performace cams and different degress??

Level 6 User Joined: 04 Nov 2004 Posts: 134

Am considering some performance cams, and i noticed the post on the other forum, with guy who modded the clio, he used some apprent reare 290 degree cams.

Could some explain what cams are available, and what the degree differences are, what effect these differences have on the engine and why?

And if some are better than others, as i noticed some posts about pulleys failing?

Nice 1 in advance

Forum Moderator Joined: 02 Mar 2004 Posts: 19978

290 degree cams are not rare.

290 degrees cams do not mean they hold the valves open for 290 degres of cam rotation, its 290 degrees of crank rotation.

Standard cams are around 250 odd degrees of duration.

Longer duration increases overlap this means the mixture at lower spoeeds goes out the exhaust, thus as crappy idle which isn't smooth until higher revs and no chance of a decent emmisions output.

However at higher revs this allows the cylinder to be scavenged better (gets rid of more exhaust gas and fills the pot with mixture).

You then have lift, higher lift holds the valve further open, this isn't ideal but nothign is, it will improve things and is a good choice over a long duration cam, higher lift gets you some of the gain without the problems of terrible idle etc.

The pullies are made from ally and are known to fracture. BenR is now making his own adjustable pullies and his are of much better quality, hes rarely on here when he is its to pm me normally! So talk to him over on cliosport, he was also doing his own cams so see about a deal from him.

Level 6 User Joined: 04 Nov 2004 Posts: 134

Cheers for the infomative response Chris Smile

in addition firstly would I be able to wak on a set of performance cams, and run the car i.e. driving it to a rolling road to be set up, will it still be driveable?

And also if I have the ECU chipped, or chip it myself with one of thse chips off ebay lets say, do you think that would sort the idle enough for not to annoy?

Also Can the chip mapping be changed to match the setup on rolling road with a laptop etc.

I basically want to put a set of cams on her, chip it, and then have it set up to run as smoothly as poss, obviously with as much output as poss, BUT still be MOTable!

ta

Forum Moderator Joined: 02 Mar 2004 Posts: 19978

if you stick the cams on it will drive, if you go for something daft like 310 degree efforts then your gonna have a hard time with it.

The e-bay chip WILL not sort it oput.

Only way to sort it out is to go with re-mappable ECU.

TBH the best mod for these engines is headwork, the gains are impressive.

Forum Moderator Joined: 02 Mar 2004 Posts: 19978

btw if you look in the gen chat forum under my topic 'bugger' you will see I am tidying up the lagunas head, its an 8v but the 16V heads are as badlyt machined/cast. easy gains to get.

Also its not my best work as its a 5 min per port job and only the bowl area.

Level 6 User Joined: 04 Nov 2004 Posts: 134

would fitting a unichip and having it set up on a rolling road so that it is specific to the cars add ons be a good option?

Forum Moderator Joined: 02 Mar 2004 Posts: 19978

its an option, good, depends if its done properly like everything else!

Level 6 User Joined: 04 Nov 2004 Posts: 134

wish i'd look into more head work when i had the head off, as i fitted new value stem seals, re-ground the valves in etc, but just don't know what to do when it comes porting!

I need a tutorial as i would love to do it myself, satusfaction of doing the job well/right and seeing the results etc

Level 6 User Joined: 04 Nov 2004 Posts: 134

Can anyone recomend, anywhere where i might be able to get info about porting a head, i.e. what the best tools are to use, they shape i'm after, what to smooth off and what not to etc?

Forum Moderator Joined: 18 Feb 2004 Posts: 7432

There was a beginner's guide in the Jan '05 issue of Retro Cars magazine. You can get a back issue of that, or I could scan it in for you if you like...

Site Subscriber Joined: 10 Jun 2004 Posts: 2317

Neal 19 16v wrote:

I could scan it in for you if you like...

Do you really need to ask Wink

Level 6 User Joined: 04 Nov 2004 Posts: 134

ER!!!! let me think.......YES PLEASE Smile

Forum Moderator Joined: 18 Feb 2004 Posts: 7432

Here you go mate

www.born-cynic.com/random/portingarticle/portingarticlepage1.jpg

www.born-cynic.com/random/portingarticle/portingarticlepage2.jpg

www.born-cynic.com/random/portingarticle/portingarticlepage3.jpg

www.born-cynic.com/random/portingarticle/portingarticlepage4.jpg

www.born-cynic.com/random/portingarticle/portingarticlepage5.jpg

let me know when you've got them saved so i can take them off my webspace.

Forum Moderator Joined: 02 Mar 2004 Posts: 19978

guides etc are all very good (well they are not really they are pretty poor) but chances are you'll make a right mess of the 1st few heads you do.

Mr Quoter-vator Joined: 16 Feb 2004 Posts: 7405

ah i actually have that mag!

Level 6 User Joined: 04 Nov 2004 Posts: 134

nice one m8, saved em.. Smile

Newbie Joined: 23 May 2005 Posts: 7

To do a proper porting job you ideally need a flow bench to compare before and after, sometimes polishing the ports is not a good solution, particularlty for low speed running as it can cause poor atomisation / swirl prior to entering the combustion chamber.
A reasonable job can be made by using dremmals drills etc if they have the speed to get a good finish.
You need to try to get as much air into the cylinder as you possibly can relying on atmospheric pressure do push it in.
Sometinmes gas speed is more desirable than ultimate volume.
You will have to come to a compromise,for wjat you want from the engine such is life.
Thought of forced induction ?? turbo / belt driven supercharger.The gains are far better than normally aspirated tuning.

Site Subscriber Joined: 28 Jan 2005 Posts: 3547

but is alot more expensive, more to go wrong, if the 16v lump was meant to be turbo'd they would put a turbo on it from production

Forum Moderator Joined: 18 Feb 2004 Posts: 7432

its funny you should say that....

Site Subscriber Joined: 28 Jan 2005 Posts: 3547

lol why's that?

Forum Moderator Joined: 18 Feb 2004 Posts: 7432

because rumour has it that renault originally designed the F7P with a turbo option in mind (its got very big inlet ports after all), but that idea got canned due to the prevailing automotive fashions at the time.

Whether or not that little story is true or not is up for discussion!