Camshafts

[greenmac80]

Ok i have an idea in the works for an engine conversion.

i wanna keep it on the downlow. so i'm going to generalise

 

for camshafts grinds or replacements on twincam motors. are there certain degrees or duration or whatever

that are kind of universal to different setups.? e.g. turbo or NA?

 

like a cam with i think 256?? duration would be better suited for NA or turbo? etc.etc.

cheers, Luc

[xmoht]

Ok i have an idea in the works for an engine conversion.

i wanna keep it on the downlow. so i'm going to generalise

 

for camshafts grinds or replacements on twincam motors. are there certain degrees or duration or whatever

that are kind of universal to different setups.? e.g. turbo or NA?

 

like a cam with i think 256?? duration would be better suited for NA or turbo? etc.etc.

cheers, Luc

 

Have you tried Google or searching the forums? Also a lot of engines have specific information on what to do performance wise for the cams. Soo if you told us what the engine was, then at least we could point to the information already available..?

[greenmac80]

i've searched for info engine specific and it only brings up camshafts for the turbo motor but i'm thinking na so yeah.

but what has confused me is that these cams for the turbo engine i've seen the saem sorta specs used in 4ag's in na so i'm wondering if there

are eny kinda universal typr ones that are an improvement for no matter what application.

and also as above.

[Trev]

So you have asked what sort of cam you should put in your engine without saying what engine you have (4age, yes there is 4 of them), If you really wanna know what cam to use you need to post what you want to do with the engine and the basic specs of it otherwise it is like saying 'I wanna build an engine, What fuel should I use'

[greenmac80]

fark it.. watevs i'm curious for the 4efe or perhaps the 5e engine.

 

i have my own reasons for this engine so don't question it. i've done search after search with no real answers. mild cam is probs the go. but what would mild be?

[xmoht]

fark it.. watevs i'm curious for the 4efe or perhaps the 5e engine.

 

i have my own reasons for this engine so don't question it. i've done search after search with no real answers. mild cam is probs the go. but what would mild be?

 

Good choice, was researching E series myself.

[greenmac80]

the way i see it is that i can pick one up relatively cheap. i have a shell that i can do trial fitting on.

i kno people that can weld etc. so for perhaps 1k i can have a newer twin cam 1.3l producing approx 88bhp OR i could spend that and more on a k motor and have not much more power.

 

 

but when it comes to NA builds there jst aint much info

[snot35]

This is very broad, but if you grab a book like Four Stroke Performance tuning it will give you a pretty good answer. It really depends a whole lot on the particular motor of course, but stock cams seem to be around the 250 something mark. Full race seem to get up around 320, rally seems around the 290-300 mark, and sports fills the gaps in between stock and rally-ish. Of course lift is a whole other matter too. I think around 30% or so of the valves diameter seems to be around the go, but please note this is really really broad.

 

Cams also differ in how quickly they lift the valves, so it's worth noting timings at .5" lift. I believe around 200 is stock, semi race is around the 220 range and 240 is starting to get more rally style.

 

Please note these are all really really broad figures. The above book will tell you a whole lot, and is a great read.

[Taz_Rx]

The only main difference you'll find between NA and specific turbo cam grinds is that the turbo cam with have a few degree more valve seperation to reduce blow-by. If you got a mildish NA cam grinded, I wouldn't be too worry about using it with a turbo later on.

[greenmac80]

Thankyou taz pretty much the answer i was looking for.

cheers,!!

[philbey]

Overlap is what you want to look at, like Taz mentioned. Basically that's the amount of degrees of crank rotation that both the inlet and exhaust valve are open together, you can imagine that in a boosted motor you'll just push boost out the open exhaust valve.

 

Research cam duration and cam overlap and you'll start to get an idea.

 

In an NA motor, overlap allows the exhaust scavenging effect to basically suck more air into the motor.

[Felix]

In an NA motor, overlap allows the exhaust scavenging effect to basically suck more air into the motor.

 

At higher RPM.

[philbey]

Yep and as we know that's why high duration camshafts are all top end power.

Edited April 13, 2010 by philbey

[greenmac80]

thanks guys very much the answers i was hoping for.. will help me out a lot.

[oh what a nissan feeling!]

The only main difference you'll find between NA and specific turbo cam grinds is that the turbo cam with have a few degree more valve seperation to reduce blow-by. If you got a mildish NA cam grinded, I wouldn't be too worry about using it with a turbo later on.

 

what he said, small cams usually have wide lobe seperation anyways (112), as this helps with torque.

 

As you get to larger cams, the differences get more and more with ramp angles, lift, and overlap all becoming more purpose specific.