Engine Balancing

[Darryl Pritchett]

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?

[Ron Earp]

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.

[shwah]

Ron is right. Better life, better power with balancing and good machine work.

[Darryl Pritchett]

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?

[GBugg]

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.

[Ron Earp]

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?

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.

[spnkzss]

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?

[quadzjr]

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.

[924Guy]

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?

Yes. All the more so in an "I" motor.

[Ron Earp]

. 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.

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.

[joeg]

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.

[wbp]

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.

[Ron Earp]

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.

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.

[Chip42]

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.

[Ed Funk]

[quote=Chip42;280558]- offset bushing cam sprockets are legal to remedy this, but not always available readily.

:D Man I want to see that thing rotate!!:cool:
Sorry!:happy204:

[Chip42]

[quote=Chip42;280558]- offset bushing cam sprockets are legal to remedy this, but not always available readily.

:D Man I want to see that thing rotate!!:cool:
Sorry!:happy204:

not eccentric to the cam, but to correct the cam timing due to the machining of the head or block.

but yeah...

[svt38]

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.


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.

[quadzjr]

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.

[MMiskoe]

offset bushing cam sprockets are legal to remedy this, but not always available readily.


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?

[pfcs]

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).

[quadzjr]

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?

It achieves the same goal. Realtive cam (Cam to Cam) timing should not change.. That would be the reason for the offset key. otherwise you would have to setup both cam gears with two offset bushings identical. That sounds alot more complicated and expensive to achieve the same goal as a simple offset key.

[Z3_GoCar]

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?

I'll provide the desent. Since it's a new short block, I'd run it for a season before I'd tear into it. Granted domestic manufacturers are noted for precison build, but they do a good job. If you blueprint now it'll move more, than if you let it go through some heat-cycles and hard use and then blueprint. In the world of Karting the best motors were those that were used first then blueprinted. Now, when you do blueprint have it ballanced too. I'm in the process of installing a stock flywheel and will definetly have my motor balanced with the new-old flywheel.

As for the cam timing, you should have picked a DOHC motor that comes with slotted cam sprockets... stock. Then the cam will be degree'ed in every time:D

[quadzjr]

As for the cam timing, you should have picked a DOHC motor that comes with slotted cam sprockets... stock. Then the cam will be degree'ed in every time:D


Some of us can't afford such luxury.. haha..

[Chip42]

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?

true for DOHCs. thanks. - it's a lot easier to buy an offset bushing kit and sproket many times than to pull/fill/align/bore/press the cam pin every time you machine the mating surfaces. besides, if you can move the cam dowel legally, then adjustable sprockets might as well be legal. and they are not.

I agree with James on running the factory bottom end for a while.

[Ron Earp]

if you can move the cam dowel legally, then adjustable sprockets might as well be legal. and they are not.

I think this is one of the failings of the IT ruleset. Factory cam timing must be stock and I'm all fine with that. But as you well know once you machine the head/block you have to do a lot of work to get back to factory cam timing specs. An adjustable cam gear would allow you to get back to factory specs cheapy and easily.

[quadzjr]

Yeah but allowing adjustable cam gears makes it way to easy to cheat and policing the matter would be near impossilbe. Without putting a timing wheel and such on the motor. Some motors it would be very hard to do correctly/accurately with the motor in the car. I believe that if you are not planning on cheating than an offset key or bushing is a very cheap solution. You can get a pack of bushings or a pack of keys for a 1/10th of the price of buying say two adjustable cam gears. Buying aftermarket ajustable cam gears to achieve the same result to me seems like a waste of money.

Provided you are not factoring in the large majority of adjusatble gears or lighter and thus a performance gain is achieved.. Which is illegal.

don't get me wrong.. I would love for cam timing to be open with the use of adjsutable cam gears. It would be easier to phase in a cam. I love making and tuning for power. On certain motors there is significant power to be gained and/or a nice curve. But if you want to keep the idea of IT being cheap racing.. the idea of adjustable cam gears just puts a bigger gap between people with money and people without.

[Ron Earp]

Yeah but allowing adjustable cam gears makes it way to easy to cheat and policing the matter would be near impossilbe.


Whoa whoa whoa...

Easy to cheat? The rules are not concerned with easy to cheat. It is real easy for me to build a stroker motor that is harder to detect than any cam timing and worth a lot more power. It is easy to do a lot of things that are illegal. But we (most of us) don't do those things because we follow the rules.

Policing cam timing is no harder or easier with adjustable gears than without. So your timing marks line up eh, cam must be correctly timed. Think about that one. I've got three marks on my cam gear and with the last rebuild none of the three wound up with the correct cam timing. But I could have easily picked "the best one", put the motor together so that the marks would line up, and the cam would have been retarded resulting in just what I would want, more top end power.

I think for the average guy (I'd put myself there) it costs me more money in machine/shop time to get a gear that is right than simply bolting on a $110 pulley and being done with it. To properly check the cam timing, no matter what gear is bolted on the cam, you've got to do some pretty fancy tricks that I don't think have ever been done in the tech shed. Motor has to be degreed and verified as correct, you'll need a dial indicator to measure valve opening events in relation to the crank shaft angle of rotation and so on.

[quadzjr]

Well yeah you could do that to cheat.. There is all sorts of things that you could do to cheat that are near to impossilbe to catch. My point is that do we need to add another one? I assume that most people would not go through the effort of building a stroker motor.. Which I know is an exagareted example.

You dont' have to spend money to get a gear right at the machine shop. If you are working with a single cam motor, you can take your stock gear, drill it out, and install the correct bushign sthat you can get anywhere almost as easy as jets for a holley.. well maybe not that easy. haha..

I just know that adjustable key ways.. and bushings are fairly easy to use and cheaper than pulleys. With ease of use from easiest to hardest to use: gears, bushings, keys.

I am not a big fan of offset keys in the first place. I have seen keys fail on other motors and providing a perfect place in the key as a stress riser for shear to occur seems kinda dangerous. But people use them.. and they do work.

[lateapex911]

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?

That's an interesting point.

The rules (and I'm a rotary guy here, so correct me if I go off track, guys!) stipulate the if correction is done, that it be done in one location.

I assume (uh oh!) that rule was written in that manner to preclude people from choosing to "fix" one, bit not the other, leading to a net gain.

My question to the experts is: If you deck the block/shave the head, is that scenario possible?

If so, the rule is trying to be "self enforcing" .

I'm just trying to get a handle on it...it's probably fine as is, but....I just want to understand it better.

[MMiskoe]

That's an interesting point.

The rules (and I'm a rotary guy here, so correct me if I go off track, guys!) stipulate the if correction is done, that it be done in one location.

I assume (uh oh!) that rule was written in that manner to preclude people from choosing to "fix" one, bit not the other, leading to a net gain.

My question to the experts is: If you deck the block/shave the head, is that scenario possible?

If so, the rule is trying to be "self enforcing" .

I'm just trying to get a handle on it...it's probably fine as is, but....I just want to understand it better.


Yes, you could return the intake cam to OE and leave the exhaust cam alone (or vice vrs) after decking the head on a single head, dual cam motor. The rule as written makes a difference on any OHC V motor w/ a single belt/chain. As you deck both sides, they move down & in making the distance between the two cam centers different so the two cams see different amounts of change. Fixing it at the crank only corrects a portion of the problem.

Also putting the offset key at the crank just makes it work harder, increasing its potential for failure (torque loads are higher).

I agree that for most people using a simple adjustable cam sprocket is far easier & cheaper than offset keys.

[Ron Earp]

I agree that for most people using a simple adjustable cam sprocket is far easier & cheaper than offset keys.

Definitely.

[quadzjr]

what DOHC V motor are we talking about that when you mill the heads that the I/E cams get out of phase realtive to each other? Maybe I am not thinking of the motor in question.. But for the life of me I dont' see distance from Intake to exhaust cam changing?

[quadzjr]

Definitely.

Still don't see how it is cheaper.. but it is a ton easier.

[Ron Earp]

Give people the choice - the end result is the same, to give people a tool to get the cam timing back to stock specifications.

Some might wish to use an offset bushing (done that), some might wish to use a offset key, and others might wish to use a real simple solution for $100 more, an adjustable cam pulley.

[lateapex911]

For the piston engine sort newbie, it seems to me that if you have a situation where the change in phasing can occur from one cam to the other, that performance gains could be appreciated, that would otherwise not be possible.

is that true??

[Chip42]

For the piston engine sort newbie, it seems to me that if you have a situation where the change in phasing can occur from one cam to the other, that performance gains could be appreciated, that would otherwise not be possible.

is that true??

if you are speaking in terms of cam-cam variation between 2 parts that are both within spec but at different tolerances from nominal, and the ability to find the cam "out of the pile" with the "best" in-spec shape and be able to time it to the "best" angle within the factory tolerances. then yes - Ron's proposal to allow adjustable gears would save everyone money by allowing them to find the "best" spec setup from fewer cams inspected.

as for cam-cam phase changes on V or H (opposed) engines: when the decks/heads are differently clearanced then the cam-crank center distance changes differently for both. This makes one bank opperate differently than the other (slightly but we're polsihing the hell outta this turd now) - there's a difference in the first place (factory tolerances) and if you build it right you must account for this even without removing material from the factory bits.

so while I disgree with the allowance of adjustable gears on account of "the class philosphy," it would make a "full" IT build and corrections for allowed machining on any build readily avaialble, and a one-time purchase. I feel that it would it would start rules creep toward unrestricted cam timing, something I'd like but am apposed to within the rules as they are intended.

in short - adjustable cam gears/pulleys have a number of advantages that would more easily allow IT legal modifications, and policing illegal adjustments is reasonably easy without significant teardowns in most cases. However they do place us on that slippery slope toward unlimited cam timing which would have significant benefit variation between makes and models and is thusly NOT in kleeping with the IT class philosophy, long term.

[Ron Earp]

However they do place us on that slippery slope toward unlimited cam timing which would have significant benefit variation between makes and models and is thusly NOT in kleeping with the IT class philosophy, long term.

I'm still having a hard time seeing how adjustable cam gears, that are to be used to adjust the cam timing back to stock after machining, is a slippery slope to unlimited cam timing.

To me this argument is like allowing port matching then leads to competition porting and combustion chamber shaping. One procedure is legal, the other is not. No matter how easy it is to cross that line we still have the rules to abide by. I'll admit I'm a bit dense, but a temptation to cheat is not something I think the IT ruleset should be concerned with.

People that are going to cheat will do so regardless of how hard or easy it is to do.

[Z3_GoCar]

For the piston engine sort newbie, it seems to me that if you have a situation where the change in phasing can occur from one cam to the other, that performance gains could be appreciated, that would otherwise not be possible.

is that true??

Yes Jake, phasing is an important tuning parameter, to trade torque for hp. In the fixed cam setups, it's like changing the angle between intake and exhaust. Actually, this is already performed by my VANOS throught the motor rev range. Further taloring can also be achieved when setting the cams up:
http://www.realoem.com/bmw/diagrams/d/a/9.png

Notice the slotted holes in the stock cam sprokets :D

[joeg]

Another (but crude) way of restoring stock cam timing is with thicker head gaskets. Indeed, for my motors, felpro sells a steel shim that looks like a head gasket for this purpose.

I don't really believe anyone would use an adjustable sprocket to simply get the timing restored to "stock." Who are we kidding? (wouldn't know what "stock" is anyways...given manufacturer tolerances). It's to phase (either advance or retard) the cam to maximize the desired power target.

[lateapex911]

Ron's point is very valid. From a rules writers perspective, I shouldn't be concerned whether I am creating an easier way to cheat. People often gravitate to really hard ways to cheat. (They'll empty a battery and stick another inside, for example...yechhh, battery acid! fun!) Regardless, cheating is cheating, and the rules can't distinguish between cheaters and followers. That's our job as drivers/owners/competitors

But, the singe point of correction that this rule requires strikes me as just that: an attempt to make sure we don't "correct" one cam, while leaving the other "wrong", which could result in increased performance that wouldn't otherwise be available.

But, the downside is that, from what has been said here, that fixing it in one location might not actually acheive the goal of equal restoration. (In all cases)

And, there are other disadvantages, or costs, such as increased potential for failure because one key is doing the wok of two, and the possible hassles to use that solution when other solutions might be more readily available for certain model cars.

Interesting....

I'm not sure I "feel good" about allowing adjustable cam gears, but I'm also not sure I see a good rational for NOT allowing them. I *do* think, though, at this point at least, it might make sense to allow multiple methods of correction, but I'm concerned with wording it so that both cams are restored to original positioning.

Thoughts?

[pfcs]

I can't think of any situation where head/block decking would change the relationship/relative timing of a pair of DOHC cams. On vee engines where the timing belt (or chain) returns to the block before going to the 2nd head (Audi V6), any change in cam timing to the 1st head caused by decking/milling would be doubled in the second head.
(Any boxer setups I'm familiar with use seperate belt for each bank which cause no such problem)
The change in cam timing caused by removal of material to reach legal C/R limits is negligible. In the rare case of OHC vee engines, even the 2nd head is very close and splitting the difference via crankshaft key adj would bring the timing marks into apparent positions. (the Audi V6 has infinitely adjustable timing sprockets so a non-issue there) Opening the rules in any way that allows non-original adjustment of the phasing ("lobe displacement angle") of DOHC camshaft pairs is defenitelty a slippery slope given the extremely limited ability of tech to measure or determine the legality of these parameters (in practical terms, change "extremely limited" to "nonexistant" with no prejudice towards tech). Changing lobe displacement angles causes HUGE HP gains.
The argument that IT rules shouldn't reflect how hard an illegal change is to perform/OR/how hard it is to detect is a stupid one. Arguing that adjustable sprockets or offset keys at the cam sprockets should be legal because they make it easier to do is even dumber! It is much better to be pragmatic about such rules. I'm sure the intent of only allowing non factory adjustments to be done at the crank is to make it VERY difficult for someone to run modified cam timing without going to the trouble of manufacturing an original looking cam(s) with different lobe centerlines, or making timing gears with relocated key positions. I promise you that the small amount of offset in the crank key won't render it a failure item.
PS: there's no way that the phasing of in/ex cams changes, no matter how the head is milled, etc because the belt or chain remains in the same relationship where it pulls across the 2 sprockets.
PS2: If there is any need to change the rules, it only applies to vee engines with no provision for cam timing adjustment. Anyone needing this rule? If it ain't broke, don't fix it. Hoping pragmatism saves our class as well as country!

[lateapex911]

The argument that IT rules shouldn't reflect how hard an illegal change is to perform/OR/how hard it is to detect is a stupid one.

Thanks! I always appreciate praise!

[pfcs]

Don't delude yourself Jake

[dickita15]

Jake,
Regardless of you perception of Phil’s lack of tact, don’t miss his point that shaving a head or decking a block should not have any effect on the relationship between two cams.

[Flyinglizard]

The factory short block will have too little piston to wall clearance.IMHO.
The factory Honda and VW pistons are within 1 gr of each other. The replacement pistons are usually way off tho. ( 3-6gr)
Deck the block, use totalseal rings, bore to .003 and it will go faster and last a long time.
MM

[quadzjr]

I can't think of any situation where head/block decking would change the relationship/relative timing of a pair of DOHC cams.

I asked that same question and never got a response.. The only way I could see that being a possiblity.. is if the intake and exhaust cams were mounted on seperate bodies..