which cams!!!!!!!!!!!!!!!!!!!!!

[Flat on my back]

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Don't bother with oversized...spend the money on valve work.

[Rusty]

Ah, different ball game there then

Look at Ross's old project and Newsh. Many use stock head and 7A exhaust cam to good effect. Flow job will get you more for sure but isn't essential, not seen bigger vales on a 3071 ,could be interesting. Might save you some pennies for other toys.

[S2central.net]

Thats gonna blow mental on well proven camshafts - 7A or RS2 EX cam along with 3B/ABY/AAN inlet - no need to reinvent the wheel there IMHO and take risk on something exotic just for sake of it - unless you have deep pockets to play with such variables. I also think you can save yourself the expense of oversized valves on this setup... little benefit in my opinion, but a nicely flowed head is always good. What I mean is the stock valves aren't really a barrier to anything for you and the factory ones have been proven mighty in many monster builds already.

If you feel you simply must get bigger valves (maybe the originals are bent or seats are damaged) - be sure and get sodium filled EX valves as per factory spec on the 20V engines.

[trackslag]

Don't bother with oversized...spend the money on valve work.

what valve work do you think? was all ready going for 3 angled valve seats uprated springs and caps, do you think oversized inlet valves arenot very good on this head?

[S2central.net]

Oh the old 3-angled valve seat and uprated spring snake oil...

Much of this is balderdash and legacy of an age when engine components had to be uprated for racing... And they marketted by people who just want your money with that mentality of 'upgraded' everything. Save your money big lad. Factory head is up for the cup... Nice head job will make it flow better if done by someone who knows what they are doing (eg anyone good with 16V Golf heads).

Valve springs only need to be strong enough to prevent valve float at very high revs. Factory springs do that very well - unless you are planning to go crazy with solid lifters, some crazy cams and 10k rpm. Otherwise - stiffer springs just add to parasitic losses.

[trackslag]

have a read of this see what you think?

http://www.pumaracing.co.uk/Turbo.htm

let me know what you guys think,make for some bed time reading

[S2central.net]

Puma racing has some great tech articles - I have no argument with what is written there, but just remember they are in the business of building race engines - and do so for many class based competitive racers where extracting the last nth of power from what regulations permit is what they are tasked with doing.

Yes a better flowing head will produce gains on the S2, but there is a low of reducing returns as the stock valves on the head are not what you would call restrictive (compared to other engines where it is/was common to get good gains from big valves).

I am well acquainted with the ideal gas laws - you want the largest amount of the coldest air flowing into that engine, but the benefit from these big valves is one tiny parameter that costs a lot of money. The turbo you are talking about has proven potential for 450bhp and more without breaking sweat and absolutely does not need the funky valves.

[Flat on my back]

.

3-angled valve seat...

Does work well, 5 is nice but gets you the last bit, but costs more than may not be worth it.

Max. velocity is at the lowest lift which is why the angle job is important. Remember velocity is what we want NOT just max. volume...once you go past a certain point you lose speed for volume.

Concentrate on the exhaust side, this is the worst in the 20v heads cos of the design, i'm still contimplating 'waisted stems' in this area.

[S2central.net]

Aww no - its descended into air velocity physics now - fluid mechanics and such - very specialised stuff here for the real head gurus... but I think you mean 'waisted stems' as per the broad shape of a notionally curvy pole dancer - as opposed to a 'wasted' one - oh bad analogy

Did the heads come from factory with single or 3-angle valve seats ?

[Flat on my back]

.

Ooooooooooooo...who's the typiest...iiiiiiiii...

Yep.

Single i believe.

I have been picking the brains of my local 'head tuner' after i stopped fondling 5k of Cossy engine parts...

[trackslag]

do you mean waisted like the onesin this pic? thinks yanks call it cut back!

http://www.034motorsport.com/product_info.php?cPath=28_63_73&products_id=395

[newsh]

I've gone back to the stock exhaust cam for the mo but may well change back again to the 7A. That graph from 034 is interesting..

[Flat on my back]

.

do you mean waisted like the onesin this pic? thinks yanks call it cut back!

http://www.034motorsport.com/product...roducts_id=395

Roger and out...

[Jamo]

Cam choice must be made in conjuction with the turbo choice.

CT/KkK turbos like the RS2 setup Garretts do not and surge and better performance is had with stock AAN, ABY or Both 7A

I've run both 7A inlet and 7A exhaust which was fine, Audi_CQ I think posted up how to get better performance from them and stop the lag that happens when you run with them both.

In the future I'll dyno the car running NM cams which should be interesting.

[S2central.net]

Interestingly they are inlet valves of course... dunno how much (if at all) you can waist the EX valves - otherwise the sodium filling escapes