Piston weight & balancing


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By scott5560 - 14 Years Ago
Wondering if anyone knows the weight of a stock 292 piston?  I am wondering how crucial it is to dynamic balance a rotating assembly?  I have 0.040 over Egge pistons for mild build but no stock pistons to compare to.  If I balance all the weights of the pieces (rod and piston assemblies) will that be decent.  How much is included when they balance an assembly ie. damper, flywheel, pressure plate?  Or are these done seperate?  Almost ready to start assembling bottom end to measure deck as pieces have come together.
By charliemccraney - 14 Years Ago
It's not really crucial for a street engine. Many engines come off the assembly line within their tolerances but not really balanced and run for 100000+ miles. In my opinion, the benefit is well worth the cost. A balanced engine will run smoother, run more economically, make more power, and last longer than an unbalanced engine. Everything from the balancer to the flywheel should be balanced. Here in the Atlanta area, all of that is included in one price. If you're not going to do the whole thing then there really is no sense in doing any of it at all.
By Ted - 14 Years Ago

The factory piston with pin weight for the Y-Block pistons is expected to be in the 675-710 gram neighborhood.  As a general rule, pistons on the light side of this will not necessarily require any extensive crankshaft rebalancing while pistons that are on the heavy side of this makes rebalancing the crankshaft much more preferred.  With all that being said, it is still desirable to have the complete rotating assembly balanced.  If not balancing the crankshaft, it will still be to your advantage to match balance the pistons with pins as well as the small and big end wights of the connecting rods.

 

Here are some past discussions regarding balancing just the pistons and/or rods versus the whole rotating assembly.

http://forums.y-blocksforever.com/Topic2688.aspx 
http://forums.y-blocksforever.com/Topic20542.aspx 
http://forums.y-blocksforever.com/Topic35212.aspx 

 

Performing a search on this site will bring up some more discussions on this topic.
By Glen Henderson - 14 Years Ago
Ted has an excellant artical on his web site. In my opinion balancing is not an option, but a requirement when building a engine in this day and time. I know that we did it for years and years, but back in the day we might have to travel hundreds of miles to find a shop that did balancing. With the cost of all the parts today, I just think balancing is good insurance.
By scott5560 - 14 Years Ago
The rods I have are balanced already.  All the piston and pin matches I have get them within 1 gram.  I would think this is pretty good????.  They are heavier then stock though by est weight Ted gave.  I have Egge 292 + 0.040" and they all come in at 741-742g w/pins.  Also guys is it recommended to replace the stock rod bolts w/ARP.  This is a mild build w/ 2 barrel and low end cam for cruisin.
By mctim64 - 14 Years Ago
Within 1 gram is fine but the pistons being as much as 40 grams over stock I would want to spin the crank up. (balance) Egge sure seems to make some heavy pistons, the Badgers that I have used in the past seem to be much closer in weight to stock sometimes lighter even.
By 46yblock - 14 Years Ago
I was told by a machinist that if the original rod bolts are replaced with ARPs, or even NOS, the big ends have to be resized.  If true, then it would seem the rods would have to be rebalanced, and they would be a little shorter.