Cam 248/248

GT500916 · #1 11-18-2004, 05:10 PM

Some of the cars that i know about have a bigger intake cam duration and slightly smaller exhaust duration... I believe the 91 240 cam has a bigger exhaust and smaller intake duration.. maybe i got them confused, but what if you get the same duration for intake and exhaust?!! will that just have a good all around performance or less or whats the deal?

My plan was either to pull cams out of an altima wich has a duration of 248 on the intake... dont remember the exhaust one, but then getting the exhaust one out of 91 240 wich has a duration of 248 as well...

does anyone know of a good cam site to get more info and learn about cams? thanks

GT500916 · #2 11-19-2004, 03:53 AM

i take it ill im on my own on this, wish me luck

Shogun · #3 11-19-2004, 01:01 PM

yea it'd be nice to learn more about them. I'm sure you've already been to howstuffworks.com. I'd sill like to learn a bit more in depth though about cams.

GT500916 · #4 11-19-2004, 01:20 PM

Quote:

Originally Posted by Shogun

yea it'd be nice to learn more about them. I'm sure you've already been to howstuffworks.com. I'd sill like to learn a bit more in depth though about cams.

yup checked out how stuff works.. and it pretty much seems like having exhaust same size as intake or bigger wont harm, because all it does it exit so i dont see a problem with having 248 intake and 248 duration exhaust... but i still wasnt able to find any info on this and if it will in a way effect the RPM range or top end power.. ill post stuff that i find useful

logik23 · #5 11-20-2004, 12:52 AM

Maybe you can be a pioneer in swapping KA cams!

nissanfanatic · #6 11-20-2004, 01:23 PM

You can also use the exhaust cam out of another 240 KA as well. Make sure it is a 91-94 though or you'll get a smaller cam.

Lift: how much the valve opens
duration: how long the valve stays open
overlap: period when the intake and exhaust valves are open. Too much is not good for turbocharged cars. Potential turbine and exhaust valve damage with power loss. Super Street just did a good article with SR cams that shows bigger is not always better with cams. Good luck.

R.W.240 · #7 11-20-2004, 04:48 PM

Yeah I couldnt belive my eyes when it showed that a Tomei High-lift 270 would make much power on a T28

You Put the 91 (intake I belive) on both sides and it gives more duration... Its only a 248 so dont expect wonders but the power band should shift slightly higher but its not gonna lose much low end as it doesnt gain that much top end.

GT500916 · #8 11-20-2004, 05:00 PM

i was thinking just probably gonna go with the altima cams... the intake on an altima is 248 and 91+ 240 is 240 ... so i want a slighty bigger intake, and i can go less on the exhaust duration, i think if i get 248 /248 then exhaust might overlap with intake? im not sure... but ill still be doing more research on this....

R.W.240 · #9 11-20-2004, 05:23 PM

Id go with the 248s all around with that much duration overlap wont be a problem...

GT500916 · #10 11-20-2004, 05:38 PM

Quote:

Originally Posted by R.W.240

Id go with the 248s all around with that much duration overlap wont be a problem...

so pretty much 248 exhaust from 240sx and 248 intake from altima should be good... but do you know why is it that most cars are bigger intake durations and smaller exhaust durations?

nissanfanatic · #11 11-20-2004, 09:23 PM

Agreed. Don't go too big on the cams. You will hate it when your car won't idle easily.

AWDSR20 · #12 11-20-2004, 09:41 PM

daiiiiiinng u people realy know u r 240 huh!!!
i have no friken clue about how much cam lift u need. if it up to me i would buy a new 1z.
i could install it dough....(yahYYYYa)

R.W.240 · #13 11-21-2004, 05:55 PM

Quote:

Originally Posted by GT500916

so pretty much 248 exhaust from 240sx and 248 intake from altima should be good... but do you know why is it that most cars are bigger intake durations and smaller exhaust durations?

They're trying to keep as much low end as possible. So to keep the overlap down they choose to ditch some of the exhaust duration since its easier to push air out than suck it in.

GT500916 · #14 11-21-2004, 07:31 PM

Quote:

Originally Posted by R.W.240

They're trying to keep as much low end as possible. So to keep the overlap down they choose to ditch some of the exhaust duration since its easier to push air out than suck it in.

so lets say i go 240intake/248 exhaust...

will this give me more top end rpm power since the exhaust will be pushed out better, but then again it might lose that power because the intake is not big enough to suck enough air in to keep up with the exhaust duration?

then lets say i go 248/240 then it will suck in enough air to give me that lowe end power, but pushing it out will be slightly harder so my top end power goes down a little therefore my rpm would start dropping 1,000 before redline?

and if i go 248/248 then it will even out to pretty good overall power and give me that top end power to go all the way to redline without dropping like it does with my stock KA 95 cams... (wich is 232 duration)

Does anyone know the correct 95 cam duration for the intake and exhaust? because i only know 232, and i couldnt find it in the manual.. i might have missed it

nissanfanatic · #15 11-21-2004, 07:38 PM

Besides what R.W. said, with the smaller exhaust duration, exhaust gas velocity is increased. This makes the scavenging effect more so down low. Basically the nerd way of saying what R.W. said.lol So yes it just gives the car more low end streetable power. And the two 248s will just shift your powerband up. Your horsepower curve will begin later in the RPM range. Tuned IHE will amplify the power. You may gain some RPM range too so your power won't taper off at 5500 like usual(or wherever yours does).

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