Has anyone tried piston expanders with alum. pistons to stop piston slap. I have a rebored engine that is still noisy.
It is your rods out of alignment!
That is the only thing that will cause piston slap!
please see this thread Kohnke,
Steve, Fact, pistons Do Not slap from being in an over size bore, they can raddle, how ever.
A piston will only slap from a Rod Alignment Issue!
Piston Knurling, and skirt expanders was a WW2 cobble fix! They didn't work!
Knurling was supposed to tighten the piston in the bore, and didn't work as it would wear off with very few miles, and with out rod alignment still had noise.
Piston expanders, were ineffective, for the same reason as Knurling.
The rods not twisted. There is too much clearance for the alum. pistons.
Okay,....someone has to ask, so I'll stick my neck out,.....what the difference between piston rattle and piston slap?
Nothing, it's just another case of Herm not knowing what he's talking about!
I am running two engines with excessive clearance, one of which should have been bored when the mains and rods were replaced. I about wore the inspection cover out checking rods and so on before I discovered the big gap between the piston and wall and realized the engine had to get good and hot before the noise abated any at all. Just finished a good tour with one of them and other than the noise, engine could not have been better.
Okay,....someone has to ask, so I'll stick my neck out,.....what the difference between piston rattle and piston slap? " END QUOTE "
A Rattle, is from a piston that has the cylinder bore worn over size, that still has rings that seat, with no oil burning, rods that are in alignment, but the piston has to much skirt clearance that lends its self to noise.
Slap will only come from a rod out of alignment, and the longer it runs that way, the worst it gets by digging holes in the cylinder, on the thrust side.
Frankie, I am not saying your stupid, it is just that everything you know isn't true.
Good one Herm, you stick to that 100+ year old idea of slap.
I'll stick with the terminology accepted around the world used since then for piston slap.
I have knurled pistons in two engines with very good results. These were engines that were .005 and .007 over. The motors are both very quit. No it doesn't wear out!!!!!!!
Herm, some thing a little more up to date for you to read. From a 5 volume reference books,
The Modern Motor Engineer.
I'm with curt on this one I've knurled pistons before and it works fine
There are 'micro peening" machines that work like a tiny plannishing hammer on the inside of the piston skirt. Basic theory is to expand the piston skirt by "peening" punch displacing metal with each blow (to the inside face). Metal needs to go somewhere so it 'Bells-out' the bottom of the piston. Apparently some motor rebuilders still have the machines to do it.
Probably still better to have pistons correct size for the bores.
I remember a kid in middle school gym class. After the first few trips through the communal shower, he took on the name "Micro-Peen". We also called him by the metric system. "Millimeter Peter", but his name was Dan.
It's weird how I read this thread earlier, and now this pops up on my regular Facebook page
Fakebook can read your web browser history BTW.
And my pistons are knurled. Engine is worn out. Still runs ok though. Was told on this forum it was a gonner years ago when it seized. Still runs. Home made piston rings and all.
I bought a set of expanders off tbay for a Model A, one engine I am running is .60 over with lots of clearance and since the A is 3 7/8 and a Tis 3 3/4, they might work. Will be interesting to see what happens.
Frankie, no engine builder, that knows anything, about Piston clearances on the Aluminum pistons would never use that chart for anything, but to wipe there .
You Boys that used Piston Knurling, pull your pistons now and look at them, The raised part will be gone, and all that will be left is the Flat design imprinted in the piston.
There snake oil. There used to be several at every swap, that looked like used once, and put away.
Piston knurling can be a good solution for engines that see limited use.
Heck I knurled the pistons on a 240z that I drove years ago. Two years later when I traded up to a XJ6 it was still quiet. But I'm just a dumb farm boy that didn't tear the engine down to check for wear on a good running engine
Then, there wouldn't be a true way of knowing, would there!
And who said it would make a difference!