Cyphear

When I built my bottom end, I had a straight LS and never really planned on reving it over 8k. I also read quit a few people (including Earl) that said most cranks are decently balanced and aftermarket pistons/rods are within a gram, so I decided not to balance it.

Anyway, my built bottom end isn't balanced, but i'm thinking about reving it higher now that I have a VTEC head. Any idea how high I can reliably rev it? Also, would a fluidyne engine damper help?

Thanks.

SovXietday

All Honda cranks are supposed to be balanced to 10K, but I would definitely run a better dampener like a fluidyne.

NJIN BUILDR

Not balancing the bottom end will not effect the ability or reliability of the engine to run high rpm.As you have already been told,the parts you have are balanced close enough to perfect.If your running stock vtec head than the stock vtec rpm is a safe place to start.

KeyserSoze

I if you wanna run higher than the stock rpm of the head then I would mosdef upgrade the valvetrain at the very least. It seems that a floating valve is one of the main failures in over rev'ing situations..............

SD_Lurker

iTrader: (4)

Wow your comment is scary, especially since you claim to be an engine builder with your name. Reliability is certainly affected by a non-balanced bottom end. A bottom end with the rotating assembly out of whack will destroy the bearings in no time. I could see if he just reused the OEM pistons and rods but when using after market rods and pistons its ALWAYS a good idea to have the rotating assembly balanced. His motor could possibly last a long time but like I said if balance is out of whack its only a matter of time before pre mature wear of the bearings sets in.

omiehomie

i know this might sound like a noob question, but im in the process of putting my bottom end together, and what entails or has to be done for balancing a rotating assembly? do have to clay it or what? just a thought

98vtec

getting all rods and pistons the same weight and balancing the counterweights on the crank like you balance a wheel.

the comment about all honda cranks being balanced to 10000 is crap. One of the main reasons, IMO, people called the h23vtec unreliable and so prone to spinning bearings was because they never considered that honda never intended that crank to be spun the RPM's of an h22 and this took a toll on the bearings.

Cyphear

Thanks for the replies guys.

No offense SD_Lurker, but i'm pretty sure what he said was correct. According to Earl (RIP!), aftermarket pistons and rods are pretty much balanced already. The only thing that needs to be balanced is the crank. Maybe you were implying that OEM rod bolts wouldn't handle those higher revs where engine balancing is important.

omiehomie: You have to have a machine shop (or maybe a performance shop that builds engines) do it as far as I know. I dont know how they do it. I think they make all the pistons/rods weigh the same amount by removing material, but i dont know how they balance the crank.

I'd definitely upgrade the valvetrain. Right now i'm not really taking it over 8k. It's making plenty of power from 4,300 on. I'm actually trying to figure out if I want to "settle" with ~400whp @ 8k (that's a guess - I haven't dynoed yet), or if I want to "shift the power band higher" via cams, IM, a built head, fluidyne (I figured $2,000 worth of parts including a fuel and ignition upgrade I need) to make something like 470whp @ 8,800RPM.

So it sounds like the bottom end w/ a fluidyne will probably be safe to 9k, although there is no way to know whether it's pretty much balanced, or totally out of whack. In retrospect I probably should have had it balanced, but I was a college student with no income at the time building this motor on my apartment bedroom floor. $100 was a ton of money back then.

Thanks again for the input. Especially SovXietday, that info was helpful! EDIT: Okay, maybe that information was "crap".

Andr3w

lol this thread delivers loads of the funny factor^ Get a load of you people with your balancing.

red02s2k

Depends on what rods and piston setup you are running. When I picked up my eagle rods they where all different weight. I know that every motor I have built I always had them balanced and every time there would be a difference in weight on the piston rod setup.

HiProfile

Actually, the reason is more likely that the H23 is suffering from bad harmonics. Scientificly speaking, 2.3-2.4L is about as big as a typical 4-cyl should be before no number of balance shafts can damped the harmonics. Balanced crank or not, its the way the power pulses wobble the crank that eat bearings. Couple this with the large stoke, the people removing balance shafts, and the sucky OEM balancer - it's no wonder they go to hell.

If you've ever had to go get a Honda crank balanced, you'll change your tune. THe D16 and F22 where never intended to be reved high, yet a trip to the machine shop leads to less than a gram of removed material.


No offense, but OPINIONS are like butt holes - everyone has them, and most of them stink. FACTS, however, are a little less 'stinky'. I've never encountered a Honda crank that was poorly balanced, at least not from the last 2 decades. Harmonics are very different from balance, do a little research on ati or fluidamper. There are many other reasons a motor will eat its bearings.

98vtec

there is a reason i stated "IMO" and "ONE of the main". I will forever have the rotating assembly balanced for a setup that was not intended to rev what i am revving it to. Cheap insurance.

if you are going to get into theory then you should be referring more towards rod/stroke and the bearing wear these "should" call for. Not so much the power pulse. You can adjust the power pulse via ignition timing to put peak cylinder pressure at the most proper crank/rod angle so the pressure pushing the piston down is not putting immense pressure and wear on the bearings. This angle of peak cylinder pressure should be where the engine makes best torque which can be decided on a dyno.

harmonics may be different from balance but balance plays a role.

Tjabo

Okay, so here's the bottom line question for me:

Assuming matched weights on all like components (pistons, rods, etc.), is it necessary to change the balance of a balanced flat crank (four-banger) for a change in bob-weight?

Thanks in advance for your thoughts!

HiProfile

A balance issue will create unusual, but even, wear all around the bearing, and a poor RS ratio or insane peak cyl pressure will place high load at the same spots as small as a few crank degrees. However, they will still be gradual onset (no instant spike), nor do they really cause any resonation - unlike harmonic vibration. That's what really can kill bearings, similar to how easily detonation can.

I forgot mention another reason why your H23's probably **** the bed - accessories & their belts add to the dampening force on the crank. Remove 3/4 of the accessories (balance shafts, P/S, A/C), and you're inviting destruction. Regardless, I've seen several stock motors babied still eat their bearings, while motors abused in race conditions last for a long time with just an alternator & ati/fluidamper.


BTW how would you explain a fully balanced b-series destroying oil pump gears when they use a solid, lightweight crank pulley?

NJIN BUILDR

I never said an unbalanced engine will not effect reliability.I said there is no need to balance the Honda engine components he has.I have spun up lots of b-series cranks on several different balancers and I would have a hard time charging anyone for my time.I would call a small block chevy crank acceptable with unbalance numbers higher than a stock b-series crank has right out of the box.The same goes for aftermarket rods and pistons.A gram or two on the piston or the rod is nothing compared to the effect the oil has on a moving crank.
I think money would be better spent on the valve train than balancing if your going from LS rpm's to ls/vtec rpm's.

Tjabo

So does a change to the bob-weight matter if all like components are weight matched? ? ? ?

Come on guys, isn't think kind of an important consideration in a discussion like this? If the answer is that it doesn't matter on a flat crank, that's cool, but if it matters, then it's one more reason balancing needs to be done. Bob weight almost always changes when you go to aftermarket parts.

blaze the chemi

I would think the weight of the piston is more of a concern at those rpm's since the piston speed is something else you need to consider on top of nearly balanced rotating assembly, but that is just a thought. That and make sure your valves close before there could be contact. Only one engine build under my belt however.

:Josh:

you dont use a bob weight on an inline four cylinder like a honda crank.

SovXietday

Just because you spin an engine higher and throw a rod bearing doesn't mean it was because the crank was off balance.

Considering I have heard the 10K number from many many reputable people on here over the years, and my own experience as far as revving "unbalanced" bottom ends to rediculous RPMs and rarely hearing any issues I would kinda stick with that. I would absolutely balance an engine if I was going to take it way up, 10K+ but anything under 9 and under 2.0L I'd be ok with. This is all IMO of course, but personally I would rather trust Honda out of the factory than joe shmoe machine shop down the street to get my bottom end balanced.

My car = stock crank, shelf Eagles, shelf Vitara's and I spin it to 8500 all the time. It's a Dseries, so stock limit of 7000. No issues here, been doing it for over 2 years too.

Tjabo

You don't? You just spin the crank bare?

quicksilver1689

some of this info is retarded, honda balances the crank with the original rotating assembly that came with the motor, so your eagle rods are all within a gram or so thats good, pistons matched closely, good also, but the counterweights arent matched for the heavier components that there supposed to counteract., why do you think when people get the rotating assembly they bring pistons rods, crank, flywheel. Im not saying that if you dont balance it bad things will happen, **** most people my self included just put the new components in and run it, and all is well no fails after many years. Not completely necessary, but it does help.

Tjabo

So you're saying they DO use bob weights then. . . . . . . . . . .

Bailhatch

I have brought so many B series cranks to my machinest...he just laughs and gives me a good deal. From what I have seen I don't think 9k is unreasonable for your average eagle/CP/Wiesco etc. build.

And Tjaibo, no one said anything about bob weights since the lat time you mentioned it. By looking at a honda 4cl crank I don't see any reason you would use them anyway...there's nothing out of balance as it sits. 2 up, 2 down

NJIN BUILDR

Inline fours such as hondas do not use the weights of the components to balance the cranks.The cranks are at least initially spun and balanced by them selves with out any bobweights.After that some shops will add the front pully/damper and flywheel and make any corrections to those parts.V6 and v8's as well as many other designs require bobweights to simulate the weight of the rods,bearings,pin,locks,piston,and ring,as well as a fudge factor for the weight of oil.No retarded info here.

Tjabo

Okay, thanks for this and NJIN BUILDR's input, but quicksilver1689 was implying that bobweights were an issue since he was talking about counter-weights and component weights.

Anyway, thanks for commenting (directly) on this bobweight issue guys!