Engine Balancing

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Darryl Pritchett

New member
I'm getting ready to build a motor for my ITA Neon, question I have is worth the money to balance a engine? Can you expect more power out of it or just more life expenctancy?
 
Absolutely. I'd expect a tiny bit more power but the big deal is longevity. Another thing you should do that will increase power a bit is have it bored with a torque plate and line bored on the crank center line to insure the cylinder bore and crank centerline are perfectly orthogonal. A lot of folks say tell you there is no power in the bottom end, so why open the motor. They are wrong.

Also, piston ring are free so investigate this for your engine....there will be builders who know how to get power using various rings. Select your pistons carefully, buy a batch and match the light ones. Degree the cams properly, the stock cams may or may not be properly ground and marked.

All those little bits of power add up to make a big deal in IT and seem to be common practice in the NE and SE.
 
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Thanks for the input. I should have been more specific. I actually got a great deal on a NEW Factory short block so there won't be any boring or anything. So on a new factory motor will you get the same results?
 
Everything Ron said applies to a "factory" motor or a junk yard motor. If you want to build a competetive motor for IT, you need to do it.
 
Darryl Pritchett said:
Thanks for the input. I should have been more specific. I actually got a great deal on a NEW Factory short block so there won't be any boring or anything. So on a new factory motor will you get the same results?
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A new factory block should be checked for the parameters I listed. I'd be willing to bet with critical parameters of your new block are checked some issues will be found that need correcting. All the build ups I've read about with new castings generally have something that needs attention. A good builder will check to make sure your new bores are squared up, the deck is square and flat, and so on.

The boring with a torque plate is important because it creates the cylinder bore when the block is under stress and distorted. The bore might be round, centered, and perpendicular to the crank in it's normal state. But when the head is torqued on the force can change the bore shape. Boring the engine with the torque plate on means you're boring into a block under stress and you know the resulting bore will be straight and true when the head is clamped on. Having a motor built 0.010", 0.020", over is many times done on new castings so this boring process can be performed - the displacement increase isn't worth anything.

If you're going to be competitive you've got to cover all the bases. You live in FL and throughout the SE IT tough. You'll need to pay similar attention to all the details in your engine build.

And yes, even if you don't check your block like mentioned at least balance the assembly, preferably with the flywheel and pressure plate you are going to use.
 
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Going one step further, is balancing really worth all that in a I4 motor? I completely understand when it comes to V motors, but in an I?
 
Like Ron said you want to balance the motor with all the accessories that you plan on bolting to the crank when it is in the motor.. (flywheel, balancer, crank pulley, etc..)

I am going to have to disagree with Ron on one point however. I don't believe that you need to line bore the motor reguardless. I believe that yourself or the machine shop will determine if the the motor needs to be line bored. Maybe they are close to perfect already? Maybe they need a light hone becasue they are too tight? In either case, I say it is worth the investigation to see if it needs to be line bored or not. Since you can only line bore your block a limited amount of times just like cylinder boring. IMHO.
 
quadzjr said:
. I don't believe that you need to line bore the motor reguardless. I believe that yourself or the machine shop will determine if the the motor needs to be line bored. Maybe they are close to perfect already? Maybe they need a light hone becasue they are too tight? In either case, I say it is worth the investigation to see if it needs to be line bored or not.
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I agree with you - you might get a block that is perfect with the torque plate installed. But, none of mine ever turned out that way. The machinist can check it.

As far as balancing, I think that one is non-negotiable.

Some of this just comes down to completeness of doing the job. You'll never know how much power you can make until you take it to the last step. If you leave something on the table you'll always wonder. And, if you don't do all of these things, and more, you'll never have a "full on" IT build. We don't have many legal ways to make power so you've got to use everything at your disposal.
 
Unless the New Block came unassembled, you will need to take it apart to balance. Accordingly, factor in the cost of any gaskets and seals for that assembly.

I would also deck the Block.
 
It seems to be a fact that some Honda engines don't require rebalancing. I know for certain that the one-two Hondas in ITC at the ARRC in 2007, and the one-two-three finishers in 2008 were running with the balance done in Japan when manufactured. We have had them checked by a very reputable race engine machine shop and they say "can't improve upon that". When pistons are replaced, the weight of them should be checked.
 
wbp said:
We have had them checked by a very reputable race engine machine shop and they say "can't improve upon that". When pistons are replaced, the weight of them should be checked.
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But you are checking the balance as you want to make sure everything is up to snuff. I think to simply assume that the balance is good is folly.
 
no argument there.

and if you're going to have the engine or at least the rotating assembly at the machinist's anyhow, you may as well have the block checked, and any linearity or orthagonality problems addressed at that time.

if this is your "learner" car and you don't expect to be competitive out of the box, then a known strong 100k miles or so street motor with good service history is usually a pretty safe bet.

decking the block - yes it can help your compression, likewise with shaving the head - and might be necessary to make the motor flat when stressed, like ron has described with the line and cylinder boring, but remember that cam timing WILL be affected by the procedure due to the change in distance between the cam and crank centerlines. offset bushing cam sprockets are legal to remedy this, but not always available readily.

just make sure that you understand the costs involved with the entire process, not just the bit of machine work itself, as hinted at by joeg.
 
wbp said:
It seems to be a fact that some Honda engines don't require rebalancing. I know for certain that the one-two Hondas in ITC at the ARRC in 2007, and the one-two-three finishers in 2008 were running with the balance done in Japan when manufactured. We have had them checked by a very reputable race engine machine shop and they say "can't improve upon that". When pistons are replaced, the weight of them should be checked.
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Having built my own engines now for several years, I am a big believer in doing all the small things. Needless to say I have had mine balanced in addition to the manufacturer. It has been said here before, 10 little things makes........ you know the rest.
 
It has been said on here a few times.. If you are going to go through the effort of stripping down the bottom end.. it would be a good idea to make sure that you take care of everything.

Bascially...

If your going to do it.. do it right.

edit: Chip is right about the decking of the head/block. On the last motor I built with minimal head shaving resulted in the cam installed (off the top of my head) 2* off. With the ecentric bushing on the Cam dowl pin I was able to set it back up to zero.
 
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offset bushing cam sprockets are legal to remedy this, but not always available readily.
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Not legal on a dual overhead cam. OK to use an offset key at the crank, but not at the cam. Someone correct me if I'm wrong. (of course this is stupid thing, any single cam motor doesn't care if the adjustment is made at the top or the bottom. Some dual OH cams get affected different amounts by decking so those should be the ones allowed to restore cam timing at the cam)

But OTOH, if you can restore things to spec (blueprint & balance), why can't you reset the pin on the cam?
 
I never balanced a Volvo or VW IT engine that I built. They are balanced very well from the factory. I've checked rods end for end and overall wts and they are very good (i.e: .5g totals variation in a set). New K&S or Mahle pistons, same thing. I've seen rod length to be more of a problem (Volvo) in a set. Maybe .008" in a set. I think balancing pretty much a waste of money in these (and it sounds like Hondas too) engines.
That said, there's many areas that attention to detail can yield big improvements that are legal and often overlooked.
All my engines were very competetive and reliable despite long use between any attention other than valvespring replacement and adjustment (Volvo).
 
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