Gudgeon pin question (1 Viewer)

[snapdragon]

Hi Guys
I am busy rebuilding my 1fz-f engine and almost done, I have rebored the cylinders and got 0.5mm oversized pistons.
But here comes the problem, the gudgeon pins that came with the pistons are very tight and I am struggling to assemble them.
I can't find anything in the service manual relating to this.
Does anyone have any suggestions as to how to solve this issue the correct way?
My brain has been floating through ideas of polishing the pins to heating the pistons, but I do not wish to do this job again in a hurry and have done everything to the book and with genuine parts only.

Any suggestions? And what am I missing?

Cheers
Warren

 

[Malleus]

I assume you're referring to the pin joining the connecting rods to the pistons, what are referred to here as wrist pins. Considering the fact the the pins are hardened steel and the pistons are aluminum, and assuming the problem isn't a burr but actually a diameter size difference, the proper solution (also assuming you have chosen to work with the parts you've been sold) is to ream the piston bores. Since the pistons are cast aluminum, press fitting the pins into the bores would probably result in damaging the pistons catastrophically (of course, I'm not there and can't see them, so I'm being overly cautious).

The fit should be what is referred to here as a line fit or a close sliding fit. What you want is a hole of the same size as the pin; no space between them. You should use a micrometer to measure the pins, and you'll need what we call snap gauges (or expanding bore gauges) to measure the piston bores, and a micrometer to measure those. Any machine shop can do this in short order, and then ream the bores to suit.

The potential problem with this method is that you have to measure each pin and each bore and size them to fit, turning your Toyota into a Rolls-Royce. As long as the pins came from the same grinding setup and the pistons came from the same boring setup, this won't be a problem, but there's no way to know that. Japanese parts aren't supposed to be manufactured this way, which is why they are regarded as superior to the "cut-to-fit, paint-to-match" method the old masters used.

FWIW, unless I had to get the engine together and couldn't wait, I'd return both parts.

 

[White Stripe]

I believe a machine shop can bore out the wrist pin hole larger.

 

[Fosters]

Heat up the parts…don’t polish or bore out anything…I believe the manual has the procedure detailed

 

[snapdragon]

Heat up the parts…don’t polish or bore out anything…I believe the manual has the procedure detailed

Yes, just found the answer. Piston must be heated between 80 and 90 degrees celsius.
Now they just slide in.

Thank you for all the help