Engine Balancing

[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.

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

[Chip42]

[quote=Ed Funk;280563]

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

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

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?

[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.

[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.

[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.

[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).