who can explain me something about camshafts?

lift is how high the valve is opened and duration is how long it is open (in degrees)

You can start getting into inlet valve opening (in terms of degrees relative to TDC) and duration of overlap (lobe separation angle and so)

Theres a lot to it. Easiest thing to do is look at the application of the cam you are looking at and see what matches your use. (beware of meaningless descriptions like "half race" though) Most of the yank cam makers give you a list of the supporting mods required to make the cam work in terms of head flow, compression, gearing, etc. so see if you can find this for you engine too.

Or start the learning curve of how to work out cam behaviour from published specs.

edit: parallel post with Slaters - agreed - you really can read a whole book on cams.

like he says tho they are all the same lift

just like slater says, all 3 have the same lift.

Which brings me to another question...
What makes me having to use stiffer valvesprings?
Is it only the lift which causes that? of do other things play a role in that too?

Is this a road car or racer?? id go with the low duration unless its an all out racer. Starlets have a old pushrod type lump don't they? 300duration is going to be a serious race cam i would think!

By all means try it, from my experiance cams of aroud 280deg duration are normaly mid range kind of cams (2000-7000rpm maybe) and cams of 300 are normaly alot more racey, we are talking 4500-9000 powerbands and stuff!, totaly useless for a road car.

Then again I'm not 'that' experianced with anything with a SOHC and 3 valves.

indeed but consider that your stock engine may make, say 40bhp at 3000rpm and 75 at 6000 but if you fit a race cam it may now make 100bhp at 8000 but now only make 20bhp at 3000rpm!

Generally what you gain up top you loose down low and down low is where it matters!

Id suggest before you go spending big bucks on a cam you read up on it a bit more. It could seriously ruin your engine if you get the wrong one.

As much lift as you can accomodate without the piston hitting the valves... And remember that the rods get longer at hot high RPM use so a static check may not tell you all...

Too much lift with a short duration is very hard on valve train parts as the rate of acceleration of the valve is that much higher meaning the inertia when it stops and changes direction is more....

Hense you need beefier valve spraings and the like but on their own they can just mean faster cam and valve gear wear as they increase seat pressure...

Like Slater has said, you tend to move the power up top with cam work, so just because you can rev to 7500 doesn't mena you want to. A lad I knew yonks ago fitted some mad cam in his Escort and he had to get like 4000 RPM just to stop it stalling when parking or doing a 3 point turn. Not fun.

I also saw a demo of a Dodge Dart which had a mild road cam fitted. They then swapped in some "3/4 race spec" job with lots of overlap and all. On the dyo the car picked up 20-30 BHP
(I forget the exact number) but all meaningful on-road testing showed the car to be slower... (50-70, 30-50, 0-60 tests IIRC)

I ran a 284* cam in a much larger engine with it slightly retarded and with bleed-down lifters to control lift at lower RPM, and even then the sodding thing was rough on idle and stalled like a curse word if you drove it in traffic before it was properly warmed up.

Did you buy it yet?

i've done a bid trough my contact in japan for the 3rd on this list:



let's hope i still have the highest bid tomorrow ;D