Update: Adjustable cam pulley

No. The way it would work is pin the pulley to the spacer at the zero position and then time the spacer. Once the spacer is timed, it stays put. Then to change cam timing you loosen the bolt, pull the pin out of the pulley and roll the cam until the pin hole lines up with hole for the advance or rerard you want, oin it, tighten the bolt and you're done. It works exactly the same way your custom system would work, but not making a pulley should cut the cost by way more than 1/2....In a batch it should be under $200 for everything.

 

I think I’m going to go ahead and make up 5 or 10 sets. The price will be about $200 for anybody that wants a set, shoot me a PM. That will let you advance or retard your cams 4 degrees in 2 degree steps using the OEM pulley, but without needing to skip teeth or put on a degree wheel and dial indicator…For example on a QV, that is enough to change from us to euro timing specs. For say $60 I could drill 6 additional holes in your stock pulleys, then you’d have +/- 10 degrees adjustment, I can’t think of any reason you’d ever want to move a cam more than that. The pulleys can be drilled at any time if you decide later you want the extra adjustment.

 

I had a couple PM questions about what I'm buildingso...It's not as slick as custom pulleys, but it is functional and a lot cheaper. $200 buys a set of 4 spacers. You will re-use your stock pulleys. For another $60, I'll put 6 more pin holes in your stock pulley to let you go +/-10 degrees instead of only 4 that you'll get with the stock pulley.

I'll post a rendering once I get them drawn. What I'm going to build is a set of 4 spacers. To use them, you turn your OEM pulley backwards. That makes room for the spacer. The spacer has pin holes on the front and the back, but not the same pattern. On the back, will be 5 holes 25 degrees apart, just like the stock pulley. On the front, there will be 14 holes, 24 degrees apart.

You put the spacer behind your stock pulley and put the pin in the center of the 5 holes and leave it there for now. Then you follow the factory cam timing proceedure, but you move the spacer on the cam, not the pulley on the spacer. What that does is get the cam in time while keeping the pin in the center of the pulley. Then to advance the cam timing 2 degrees, you simply loosen the main bolt enough to pull the pin and move the pin 1 hole clockwise, roll the cam a touch to get the pin in the hole and tighten the bolt back up. Your done. For 4 degrees, move the pin 2 holes. To retard it, move the pin counterclockwise. That's it, it's a very simple solution

Again, it is not as cool as custom pulleys, but the truth is that you'll probably only ever mess with cam timing while your dialing in the engine ont he dyno, after that you'll never touch it. Also, the pulleys will be hinden behind the cover anyway, so no one but you will very see the way cool custom pulley anyway. This is a relatively simple solution to make cam timing changes pretty easy...probably not quite as easy as with a custom pulley, but way way easier than with the stock set-up.

 

I on it...it wouldn't work if ferrari hadn't made them that way for me.

Again, it's not as nice as what you're planning...but it will do the trick.

 

I see Sponsor Nick has aluminum pulley sets available, I son't know how much they cost....I'm always scared when a web site shows parts without a price

Anyway, they would work with the spacers I'm making too making them adjustable pulleys.

 

I bumped this thread to ask a question that may hopefully help everyone out, not just me. I broke my winshield somewhere between R&Ring it, so to fund a new glass (F funds are down over this way) I put my set of pulleys up for sale. I can get more later, Scott will make more, so not a giant loss, but it suddenly became a guessing game as to what exactly these parts would fit.

My 308's have engine numbers of 2283, and 2393. Scott had been of the knowledge that there was a design change to the drive sprockets beginning with engine number 00134, so I have the "late" style. But I do not, at least on engine 2238. It appears this engine uses the early style. The stock drive sprockets are pt # 104914 early, and pt #112018 late. As far as I can conclude, the 308 changed seperatly between the GT4, the GTB, and the GTS, with different engine cutoff numbers depending on car model. Engine 3044 for the GT4, engine 1104 for the GTB, and engine 3944 for the GTS. But thats off eurospares so there is no way to confirm anything. But its probably "reasonably" accurate. But at any rate, the drive sprockets wouldnt have fit my car anyway.

Then the question of the cam pulleys was considered. It was brought up that these would NOT fit a QV, as the cams on the QV were said have a smaller boss.

So I spent the other evening paging through Eurospares and the owners site websites, comparing cars and part numbers.

I was surprised that no one mentioned or noticed this, but the stock 308 cam belt 107833, fits all 365 and 512 Boxer engines up through the BBi, the cam drive pulleys, part number 104914, fit the 365 BB and the early 512BB. Then it appears there is a change that takes place somewhere between the BB, and the BBi, and the BBi takes the 112018 drive sprocket.

On the cam pulleys themselves, the original part number 108033 and 108044, was superseded to part number 110994 and 110995. All of those have now been superseded by part number 113097 and 113098. All these pulleys should be interchangeable, as regardless of what you have, the 113097/8 supersedes them all (as far as the two websites show). The 113097/8 are listed as fitting a QV, and I cant find any cutoff. The drive gear 112018 fits the QV up to engine number 117598. According to both websites the 308 cam sprockets should fit a QV, all the 365 and 512 engines both carbed and injected, and in fact should even fit a 288 GTO.

When this got started there were guys asking if these parts would fit the 12 cylinder cars, and it appears they would. The 365 Boxer and the 512, both used the same belt and pulleys. The only distiction was the change in drive sproket the same as the early 308. The only question remaining is will the cam sprockets in fact fit a QV, and would these cam sprockets fit under the timing cover of a Boxer. By the looks of it, if Scott fabricated a drive gear to match part number 121273, he would have parts that would fit the entire series through the 328 and 288 GTO, and possibly the F-40. But looking at the TR and 512 TR, its an entirely different design from the boxer and nothing crosses over at all.

Could anyone confirm or deny the (early) QV cam boss being smaller or the same size as the 308? I dont see how they can be different if the part numbers are the same as a 308, but who knows.

 

Scott ---

So, you have (2) pieces of AL7075 clamped together with threaded fasteners... And, these fasteners have no locking features, and the clamped joint has no shear feature(s)?

In the Aerospace / Aircraft industry, we have an Engineering mantra about friction --- "When you don't want any, expect some - When you are relying on some, don't count on having any."

You are trusting friction to keep these (2) parts from slipping against each other --- that is a bit spooky. If you (or whomever you license it to) decide to market this product to the public, I suggest you get some product liability insurance or keep a cash reserve on hand to cover the damages when a customer, using this product, has their engine destroyed when it jumps valve timing as a result of this device failing by critical slip.

I'm not trying to discourage you or piss all over your idea --- quite the contrary, I admire your efforts. I'm merely offering some friendly advice (i.e., a warning to protect yourself and to be conservative) ----- take it, or leave it...

I wish you the best of luck...

 

Actually, I just took the time to review all the previous posts, and it looks as if you've already addressed this via your concept with the shoulder pin(s) --- there you go.

As for locking the fasteners (I apologize in advance if this also already has been stated, and I've missed it), you may want to consider locking helicoils (as opposed to the free-running type). The only caveat with the locking coils is that they are only good for 10-15 installation cycles (this is the number we determined in our own testing --- the folks at Helicoil will tell you a different number). So, you would have to spec to your customers that after some amount of loosening / re-tightening, the units would have to be "serviced" by replacing the helicoils --- not such a big deal, and could probably be coordinated with the belt change service interval for most folks.

Again, good luck --- I hope this proves successful for you.

 

Yikes! As a fellow engineer and long time professional motorsport / aerospace machinist, I feel a need to jump in here in Scott’s defense…

Your mantra concerning friction is *extremely* well put and well worded. Thoughts all should take very seriously. However, the design that Scott uses in these sprockets is one that has been successfully employed for well over thirty years. I have personally built or been lead in the design phases of countless engines over the last 30 odd years that all utilized this exact same principle. Not one of the adjustable sprockets I have seen or installed in that entire time has had any sort of locking fastener or pin that limited rotation. And I have never had one move on me in that entire time.

The concept here is one of not slotting the sprockets enough to allow valve to piston interference in the first place. Should the fasteners back off and the sprocket rotate in relation to the cam all you end up with is a motor that runs like crap. Nothing catastrophic…

Agreed that this would be well less than poor design in an aircraft or other critical application. But that’s not what we have here. Scott has done a more than adequate job in accounting for the possibility of slip and has produced a product that does exactly what it should. And is rather well made to boot…

Rob Stewart

 

Im sorry, but what a load of crap. For virtually every engine in the world with a belt driven cam, there are aftermarket adjustable cam pulleys available that share the same basic design and fastener technology as these. These pulleys are no different than any you could buy for a Honda or anything else in the world.

The crankshaft dampener on the 308 has the crankshaft bolt held by torque and friction, as do the clutch plate to flywheel bolts, flywheel to crankshaft bolts, rod cap bolts, main bearing cap bolts, timing belt drive sprocket nuts, timing belt tensioner pulley lock nut, and the timing belt tensioner to engine bolts. In the driveline, the transmission input shaft lock nut, main shaft lock nuts, ouput shaft lock nuts, differential to ring gear bolts, drive axles axle flange bolts, and the stub axle lock nut are all held together by friction and torque. So are your wheel bolts by the way. All engine accessories such as the alternator, water pump, air pumps, and all their pulleys are secured with friction nuts and bolts. Not only is a Ferrari put together that way, but so is everything else in the world outside of aircraft. Can you imagine the potential damage the flywheel would cause if it came loose at high speed, or the crankshaft dampener? And how about if those timing belt drive sprockets or tensioner fasteners came loose?? In the situations where wheels are bolted to aircraft, all bolts are safety wired. And that is the only industry that does it. Why are you not as adamant that the wheel bolts be secured with safety wire? Surely there are cases where they can and have come loose, arent there?

The CAA, and then the FAA chose to incorporate safety wiring everything long before most of us ever breathed air. Most of the old timers that have been wrenching on airplanes for over 50 years frown at it all the while theyre cutting up their hands doing it. Its really unnecessary for the most part with good fasteners. For every case of a bolt somehow loosening, there are cases of safety wire coming loose and causing damage. But a bolt came loose back in 1920 something, and some fool decided safety wire was good practice. And with the war effort going in the 40's, slowing down work progress made jobs last longer and kept more idiots working doing menial labor. I guess if you have a problem with these pulleys, dont buy any. But the only way that thing will ever let go is if all 5 bolts back out. If a person doesnt know how to tighten any of the other bolts I mentioned, they shouldnt be anywhere near a machine with a wrench. Thats why they decided to license aircraft mechanics, so idiots wouldnt be wrenching on them. Quick, go out and cross drill all your fasteneres and safety wire everything, wouldnt want anything coming apart. Its no small wonder all our labor and manufacturing is going to China.

 

Moku ---

I'll take your word for the implication that a 20 degree (+10 to -10 range) change in cam timing on a 308 engine wouldn't cause a valve to hit a piston --- I'm not that familiar with the specific geometry.

But, you won't find too many applications out there where a sprocket / gear / hub isn't keyed or splined in some fashion to its shaft. And, using locking features (or thread locking adhesive) for fasteners on rotating parts is standard engineering practice...

Better is always the enemy of 'good enough'.

While I don't know him personally, Scott impresses me as a reasonable guy (from his posts here on F-chat) ---- I doubt he'll feel a need to be defensive from my comments... Critique from peers is a vital part of the engineering design process. The technical world is not about ego --- it's about achieving the best possible result, and is almost always a group effort.

If Scott didn't wish to hear anyone's opinions, I doubt he would have posted his idea...???

And, everyone here is free to dismiss mine... hopefully with a little more tact than calling them "a load of crap". I'm not going to argue with you, Paul --- I'm sure you can find someone else with whom to do that...

 

Scott and I actually had a pretty long discussion back and forth about adding a locking pin feature to the design. He was receptive to it, but space is a problem. I'm pretty sure it won't slip the way it is, there are many similar pulleys out there, but without a pin, I didn't want it on my engine, plus I didn't really need one anyway.

 

In no way am I disagreeing with your tenets of good design and engineering. In fact, I lead my life by them and have for a very, very, long time. It’s very solid practice. Of course the best possible result usually lies in a group effort. That’s exactly what has occurred here. Of course critique from peers is vital. Scott has had plenty, believe me! Ego hasn’t played a part here in the least. There just isn’t room for it.

No one said these were “good enough”. The idea from the start *was* to end up with “better”. And Scott has gone and damn near produced “best”.

Again, not dismissing your tenets. They are obviously well founded in traditional engineering practice and ones that I strive to uphold myself. The point is you’ve jumped into a design process that was complete a long time ago and was originally based upon solid, well tested design philosophies. Ones that have held up over decades of rigorous real world testing. I refer you to Jesel’s belt drive: A simplistic design that hasn’t changed one bit in something in excess of 25 – 30 years. I’ve used these on various motors of *huge* output without trouble for as long as I can remember. And they never, ever, fail or slip.

 

I appologise, I didnt really mean to "argue" with anyone in particular. I guess it just hit a nerve as like was stated, this was designed long ago, and everyone at the time had the ability to offer input.

A person could keep designing and designing forever, and no matter how far or how long you kept on trying to make it bullet proof there would always be some risk. Nothing is so well engineered that failure is impossible. But in the case of car engines, and in this case a 308 engine in particular, there are far more pieces on these engines that could offer trouble than this pulley. In fact its whole "raison de etre" was to make the 308 belt drive MORE robust. Bullet proof.

It seems so often today that instead of a good education and the promise of a better life creating hope, instead it seems to breed great fear. Fear somethings going to break. Fear something is going to fly apart. Or fear of being sued by a vicious society hell bent on destroying the one thing that made it the greatest nation on earth, freedom. Now instead of being free to create, or brave enough to accept some risk, instead we have to shelter ourselves away in fear of failures and of financial ruin by litigous thieves. Everyone else out in motordom have no fear, they create and try things all the time. But as you move up the scale towards exotic machinery, you suddenly find yourselves surrounded by fearful people. I keep wondering more and more each day, as more and more people tell us all what we can not do, how we ever got out of the cave. Our daughters fourth grade teacher had a large sign on the wall that said "perfection is impossible". It made me angry. Were teaching kids today to not even try, and teaching them that it wont even matter. No wonder Ed Gault gave up.

 

Nicely put!

But where Ed Gault retreated Scott has prevailed and continues to offer well thought out, well engineered, and very well crafted work. There's something to be said for that these days...

 

Paul ---

What drives people to be conservative is not always fear or a penchant for being anal-retentive --- often it is simply a cost / risk analysis. People may be nervous about failure of a part on their exotic car simply because it costs a hell of a lot more to fix than their Honda when it breaks (and not everyone who has a Ferrari is a millionaire --- some are just enthusiasts who have invested a good chunk of their life savings for the thrill of ownership). People may be extra cautious about the construction of the bridge they're driving on or the aircraft they're flying in because if it breaks, people can die.

For what it's worth, before returning to Aerospace, my career took me to McLaren as a chassis engineer for a short stint. So, I do know "a little bit" about taking designs to their edge of risk in motor sport.

Don't fret guys, I'm off this thread --- won't "hassle" you anymore.

I would just like to close with this --- Scott (plus whoever else has a stake in this design), I sincerely hope you succeed with bringing this product to market -- it's a great idea. And, I hope all who choose to run these on their cars, do so with a lifetime of happy, trouble-free, motoring. Honestly...cheers to you.

 

You worked for McLaren? then maybe you can tell us how ferrari does it on their F1 cars

 

It's on the market.

See http://www.ferrarichat.com/forum/showthread.php?t=106182 for links to pics

 

Mine should be here "any day now"...
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Thanks --- made me laugh a bit there. That was well after my time. They weren't winning back then (nothing to steal) - LOL

 

I hoped you'd find it funney

 

That would be a six pack at this point...