Tight wrist pin

[DWP]

Try to install a set of mahley pistons. 3 of the wrist pins I can just about push in with my fingers. The 4 th one is tight. Need some tapping with a brass hammer. All pins measure 8665" . I seems one of the pistons is bored a little under. Is this something I need tt worry about?
DWP

[mark tucker]

YES!!! do not assemble it tight.even with the floting rod, you do not want it tight. is 1 side tighter than the other? if so it may have a lip or burr.swap pins to see if the pin is afu(it can be the right size but still afu/bent barrel or hourglassed) . if the piston needs honed have a good automotive machine shop with a rod station do it, You can not do it your self (unless you happen to have a rod resizeing station and have the vw size mandrill)

[jfats808]

No it isnt something to worry about. Clean the pin and bore well, lubricate and install. With the clips holding the end, there isnt a worry of it needing to move back and forth much. Teflon plugs is another story.
If theres burrs causing the pin not to ride smoothly in, then thats an obvious one there. Lots of aa sets ive done lately had a.tight fitting or two pin ride. Though tbh, ive never had an issue with a mahle set to date.
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2276 IDA's 86C 11-1 DD

[modok]

The pin can rotate in the rod bushing when the engine is cold, so unless the rod bushing is also too tight you are ok

When the piston warms up it should be plenty loose. The old style cast pistons required the pistons to be heated over 80 degrees otherwise the pin would not budge. It was in the instructions back when stuff came with instructions

[skills@eurocarsplus]

[mcmscott]

Also if your work environment is cold, as in Pennsilvania where it snows ass deep to a nine foot indian, then this problem is more prevalant

[Wasted youth]

2.0 Air cooled, CV series. A very high mileage engine.

Removing wrist pins from connecting rod required brass drift and about 15-20 solid whacks with a small hammer. Wrist pin bearings/bushing are discolored and heat streaked.

I am not an engine builder, but for a high mileage engine, the tightness of these confused me.

What's going on here? I can only surmise the wrong thickness wrist pin bushings were used, but I only show one size for this model engine

[modok]

It was probbly just gunk. Clean the gunk off the parts and check the fit again.
Clips often burr up the piston too, need to heat the piston slightly and de burr where the clip rides to have any chance of the pins coming out of the PISTON easily. ANd it could be you ended up marring the bushing hammering the pin out, or not, or it's just gunk, hard to say.

If you want to know how wrist pin bushings work read this one, it was only yesterday.
https://www.thesamba.com/vw/forum/viewtopic.php?t=798684

[Wasted youth]

Thank you. That was a very interesting read. The 2/10,000 inch tolerance specs were a bit of a surprise.

I will clean the parts and reassess.

[modok]

It says so in the manual

Size spec is .8664-.8667

For type 4 .9454-.9447

But they did like it tight, tighter than I like.

I prefer .001 per 1 clearance, as a general rule

Thanks to advances in oil and filters and airfilters, these parts wearing out is far less of a problem than it once was, but still watch out for oil being diluted with fuel.
Pin bushings suffer bad from oil dilution or FINE dust.

Pin bushings do not spin very fast, and they run hot, so the oil film is thinner than on the main or rod bearings.

[Wasted youth]

That is interesting to think about.

There is not a hell of a lot of radial movement there compared to other parts, but that location is also right next to where it gets hotter than two rats getting nasty in a wool sock.

[rodgersbadassbus64]

Please dont flame me… a wheel cylinder brake hone and use kerosene for a wetting agent.
_________________
Like some other respectable members, "why buy what you can build"

[modok]

Your not even in range of my weed burner.
I think
Being able to measure the result of your work comes BEFORE achieving the result. Otherwise what...you just hoping you achieved it?
And if the part DOES match teh blueprint, then it matches the blueprint, doesn't matter how you did it, with hand tools or a stick and a rock or a fancy machine or black magic.

And far as reading the manual, well, I respect those that choose not to do so, the same way I respect a medical test subject or a crash test dummy.
Thank you for your sacrifice, reinventing the wheel. I mean after all, maybe we didn't invent it right before, these things do need to be checked from time to time to make sure.

[Wasted youth]

As you mentioned earlier about gunk... the oil varnish of years of service was enough to make it more difficult to disassemble than how my mind expected.

Considering the solvent and 5,000 grit paper and plenty of annoying elbow grease, the pins now reassemble snugly, but not tightly. The bearings are past their service life, but it was interesting to toy with.

A honing tool would not provide enough control to prevent a very quick over-reach on the very minimal clearance specs.

[modok]

Cool.
BTW there are many kind of hones.
It works if you use the right tool for the job.

Just Google "connecting rod hone", and you can see what they look like.

[brass gears]

[Wasted youth]

[raygreenwood]

[modok]

No, and no
Nobody reams rod bushings, I mean you could but I don't see why you would.

if you want to hone connecting rods, the most logical thing to do is use a honing machine for connecting rods.
And the most commonly used tool for boring connecting rods, is a machine for boring connecting rods.

Sunnen is the biggest name in honing, and Robbi is the biggest maker of rod boring machines right now I think.

A sunnen rod honing machine is not a rare thing, I have two at work, one at home, and two friends that also have one, so that's five I could use at any time. I bought the last one for 150$ at an auction and it came with a boatload of Tenesee abrasives honing mandrels. The basic machine hasn't changed much in 100 years. It's like a drill press in that you don't need a drill press to drill a hole it just makes it easier, so to hone a hole you need the right honing mandrel, and you can also use it with a low speed drill with the right adapter, which is what you do if the work piece is large, like honing a truck axle for a kingpin.
You could get yourself setup to rebuild conrods for under 2000$ in tooling, very realistically. But yeah I know you don't want to do that for a living and don't have the space to put one.
The whole point of why I have a machine shop is so people can build engine without having to buy an entire machine shop.
These machines are considered required to rebuild engines, many people will say you can't be an engine builder without access to these tools.
At one time EPW required you show that you have a boring bar and rod honing machine before they would let you be a vendor.
Now of course you can still be an engine builder, you don't have to mine the ore and machine every part yourself and have your own oil refinery to make your own lubricants, what you can't do, you have to have somebody else do it, everything is a team effort really.

[chrisflstf]

Anyone know why these wrist pins have a wide and narrow band of discoloration on them?

Its on an older motor I just tore down. Just curious what it indicates?

Edit: never mind, its just the exposed area of the wrist pin