First look at this link showing what im working off for this idea

http://auto.howstuffworks.com/camshaft3.htm


Ive lways been looking for practical ways to build a sbc with variable cam intake ect. So this week in advanced auto (high school class) we have to do a paper on engine systems i chose varible cam designs. I found a bunch of complex and ovehead cam systems that could work with a pushrod engine but it wouldnt be practical due to excesive block,valvetrain mods. Finaly found a system that can be relitivly simple to adapt to a pushrd engine compared to other systems. It is the ferrari system, it uses a cam with a lobe shape that goes from low lift to high lift my moving the cam in and out of the block changing the lobe shape the lifter is riding on.

LIFTER

You can put it on a SBC by modifying a stock or aftermarket roller lifter so the roller instead of being flat make it round so it seats in the center of the lifter. Rather than on the edge because of the lobe shape.

CONTROLS

I havent figured out how to move it in and out exactly but i have an idea. I would use an old $50 laptop with a program that takes the incoming rpm signal, the throtle position, and boost (for turbo engine) then it reads of the graph like a efi fuel map but this would be changing the cam. My brothers friend that is a program designer says he can easily make me a program like this for free. But i dont know what kind of actuator is controlable like what i need. It has to go in and out relitive to the incoming signal or volts, im shure theres somehing like this out there. If you know a actuator that is capable of this tell me.

PROBLEMS

A possible limiting factor may be that the cam jounals can only walk ~5/8. I would have to get custom cam bearings with smaller oil holes and the rear most bearing will have a passage milled on the outside on the bearing going to a relocated oil hole fuher fowards. I would have to do this becasue the stock oil hole is ~3/8 from the rear of the block limiting movement, if the cam moves so the holes are no longer covered the oil pressure will drop adn eventualy sieze the cam or cank. If it is possibe i might be able to get the journals on the cam made extra large.

A problem is I loked at stock chevy lifters and the pin that retains the roller seems to be un removable. It looks like thy put he pin in and stamp it on both sides expanding it and permanantly fixing it in the hole. almost like a rivit. but mabey an aftermarket lifer has a c clip I will have to look around. or i cna just get the pin pressed out and somehow put a new pin in.


I asked comp today if they are capable of milling me a roller cam that has a varible profile for this system. I also asked if thay can have the lobe seperation and advance change as it goes down the lobe to take full advantage of the system. I will post there responce when i get it. Also i will ask my machinist about how to build the cam and system tomorrow when i go pick up my engine parts.

Im am absolutly going to attempt to put this system on my budget 267 turbo engine but it might at first be only a 2 stage system using a stock vette roller cam and have a smaller lobe ground onto 1/3 of one side of the lobe. I would then hand blend the transition from the 2 profiles on the midle 1/3. I beileve will rig it with a pressure actuator that pushes the cam in to chnge to the bigger cam after the turbos kick in at ~3000rpm or less hopefully! once i work ou the bugs i will step up to a contiusly varible system with a new cam and computer controls.

Can you imagine a +500 hp N/A 350 and still have as much vacume as a stock engine, being totaly streetable with a low sall converter.


If anyone has ANY info or suggestions please post it.

 

this is waht comp cams response was


Eric
I did some cheacking for you about this project and as of right now we really wouldn't have enough time for a project like this one. You would be looking at least two years before we could get time for something like this. Wish I could have been more help.
Thanks
Shane

oo well, now I have to find a custom cam griner or someone with a cnc machine to make me the cam lobes. Im going to try contacting ferrari enginers about how they made the lobes but they will most likely not repond. I will try it if i can find a contact.

 

Most of those systems I've read about use hydraulic actuation. I'd wonder how they keep the cam in position... I mean, the lifter would always want to push the cam towards the back of the block.... riding down the anglular lobe profile.
Neat concept though. I'd imagine that something like this would require quite a bit of engineering know how to pull off. More than most high school students are capable of.

On the cam thing, I'm not surprised Comp wouldn't be game for such a thing and even if you can find a grinder who will tackle it... the price is going to be otherworldly I'm sure.

It is intriguing though, I'll give it that.

-Mindgame

 

This is a large project, both in time and $. Perhaps rather than try to build an operating engine, you might consider building a mockup longblock which just turned over with a starter motor and demonstrated the variable cam. You could just do one cylinder then and the cam profile wouldn't have to have the accuracy of one that would operate at actual engine speed.

Now for the wet blanket part, which I hesitate to post: you probably aren't looking at more than 5% - 8% power difference from variable lift/duration without changing other things in the engine. You really need to have two cams so you can change phasing (separation angle). Look at the GM future stuff article in the current Car Craft. They show a 2 cam in the block pushrod V8 with variable phasing on the exhaust cam. At least you could get some ideas from it.

Bottom line, keep at it and Good luck!

 

Now that you mentioned it im going to make the protype first i will just hand grind one pair of lobes (int+exh)on one of my vette cam i have and modify one lifter.

I never even though of the fact that the distributor wont be lined up with the gears and also since the oil pump runs off the distributor im going to have to design a oil pump system that runs off a pulley like a dry sump system. The distributor will be easy I can mount the distributor on top of the vavlecovers or huging the block under the headers and have a 2:1 ribed belt or chan and sprocket off the crank. I can get the belt and ribed sprocket from a junkyard off a dohc engine for free becaus my friends parents own a junkyard.

Changing the lobe seperation wont be hard i can have a cam grinder make multiple grinds each pass over .1 than the last and using a biger lobe and changing the lobe center slowly. I dont like the idea of using the oil control becase it will only have 2 stages and sound like those hondas with vtec ffffffffaaaaaarrrrrtttttt .

With computer control it can be tuned to perfection at every rpm and load. I plan on geting g tec pro and that will help me tune the system alot if it works as good as ive heard, and save me a fortuine over going to a dyno.

Thanks for the support and help oldssroker!

 

Hofstadter's Law applies here: "It always takes longer than you expect, even when you take into account Hofstadter's Law."

Also apply his law to the cost.

I applaud your enthusiasm. Don't get too discouraged when you hit walls. Just because others haven't made it work doesn't mean it won't. Of course it could mean the gains aren't worth the effort and cost. Do it for the pure joy of it, not because it will be a world beater.

For What It's Worth (FWIW), one of the contestants in the Engine Master's Challenge built a variable cam phasing mechanism into his SBC. Basically it could retard (or advance) the cam at a certain rpm. It worked, but didn't give him any significant more power/torque. He disconnected it for the competition. Cool guy; he reminds me of you.

 

It also seems like the timing chain would bind somewhat with that much movement. How did ferrari get around this? Gear drive?
I seem to remember something about non roller cams being ground with a slight taper to keep the cam forced back? I'm sure it's not much but I wonder if someone like comp cams could easily apply this to a roller cam profile?

 

Move the cam inside of the cam sprocket. A spline should work.

Flat tappet cams are ground with a slight taper, but not with different profile on one end of the lobe. The grinding wheel is just dressed (shaped) at a slight angle, and one profile is ground.

 

Spline makes sense.
I realize it wouldnt' be on separate lca's or intake centerlines but if you moved the lifter up the taper wouldnt lift and duration increase?
I don't think my idea would work to well anyway because the base circle would be tapered too if they ground it like that.

 

Yes, and you don't need this to do it! I have one in the shop right now.


Anyways, this is a great post. Got me thinking alot tonight, and Old SStroker too!

There might be a way to phase the cam (advance/retard) and have it change the duration/lift at the same time, but they would not be independantly variable, you would get the phasing and duration change all at one time.

I think this is great, being able to make this cam work is whole different thing.

The oil pump problem is easy to solve! use a LT1 type oil pump drive, that will work.

Timing chain is easy, it would have to slide along the cam, you guys figured that out already!

Distributor, still thinking about that, CRANK TRIGGER or LS1/LT1 type ignition control. This too!

Hey out of the box thinking is what this is all about. Not many people here know that I was a art/film/photography Major in College. My education was not about learning practical things but to learn how to think. That's what I took from it. That's one reason I think about engines differently, kind of self taught, and definately taught by the Old guy. That combo keeps me thinking differently about everything. I like engine theory and design, that's why I do it, nobody ever said you had to go to school to learn it. In fact most things about engines you will never learn in a classroom, they are in books here and there, places like this forum, other car guys (the right ones, not ones who think they know) and your own personal experiences.

This is really a kick *** thread. Didn't I already say that?

Bret

 

We currently build and market a product that allows for variable cam timing. Our product uses a phasor that alters cam to cam sprocket position, cam torsionals are used to "power" the phasor, and the cam timing is controlled by a microcontroller using engine data. Our applications include both over head cam and cam in block engines. You may email me for more specific information.


zbullock@morse.bwauto.com

 

Yea shure you have a 500 hp engine but, whats the torque at 2000 rmp may i ask? And what stall converter do you have to run to go the fastest? and do you drive it every day i highly doubt it. Alslo an engine with varible duratin will have more AVERAGE HP yea peak is great but the car will go alot faster with a much smother and almost infinatble powerband well at least as much as the bottom end can handle. It will also sound stock at ildle and howl when you rev it up instead the power starting to push you as you near the peak then stop pushing as hard one you pass it it just keeps geting faster and faster and faster.....

I was playing around with desktop dyno and built a 350 with AFR 190 cc heads single plane and keeping a 112 lobe seperation with the cam straight up. I was gaining 150 ft/lbs at 3000 rpm and 174 hp at 7000. Thats with a small side profile of 200@.05/.42 lift vs a big lobe profile of 260 duration/.62 lift. If wanted i could make it keep going higher and higher but im trying to keep it real. I dont have money coming out of my a$$ for the parts to handle 8000 rpms! And the spring pressure will make the roller wear alot faster because of the small contact point.

last night i started reshaping the lobes using my vette cam but my parents didnt apreciate me grinding in the basemet at 9:00. So i will finish the 2 lobes within the next few days. And i will post it if anyone wants to see it once its done.

Today i went to the machinst to pick up the parts for my engine, wich werent done yet , droped off my bros block and was talking to the race engine builder about designing the cam and system. He pointed out that i would have to do somehhing about a thrust surface on the cam gear holding the cam from wallking back. But the solution is simple remove the surface on a lathe. I asked him about building the cam and he dosnt have the machines he sayd contact crane or crowler because they make real custom cams not cams with existing lobes as templates but they actuaty can make new lobes for one cam. He sayd he still doent think they are capable of steping it down like how i need. Also he sayd it has to be hardened so I have to send it to a cam company after coming form the machinist to get it hardned.

So now I think my only option is cnc. Im drawing up a rough design on cad and asking for a quote for a cam if i proide the blank from this maching company. www.tmlimited.com I could try to make the lobes on my friends mlillig macine but it would take weeks to get all the lobes done using the system tappet cams are made 1 degree at a time. It would be a total of 5840 times i would have to change the anagle and lift before cuting so F that! and if i mess up one measurments i can destroy days of work.

How much is the crank trigered ignition system? because i can make a pulley type for cheaper i believe especialy if i use a junkyard cam pulleys and belts to drive it.

I was thinking its possible to make a dry sump sysem using 2 chevy oil pumps one drawing from pan into tank and one presurizing oil runing off a pulley. Kind of a getto setup but if it works and would cost less than $100 in parts consisting of 2 chevy high vol pumps, some copper piping, a tank i can weld out of sheetmetal, and pulleys. If i use a cam belt for the distributor i can run the pumps off the belt using the gear that was for the second cam on the engine i pull the parts from to drive the distributor. This system would not only solve my problem of driving the pump but gain some hp from the dry sump.

 

I dont want to just change the advance less than 10% hp and toque can be gained from that alone. Ive already looked into that and droped that idea. I have posted about that idea a while ago but its been erased from the forum memory aleady.

 

A few thoughts:

1) You've got the right idea that average torque and (therefore hp) in the engine's operating range is what's important. How one gets there is the key. It doesn't necesarily need variable cam duration/lift to do it.

2)The engine SStrokerAce spoke of was built for the Engine Master's Challenge. If you are familiar with the Challenge rules, engines were graded by average torque and average horsepower from 2500 to 6500, not peaks. I was present at every dyno pull that engine made. It idled at 900 with NO lope at all. That's the slowest it would go with the idle screw on the 950 cfm HP Holley screwed all the way out. It had about 400 lb-ft @ 2500, and peaked torque above 525 lb-ft at 5000, and power well above 550 about 62-6500. Ok, it was a 365 not a 350 (Big ovebore!) If you haven't guessed, the cam duration was rather mild, but the lift was high. In other words, it was an "aggressive" profile, with negative 3 degrees of overlap at .050 lift. You don't need high duration if you do it right. You certainly don't need 260 @ .050. You don't even need 230. Oh BTW, this was on 92 octane pump gas.

Yeah, if he were to drive it everyday, he might back the compression down a half point or so. The point was that you don't need variable cam timing to achieve 500+ hp or lb-ft, with a high vacuum/low speed idle with a 350 SBC. You do need excellent heads with relatively small ports. With a stock LT1 or LS1 converter this engine would stall a few hundred rpm higher because of it's low end torque. That 2000-2200 would be more than enough.

3) Desktop Dyno isn't a bad program, but it is very basic in it's approach. You might learn a lot if you used Engine Analyzer Pro by Performance Trends.

4) Just varying cam timing isn't a magic solution. The valve timing has to compliment the rest of the induction/exhaust systems on the engine. Cam timing is the last thing you need to specify on an engine, not the first. The intake size, flow, etc. that works well with 200 degree timing isn't what works well with 250 (or even 230) degree timing. IMO, there's much more torque/power available from good flow and good port velocity. If that's good, you don't need as much "cam", so all those nice-to-have things like low rpm, smooth idle, low rpm torque, etc. fall into place. It has to be the whole system that works together. That means that as you change cam timing, you need to change port size (difficult) or port length (done often). It's easier with multi valve engines, too.

5) Listen to your engine builder. Cam lobe surfaces are probably the most critically machined surface in an engine. They are ground, not milled or shaped. Deviations in the surface which are even difficult to measure can be critical at speed. Even a slightly unbalanced lobe grinding wheel can produce a cam that loses 20-40 hp for no apparent reason. It has happened. Even CNC grinders aren't always capable of producing an accurate enough surface for the most critical race cams. Generating the variable surface you need may be beyond today's cam-grinding technology. I don't think you'll get much help or satisfaction from cam grinders. Not because they don't want to help you, but because they can't.

6) If all you wanted to do was change lift, but not duration, look no further than BMW and their variable lift intake valve system. It's a variable ratio rocker which is relatively simple. Well, almost nothing in German car is "relatively simple". It works well enough to be able to eliminate any throttle plates!

Theory is great, and your variable duration/lift has merit. Making it work is the challenge. Making it work economically is an even greater challenge. Good luck!

 

turb0racing,

You can get about anything with enough $. Now if you said 500+ft lbs out of a 350 for the street, that's impossible! Well you can do that too, but it's much harder.

Old SStroker cleared that up already, yeah I do have one and yeah, it makes that much power. It does cost about $15K in parts though.

You need to find much better heads than the AFR 190's. The peak flow of those heads is about what you need @ .400 of lift to start with. Look at the numbers for the CNC ported AFR 215RR's and you would get a little closer.

You have a great start for being your age. Lately I have been amazed at what some "kids" know, and that's coming from a 24 year old. Keep it up, but don't be so fast to step on your ****. I know I've learned that lesson.

Bret