cam options

ok i have heard that the best cam for a 8v is the kent ast2. is this the one and only??

as i have also found another that looks better. its a nvo63, and this is a 1600 camshaft rather than a 1300 cam (ast2).

the engine is a 1600 and will be running mapable management.

spec

AST2

power band 3000-7000
valve lift 10.33 mm
duration 290 degree
timing 36/74 74/36

NVO63

power band 3000-7000
valve lift 11.80 mm
duration 312 degree
timing 52/80 80/52

just looking at these figures the nvo63 looks alot better. and this cam can still retain the hydraulic lifters. what do you lot think?

bruce

as far as i understand it the NVO ones were for injection engines as they had a different overlap to the AST series


im looking at a 320deg hydraulic cam :-) should be nice

id say get a kent AST2

I've got an ast2 going in my gsi with my twin 40's. Can i not use the hydraulic valve lifters? I've seen solid lifters but they cost fook loads :o

dunova you can use hydralic lifters!!

and camb i will be using mapable management (injection) so you not think i would be better with the nvo63!! and from what you said the ast2 is more suited to carbs!!!

bruce

Relief :P

And as for the cam i'd go for the nvo63 with mapable management- i think you would see better performance with it than you would the ast2. As you said, the ast2 is better suited to carbs.

the nov cam would be good and give more power than the other, as the duration is longer and lift is more. but you may suffer lower end power and rough idling. proper rally style though.

when i compared the figures the nvo63 is going to give more power, but the ast2 has been praised by alot of guys. but they have all been running carbs. its could be better suited to the 1600 engine im not sure that is why i asked. did dan not experement with lots of different cams before sticking with the AST2??

as for it not idling correct mapable management will sort that out. will run straight when set up.

bruce

rough idleing is a bit of myth. Friends cams are 308deg and idels just as smooth as mine 8)

ive never seen or had a car with a cam in that doesnt have a rough idle. My 2lt idles from 900 to 1200 you can hear it rev then drop. My brothers 1600 does the same, so did my 1400. You can spot a car that has a cam in by the way it ticks over, well i can anyway

im sure the only reason it sounds rough is because the ecu does not understand what the cam is doing as it has certain values to work in between. but with carbs or a mapable ecu it should run fine.

bruce

might be the case for the 2lt i suppose but my 1400 was on 40's

you will def need to map ecu but it wont idle better? its the opening durations of the valves that makes it tickover rough, therefore with the valves being open longer you get more valve overlap! this is what causes rough ilidling and poor low end power.

my cam is a 300 deg one and sits at idle perfectly on 900 rpm. its lumpy in the sence that the exhaust pulses a lot but if i wind the idle to 1000 it even gets rid of that,

Quote:

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you will def need to map ecu but it wont idle better? its the opening durations of the valves that makes it tickover rough, therefore with the valves being open longer you get more valve overlap! this is what causes rough ilidling and poor low end power.

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Agree with md, my kent 296 idles as smooth as a standard one, infact none of my cams have had a 'rough' idle

The only thing i can see with more lift and duration is emissions. Mine gets through an mot but only just, kinda, almost. with more lift and duration the overlap is likely to be alot more and hence if for road use it 'may' cause problems acquiring an mot certificate but that would be a suck it and see approach.

I did try a few cams, but that was the progression of the engine and getting it just right. Only way to find out if the cam is what you want is to get it and try it, if it isnt quite right then you can always try again.[/quote]

yeh im sure if the engine is sett up correctly the engine will run smooth tick over.

thanks for the input guys i will prob go for the nvo 63 as it does sound like the one im after. i take it none of you have used it before?

bruce

I wouldn't worry about MOT emissions, you can just plug in the laptop and lean it off till it passes then return it to the map it normally runs :lol:

Quote:

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Originally Posted by broos3

yeh im sure if the engine is sett up correctly the engine will run smooth tick over.

thanks for the input guys i will prob go for the nvo 63 as it does sound like the one im after. i take it none of you have used it before?

bruce

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good choice! i dont know anyone that has used that cam but my mates have used similar cams and myself. you will notice alot of difference through the higher revs. are you buying a vernier aswell? you will need one of these to 'fine tune' the cam on the rolling road.

yeh the cam need a comp valve spring caps and uprated valve springs and i have both and yes got a vernier aswell.

bruce

correct me if i'm wrong, but isn't the problem with injection and big cam's due to the air flow meter? alot of overlap causes a pulse up the inlet track which when it hit's the AFM it send's the ecu daft? as you are having a mappable ecu, you won't have a AFM. that's one of the reason's to swap to mappable, so you can run bigger cams.

i might be talking bollox about the theory of it all, but i think i've got some of it right. i've got a book somewhere that explains it all, i'll have a look for it.

the bst thing to do would be to ring piper and kent (other cam manufactures are available) and see what they recommend, then choose between the 2

i was also told the ast1 is quite good, worth a look

ast 1 spec

power band 2000-6000
valve lift 10.55mm
duration 270 deg

does not realy look that great ben, well not what im looking for.

bruce

hmm, i must of been thinking of a different cam

the ast range of kentcam is designed for use with carb's on the vauxhall 8v engines.

The NVO51/61/63 etc are for injection. Not sure about mappable injection though.

Someone on here said they fitted an ast2 to their GSI and only got 2bhp more.

indeed, some lairy cams can send "stationary" pulses of air back up and they can stop at the air mass meter and effectively cause the flap to close

ummm, this is generally when you have a cam with a fair bit of overlap and you are still using a plenium chamber.... a big problem with the rover k series...

the reason that a 'wild cam' can sometimes (or all the time depending on how much overlap) be rough at idle or low revs is because of the overlap, when the inlet and exhaust valves are open at the same time you will get scavenging, where inlet gasses go out the exhaust valve, this helps remove all exhaust gasses, at lower speeds this is a fairly large percentage of the air going into the engine, resulting in starvation.
some of this can be helped with a mapable ecu but does not cure the problem, it will generally 'clear' at slightly increased revs because it can now breath properly because the engine speed has increased and is therefore pulling more air through the engine meaning that as a percentage, less is lost from the 'scavenging'.

More overlap = more scavenging = more airflow = more power

generally increasing valve lift will not increase the power of an engine unless it is already scavenging more than can be inhailed/ exhailed throught the available opening, at wich point larger valves would usually be needed also

Unless it's a turbo cause then your duration is limited but lift isn't :lol:

ha, think ya clever do ya, well it still applies, ah but without overlap you will end up with exhaust gasses left in the engine which will reduce its efficiency and hence power, everwondered why a WRC car sounds so shit when they first put there foot on the throttle at lowrevs even with antilag?
Plus with a terbo the thing that will generally limit the amount of overlap is actually that you have to have a plenium chamber.

Duration = overlap = scavinging = airflow = power