Some cam timing Questions...

T

threewebers

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Is there a motor guru here?I have a 292f Schneider cam and have a few questions...
I have checked the intake opening at .050 and my degree wheel is reading 22 degrees when the cam card says it should open at 14 degrees,I know that I could have the cam gear machined so that it's adjustable. I called the cam company and they said if make it open at 10 degrees this would be ideal?I'm lost now,Why wouldn't the cam card say 10 degrees? I'm attempting a street/trackday motor nothing to wild 10;1 JE's 45 dcoe's headers and a mild port job ,billet rockers and a few other things to improve reliability....Any suggestions welcome and thanks up front.
 
Follow the Cam Card ( yellow brick road- oh my!)

Threewebers,

There must be more to the story. At 8 degrees off something is unusual. Just offsetting isn't recommended unless you're very intentionally doing it for a specific reason like shifting the torque/ hp up or down and even that shouldn't be done to that amount without possible consequences.

Let's assume you found TDC and repeatedly. And that slack on the chain was negligible. And that it didn't jump a tooth and was spun several times to settle things.. And that in checking, it was always clockwise, unless you go past and the forward to the specified lift/ opening to take up chain slack.

The card- does it also show closing at the same? Usually you check both sides from base circle . Are you familiar with the centerline checking method? I would absolutely follow the card and only consider it good if I was off by less than 1/2 degree.

Even if the block was decked, head skimmed, etc, I wouldn't expect to see that kind of difference.








What else is shown on the card?
 
Could you post a pic of the cam sprocket from several angles at EXACTLY TDC???
 
The cam card states to use .oo6 lash on the intake,.008 on the exhaust @.050 intake opening is 14 degrees btdc,closing 50 degrees abdc, I've used a digital dial indicator found tdc,setup the indicator using the valve spring retainer and very light springs and came up with 22 degrees opening at .050, closing at 32 degrees, I will run the intake lobe center but i still lost on the optimum crank degree to open the intake?When I spoke to schneider racing cams they told me to make it open at 10 degrees but would not give me a explanation,this is a mild cam but I would like to set it up the rite way...Thanks I'm a beginner engine builder.
 
TDC and Cams

Threewebers,

TDC is located using a piston stop. Regardless of whether the wrist pin is on center or offset, there is always a area of several degrees in crank rotation at TDC where the piston isn't moving up or down. This is caused by the clearance stacking and the fact that it takes several degrees of rotation for the rod to go over center. (Clearance stacking is the result of the wrist pin to wrist pin bushing, rod to crank clearances, etc.) If this stacking error didn't exist, you wouldn't be able to turn the engine over, it would be bound up tight with 0 clearances.

You will also need to fabricate a piston stop from an old spark plug. You need to do this to verify your degree wheel/pointer is set exactly at TDC after you've assembled the head to the engine. (You won't be able to leave the rig on the engine during assembly) This allows you to move the pointer to match up with the 0 degree mark on the degree wheel. When you degree the cam you'll need the mount and dial indicator. The tip of the dial indicator will be setup to ride directly on the cam lobe of the #1 intake or exhaust valve. The engine is only turned over in the running direction of rotation, you set the cam per the manufacturer's specification sheet. If you don't have the spec sheet or don't believe it, you'll have to fully degree the cam for intake and exhaust and run a few simple calculations to determine the actual cam specs. Then go from there.

From what you've said so far:

292+14+50 = 354
360-354= 6 degrees/2 ( before and after center)= 3 degrees stacking

You're probably picking up the other two degrees in the valvetrain vs. block.

Still curious as to how they set up lift with the webers vs. FI.:twisted:
 
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