In the very-near future I'm going to re-build my original '57 312 street motor (ECZ-G heads & original "T-bird" cam) for use this coming summer.  I'm interested to know what the range of original factory piston weights was so that I can try to select new pistons of similar weights - this to eliminate the need to re-balance the original crank.

Any and all feedback / advice appreciated.

Thanks, JLB

http://www.ford-y-block.com/dimensions.htm

Here’s a list of the recent 312’s that have been balanced at this shop. 

Unfortunately on most of these, the piston and pin weights listed are the replacement pistons and not the originals.  I looked in particular at the balance work sheets for the STD bore 312’s and they were 292 blocks bored 0.050” and using cut down 312 cranks.  No help there.  One bright spot though is a notation on one of the balance work cards saying that the original STD bore 312 pistons with pins for one of the balance jobs was 761-762 groms before being replaced with another oversize set.

FYI, A new Silvolite 312 + .060 with pin comes in at approx 755 gm,

In looking at the various information presented, it looks like I have more work cut-out for me as the weights listed are all-over the place  -  including a researched previous post indicating ranges of from 675 through 710 grams.  The information returned to me in this post shows a much wider variance ("hollowhead" down to 585 grams), of which I'm not now sure what to do.

Ted, I know that I should ideally have the crank re-balanced (and you are prohibitively too far away for me to afford the shipping and balancing costs); have you any further suggestions either having it balanced locally; or, what pistons to use with the existing factory crank (I have no problem doing a very precise static balance of pistons and rods?).

Regards,   JLB

But Charlie’s overall assessment is correct.  Having the engine balanced by an independent shop will insure a much more precise balance job than what the factory originally supplied.  Factory weight variances do tend to vary for a variety of reasons.

Very unusual winter so far: Almost NO snow, and temperatures WAY above normal.  In the 20's & 30's (up to above 50); normally have a few weeks of steady minus temperatures right now (many times a week or two of -30  -- have been called out to work once at -65!!!!!   --  cannot even try to describe how cold that is).

I'vew learned a lot about what Southern folks go through with hurricanes, heat, and varmints; we go through "different" issues with winter; but, no hurricanes, very little summer heat (we like it at 65 -- 75 degrees), and no varmints - other than misquitoes can get nasty sometimes.

Regards,  JLB

I just got to thinking that I've been working on Y-blocks for 50+ years now (wow, where does the time go???); but, still a lot to learn from the "smart guys" on here.  My 44-year-old eldest son is now working with me on this  --  he'll most probably inherit the car, as he's the only one interested, besides one of the grandkids / maybe.

Thanks everyone!

I'll let folks know what's happening  -  won't be for a few months yet, though.

Regards,   JLB

Sorry, but you just asked piston weight, not with pins and locks . And 585 was what Mummerts list gave us

Thanks for pointing that out; my appologies if this caused confusion for anyone else besides me.

Thanks again to all for their comments.

Regards,   JLB