Neutral, 28oz, 50oz balanced??

[RyanSG]

hey guys, decided i'm gunna go with a Dart 302 block with a 331 stroker kit (all 4340 forged etc) I'm running a single t-70 with aluminum heads etc..... My question is, with the turbo what type of rotating assembly balance should i get. I can get the 50oz, 28oz, or neutraly balanced... However i'm not sure as to why you would get one or the other.... I know stock it's 50oz and i herd with a blower most ppl stick with that... With a turbo though there isn't any pull on the crank so i can loose the 50oz and get a 28oz or neutral balance.... Which one s better and are there different costs for each? I guess i just don't want to order the wrong balance for my motor, or at least know what each is used for....

 

[Grn92LX]

Neutral (0) and go bigger than 331. Do a big bore 3.40 stroke combo. I think it comes out to 363 or 364".

 

[pb_paulie_b]

If you have a choice, less is better. Most 302 and their stroker kits are 50oz. 351's and their kits are 28oz. The more the imbalance is the more rotational weight you have to swing around...PB

 

[RyanSG]

Eh still prob gunna stick to the 331... i was figureing on the 0oz though but what would be the advantages compared to the 28oz balanced assembly? Just tryen to understand as to why each one is better then the other etc...

 

[pb_paulie_b]

less weight swinging around on the crank lets your engine rev faster + less stress on the rotating assembly.

 

[RyanSG]

ahhh ok, it's pretty much go as low as you can go. And depending on the kits yu can get will depend on the balance... Thats what i was wondering then thx guys!

 

[onefstsnake]

so if he ran a 0 oz balance would he still run a harmonic balancer?

 

[larrendeuce]

I don't build engines so I don't claim to be an expert. However stock 50oz cranks were cast lighter, needing the weight on the end to balance the assembly. The benefits are cost, and tradeoffs are vibration are harmonics. A neutral balance has the assembly balanced internally. No external weights needed. A good harmonic balancer is always required.

 

[Rick 91GT]

Go "0 or internal balance" depending on the internals used and your bob weight you may need some Mallory to get it to go internal. It is much easier on the bearings and will be very smooth revving no matter how high.

Most stroker cranks are made to go 28oz or internal, 50oz tends to turn the counter weights into swiss cheese. Allentown huh, I'm from Hanover (York County)

Rick

 

[FastDriver]

What you're referring to is the external counterweight to offset the imbalance of the crankshaft. The less external balance you need, the more internally balanced the crankshaft is. External balancing isn't perfect though. The crankshaft still tends to flex with oscilations due to its internal imbalance.

The biggest benefit of an internally balanced crankshaft is revvability. You can take an internally balanced crankshaft more reliably to higher rpm. 50oz imbalance is perfectly fine for taking a motor to 6k rpm, for example. If you're going to have a screamer, which i doubt based on your turbo selection, you want a neutral balance. If not you can get away with less. It may not cost much at all to get to that neutral balance. If it costs a lot, then you are forced to a decision.

Neutral (0) and go bigger than 331. Do a big bore 3.40 stroke combo. I think it comes out to 363 or 364".

Mike, you've got to stop doing this. 3.40 stroke works great unless it's built wrong. If he's already got the rods for the 331, he's likely to have 5.4" rods and they would be wrong for a 3.40. So at least bring this up when you make this recommendation for people who probably don't know any better. Otherwise, you'll talk them into making a mistake. Unless it's a race car, much more important than stroke is correct piston design.

Extra bore is going to increase the area upon which cylider pressure acts on the cylinder heads. This causes additional lift on the heads. With the right parts (bolts, and head gaskets) it's not a big deal. It really isn't necessary though, especially at max output where all the matters is the capability of the turbocharger.

 

[RyanSG]

well from what i've been hearing gunna be going with the 28oz or neutral... depending with what i go with.... still looks liek it's gunna cost about 4 grand to get just the short block.... which is basicly about a grand more then i wanted to pa so we'll have to see... although i'm prob going to go with a 347 or 331, still looking into that, gunna take a look at my heads and see what they flow etc and the CC's so we can see what type of pistons are needed etc.... Dunno just so damn compicated i honestly don't know enough about building a short block so i'm kinda backed into a corner with what to do.... Te main power is going to be done with the turbo, and yes i've herd go bigger go bigger do a 427,or 408 etc etc.... thats great, for N/a... i don't even need close to that to make 800hp... a 331, or 347 can make 800hp easy... so gunna stay with the smaller cubes in hope of saving a little money and just useing the turbo to do it's thing... The dart block costs so dam much but it's worth it and it's bullet proof so i'm gunna stick to that... as for the crank etc, the one person said a cranks gunna be 1800.... i don't see why i would need such an overkill crank nor did i think they were that much to begin with.... I guess i just gotta research it some more and see what happens, i almost have to go to them and say i want this this and this in a dart block... do it and be done with it, other wise they gave me to many options and they all seemed to be more and more expencive as they talked... Ayways, thx again for the help guys! Hopefully i can get this figured out and keep the stang... although i'm getting rdy to just give upon it

 

[302RollinHard]

Alls I can tell you is remember whatever balance you get. If you ever get a new flywheel or your flywheel turned or anything make sure they don't "balance it" for you and that you remember to buy the proper balanced replacement. Also if you forget and put the wrong balanced crank pully/harmonic balancer on the crank-bye bye 4 grand engine. I too vote for the 0/internally balanced piece if you are starting from scratch. They will rev smooth and as high as you want them to.

 

[FastDriver]

I recently did the dart block, thing. It snowballed me into spending about 3x the amount I planned on as a result of why not.... People always recommend the expensive stuff. "you need a neutral balance..." "You should go with billet stuff...." "if you're going to put so much money into it, why not get custom pistons and rods?..." I got sucked in.... I'm not that upset by it, but I've definitely gone way overkill for the setup I intend. Make a plan and stick to it. It's overwhelming at first.

The important thing is to make a realistic goal, and build your combo for that. In order to save money, when faced with a choice, you should always ask yourself, "will the less expensive part be enough to accomplish my goal." In my case, I made a goal, but I also wanted room to grow beyond that goal. So I just went ahead and bought all the best stuff.

Chris

 

[1991vert]

i went neutral balance on my dart block 347. power adder will be a novi2000

 

[RyanSG]

28oz it is!

Wulp it looks like 28oz it is, least thats what we're builden it up as.... now i know this will sound stupid but how will i know where to orient the flywheel so the 28oz weight is at the correct spot? From what i was glancing at it looked liek the bolt pattern may only fit 1 way but i just want to make sure.... I've always marked my stock on and just replaced it by going off of that... But since this will be new i wasn't sure of how top orient it......

Also i was going to go with a cast steel crank.... however i'm getting a bit skidish and was wondering to upgrade to a 4340... not sre of all of your input on it though.... It's going in a mexican block with ARP studs for the mains etc..... is the 4340 worth it or just a good cast steel?

 

[FastDriver]

You're right about the bolt holes on the flywheel. I don't know what HP level the cast crank is good to, but if it were me, I wouldn't consider a cast crank on a turbocharged 331. I don't know what the T70 is capable of altogether, but you'll probably be capable of making 700rwhp or more with that combo I'm going overkill with a billet, but at a minimum I think it would be a bad idea to go with anything less than a forged crank.

Chris

 

[5spd GT]

Neutral (0) and go bigger than 331. Do a big bore 3.40 stroke combo. I think it comes out to 363 or 364".

It would be a 363 cubic inch engine.

Nothing wrong with going with a 331...

 

[90mustangGT]

Whatever balance you go with, 0 being the best, be sure to have the rotating assembly balanced.

Don't forget that the weakest part of the engine is the block.

331 better for revving? I know guys running the stroked 351's with 4.0-4.15 stroke revving to 9000rpm.

 

[RyanSG]

ok good so the flywheel will be easy install then lol...
Yeah i'm doin a 331 since you don't have to clearance asnything on the block... anything over a 331 you have to start cutting.... and trust me i want to take as little as i can away from the block... It's a mexican block so it should be good to go i'm shooting to be at 550RWHP.... I think i may end up putting the forged crank in since i won't be able to sleep otherwise.... Yeah the turbo setup is able to put about 700hp out.... I know everyones allway hept up on displacement but i see no real reason for it. I like the turbo setup so i kept the stroker to a minimum.... I was even happy with the 306 had plenty of power on the street outa boost and just nasty in boost... So hopefully the 331 will give it a little more low end TQ and still be easy on the block....

 

[88Stang331]

+1 for internal ballance. Easier on internals and what not, less rotating mass. However from the research i've done it is more expensive granted i've only checked out SCAT and EAGLE.