balancing pistons????

[vislaguy]

I am balancing my 44 mod motor and the rods were easy but I need to shave 6.1 grams off one of the heavyer pistons and thats alot of aluminum and I'm not sure where to remove material.Can you remove off the skirt,does this affect anything?? is all the porting flow working above the rings??? so if the skirt is cut some and it reveals ports when the piston is at tdc does it effect the flow or anything eles??? thanks mike

[Steve77t]

You can take the heavy slug and introduce it to a ball mill and milling machine. To cut that much you are going to have to attack the underneath portion of the head of the pistion. You need to work under the thickest part of dome. You can also remove material from above the wristpin hole on the wrist pin bosses. taking off the skirts wont give you enough as your piston will then only have the dome and ring lands left.
steve

[Dave M]

New Pistons

I would try to find another piston that more closley matches the weight you need for balancing. Steve is right, that is a lot of weight. Pistons are cheap compared to making one so weak it will explode inside causing more damage.

[vislaguy]

cheap but hard to find

Im using the old mark 58 pistons so there a little harder to come by then the newer style so what about welding a little metal to the inside of the piston base or what about some epoxy in the base to add a few grams,something like marine tex do you think it would hold???just wondering?? thanks mike

[Mike Schmidt]

No weld....No Weld.....

A good welder could add the weight you need, but your going to heat the aluminum up to the point where your going to ruin the heat treatment of the piston. If you could find some one to re-heat treat the piston, you would have to re-machine most of the finished surfaces. Not worth doing...

I have not seen a 44 piston in years, but I would concur with Steve that you should be able to mill / rotary file that amount out without harming the piston.

Don't even think about Epoxe.

Michael D-1

[alky6]

About the ports being uncovered

One point to note. You asked about the ports being uncovered. This is ok, as long as the ports being uncovered are the transfers. At TDC, if the exhaust is uncovered, you're going to run into trouble... This may only occur if you widen the exhaust ports at the bottom of the port. Do not remove any material from the piston skirt as the piston needs the length for lateral support.
Another way to handle balancing is to balance both the rods AND the pistons. Weigh them together as they would be installed on the crankshaft. Mix and match until you get it right.
-Paul

[win-or-flip]

i dunno how old this thread is but...

i may be wrong here so correct me if i am. but in the 500 motors they used to have like a pocket in the cylinder and there was a hole "machiened" into the side of the piston that was located perpendicularly (is that a word?) to the wrist pin holes. this just helped to get a little more FUEL/AIR to the combustion chamber. so it was a bit like a 3 and a half port motor versus 3 or 5 ports. like a "cheater" port i guess you could say. but anyhow. some of these pistons are still floating around and people use them in 500 motors and they don't effect perfomance any. so if you wanted to you could machiene two of these holes into the side of the piston skirt as long as the weren't exposed to the exaust port at top dead center. so check on this before you do anything becausee i dont want to be responsible for costing anybody unnessecary repair bills.

[Steve77t]

i may be wrong here so correct me if i am. but in the 500 motors they used to have like a pocket in the cylinder and there was a hole "machiened" into the side of the piston that was located perpendicularly (is that a word?) to the wrist pin holes. this just helped to get a little more FUEL/AIR to the combustion chamber. so it was a bit like a 3 and a half port motor versus 3 or 5 ports. like a "cheater" port i guess you could say. but anyhow. some of these pistons are still floating around and people use them in 500 motors and they don't effect perfomance any. so if you wanted to you could machiene two of these holes into the side of the piston skirt as long as the weren't exposed to the exaust port at top dead center. so check on this before you do anything becausee i dont want to be responsible for costing anybody unnessecary repair bills.

Yes on König type motors the hole you referr to uncovers a puff type port. Yhis port is conected to the crankcase thru the underside of piston and at BDC charge passes through piston to combustion chamber. If there is not a channel in cylinder for this a hole in piston is pointless. fingerports have long been done on Mercs Königs and others for years and is no big secret. Still the easiest way for weight removal is under the dome for big amounts and just above the wristpin bosses for less amounts. Thin wrist pins too are good but if you have a heavy slug for a piston, The pin will squash like a egg shell. Extented weight is worth the trouble to get rid of for durability and power

[rbtv7]

Heavy piston

Since you are weighing the wrist pin a nd piston together-- way not cut slots in the ends of the wrist pin. An eighth inch wide carbide cutter should get the weight reduction ya need

[Steve77t]

Since you are weighing the wrist pin a nd piston together-- way not cut slots in the ends of the wrist pin. An eighth inch wide carbide cutter should get the weight reduction ya need

If you do that you will invite disaster to the motor for the sqashing reason. The best way is to remove material from offending slug. With all the writing and discussion about this subject the work could have been done by now

[David_L6]

If you do that you will invite disaster to the motor for the sqashing reason. The best way is to remove material from offending slug. With all the writing and discussion about this subject the work could have been done by now

Ya gotta remember that Burt has been chea...... UH,...... UM,...... fooling with these motors longer than most of us has been alive. If he says it'll work I'd have to try it and prove him wrong before I said that he's wrong.

[David_L6]

to add a few grams thanks mike

DON'T ADD weight to anything in the motor!!!

[Dave M]

Order

If you order new pistons, they should all be real close in weight. Last time I ordered new pistons from Mercury they almost did not need any balancing.

Otherwise visit your local junk yard and bring your scale, and find one that is in decent shape and closer in weight. You can only remove so much material before you begin breaking pistons under race conditions. It sounds like you have to remove a ton of weight from your posts.