Cams Duration Vs Lift

[blk180]

Im looking to get a set of cams soon and was looking at 3 choices

1) Tomie PONcams 260 in & out 9.2mm lift

2) HKS 272 in & out 8.7mm lift

3) HKS 272 in & out 10.2mm lift

Qustion is what would you go for i have 2530s on a buildt buttom end. Car will be mosty daily with some track and drag days throw in. which will be the best mid range and which best top end? Thinking of going T04Z later down the track.

Aslo besides springs what else needs to be done to fit the HKS Step 2 cams.

Head also has bronze valve guides.

Thanks Brad

[Adriano]

For your setup, i would recommend HKS 264deg inlet and 272deg exhaust, is this a street car? This setup allows a nice idle with good fat midrange which is great for the street.

[blk180]

so 264in 272 out any reason for for the smaller intlet cam.

[DVS JEZ]

anything bigger than poncams and youll need to upgrade your valve train, solid lifters, stronger springs etc.

poncams are good cause they just bolt in,

cheers

[pnblight]

Im looking to get a set of cams soon and was looking at 3 choices

1) Tomie PONcams 260 in & out 9.2mm lift

2) HKS 272 in & out 8.7mm lift

3) HKS 272 in & out 10.2mm lift

Qustion is what would you go for i have 2530s on a buildt buttom end. Car will be mosty daily with some track and drag days throw in. which will be the best mid range and which best top end? Thinking of going T04Z later down the track.

Aslo besides springs what else needs to be done to fit the HKS Step 2 cams.

Head also has bronze valve guides.

Thanks Brad

the poncams 260deg 9.15mm are a great upgrade and very hard to beat valve for money (bolt in)

i wouldn't go long on the exhaust than inlet as a friend of mine recently found out (better all round results are gain with matched) Tomie recomend nothing over 260 deg for street use (check there web site for turbo and cam combos)

http://www.tomei-p.co.jp/_2003web-catalogu...harger_rset.htm

All this said from my observations

street/track 260/260

drag/street 270/270

so if you want more drag and out right hp over responce the 270/270 might serve you better. Also with that same goal you might find it worth it to go to a stage 2 10.25mm+ cams (don't forget it will cost alot more with aftermarket springs and having to reshim the head)

i am yet to be convinced that going to stage 2 level on 260deg is worth the money and hassel for possible results(but who knows i have been playing with the idea of upgrade them soon)

pete

[shanef]

i always thought the reason to go for a bigger duration on the exhaust side was to overcome the issue with the 26 heads having poor flow on the exhaust side?

[pnblight]

i always thought the reason to go for a bigger duration on the exhaust side was to overcome the issue with the 26 heads having poor flow on the exhaust side?

well not on a ported head i know that much for sure "gav" has been down this road and by just bring his inlet cam into line with the exhaust made good alround gains from memory.

pete

[Beer Baron]

anything bigger than poncams and youll need to upgrade your valve train, solid lifters, stronger springs etc.

poncams are good cause they just bolt in,

cheers

actually there are quite a few other options than the 260/9.15 poncams that will bolt in. no need for any valvetrain upgrades (i assume you mean rocker arms or valves) as for solid lifters, RB26 already have solid lifters so no need to upgrade that. stronger valve springs would be a good choice though if you are running a lot of high rpm, and high lift/long duration cams, particularly those with a different base circle/high ramp rate.

[blk180]

Differnt base circles like JUN 264in&out 9.7mm lift cams do you need to reshim the head?

[Beer Baron]

I'm assuming you mean replace shims to re-set the valve clearances? if so, then yes you most likely will. it's just a case of install, measure, replace shims as needed to get the required valve clearances. if you meant shim the head as in space it or something, then no. head modification is not needed.

[heller44]

For a cam with that amount of lift, would you need to clearance the head for the cam lobes?

[Beer Baron]

9.7 should be ok, but dont take my word for it! if it did need some material removed it wouldn't be much.

[2rismo]

Click Here if you have no idea what people are talking about.

[Eug]

Click Here if you have no idea what people are talking about.

thanks!!! certainly cleared up my ferrari questions!

[Adriano]

Realistically, any cam change will reqiure the shims to be at least checked, most likely replaced, as no two cams are exactly the same, and valve recession will have occured since they were last set, going slightly longer in the duration whilst maintaining under 10.2(i think)mm lift, gets around the need to upgrade springs, and modify the head. AFAIK, the stock cams are 240 deg, and i have heard of up to 310deg cams being used in drag cars. i believe the theory of using a bigger ex cam is that in a turbo car, the inlet is pressurised, and the smaller car increases cylinder filling, whilst the restrictive head/turbo exhaust side)compared to a n/a car) can use the additional scavenging time without adversely affecting the drivability, but i could be talking out my arse. What sort of driving do you intend to do? Whaw sort of hp are you after? There are plenty of GTR's that make 350rwkw with standard cams.

[blk180]

The car will become a weekend car soon. So some drags(tell i get kicked) and track days i guess. Would also like to be able to increase limiter too 8500rpm.

Power wise i guess 350-370 with 2530s if i change to T04Z later 420-450kws.