71 383 piston weight

[velrob]

Can anyone let me know what the OEM weights are for pistons ?

My rods and pins are already together by the machine shop.

i want to weigh them before putting everything back together.

how close should they be to oem or if they dont need to be close to oem weight how much variation can there be between each piston with pin and rod already together?

thanks

 

[wyrmrider]

What you do for balancing is to weigh the big end (with rod bearing) and small end of the rod with pin rings, piston. locks
together you can do the same thing
weigh the piston end at the rod center and weigh the big end with bearings
add the rings
you should be good to go to balance
If this is the same crank as the rods and pistons are from just put it together
stock pistons are heavy
if this is going to see any racing go lighter pistons
rods are plenty strong especially with Direct Connection rod bolts- if you do use them post up the torque specs
tks

 

[velrob]

the pistons are new along with rings

I am using the original crank but it was machined and balanced.

the machine shop that did my block gave me the rods and pistons already together so I'm guessing he may of already weighted them.

I want to weight the whole assembly to see if they are similar. I want to know how many grams each piston/rod assembly with rings can be in weight. like 1 to 2 grams? if they are farther apart then I need to take the steps you mentioned.

 

[wyrmrider]

Better check with your balancer
was the crank balanced with your new pistons and etc?
or was it balanced previously- can't tell by your post
check and see if he checked all the pistons for balance
this is usually done after the rods are matched
sometimes the rods small ends can't be balanced so you do it all with the pistons but that is unusual
pressed pins- best leave them alone

 

[velrob]

the crank was machined by a different shop. the guys that did my block and heads sends their cranks to another shop to get machined.

the shop that machined my crank didnt have or touch my pistons.

 

[velrob]

I got a scale and was measuring the whole piston assembly and two of the pistons have 20grams in difference

the caps seem to be shaved on some spots. I guess the guy before me took some material off for whatever reason. should I sand down the other 6 Caps to come close to the two lowest caps? 1971 totals grams is the lowest weight versus 1991 the highest. this will be a stock motor with a comp cams 268h mild cam with stock 750 holey and stock intake

 

[dvw]

I got a scale and was measuring the whole piston assembly and two of the pistons have 20grams in difference

the caps seem to be shaved on some spots. I guess the guy before me took some material off for whatever reason. should I sand down the other 6 Caps to come close to the two lowest caps? 1971 totals grams is the lowest weight versus 1991 the highest. this will be a stock motor with a comp cams 268h mild cam with stock 750 holey and stock intake

NO. You had the assembly balanced, correct? The caps, small ends will require different amounts removed to match weights. Educate yourself on balancing here.
Doug
http://www.hotrod.com/articles/ccrp-0803-engine-balancing/

 

[velrob]

ya im installing it as it is. the only things changed in the motor are the pistons/bearings/cam

i asked the guy that did the machining and he said it doesnt need balancing

so i guess i will see