Gudgeon(Piston) Pin + Piston + Rod Matching

[stradlater]

Say you pull apart an engine.

and you dismantle the rods (keeping the caps with the rods), pins and pistons. Which bits are relevant to which (paired)?

Is it important to keep the pin with the rod or the piston? Save for getting them balanced, is it important to keep the piston, rod, pin pair? Is is necessary to get new circlips?

What I'm getting at here is, I'll probably be using different rods with my GZE pistons from that which they came with. I need to know whether to use the pin from the rod or the pin from the piston. I'm inclined to think that the piston and pin are the pair rather more than the rod and the pin.

Anyone actually know?

And, if you buy new rings, do you get the little oil rings at the bottom as well? Or do you keep those and re-use them?

[Forcefed6]

Pin is generally paired up with the pistons. Little end of conrod is just a brass bush and is a replacable item.

Ring sets come with ALL rings to fit pistons. 2 compression rings, 2 oil rings and the spacer ring.

[stradlater]

Is the little end bush worth replacing?

And how the fuck do you get them out?

[Forcefed6]

Nah they don't really ever need replacing.

If the do, it is best left to a machine shop to do, as it is a press out/in job.

[stradlater]

cool
that's what I thought
so the pin is relative to the piston, not the rod.

so important to keep the pin+piston pair when getting machined, yes?

[roadsailing]

probably not crucial, but you might as well keep them together, buy some ziplock sandwitch bags and keep everything together.

(write what piston it is while you are at it)

[stradlater]

keep which bit together are you saying?

[roadsailing]

piston with gudgeon.

what are you getting machined on a piston?

[30psi 4agte]

STRAD: if you put just the gudgeon in the rod and test for free play (wobble) the gudgeon. How does it feel ??

What im getting at is that you those bushes in the small end of the rod do wear , so it would be wise to check them and replace if needed.

On different note. How free do the pins move in the pistons?. When i prept my GZE pistons, I ended up gently cleaning the hole (gudgeon hole)in the piston with some 1200 wet n dry to make sure that every pin moved freely in the piston when oiled

Its a fine line sort of thing. ....... You want the pin to beable to move but not be sloppy or they will knock , which i dont have to tell you is bad..

[stradlater]

Yeah, but I guess it would depend on which pin you are using in which rod. :-)

But I see your point.

[allencr]

cleaning the hole (gudgeon hole)in the piston with some 1200 wet n dry

I WOULD NOT DO THIS!
It is near a 'mirror' finish from the factory, and even your gentle 1200 won't get close to it. The expansion rate of the aluminum compared to the steel is quite different, so a loose fit when cold is not what it needs.

[30psi 4agte]

"I WOULD NOT DO THIS"
Yeah when they are new but even then some pistons are along way from perfect.!
By cutting the gentle part out of my post you make it sound far worse than it is.

often when the pin is pulled out after long use it will leave marks in the piston, like small scatches.+ the wear maks that the gudgeon has caused over time.
These should be removed. A gentle wipe with some preferable used 1200 will be of no harm at all removing almost no material but cleaning the surface of the piston and allowing the piston and pin to operate how they were intended to.



STRAD: In the end its up to you if you choose to do this or not. I say every little bit counts ! I have been blueprinting ( if you want to call it that) My pistons like this for years. If the way my 4age performs is anything to go by then........

[stradlater]

Hrm. Interesting thoughts there guys.

My pins are exceedingly difficult to remove, I'm talking hammer and some other shaft like device to get them out. They are well stuck.

That said, I'm not entirely sure I want to rub them back like you've suggested, I can see the harm in doing so, particularly with my very bad fine motor skills. I'm going to get the pistons machined back at the top (take off 1 mm or something) and then cleaned. I'll probably leave it at that then, but we'll see what happens.

Thanks for your inputs guys!