Cam Lift Low-down

[padey]

ATM i'm stocking up on parts for my engine build.

Regarding cams, what is the low-down on lift? I'm getting the head ported, so i can go as much lift as i like.

i've been told that you should go as much lift as you can. Is that true?

padey

[skylinekid]

depends on wat kind of setup and everything ur gonna run. more lift is harder on parts tis the only thing

[padey]

depends on wat kind of setup and everything ur gonna run. more lift is harder on parts tis the only thing

Dude, you are not on NS.com.

Anyone with any technical info?

[skylinecouple]

Are you prepared for stronger springs ? At some point the cams will be too agressive for the springs to control so stronger ones are needed, however, for most street setups a mild cam is all that is needed. A bigger turbo will do ninety percent of the work. Look in the RB20 section for other setups as being the first to try something new is over rated.

[padey]

Are you prepared for stronger springs ? At some point the cams will be too agressive for the springs to control so stronger ones are needed, however, for most street setups a mild cam is all that is needed. A bigger turbo will do ninety percent of the work. Look in the RB20 section for other setups as being the first to try something new is over rated.

Yes, I expect to use bigger springs. Most cam kits I've looked at have springs for cams over 9.15mm lift.

For example, if I use 260 in/ext cam with 10.5mm lift in my RB26, what difference is it going to make with a 260 in/ext with a 9.15mm lift cam? How does a larger lift cam affect that characteristics of a RB26, assuming all supporting mods are in place?

[Duncan]

...i've been told that you should go as much lift as you can. Is that true?

but no-one has answered this bit of the question yet? what if anything is the disadvantage of running bigger (or much bigger) lift

[supercharged88]

When using high lift camshafts it's not only the valve float issue created by weak valve springs that you must consider.

You must make sure ,

you dont have coil bind issues at full lift,

you must have clearance between underside of retainer to valve stem seal and valve guide,

you must have enough piston to vavle clearance.

if using larger valves, with big lift,high duration camshafts make sure on overlap the inlet and exhaust valves dont touch each other.

Lift is part of the equation,

Duration is where you need to do your home work.

Duration is what will be one of the most important need to know specs of choosing the right camshaft for your combination.

The higher the duration the higher in the rpm range you will make power and the harder you will have to rev the engine.

Lobe seperation is another critical issue.

The closer the lobe seperation and the larger the duration the more valve overlap you will experience.

Valve overlap is unavoidable.

Reducing this in a turbocharged or supercharged application isnt.

Its called correct camshaft selection or can be altered (reduced) through variable timing gears.

Large duration camshafts also suffer from more valve reversion on overlap.

Creating pulses back through the inlet side.

Not so much a problem on a GTR with 6 throttle blades as there is not really an inlet manifold as such to have these pulsations effect anything.

MAF sensor tuning can be a little trickier on FC with big duration camshafts,as far as idle and light throttle cruise is concerned,on engines with 1 throttle blade.

I tune engines using MAP or MAP THROTTLE if GTR.

ECU of choice Autronic.

[padey]

I'm still in the dark regarding the benifit of extra lift. With were i'm at with my engine build, putting in higher lift cams isn't a costly exercise. I just want to know what it will do to the charateristics of the engine...?

[supercharged88]

More lift = more air into the engine and more exhaust out.

Engines are air pumps.

The more oxygen you can get in, and mixed with the correct amount of fuel, the more horsepower you will make.

Simple as that.

It's duration that has the biggest effect on your engines charactoristics.

You must establish what you want to do with your car before choosing camshafts.

Drag racing, Drift,Circuit Racing, Street/Strip etc.

Duration is the key word here.

EG: 220deg duration @ 0.050 is a small camshaft that would work well in street applications.

Useable power range normally 2500-3000 rpm to 6000 rpm.

300deg duration @ 0.050 is a cranky piece of gear, application Drag Racing.

Useable power range normally 4000 - 5000 rpm to 9000 rpm.

Above mentioned examples are NOT exact figures but are stated to give you an idea.

You can have a camshaft/s with 9.5mm of lift and 220 deg duration for street.

You can have a more aggresive camshaft/s ground with 9.5mm lift and 260 deg duration,this camshaft will make more horsepower but at a higher rpm.

Camshaft selection also comes back to engine hardware.

11 mm lift 300 deg duration on an engine with stock internals and standard turbo charger is pointless.

What do you want to do with your car,what is done to your engine.

I have made 625 hp @ the wheels with a customers car using only Tomie Pon Cams, but had the engine and turbo charger to support such a figure.

I know that if i want more horsepower with that combination i need more lift and duration and another set of springs.

However this is a street car and the owner dosnt want to sacrifice drivability.

So lift increase with no duration change = small/ marginal performance gain.

Lift increase with duration increase = more gain in power.

Edited July 23, 2008 by supercharged88