Balancing new pistons required?
Thread Starter
Drifting
Joined: Jul 2005
Posts: 1,623
Likes: 29
From: The Netherlands
Balancing new pistons required?
Stock 350 ashtrays (cast alu) are going to be replaced by hyper flattops (crank, rods also stock). Should I weigh each old piston and make sure the weight of the new pistons is distributed likewise? Say piston nr. 1 is 3 grams lighter than nr. 2, this should also be the case with the new pistons?
Thanks!
Thanks!
Team Owner
Joined: Apr 1999
Posts: 21,953
Likes: 1,445
From: Reno Nevada
2024 C3 of the Year Finalist- Modified
first of all the factory never really balanced their motors. So you need to take your rotating assembly to a quality machine shop and have them balance it and press on your new pistons and # mark each rod
Burning Brakes
Joined: Jul 2008
Posts: 923
Likes: 37
From: Green Bay Wisconsin
Hello,
You can weigh all the new pistons and find the lightest one, then remove material from the other new pistons until they all weigh the same as the lightest piston. Do the same with each piston rod without them being attached to the piston.
The weight of the old pistons means nothing.
This is simple and easy to do and costs nothing.
If you have big $$ to spend, have the engine balanced and blueprinted by a professional mechanic. If not then do the above for a slightly higher reving better running engine.
Hope this helps,
Douglas in Green Bay
You can weigh all the new pistons and find the lightest one, then remove material from the other new pistons until they all weigh the same as the lightest piston. Do the same with each piston rod without them being attached to the piston.
The weight of the old pistons means nothing.
This is simple and easy to do and costs nothing.
If you have big $$ to spend, have the engine balanced and blueprinted by a professional mechanic. If not then do the above for a slightly higher reving better running engine.
Hope this helps,
Douglas in Green Bay
Melting Slicks
Joined: Mar 2006
Posts: 2,465
Likes: 0
From: Orange Park Fl
Get the rotating assembly balanced if you want it to last.
God bless, Sensei
Le Mans Master
Joined: Jun 2004
Posts: 6,231
Likes: 65
From: Seattle WA
St. Jude Donor '14
Balancing a rotating ***'y usually costs somewhere around $250 and it's a steal considering the amount of work involved by the shop. It also pays off in smoothness in the engine and to some extent durability - especially if the engine will regularly see 5500+ RPM.
Having said that, if the weight on one throw (the "bobweight") is within the tolerance range for the engine you don't *have* to balance it. This is one of those corners you can cut in a performance engine...but given how much you're already spending doesn't make a lot of sense.
FWIW, weight matching components doesn't buy you anything other than the first step in balancing.
This is a generic answer to the question, as there's not a lot of specifics on your build.
Having said that, if the weight on one throw (the "bobweight") is within the tolerance range for the engine you don't *have* to balance it. This is one of those corners you can cut in a performance engine...but given how much you're already spending doesn't make a lot of sense.
FWIW, weight matching components doesn't buy you anything other than the first step in balancing.
This is a generic answer to the question, as there's not a lot of specifics on your build.
Drifting
Joined: Aug 2004
Posts: 1,883
Likes: 124
From: Lubbock TX
That doesn't help much when the factory rods are all over the map as well. Making them all weigh the same does some good, having the counterweights match the weights of the piston and rod is actually what balancing is all about. Your bearings will love you for it along with anything that's affected by vibration including your right foot! I have all my engines balanced by my local performance shop, even a "stock" rebuild and most certainly the bigger, expensive stuff.
Thread Starter
Drifting
Joined: Jul 2005
Posts: 1,623
Likes: 29
From: The Netherlands
That doesn't help much when the factory rods are all over the map as well. Making them all weigh the same does some good, having the counterweights match the weights of the piston and rod is actually what balancing is all about. Your bearings will love you for it along with anything that's affected by vibration including your right foot! I have all my engines balanced by my local performance shop, even a "stock" rebuild and most certainly the bigger, expensive stuff.
Budget is a tad limited as you'll all understand with this crisis running the world, so I'm trying to go for the best bang for the buck
Why is it that the factory didn't balance their engines?
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Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,116
From: Crossville TN
If you have an engine with a 'red line' above 5500 rpm, balancing might be a good thing to do. The 'out of balance' impact grows exponentially with engine rpm; so, it's more important the higher the max. rpm.
Le Mans Master
Joined: Jun 2008
Posts: 5,284
Likes: 235
From: Rockledge FL
Navigator
Joined: Jul 2009
Posts: 9
Likes: 0
Car Craft article
There is a very good article in the new Sept Car Craft magazine on this topic. It is in the "what's your problem" section. Deals with "rotating weight" and "Reciprocating weight" , "internal" and "external" Balancing. Lots of good info!
