What were your noise symptoms when hot, cold, at idle, revving up, revs coming down?

 

By waist pin I take it you mean gudgeon pin the small pin at the small end of the con rod, I have in the past rebuilt several engines and every one required to warm up the piston to push fit the pin in , usually boiling water would do the just fine or a low oven, so does the con rod move on the pin , but also can you push the pin out of the piston, if so it possibly the piston that worn, the pin should not normally move in the piston unless it warm

 

Engine ran great, did not heat, plenty of power, but as soon as it warmed up, the loud metal on metal banging sound started, and increased and decreased in sync with the rpms.
No cylinder damage, or signs of pin movement.
Just that when the metal connecting rod taps against the side of the aluminum piston...That is the sound.
As said before, it was most likely the bad bearings, but I'm hesitant now to rebuild it all without new pistons.

 

Yes, wrist pins, I'm in the U.S, gudgeon pins is more a UK term.
The pin is Not moving now(parts in hand, pin, piston and rod assembled).
The press fit appears fine.
Heating up the piston wouldn't be enough for assembly either, they must be pressed in.
My concern is if it is expanding to out of spec under normal engine heat, and the pin is basically rattling in the piston.
I have no signs of this, no visible wear or play, other than the noise, which again, I think was the worn bearings. But, given the issues these engines have, I'll likely replace the pistons too, most everything else is new anyway.

 

Well, I'd think oil pump banging if only heard when hot at idle or below 1500 RPMs.

Something like a wristpin causing rod slap or piston slap would continue through all RPMs no matter how high you revved, I'd think.


Also, I don't know why you'd replace all pistons. Money is no object?!

I'd take that one loose piston/wristpin/connecting rod to a local race track shop and I'd bet they'd have a quick+cheap fix (maybe an oversized wristpin??). If not an oversized wristpin, maybe have that one piston machined-out for bushings?

 

If I had one in question I would either do all the pistons it’s what $5-600 or replace the one in question if money was tight for $80 ish. If you have the motor apart for a full refresh why not do them. If you are keeping the truck it makes sense to bullet proof as much as you can while you’re in there.

We aren’t talking crazy money here while doing a full rebuild.

 

The noise Did increase with rpm, and Did continue After I replaced a cracked oil pump.
Money Is an object, I don't through $500 around like change, but, with around $3k in new parts, what's another $500? Alot, but I think worth it(I really wanted to spend that in driveway gravel, lol).
As for the one piston assembly that I said "could be" loose; it is that the Rod slides on the pin a little easier than the others, yet there is no play or slack that can be felt.
That could be as simple as more oil had ran off that one, was a thinner film, and it moved easier.
That made the rod slide and tap the internal edge of the piston...and that clack sounded just like my engine noise.
Which started my speculation. That could there be an out of spec pin or piston(I don't want to consider rods too, but couldn't rule that out either really) After things heat up, since different metals expand/contract at different rates, that something goes out of spec and rattles.
The reason I think the pistons Are good, is because O.D and skirt O.D are in spec. The cylinders still had a good cross hatch and no visible damage, and I was able to use standard size bearings.
Considering I just rebuilt this thing, only to get coolant in 3 cylinders before it cranked, and have to source another block and start over, I just wanted to see if anyone had found a wrist pin or piston as one of the many causes of the dreaded D2 tick.
Most of me says these pistons and pins are fine, but there's that small nagging voice that says, don't cheap out last minute and regret it after.
It's funny that I bought a new set of rings already(10 actually, just in case I break or overgrind any)...and new pistons come with wrist pins...And rings...which I'll have to swap out for the gapped ones, lol.
Thanks again

 

I agree, and have been leaning towards buying a new set before even starting the thread. Since, I've talked myself into it.
I want a good engine that lasts for me.
And, if I sell or trade it, I don't want to dump it on the next guy. Any or all issues will be obvious or disclosed.
I'de refer any future owner here anyway(if they weren't already) and they can see what's been done.
Thanks

 

My Dad made a pin and fixture last week to remove the wrist pins. It works great(now to remove the other 7).
I will measure this one this week at work(computer, not an inside and standard mic).
The pin in this one has worn the hole in the piston oblong.
Not visibly, but you can feel the pin roatate an 8th of a turn either direction, then tighten up.
Typical wear of pin rotation in sync with the rod's stroke.
I need to confirm now that the pin is a press fit in the rod, and the pin should turn freely in the piston, as in many engines.
Before taking this piston off the rod, the rod slid on the pin, and the pin was tight in the piston, the opposite, and indicating excess wear, so I'm curious what the rod, pin, and piston will measure.
My guess of pistons and pins being another cause of the typical D2 warmed up tick(metal on metal hammering sound) is looking more likely.
I will update with measurement results.

 

After measuring the wrist pin, connecting rod pin hole I.D, and piston pin hole I.D, I found;
The connecting rod in spec at(measuring both sides)
.9438
.9440
The wrist pin
.9447
.9449
The piston
.9454
.9459

According to spec, the piston hole the wrist pin goes in is
.0001- .0004 oversize
This was measured on a QV machine, very accurate, but even a slight shadow(regardless of adjusting it's light) could cause this much error.
Also, this would be measured normally with an inside micrometer(we do not have one that will read quite that large, biggest is .2 shy, anyway...)
So, as I also said previously about 4 decimal places on the piston diameter, being measured with a micrometer, I cannot belive that you, me, and the next guy will all get the same reading when measuring a dimension so small with a micrometer.
That the .0001- .0004 oversize I got is small enough under the circumstances to be chalked up as error.
Not to cut corners, but this is a low rpm smallblock, not an aircraft.
All 8 piston diameters and bores are in spec.
All 40 rings are gapped to spec(back in their packages, not yet on pistons).
All I need to do is put each piston in it's bore, upside down without rings, and measure piston to cylinder wall clearance, and I will tonight. Given the other measurements, I have no reason to belive that they will be out of spec.
My only minor concern at this point is the rate at which cast aluminum expands under heat vs hardened steel.
Which I need to do more research on.
That the piston is not expanding more than the pin, and causing a larger gap, thus creating a loose fit, and therefore noise.
I don't think it will, but if I get an engine tick after start up, I will have proven myself wrong(hopefully not).
I had also mentioned before about the pin being able to turn freely in the piston(and it does), and that after rotating the pin either direction, it would get noticeably tighter(even though it would still continue to turn, as it should).
That I thought this tightness was from wear from the normal back and forth turning of the pin from the rod's up and down stroke. When what it actually is, is the pin rotating up to and against the oil grooves in each side of the piston pin hole.
Anyway, this post was/is me thinking out loud as I chase gremlins.
I hope something here can be beneficial to the next guy, and I appreciate everyone's input.
Assuming my piston to bore spec is good(as it should be), the bottom end may be together over the weekend, depending on what else comes up.
Thanks