Knurling pistons

[k-star]

Robert, How many engines have you built like this using knurled pistons? Share all your data from the failures using this process.

[k-star]

Funny, I remember in the late 70's and early 80's taking engines apart that had knurled pistons in them and I never seen any excessive wear in any of the cylinders.

[k-star]

I have a knurler i picked up for a rainy day. Never used it though but i know the process works to a degree. The trick is to knurl them up big and put them in tight so they clearance themselves. The coating may be a little more kosher these days. If you decide to pursue it i could probably loan it to you.

Maybe I can just run out to your place one day and we can knock them out?

[Wolfplace]

Keith
Industrial stuff was commonly knurled with no ill effects & I have used it to "save" some fairly unusual stuff in the past
As stated above you knurl the skirt for zero clearance, actually "finish sized" with a file til the piston went into the bore snugly
Probably not going to last like a new piston in a new bore but it will certainly work for something like this

I still have the old K-Line knurler sitting in a corner gathering dust just in case,,,,

[340king]

I used the knurler on a set of custom Ross pistons for a stroker big block Mopar after a couple of them got hurt due to an overheating/clearance issue. We had to knurl three pistons if memory serves me correctly. He raced that engine all season after that and even ran it on nitrous at cheaters day with a sprint car wing on it. He was bad fast until he ran out of nitrous. It works, just follow the instructions as detailed here.

[Dan Timberlake]

This is a question I though I would never be asking. I have a customer doing a high dollar restoration. The engine is 100% correct down to the factory original pistons. He dropped off the block last week. It had the machine work done to it maybe 20 years ago, but never assembled. The bores are about .0030" over stock size now.There is some slight surface rust in the bores. I am sure I can clean it without going bigger then .0035". It is a 350 Chevrolet with factory forged pistons.

..............

Which pistons and which engine? New old stock/ or replacement pistons.
I

Aftermarket overized piston instructions used to say that the pistons would be finished to have an acceptable clearance in a bore finished to the nominal overize.
Most shops would not dare proceed to finish a block without checking all the pistons.

Aftermarket std piston instructions used to say that std pistons would be furnished somewhat oversized to fit in the full range of factory "standard" bores.
I never got to work with many "standard" pistons, so I don't have any idea what somewhat oversized really meant. +0.001, + 0.002, or ???
If you are finding the block is a full 0.0035" over standard I'd try to dig up the clearance specs for the piston.

In the 60s and 70s Shot peening the skirts inside and out with coarse glass generally expands the skirts a thousandth or more (carefully masking the grooves, lands and pin bores ) and still looked really good after some serious street abuse. At least as good as the TRWSpeed Pro wavy finish.

[robert1]

Robert, How many engines have you built like this using knurled pistons? Share all your data from the failures using this process.

I've never built an engine with knurled pistons so therefore I've never had a failure doing so. Neither do I knurl guides to restore them. I haven't even seen anyone try it in the last 30 years. I did see some early in the many years I've been in this. It's between you and your customer. Good luck and happy knurling.

[k-star]

Robert, How many engines have you built like this using knurled pistons? Share all your data from the failures using this process.

I've never built an engine with knurled pistons so therefore I've never had a failure doing so. Neither do I knurl guides to restore them. I haven't even seen anyone try it in the last 30 years. I did see some early in the many years I've been in this. It's between you and your customer. Good luck and happy knurling.

So what you posted is just based on an opinion and zero facts?

The thread wasn't about knurled guides.

[needforspeed66gt]

Robert, How many engines have you built like this using knurled pistons? Share all your data from the failures using this process.

I've never built an engine with knurled pistons so therefore I've never had a failure doing so. Neither do I knurl guides to restore them. I haven't even seen anyone try it in the last 30 years. I did see some early in the many years I've been in this. It's between you and your customer. Good luck and happy knurling.

Considering the fact that you're speaking from a position of ignornace, why in world would you tell people who have actually used this process that they are wrong and you are right? Talk about sticking your foot in your mouth.

OP - knurling will be perfectly acceptable for what you are trying to do. Is it the most desirable way of setting up piston to wall clearance? No, of course not, but like you said the restoration people can be quite weird. Really, the only downside that can affect you long term with the knurling is that due to there being less surface area of the piston supporting it, it can wear out faster if subjected to higher side loads due to any detonation. We have an old piston knurler up the attic at work which hasn't been used for decades, but there was a time when labor was cheaper than parts, and knurling a set of pistons was a perfectly acceptable cheap alternative to boring oversize. People would have a cheap knurl job done and be on their way down the road and perfectly happy for tens of thousands of miles.

I have used the build-up skirt coating from swain tech a couple of times and it's a similar process, they build it up and you're responsible for sanding it down a little to match your bores and even them up.

You're not going to have a failure due to knurled pistons, and the scuffing at the bottom of the bores is solely due to lazy machinists who neglect to properly chamfer the bottom of the bore after honing.

[sam-missle]

Hey Keith, You can knurl pistons in your lathe, put the piston in the chuck, lathe in nuetral, knurl tool in the tool holder, rock chuck back and forth by hand, file to finish.

[Dave Koehler]

Sam,
The lathe doesn't have the built in "give" that a purpose built piston knurling machine has so it can follow the cam of the piston skirt.

[robert1]

Robert, How many engines have you built like this using knurled pistons? Share all your data from the failures using this process.

I've never built an engine with knurled pistons so therefore I've never had a failure doing so. Neither do I knurl guides to restore them. I haven't even seen anyone try it in the last 30 years. I did see some early in the many years I've been in this. It's between you and your customer. Good luck and happy knurling.

Considering the fact that you're speaking from a position of ignornace, why in world would you tell people who have actually used this process that they are wrong and you are right? Talk about sticking your foot in your mouth.

That's my opinion you don't have to like it. I don't like Miller beer. If it makes you feel better calling me "ignornant" have at it.

[sam-missle]

Sam,
The lathe doesn't have the built in "give" that a purpose built piston knurling machine has so it can follow the cam of the piston skirt.

Very true, You won't knurl the whole piston my way, but it works great this way, You can also move the tool holder in and out horiz. too.

[needforspeed66gt]

Considering the fact that you're speaking from a position of ignornace, why in world would you tell people who have actually used this process that they are wrong and you are right? Talk about sticking your foot in your mouth.

That's my opinion you don't have to like it. I don't like Miller beer. If it makes you feel better calling me "ignornant" have at it.

Calling you ignorant isn't an insult, it's a statement of fact based upon the information that you presented saying that you have never worked with them personally, compounded by the actual hands on knowledge that some of us in this thread do have in regards to the process which conflicts with what you said. You have proven yourself to be ignorant on this subject just like I'm ignorant about how to build a rocket ship....major difference is that I don't go telling NASA engineers that they're doing it wrong.

[lorax]

Hey Keith, You can knurl pistons in your lathe, put the piston in the chuck, lathe in nuetral, knurl tool in the tool holder, rock chuck back and forth by hand, file to finish.

In my high school auto shop, (YEARS ago) we had a piston knurling machine that looked like a lath. The motor had a flywheel and a connecting rod/arm that went to the lath chuck. You set the degrees of "rock" in the chuck by where you set the connecting rod on the flywheel. Kind if like a locomotice back and forth deal.

The lath chuck rotated maybe 45* back and forth, and you pressed the knurling tool into the piston. If the piston had a cam ground into it, it simply did knurl it as deep on the sides as the middle. It was called a Lubri-knurl or something close. Thing was used as much as any machine in the shop except maybe the drum lath.