HAHA you can get me some 280 grins LSJ cams

 

Yes.

Jester, come out to TJs in new stanton with us. Chicken and beer at 6:30. I'll be tunin an ls2 GTO while we're there.

 

mmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmm

chiken unt beer...

 

I have to work til 8

 

HAHA! Nice.

Hey Jack, I'm surprised you didn't say anything about the RR license plate. About the only perk of living in PA.

 

So I can follow you over there if you leave after 8 lol

 

If you degree the cam you can see the dial gauge opening from .000" lift and up and it will come out to the advertised duration. The reason to use 50 thousandths lift as your starting point is because that is the amount of valve opening that must take place to show measureable flow through a head.

If you ever flow bench a head, take the valve and screw it down to around 20 thousandths of opening; almost no air will be flowing at all. Then screw it down to around 52 thousandths and the head will start to flow.

Also, you actually want to take the lift and multiply it by rocker ratio so that you can calculate how much the valve will actually be open at X degrees. I'm just adding this cause you're definately right, minus a few little details .

 

280s sound like this

http://www.youtube.com/watch?v=g4sQTzb1o9E

First is open dp
2nd is full exhaust

Dont expect 280s to idle or drive like stock either....rices car also has a fully ported head

 

You can't use the term 280's or 272's so generically. I've been looking at cam specs latly and different brands with have different results. For instance, the HKS 280 cams have a duration @ .050 of 222 degrees and a lift of 10.5mm, with a lobe seperation angle of 110 degrees. The Revolver 264 cams have a duration @ .050 of 223 degrees, and a lift of 11.5mm, with a lobe seperation angle of 107.5 degrees. That 264 cam would have an insane lope, and make more power than the HKS grind, even though its classified as a 264 cam. My cams will be based off the revolver 264 grind. Should make power upto around 8000 rpm even with the eaton.

 

What makes a cam lope has nothing to do with the duration. I think that's what you're getting at. What makes a cam lope is it's seperation angle.

 

IN the sport compact world...esp in dsm a 272 or 280 or 264 is instantly reckognized as a HKS spec. If its not then u specify. In the beginning we specified hks spec.

 

Yeah, and the lobe seperation angle also determines where the power band is. The higher the seperation angle, the lower rpm the power band will be in, and vic versa. A 107.5 degree lobe seperation angle (like mine) will probably have trouble idling below 1200 rpm, and will make power into the 8000 rpm range. Thats why if you look at any cam catalog almost all the cams specified as a "street" grind, have a 110 degree or higher seperation angle.

 

Yep. The only thing is, we do want a lower than stock lobe seperation angle (Like you have), just not too low. Since we don't have an NA car we do not want as much of the valve overlap because in doing so you will lose air mixture straight to the exhaust (Some of this helps but not too much).

It looks like you have a good grind. There is more than one way to go about it but I think, a slightly lower lobe seperation angle with a bit of added lift on the intake side and a decent amount more on the exhaust side (To help exhaust all of the gases).

Duration is the part where you have to make a compromise especially on a boosted car. On one hand you don't want to waste any of the power from the expanding gases by opening the exhaust too early; but on the other hand you have alot of exhaust to get rid of, so you must make a compromise.

A good rule of thumb I find is that on a supercharged car, due to the fact that it is boosted and the way it produces it, you can make slight changes to intake lift and duration (Don't really have to), but what matters the most is the exhaust side. Since air is being forced in, as long as the valves can flow what your engine demands on the intake stroke you're good. On the exhaust stroke is where it counts because it's not "boosted" per say, like the intake is, therefore you need to give it a little more room and time to get out.

The reason why valve overlap is good at all on a supercharged car is because with a little overlap it will help to initiate the flow of exhaust out of the combustion chamber.

Edit: I know you probably know this, I was just adding it in.

 

You know your stuff man, but yeah I did know that. The cam setup I'm using has a 222 degree duration @ .050 on the intake side with a 11.4 mm lift. The exhaust side is 223 degrees of duration @ .050 and a 11.5 mm lift.

 

Looks good.

 

Little cam comparison, before and after:

Stock:
Intake Lift: 10.04 mm
Intake Duration @ 1mm: 196.50
Intake Centerline: 100 degree

Exhaust Lift: 10.04mm
Exhaust Duration @ 1mm: 191.70
Exhaust Centerline: -115 degree

Stock LSA = 112.5 degree


My new 272 grind:
Intake Lift: 10.80 mm
Intake Duration @ 1mm: 214.00
Intake Centerline: 110 degree

Exhaust Lift: 10.20 mm
Exhaust Duration @ 1mm: 214.00
Exhaust Centerline: -110 degree

HKS 272 LSA = 110 degree

 

Sounds good. I really need to learn about cams. Blown 4-banger is helping, but I really need to sit down with a book one day (or week) and learn it.

 

Jesus christ that things sounds mean as hell.

 

Damn man...I just can't wait to here some pulls...just sick.

 

I believe you have it backwards. Lower seperarion angles have a lower torque peak.

Pierre

 

uh, no. If you have a high seperation angle then yes, but the lower your seperation angle, the higher you power curve is gonna be. Hence why my seperation angle is 107.5 degrees, thats almost unheard of for the street Yeah I'm crazy

 

And I quote from Crane Cams

"This separation determines where peak torque will occur within the engine's power range. Tight lobe separations (such as 106?) cause the peak torque to build early in basic RPM range of the cam. The torque will be concentrated, build quickly and peak out. Broader lobe separations (such as 112?) allow the torque to be spread over a broader portion of the basic RPM range and shows better power through the upper RPM. "

Here is the link http://www.cranecams.com/?show=faq&id=2

If you use adjustable camshaft sprockets you could fine tune lobe seperation and camshaft advance and retard.

Pierre

 

That Crane guy must be wrong

Hey Witt so where these "welded up" regrinds? or do you now have an altered (reduced) base circle. There's only 2mm total travel in the Ecotec lifter(aka fixed lash adjuster). IIRC stock is -1.0mm lash (preload) so you dont have much room to work with. Where's your base circle at?? They noisy??
Wop

 

LSA = Lobe seperation angle

. A wider LSA will result in a more tractor like, smooth and even torque curve that is broad. A tighter LSA will have a torque curve that targets a specific RPM. Yes the power will drop off after you have passed the engine speed in which the cam was ground for.

In other words; it is true that you go with a narrow LSA to build peak torque more quickly and in the engines powerband. It is a similar principle to turbocharger selection. If you want smooth even torque (Street setup) then you would want to get a specific turbo which would build moderate boost through the entire rpm range. If you want a drag strip setup you would want a turbo that builds large boost through a specific range in rpm when you need it to produce max power.

Edit: Blown4banger never said anything about peak torque; he said that the tighter/lower seperation angle will shift your powerband higher. It will cause you to produce less peak torque with the tighter LSA but the torque will build quickly therefore doing more work over the amount of time alotted.

 

witt im glad ya like em hey guys im fullthrottle from the redline forums. i can have these cams and the 280 grind ground they can be done on blanks or your existing stock LSJ cams.