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.
Engine Balancing
- Thread starter Darryl Pritchett
- Start date
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
New member
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
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
Some of us can't afford such luxury.. haha..
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.
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Ron Earp
Administrator
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.
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.
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.
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Ron Earp
Administrator
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.
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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.
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.
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lateapex911
Super Moderator
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
Administrator
Definitely.
Still don't see how it is cheaper.. but it is a ton easier.
Ron Earp
Administrator
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.
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
Super Moderator
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??
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
Administrator
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.
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Z3_GoCar
New member
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:
Notice the slotted holes in the stock cam sprokets
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.
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
Super Moderator
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?
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?