Balancing pistons.

[zenoahphobic]

I would have used sierra piston kits way before I used wiesco.
years back we had some issues running wiesco pistons.
usually it was an oem bore size and improper break in.
then you had the cold seizure issues that all forged piston have.
back in the day you had to idle them for 8 hours before running it up.

Wiseco are used throughout motorcycle and jet skis without much complaint.

How many years ago were these issues you speak about? To be fair do you know of any recent specific issues with them?

[zenoahphobic]

I’m rebuilding my 2002 90TLRA and i’m putting in Wiseco pistons. Should I dremel out the edges marked with red or drill small pieces out with a big drill marked with yellow. Have to take off about 1 gram from one piston. Any suggestions?

You want this piston the SAME as the others. Balancing is not the same as same weight.

Ideally you need to know where the weight differs and that is difficult. The only way I can see doing that is to measure it to find if there is some dimensional differences.
This assumes that the metal itself is the same. You can also try to balance the piston on a precise rod to see if it topples the same. Very sharp eyes or instruments are needed.

Just looking at this from left field, as you may be removing weight from an area that may not be where it is in excess, sure getting the same weight but may be getting the piston further out of balance!

Oh and if you grind anywhere inside the piston you will be setting up an area for stress cracks, this may however be negligible for the performance demands of your particular engine.

Then again what is 1 gram? If I were to do it without being able to determine where this excess gram is, I would take it off the skirt at the sides, not where the skirt toggles.

[rodbolt17]

it is just like casting a bullet.
my 300GR .421dia mold tosses bullets as much as 5 gr from 300 = or -.
if I was match shooting I would weigh all bullets and discard any not 300Gr.
however I am shooting them in a 41 swiss vetterli bolt action that holds 12 in the tube and was made in 1878.
on the wiesco I never had any issues with them as my machinist had already figured out the over bore issue.
if I was building a 14,000 RPM hydro I would blue print and balance.
for a stocker that wont see operation above 5500 why bother.
the last 455 olds I built had TRW11/1 forged and a machine shop in fortworth did the balancing of the pistons rods and crank. them line bored the mains and squared the deck to the shaft bore line.
used a set of C casting heads with the center ex port welded.
did all the chamber cc'ing and valve and port work myself.
A friend had a valve facer and the hard seat grinder.
I made my own adjustable rocker arm set up that terry at completion cams had me send a sample and they now market the kit.
gotta remember this was the summer/winter onf 1985/86.
that's pretty much what you had to do to shift at 7200 with a 455 olds.
M-22 4sp and an O type 3.90/1 posi 12bolt rear.
was a fun car.
my 73 chevelle simply ran a mostly bone stock 400 smallblock with a turbo 400 and a 2.32 gear set.
when I joined the navy I sold the 73 bought a 77 with a blown 305 with about 30,000 on the odometer built it back stone stock,,had deckers transmission in Cleburne Tx build the turbo 350,replaced the axle bearings went through the A/C system.
wanted it dead reliable for the wife while I was gone and a vehicle any shop could work on.
put a 350 watt Alpine sound system in it and listened to kids cassettes from Cleburne TX to kitty hawk NC.

[pstephens46]

it is just like casting a bullet.
my 300GR .421dia mold tosses bullets as much as 5 gr from 300 = or -.
if I was match shooting I would weigh all bullets and discard any not 300Gr.
however I am shooting them in a 41 swiss vetterli bolt action that holds 12 in the tube and was made in 1878.
on the wiesco I never had any issues with them as my machinist had already figured out the over bore issue.
if I was building a 14,000 RPM hydro I would blue print and balance.
for a stocker that wont see operation above 5500 why bother.
the last 455 olds I built had TRW11/1 forged and a machine shop in fortworth did the balancing of the pistons rods and crank. them line bored the mains and squared the deck to the shaft bore line.
used a set of C casting heads with the center ex port welded.
did all the chamber cc'ing and valve and port work myself.
A friend had a valve facer and the hard seat grinder.
I made my own adjustable rocker arm set up that terry at completion cams had me send a sample and they now market the kit.
gotta remember this was the summer/winter onf 1985/86.
that's pretty much what you had to do to shift at 7200 with a 455 olds.
M-22 4sp and an O type 3.90/1 posi 12bolt rear.
was a fun car.
my 73 chevelle simply ran a mostly bone stock 400 smallblock with a turbo 400 and a 2.32 gear set.
when I joined the navy I sold the 73 bought a 77 with a blown 305 with about 30,000 on the odometer built it back stone stock,,had deckers transmission in Cleburne Tx build the turbo 350,replaced the axle bearings went through the A/C system.
wanted it dead reliable for the wife while I was gone and a vehicle any shop could work on.
put a 350 watt Alpine sound system in it and listened to kids cassettes from Cleburne TX to kitty hawk NC.

How did you end up picking Kitty Hawk? Just curious. Nice place, no doubt.

[stoker2001]

You want this piston the SAME as the others. Balancing is not the same as same weight.

Ideally you need to know where the weight differs and that is difficult. The only way I can see doing that is to measure it to find if there is some dimensional differences.
This assumes that the metal itself is the same. You can also try to balance the piston on a precise rod to see if it topples the same. Very sharp eyes or instruments are needed.

Just looking at this from left field, as you may be removing weight from an area that may not be where it is in excess, sure getting the same weight but may be getting the piston further out of balance!

Oh and if you grind anywhere inside the piston you will be setting up an area for stress cracks, this may however be negligible for the performance demands of your particular engine.

Then again what is 1 gram? If I were to do it without being able to determine where this excess gram is, I would take it off the skirt at the sides, not where the skirt toggles.

not trying to start argument,but way overthinking this..thinning skirts is a bad idea as they can collapse!best place to remove weight is under dome like picture in #1 post or thick part of wrist pin boss above pin.Sorry,its not rocket science..ideally you want to weight balance the slug,pin,rings and circlips.connecting rods move in 2 diff directions,so they require balance beam/trapeze to weigh big end seperatly from small end..just my 2 pesos..carry on

[rodbolt17]

ya way over thunked it.
you DO NOT thin the skirt you simply shorten it slightly.
just like you were gonna make a slipper skirt back in the day.
the piston skirts on a Yamaha 4 stroke are works of art.
but NO NO NO on any materiel removal from the dome or wristpin area.
unless you wish to post about a piston ripped in two and the wrist pin just whooped the snot out of the cyl.

[holmen78]

I left rods and pistons untouched and assembled pistons in block. Modifications is only the Phase 1 kit from Hydrotec, so I don’t think it will rise top rpm much, if all. Last summer wot rpm was 5300-5400 with stock engine and a Ballistic 19” ss prop. Might balance them in future if i raise the the ports and adding finger ports. Want it to run nice with the Wisecos next season, might modify further next winter if everything works well next summer and if I’m hungry for more speed .

[pstephens46]

I left rods and pistons untouched and assembled pistons in block. Modifications is only the Phase 1 kit from Hydrotec, so I don’t think it will rise top rpm much, if all. Last summer wot rpm was 5300-5400 with stock engine and a Ballistic 19” ss prop. Might balance them in future if i raise the the ports and adding finger ports. Want it to run nice with the Wisecos next season, might modify further next winter if everything works well next summer and if I’m hungry for more speed .

Starting to sound like a bass boat forum. Good info though. Not many here are rebuilding/porting motors.

[walleye1]

[stoker2001]

I left rods and pistons untouched and assembled pistons in block. Modifications is only the Phase 1 kit from Hydrotec, so I don’t think it will rise top rpm much, if all. Last summer wot rpm was 5300-5400 with stock engine and a Ballistic 19” ss prop. Might balance them in future if i raise the the ports and adding finger ports. Want it to run nice with the Wisecos next season, might modify further next winter if everything works well next summer and if I’m hungry for more speed .

Wayne Worthy at Hydrotec is the GURU when it comes to hotrodding yamys.been at it for a long time and makes some impressive HP to give those Racing mercs a run for there money!Speed is addicting and costly,how fast $$$ do you want to go is question of how big is your wallet..LOL.I still have the desease,been 128MPH in my 18' Mirage Jag river racer with 2.5 S3000 race merc and still have it...

[rodbolt17]

yep, not only does speed cost money. there are only so many horsepower hours in a modified machine.
that is why you see so many NHRA and Nascar drivers running 3 yr old engines on last years gas,

[rodbolt17]

why did I pick Kitty Hawk?
I run my family on both sides to this area since 1756.
my wife and 3yr old daughter stayed with my grandfather until I got out of boot camp and started FC A school and got base housing.