Folks,

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

55 Ford Crown Victoria Steel Top

Bump.  Anyone??  Thanks,   JLB

55 Ford Crown Victoria Steel Top

About 585 grams each.

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

 Seppo from Järvenpää, Finland
www.hollowheads.net (just click the hole in the head to proceed)

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

 

		MANF	CID	Bore	Rod Jrnl		BWT						Type	Piston/Pin	Pin Locks	P.Rings	Recip Rod	Rot. Rod	Rod Brgs
1		FORD	312	0.030	0.010		1962						YBLK	711.5	4	54	180	458	44.5
2		FORD	312	0.040	0.030		1986						YBLK	725	2.5	54	176.5	460	51
3		FORD	312	STD	0.020		1938						YBLK	681.5	2	54.5	179.5	458.5	48
4		FORD	312	0.060	0.020		2020						YBLK	778.5	2.5	56	175	452	48.5
5		FORD	312	0.030	0.020		1888						YBLK	626	4	54	180.5	458.5	49.5
6		FORD	312	STD	0.020		2018						YBLK	754.5	3	54	181	459.5	49.5
7		FORD	312	0.060	0.010		1990						YBLK	735	1	59	182	455.5	45
8		FORD	312	0.060	0.010		2032						YBLK	777.5	2.5	54.5	181.5	458.5	45.5
9		FORD	312	0.030	0.020		1978						YBLK	713	2	57	182.5	458.5	49.5
10		FORD	312	0.030	STD		1998						YBLK	742	2	58.5	181.5	460	43

 

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.

Lorena, Texas (South of Waco)

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

  AussieBill            YYYY    Forever Y Block     YYYY

 Down Under, Australia

I have some original pistons standard bore with rods still attached.  Do you want me to weigh one then you can subtract the parts weight?   

Thanks very much to all!

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

55 Ford Crown Victoria Steel Top

At the minimum, you can try to match them to the weights of your current pistons. Forget the weights other people have measured. You must know it worked reasonably well with what you had so make your old pistons your baseline.

If you are machining any of the other components, then I'd suggest rebalancing. You'd be surprised just how much a simple machining operation can throw things out of whack. If it is cost prohibitive, I can understand but if not, balance it. You'll be glad you did - you'll notice just how out of balance it was.


Lawrenceville, GA

I looked through the scrap aluminum here and there are no stock 312 pistons laying loose here so no help there.  The 585g piston value plus the 143g wrist pin weight posted on John Mummert’s site would be a reasonable target though.  Err to the light side for the piston and pin weights when match balancing as the existing crankshaft balance can tolerate lighter rods/pistons versus pieces that are heavier than stock.  If you have a 312 with std bore pistons, then those would be the ones to weigh as nothing says the weight spec didn’t change throughout the years of production.  Be sure to weigh and include the factory piston ring set and locks in your values as those component weights do vary between manufacturers.

 

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.

Lorena, Texas (South of Waco)

JL, Tell us where you live, Ted's in Texas.

Frank/Rebop

Bristol, In ( by Elkhart)