Just a little feed back on this subject. The Y I am rebuilding is just a stock, non racing, 292 that is .060 over. I just have a set of cheap Sealed Power/Speed Pro pistons and weighed them this weekend, all were within + - 1.5 grams of the OEM weights..

Thanks Ted, I found the OEM weight. I was also just wondering why a replacement piston manufacturer would make a piston 63 grams heavier like the original poster asked about?

See if this link to a past thread regarding oem piston weights helps.
http://forums.y-blocksforever.com/FindPost59692.aspx

Lorena, Texas (South of Waco)

I'm not that familiar with all the Y-Blocks but one of my racing engines has a nuetral balanced crankshaft so as long all the piston/rods/bearings/rings weigh the same I'm good. (yes rods are evenly balanced). We just completed our scrub dirt track engine with different Pistons and 2 replacement rods and the crank was quite about out with new combined bob weight. Our machine shop does not regrind cranks but does everything else. He goes a lot farther when doing race engines but surpasses factory specs for any street engine. I, like most here, will say even if it takes alittle more time, balance your engine; you will never be sorry. Good Luck.

56 Vic, B'Ville 200 MPH Club Member, So Cal.

An unbalanced engine will not last, I find the first problems seem to be oil leaks (front seal or rear seal), oil pressure will start to drop off as the main bearings get worked by the unbalance, after that the end is near. 

I've been unable to find info on what the OEM pistons weighed? I need to check the weight of the new pistons I'll be using soon. I didn't have my last engine balanced, it was a budget build just to get the car running temporally, it turned out vibration free and has 6,000 miles on it now and runs like a Swiss watch.

An unbalanced engine...

https://www.dropbox.com/s/m6xql51nelz6ej0/2014-08-08%2012.41.54.mp4?dl=0


Hyvinkää, FI

For all interested there is a very easy program found on the KB Piston site for static and actual compression ratios of your engine. You need to know the cc of the head chamber, where the piston is in the block and diameter/thickness of the gasket. Cam timing if actual is wanted.
I've used the program countless times and was shocked to see what different thickness of gaskets did to the compression along with the compression height. We put an engine together with no rings measured the piston height, disassembled to machine the block for what we want. To me this is normal with off the shelf pistons in racing. Being we assemble our own engines this "blue printing" is our way saving costs. Good Luck

56 Vic, B'Ville 200 MPH Club Member, So Cal.

Alan.
I’d love to say that you would not necessarily need to re-balance a stock rotating assembly but that’s not the case.  I’ve balanced a number of stock oem engines and most need extensive work to put the rotating assembly back into a state of balance that’s acceptable.  The factory variances alone will warrant even an original engine with no replacement parts to be rebalanced.  Anytime parts are replaced or pieces are remachined, then balancing is recommended.  Here’s an analogy.  You wouldn’t install new tires on wheels without rebalancing so in the same train of thought, you would not install new parts within an engine without rebalancing.
 
The fact that the pistons are considerably heavier than the originals puts the crankshaft in a state of underbalance which is the wrong direction for the balance attributes to be in.  If the pistons had been slightly lighter than the originals, you might have gotten away with the piston weight difference assuming the connecting rods and crankshaft balance attributes were in the neighborhood.
 
As with most budgets, you’ve run into a couple of items that will be worth the extra money in the long run by doing them.  Balancing will improve the engine performance and overall life as well as reduce any perceivable vibrations that would come about from existing imbalances.  Decking the block will also restore the compression ratio to the original factory specs and also keep the engine running within its original performance expectations.
 
Thanks to everyone who commented prior to this as the comments are spot on.

Lorena, Texas (South of Waco)

Does anyone make standard pistons that are more appropriate for this application?


Paul