Dumba$$ seeks advice-how hard is it to notch pistons?

[RustyCaddy]

i have been dremel-ing an old NA piston that was lying around to see how well it would cut and how accurate i can get using an old turbo piston as a template.

It seems pretty straight-forward but are the kind of small differences that are inevitable with free hand work times 4 pistons going to unbalance the rotating assembly?  If i could notch a new set of NAs that are in the garage (and were cheap) it would save a lot of $$ over true turbo pistons.

None of the shops around here are willing to give it a try.

And the OEM VW turbo piston has some kind of steel band on the inside...are modified NA skirts going to be too weak to trust?

Thanks

[R.O.R-2.0]

it can be done, but the TD pistons are made so they have ALOT less thermal expansion..

you can weigh the pistons on a small parcel scale, or any type of small scale, i would make sure they are all within 1/10th of a gram..

[RabbitJockey]

i believe the td stuff is a different alloy like ror says, could be wrong tho.  and like he says, if u make them all weigh the same when you're done i don't really see what it would hurt assuming u make everything smooth when you're done

[RustyCaddy]

sounds like it is do-able with some practice.

i have been holding onto some 1.5l KS pistons if i get the nerve might give them a try into a MF block with a 1.5 assembly.  Otherwise the 1.6es could go with the turbo crank and rods.

Thanks for the help...

[CRSMP5]

16+ years ago i had a modded set of na pistons made up for a td... guy used a mill to do a big happy face smile in it.. that engine was still going last i knew 8 years ago... owner finally moved onto tdi.. so will not say its a big differance in alloy.. but it did work.. and was simple..

[R.O.R-2.0]

16+ years ago i had a modded set of na pistons made up for a td... guy used a mill to do a big happy face smile in it.. that engine was still going last i knew 8 years ago... owner finally moved onto tdi.. so will not say its a big differance in alloy.. but it did work.. and was simple..

the alloys are quite different, not sure of exact names/numbers of the alloys, but there different. the TD pistons even have steel supports cast into the piston, to keep thermal expansion minimal, and strengthen the piston at the same time..

no reason you cant run n/a pistons with oil squirters, because im running n/a pistons WITHOUT oil squirters..

[theman53]

That seems odd. Steel and Al having different rates of expansion it would seem that a steel ring would be worse than nothing. They would always fight eachother. But I am not a metalurgist and they probably used some super steel with super Al and that is why they are around 100 each for a roughly 3" piston.

[vanbcguy]

That seems odd. Steel and Al having different rates of expansion it would seem that a steel ring would be worse than nothing. They would always fight eachother. But I am not a metalurgist and they probably used some super steel with super Al and that is why they are around 100 each for a roughly 3" piston.

That's pretty much it in a nutshell - aluminum expands more than steel, so the steel ring restrains the aluminum, reducing the ACTUAL expansion.  And yeah, they use some pretty nifty alloys and things!!

[sdwarf36]

it can be done, but the TD pistons are made so they have ALOT less thermal expansion..

you can weigh the pistons on a small parcel scale, or any type of small scale, i would make sure they are all within 1/10th of a gram..

 A TENTH of a gram??? Who told you that?
 We balance race motors all the time at the machine shop I'm at. Road race + Drag stuff that turns up to 9k. A race balance has us to keep the pistons within a gram or 2.  If we told some of our customers "If we balance you motor within a 1/10, it will give you 2 hp---but costs an extra $5k"-they'd do it. And if there was any gain, we'd be doing it.Theres nothing to be gained.

 If you are trying to notch a piston for valve clearance, here is a (fairly )quick + easy way.

Put your pistons in the block-with rings on or tape on 1 skirt (to cut down on rocking).

Take a pair of old  valves-get a piece of tool steel (an old lathe cutter)-and use a die grinder with a cut off wheel to make a piece -maybe a 1/8" wide and length from the center of the valve to about .040 off the valve. Braze the cutter to the valve.
 Put th3 valve in you cylinder head-figure out how much you need to remove from the piston-get a 5/16 drill stop (little collor with a set screw to set depth) + set that distance between the top of the guide + collar.
Put the head on your motor-tighten the head down. (without head dowel pins, alighnment will be tricky.) Chuck the valve in a drill + carefully let it feed down.
 This how it used to be done--and with a little practice, you can get exacting results.

[rabbitman]

He's trying to notch pistons for oil squirters not valves.

ROR did you mean tenth of an ounce?

[R.O.R-2.0]

He's trying to notch pistons for oil squirters not valves.

ROR did you mean tenth of an ounce?

i measure everything in grams, not ounces.. grams are much more exact. 1/10th of a gram is a much finer measurement than 1/10th of an ounce.

and yes, i know, notching for oil squirters. ive been fully aware since the first post i made.

[sdwarf36]

Oops! I shoulda known that.

[R.O.R-2.0]

and i know it isnt necessary to balance everything to 1/10th of a gram, but i don it anyways.. ive only balanced my own engines, and i try and MATCH the weights of everything.. not just within a gram or 2.. it usually takes me an extra 20 minutes to match everything, rather than balance things close..

[RustyCaddy]

Thanks again for the help...might have to go to Portland for the mill work afterall.

[R.O.R-2.0]

Thanks again for the help...might have to go to Portland for the mill work afterall.

send them to me, i will do it for you..