a machine shop about 30 min to do a set of 8 properly. A little LPS or assembly lube on the pins is also a *Must-do* and when priming the engine with a drill or if it's on a dry sump rotate it with the plugs OUT for at least 30 min. by hand on the crank bolt or blower pulley with a ratchet to get all that lubed up and that has no relevance to the interference fit but your bearings and cam will thank you for a long time. Another little trick is to fill the wrist pin with a few cc's of oil before you put the piston in the compressor. That way when the engine is dry cranking that oil will seep out and lube the rings and cylinder walls a little extra. If I ever saw a shop hit it with a torch I'd be finding a new shop fast. If you can't find a shop to do it local. - mail them to my shop, I'll do it no charge. Just cover the shipping. Don't let someone f*ck up your engine.

Rob

Fraser Competition Engines Chicago, IL.

Any idea what the target temp is? We do full-floaters only. I used to do VW Porsche, we would put the timing gear in oil heated to boiling on a hot plate before pressing it on the crank, torches were for verboten.

Depends on the piston, (cast vs forged) the alloy and center taper of the pin, the size micd' out .0001 increment, the rod( Alum, steel,ect. ) the heater has a knob on it to adjust target temps on both coils. To be honest, I could not even tell you the temp. I am just so used to doing it it's second nature I go by feel of the pin going in.

Rob

Fraser Competition Engines Chicago, IL.

I have a local shop that does use a rod heater, I had already contacted them prior to posting - I just did not want to spend money on something that (in theory) I could do myself. Thanks for the details in your posting. Reason that I asked this question in the first place:

I suspect a broken valve spring (never experienced one before) at 120K miles on an engine that was on target for being a 200K to 250K mile motor. THe head is now more of a modern art sculpture than a useable head:

That reminds me of my VW Porsche days!. I would weld that if it was something rare like a Lotus crossflow head.