Is this cam what it is supposed to be?

[digger]

Digger -

That's exactly what I am looking for.

Also, I notice that you mentioned a reason for the MM exhaust duration being much smaller than the intake duration. Jim Rowe once told me that one reason why he did that was to maintain some compression in the cylinder. Apparently it helps to keep some of the tourque and low-end power which is often lost with bigger cams. He made up for the shorter duration by using an extremely high lift, something which stock rockers and springs aren't capable of supporting. His solution was then to create progressive rate springs which have a lower peak pressure even at such high lift. Of course, I may have totally misunderstood him.

if he wanted torque in the lowend he shoudn't have done what he did with the inlet side thats where the compression is made, the dynamic compression in that thing means it throws alot of what comes in back out and needs min 12:1 CR IMO, it relies a fair bit on inertia that one....you could go larger on the MM exhaust side without much detriment to torque if you set the ECL appropriately without hurting emmisions and idle quality. It is a pretty quick ramp

[structured]

Digger -

That's exactly what I am looking for.

Also, I notice that you mentioned a reason for the MM exhaust duration being much smaller than the intake duration. Jim Rowe once told me that one reason why he did that was to maintain some compression in the cylinder. Apparently it helps to keep some of the tourque and low-end power which is often lost with bigger cams. He made up for the shorter duration by using an extremely high lift, something which stock rockers and springs aren't capable of supporting. His solution was then to create progressive rate springs which have a lower peak pressure even at such high lift. Of course, I may have totally misunderstood him.

[digger]

what does it say on the end of the cam?

It doesn't plot out like a 288 when you look at the overlap

I measured a 288 a few weeks ago at the valve and plotted the result

http://www.e30tech.com/forum/showthread.php?t=108802

[structured]

Pics of cam:

[structured]

- I uploaded a better image. Don't have a bigger one available. I can upload a better one later if you still can't see.
- Yes, it has the Schrick logo cast into it.
- I am measuring the cam while the engine is fully assembled and out of the car.
- The location on the chart is the crank location in degrees, not the cam location.
- 0 degrees on the chart is TDC.
- Right now, I calculated the exhaust peak timing to be at about 119 degrees (9 crank degrees advanced from spec). That is only because I haven't adjusted the cam gear yet.

While measuring lift, I had the dial indicator pointer sitting on either the eccentric nut or on the eccentric. I know that this will give a false reading but I was unable to place it directly on the valve retainers. Instead, I multiplied each lift value by the ratio of the (spec lift/measured peak lift). Once I measure the cam lobes, I will adjust that ratio to be the (actual valve lift/measured peak lift).

As for the rocker arm ratio, I measured at the valve (not the lobe) so it isn't relevant just yet. I will need it to convert from the lobe lift to valve lift.

[nando]

is that chart in cam degrees? if it is you need to double it for crank degrees which is what cams are spec'd at.

also - the quoted peak lift value from schrick is without valve lash. typical valve lash is .025mm or .010". I believe the advertised duration is measured without lash and right at valve open/close. Industry standard is .050" open/close and with valve lash. if you're measuring this on a head, you've got valve lash there that would add some duration. if you wanted to get a better measurement you'd set the eccentric to 0. the rocker arm also multiplies how the valve opens/closes (it's abuot a 1.25:1 ratio, but it varies with opening time).

got a higher res pic of that chart? or a pic of the cam? is it stamped "schrick" between cyl 1 and 2?

I think if you wanted to measure it and find if it matched schrick's specs, you'd have to measure on the cam lobe itself and not the valve.

[structured]

So I have this Schrick cam which has a 288 serial number on the end. I bought it second hand and while I was always a bit suspicious of it, I never had a chance to verify what it was until now. I assembled my engine and measured the cam today. Here is what I found:



Now, I hope that I made a mistake somewhere, but the duration does not look anything like 288 degrees. Am I missing something?

Ignore the lift values. I adjusted them to match the 288 cam spec because I was unable to locate the dial indicator's pointer directly on the valve retainer. The actual measured values were a bit lower than what you see. I am going to measure the lobes to check the actual lift this week.