ok, im doing a 250 build and have a scratch in my crank, i could get the crank reground which starts at $100 and could quite easily be more... called summit cuz im also boring it out from 4.03 to 4.04 and they said if i just make the new pistons the same weight as the average of all the old ones, the assembly will still be balanced

my roommate offered me his old crank (which he claims only needs polish which i can do for free) and a rebuild 600cfm holley for $150

if i buy his crank then theres no way my assembly would be balanced right? or am i wrong?
also would this be enough carb for a 357 with vortec heads and a 230/236 cam?

 

Yes for best results you would need to get it balanced to your bottom end. At that rate i would check to see what it would cost to have balanced because its not exactly cheap may be better off with the regrind if its really needed. The reason is not only is in not cheap to balance a crank unless you can remove the pistons from there wrist pins they may charge you for that too. Also if they need to add weight rather than just remove guess what you get charged for that too and its not cheap lol. However if your replacing the pistons too it may be cheaper to get a new pre-balances kit from summit.

 

ya i removed the wrist pins from the pistons already cuz i am getting new, so thats not an issue, i can rebalance the pistons, i have the tooling for that, but idk what goes into rebalancing the crank so idk if thats something i can do or not (this is also assuming that the last person who bored it .03 over got it balanced for those pistons)

does summit have a kit to balance the assebly, or do you mean buy an already balanced assembly, cuz those start at 400+ for the kit and another 150 to have it balanced vs 100 for the pistons and 100 for the crank

EDIT: when summit sells a crank thats "internally balanced" what is it balanced for? cuz they have 3.75 cast cranks for the same price as 3.48, so it MAY be worth snatching one of those up for $170 (plus the 3.75 cranks are externally balanced so i dont have to worry about it, jsut ganna cut from the harmonic balancer right?)

 

Anytime you make any changes to the crank, pistons, rings, rods you need to rebalance the rotating assembly (considering they were balanced before). I think I spent an extra couple of hundred bucks on balancing my engine and I think it was worth it. Just make sure you send your crank, rods, bearings, pistons, & rings to the machine shop. A good machine shop will want your flywheel/flex plate and harmonic balancer too (even for an internally balanced assembly). The "already balanced" kits you see in Summit are balanced but they aren't balanced to the extent a machine shop will balance everything.

Don't let Summit or anyone else BS you. No one can sell you new pistons that are the same weight as your old ones. You would first have to weigh each one to the exact gram and then have Summit or whoever go weigh each piston to find matches.

 

i know that, lol im ganna buy pistons and machine them myself to the average weight of all the old pistons (assuming the old assembly was balanced)
my question is: if i do that, will the assembly be balanced?

ps- i just emailed the kid i bought the motor from to see if it was balanced before

 

Yes, if it was balanced before, and you can remove enough material. You might find that the new pistons are lighter than the old ones though.

 

I work in a engine machine shop, we are doing a nasty 305 as we speak, we balance our motor to 00 grams on each end, if you are going to have it balanced, you need to take all the rotating assy and flex plate with damper. dont let anyone feed you any crap any other way. double 00 are very easy to get. get it balanced