Cam Profile - Regrinding

[oldcorollas]

some nice graphs of lobes at bottom of this page.. the straight sided roller cam is very aggressive...
http://www.compcams.com/information/Products/Camshafts/

and another big lobe


edit, what you need to choose is maximum lift, and then rpm range you want it to work.
ie.. 3000-7000, 5000-8000 etc....

once you know maximum lift (mechanically limited) and the duration at 50thou (for the rpm range you want), then you can start talking about ramp rates.. and then that will determine how strong your springs need to be.

once you simulate (even with graph paper etc) a convex lobe, you may find that it is not the most ideal shape. but by all means try it

[abently]

err... what are you talking about abently? what is so different between this "carby head" and "efi head" you are talking about?

Ah ok, yeah some carby heads have the cam that can only come out through the side of the Head not from on top..... which is then very expensive to modify.

[kylestyleup]

Are you saying that the word "mild" made you think that the shape was convex? I am not too sure if this is just a cross language issue. The term "mild cam" in English just means not too much bigger than standard. I have never heard of and never seen a cam with a convex ramp like you showed before.

I know what "mild" literally mean....
"Mild Cam" - this one I'm not sure of...
Well I just look at it logically that "mild cam" is to be able to turn it with lesser force.
I figured that a convex shaped flank will gradually push the racker or push-rods (valve).
With this shape (I think), will lessen the turning effort to get to the top of the lift (nose).

Like a sword...
curved sword will slice better than a straight blade which will need greater effort.

This is only I believed will be good for exhaust since I wanted a concave for the inlet.

[styler]

you need a cam grinder to grind a cam profile for you, its more
complex than it looks and also needs special machines.
fill in the sheet that the cam grinder needs and they will find a profile
to suit, eg - www.tighecams.com.au

and on some motors any more than a mild profile will require hardfacing -
welding up the lobes bigger OR a blank camshaft which is expensive.

you cant just go to a machine shop and grind away!
camshaft has many parts - base circle, ramp, flank and nose,
lobes must be exactly the same, machining must be precise.

also as has been said the valvetrain has to be able to work
with the cam so look at that too, especially if you are going
a big cam.

[oldcorollas]

I know what "mild" literally mean....
"Mild Cam" - this one I'm not sure of...
Well I just look at it logically that "mild cam" is to be able to turn it with lesser force.
I figured that a convex shaped flank will gradually push the racker or push-rods (valve).
With this shape (I think), will lessen the turning effort to get to the top of the lift (nose).
This is only I believed will be good for exhaust since I wanted a concave for the inlet.

in this case, "mild" means "not aggressive"

the way they name different grinds of cam, or stages, changes depending on the grinder.

most will have something like
1- stock
2- mild (more aggressive than stock, but more mild than the next stage)
3- street (more aggressive than mild, but still friendly for street use)
4- aggressive street (more aggressive than street, has lumpy idle, can be stalled more easily, and makes power up higher in rpm range)
5- race. this is usually most aggressive, and not suitable for street use..

this is totally generalised, and there many different grinds in between.
this "mild" refers to the lift and duration, not specifically to the shape of the ramp.

the profile of the cam, ie the ramp rate on opening and closing, will ideally give the valve sinusoidal movement, as this minimises the spring strength needed.
any change away from sinusoidal requires a stronger spring to keep the valve in contact with the cam.

anyway, the duration and lift of a cam usually determines if it is called "mild" or "aggressive", with longer duration and higher lift becoming less mild and more aggressive.


of course you can have a mild cam with short duration and small lift, with an aggressive ramp rate .. these are often called "rally" cams...

[wilbo666]

I know what "mild" literally mean....
"Mild Cam" - this one I'm not sure of...

Your sword example isn't a good one...and doesn't apply!

A mild camshaft generally means:
>Mild (i.e. small) increase in lift
>Mild (i.e. small) increase in duration

http://dictionary.reference.com/browse/mild

Cheers
Wilbo

[jimmmayyy]

hey kylestyelup, i'm curious as to whereabouts in Manila you're gonna get a cam ground? Like the guys have said, its better to get somone who has some experience with cam profiles for that engine. YOu'd have more idea than me about good machinists there, but it might even work out better for you to get a cam from here sent over.

[amichie]

My recent experience with cams for an NA engine (stage 2 brian crower cams in my 7mge) is if you increase duration you also need to increase the compression ratio to get the full benefit.

If you have the option of getting increased lift without too much increase in duration then this may be a better option.

[allencr]

Pleeeassse!!! I wanna see a 'concave flank, or where you've gotten this idea from!!

Edited for ignorance
************************************************** *********************
Thanks.
http://www.camshafteng.com.au/conclobe.htm

[amichie]

Roller cams always look different even if the valve lift profile is exactly the same as an equivalent non roller cam since the cam and follower always act in the centre. With a cam and bucket style cam follower the closer to the edge of the bucket that the cam touches shim/bucket the greater is the valve acceleration on opening and closing. In this case a completely rectangular cam lobe will give maximum acceleration of the valve when opening and closing. But obviously this is not practical.

[kylestyleup]

hey kylestyelup, i'm curious as to whereabouts in Manila you're gonna get a cam ground? Like the guys have said, its better to get somone who has some experience with cam profiles for that engine. YOu'd have more idea than me about good machinists there, but it might even work out better for you to get a cam from here sent over.

Try to look for a school called EARIST in SampaloC Manila.
They have the best Machine professors and trainers to produce
professional machinist that are deployed allover the world.

I will not do this by myself but I will coach-in the machinist to do my profile.

[kylestyleup]

Pleeeassse!!! I wanna see a 'concave flank, or where you've gotten this idea from!!

I'd suggest searching & reading & comprehending more, before a machinist hurts the cam or you or both.

OK I did a research. I suggest you too.



http://www.camshafteng.com.au/conclobe.htm

[kylestyleup]

Your sword example isn't a good one...and doesn't apply!

Cheers
Wilbo

Of course it does.
Try slicing (not chop) a curved knife to a meat vs a straight blade with same sharpness and effort, see which slices beautifully.

Try a square wheel even with rounded corners vs an oval wheel to a toy truck.
Which do you think will roll better.

It's physics.

[jimmmayyy]

Try to look for a school called EARIST in SampaloC Manila.
They have the best Machine professors and trainers to produce
professional machinist that being deploy allover the world.

I will not do this my self but I will coach in the machinist to do my profile.

Yeah cool, I didn't know that EARIST was a tech school, i thought it was an IT college or something. Thats the one near Nagtahan? I'm always interested to know whereabouts all the car nuts go for go fast bits coz no one seems to know, lol.

[Joshstix]

Not too sure that copying a method that was most used in the early 1900's and specifically for roller followers or curved finger followers is going to be the best plan for getting more performance out of your 18-RC. I mean technology has come along a fair bit in the last hundred years or so.

Good luck with it though I look forward to seeing your results.