Yea those heads are a bit small but the engine its based on is a N/A version of my future street turbo engine with higher comresion pistons. im realy going to be runing poretd vette heads so i just figured afr 190 are close to the flow ill have. and the my second reason i want the system is to make the turbos spool earlier. With the turbos I inted to use, the small port size is close to optimal. I feel over 200cc on a turbo 350 engine is overkill. About the precision on roller cams i belive are milled not ground isnt that why they say billit roller cam? or is it only billit because they make the blank out of a solid piece but then just grind it with a cam grinder?

and what do you guys think about the homemade dry sump?

i ralize changing the pasing will be better but then the cnc machine ill have to be programed for more operations wich will cost more i believe.

 

Roller cam blanks are steel. This is needed because steel rollers run on them. Flat lifters which have 'feet' that aren't steel don't run well on steel so the cams are cast iron. Bearing journals and lobes are hardened.

Steel roller cam blanks are turned and milled from steel bars (aka a 'billet'), usually 8620, a low carbon chrome-molybdenum alloy steel. The bearing journals and the cam lobes are "case hardened" and then ground for size, shape and finish. The balance of the shaft is often prevented from being case hardened (carburized actually) by copper plating it maybe .001 thick. It costs more to strip and dispose of the excess copper after heat treatment, so many roller cams have the characteristic copper color left on the unground areas. It's not there for any esoteric reason; it's the least expensive way to manufacture it.

If aftermarket roller cams could be successfully made from castings they probably would be. Remember 'billet' in a part description usually means the average consumer will happily pay more for it, even if it's the cheapest or only practical way to make it!

A normal cam lobe has a two-dimensional shape; you can draw it on a flat piece of paper. It has depth or width only so the lifter has a place to rub. Notice how some OHC cams are much narrower in the base circle where the loads are minimum, but get wider in the lift area where the loads are higher. As was mentioned before, a flat-lifter cam is slightly tapered by dressing the grinding wheel on a angle parallel to it's axis. However the lift and duration on each end of the lobe are identical; it's just a smaller base circle and a two-dimensional lobe.

The problem is grinding 3- axis lobes. If you want different shapes on each end of a lobe due to lift and/or duration changes, imagine how the grinding wheel would have to move to achieve that shape. Even CNC cam grinders only move the wheel in-out as the cam blank rotates. They don't 'yaw' the wheel. Grinders which do have this capability usually only can make circular sections, not cam-shaped ones. They would also need small diameter wheels which wear out faster than the 24 inch diameter wheels normally used for non-inverted flank cam lobes.

Now because the shape is so complex, and the case hardening is only about .030 deep, you'd have to rough shape the cam lobes prior to heat treating, which would mean an additional grinding operation or CNC profiling. That's only money. The problem is not having the equipment readily available. Sure, it can be done, but, to my knowledge not on cam grinding machines. That means many many thousands of dollars of programming and machine time on machines costing seven figures which are making aerospace-type parts at astronomical (pun intended) prices.

What I saying is while it's possible, it may not be practical. If there are $15,000 worth of good parts in a 500/500 very streetable SBC, is it worth 30-50% more to get continuously variable valve motion and maybe only a little more power and streetability? Maybe not.

If and when solenoid operated valves see production, where cost is always a concern, variable lift/duration will be easy to change. Of course, variable intake tracts will also be needed to take full advantage.

Currently changing the phasing (variable timing, not variable lift/duration) is accomplishing quite a bit in power, emissions and economy without the complexity of VTEC. This works not only at full throttle, where a few % of the street driving is done, but at part throttle also. IMO, building a 2 cam-in-block SBC with cam phasing would be more doable and perhaps almost as effective as variable lift/duration. That's the practical side speaking, not the out of the box side.

 

I just though about how to machine a cam myself with high tolerances. I can get 2 lobes made on a oversized scale (4x bigger) one big high rmp profile and one small low rpm one. I can fabricate a machine that has a grinding wheel that moves in and out like a normal grinder but also changes the ange in relation to the cam withthe pivot directly below the grinding surface. I would accieve controll of this by having the diffrent cam lobes being read sepratly by rollers attached to a large se saw style lever. The poins where the rockers go to wil have to be 4x out further from the ceneter of the lobe to the outer edge wher i want the lobe to be ground.The ratio wil be 4:1 so the lobes have more force to rotate the grinding wheel angle. So this will make all the lobe profiles between the 2 lobes. Springs will hold the grinder from backing off the lobe.(get it? im having toruble trying to explain it).

I have to look into how normal cam grinders are designed then i will start drawing the design on cad. I will hopefully make it out of thick steel 1" or thicker all surface ground for turueness.

oldsstroker do you have cad because If you do I can send you the design (hopelfully by monday)and you can go over the flaws.

 

yea im stuck, how do they change for each lobe with the difrent angles and center it on the lobe. Do they move the cam or the grinder?

 

Yeah, do look at how mechanical cam grinders work. Try 10X size "masters" vs. 4X size.

You seem to be regularly reinventing the wheel.

By the way, "precision" of the surface of a cam lobe isn't measured in .001s or .0001s; it needs to be in the millionths of an inch. Remember, valvetrain design works not only with lift, but velocity, (the first derivative), acceleration (2nd), jerk (3rd), and the 4th, 5th and maybe 6th derivative. Ask your calc teacher to explain them. One might call them 'snap', 'crackle' and 'pop'. They effect the dynamics of the system, so very minute irregulatities in the lobe surface can cause big problems at higher rpm. That's part of what makes cam grinding somewhat art as well as science.

Hey, if it were easy, everyone would do it.

 

and another thing i realized i can change the lobe sepp by puting the 2 lobes in with a difrent lobe seperation so it changes across each final lobe.

 

Generally the cam indexes radially to align each lobe and the grinding wheel moves laterally along the axis of the cam from lobe to lobe. If intake and exhaust are different lobe shapes, you do the whole thing twice. That's with a mechanical grinder. CNC grinder can be programmed for each lobe. What CNC makes up for in speed and convenience, is often a trade-off with not being able to generate as accurate a lobe as a mechanical grinder which follows a "master cam" lobe.

 

http://www.nvbackflow.com/engines/cams.htm
I found how im going to make it check out this home made cam maker he had more pics of it in the photo galley. I would make it change the angle by having the 2 master lobes far apart and just have the grinder have a bearing alowing the assebmly to tilt. You have no i dea how excited i am. I can do it in my basmet and make multiple cams fairly easily . awsome!!

 

What you need to worry about more on a turbo set up is the exhaust ports, exhaust valves and the cam timing. A large Intake port is not going to hurt. In fact if your intake port is to small on a turbo engine it will limit HP. Getting extremely high exaust gas velocity is the key to getting turbo spool up, that and having the Turbo bearings and turbine the right size.

200cc on a healty 350 is not overkill.

Bret

 

ok so now i have an idea how i can make the cam. Now how would i control the movement of the cam in and out of the block. i was thinking a linear actuator would be good and have it on a long arm so it is geard downa and i can get more precision in movemet. Do they make actuators that are like servos (im thinking r/c cars) that change there position depnding on the input volts.Thatway i would jsut have a computer regualting the volts via ohms. otherise i would have to have a motor geared down and have sensors telling the computer what the position is adn that would be mor e complicated. so if anyone knows about the name of the actuator i need tell me because ive been looking and cant find the type of actuator i need.

 

In order to get exhaust velocity to spool the turbos. You need smaller intake runners so cylnders fill more completly. Ccomapys build heads with big runners this is what most people go by when talking abut chevy head sizes barley ever mentioning the exhasust becaue its almost always close to %80 of the intake(somewhere around oplimal). We do simply because were americans and must always use the bigger numbers .

Ok so what your saying is get high velocity. You cant get big intakes to flow the small amount of air needed to accieve low rmp cylnder fill. Because objects (or air) in motion tends to stay in motion, So if you get the velocity up using small good flowing intake and exhasust and small advanced wide lobe center engine. This make the valves open up later so the cylnder builds up vacume then pop the valve open for a short time. The air gets sucked in with a huge powerfill busrt of vacume. Thats a low torque motor. A turbo motor needs a medium flowing intake and medium flowing exhaust the reason for this is turbos have backpresure on the exhaust especialy at no boost points becaue its used to spool the turbos. With big heads and a big cam the duration is high and also the overlap. So if there is a restriction in the exhasut the air will reverse flow and go out the intake becaue its the easier way out. By incerasing the intake and exhaust volume you slow the air speed therefore decresing throtle response and increasing lag. To accieve the high hp all you do is turn up the boost higher that the engine with big heads.

Im talking street turbo engine anybody with alot of $$ or have a passion for building a car they only drive at the track then drive some pos during the day. They can design and build a big hp 550 350or 383. Then put turbos on it and get 1300hp chuging 110 octane by the seond. But will it ever be streetable? Althoug it would be an godly motor

 

I was thinking you know how the lobe profile has to be designed so the lobe dosnet float but it is opening the valve as quick as posible. now if i use 2 lobes to grind it. I would have to use pethagroean (not spellt right) therom to got the lobe profiles between the 2 profiles. Should i figure the profiles out and bring it to a cam designer to check if it will float the valves or not?

 

Interesting thread. Me likes.

I know this has already been addressed, but, the lobe grinding of that variable lobe is a huge obstacle. If you can somehow overcome that, the other things are small in comparison.

The lifter issue could be overcome with some Schubeck profiled lifters. They are a very hard composite lifter that should work with the "sliding" action of the camshaft. Here is a link: http://www.schubeckracing.com/ Durability is a non-issue with these, but they are $$$$$$$ spendy at around 900/set. Schubeck thinks "outside the box" also, and if you approached him with your idea, he may have some suggestions and may even donate a set of lifters to your cause. You may want to contact him.

I wish I could offer some more help to you, but I think most of the obstacles have already been addressed.

I would suggest using an LT1 block to overcome the distributor gear problem, and it has a front mounted distributor and pickup. If you have the means, use the fuel injection to eliminate the need for a crank trigger system altogether. This would also simplify tuning for the radical timing issues this variable cam system would dictate.

Good luck with your project. Props to you for the way cool ideas.

Mike

 

If you are serious about such a venture and have the capital to back it you can work on your design with MTS-SA, which is a subdivision of MDF Technologies, Inc. They have the 5-axis machinery necessary to produce the lobe design in question.... Kopp and Landis CNC camshaft grinders. Prototype work is nothing out of the norm for them.

You can call:
1 (760) 753-2505
or Fax:
1 (760) 897-2228

Encinitas California

Take care

 

This weekend im going to ask one of my dads friends thats a big car guy that makes alot of cash if he want to sponsor my project, due to the fact i barley have enough cash to build my own engine. I can use his funding make the grinder I designed. the grinder should be able to make a lobe with diffrnet labe seperation and advance/retard. But first i will get the duration/lift. i realised im going to have to locate the lobes at exactly the right spot otherwise i would have diffrent durations for each cylnder. How would i measure where the cam is on the grinder i was thinking of having a cnc machine drill precision holes to lock the grinder at the right distance. What system is used in real mechanical cam grinders? I havent found one shread of info on mechainacil cam grinders. And there are no cam grinding services near me. Aslo how do they know what angle to put each lobe from another? For this i was thinking to use a large wheel on the lobe master shaft and have another seprate but paralell wheel going to the gears that keep the cam and master spining together. This will act as a coupling to allow me to locate the lobe at the corredt angle. The second wheel will have bolt holes precision drilled in it and the degree wheel will have holes coresponding to the other holes for each lobe. I have the rough sketches done for the grinder and will be transfering it to cad in 3d soon.