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OK, I got the XE 268 cam and it says to install at a 106º manifold center baseline? what would that be, there is a dot on the timing gear, woudl that be with the dot facing straight up....and also on the crank gear, there are 3 slots for the groove that sticks out of the crank, one says A, one R, and one 0...i put it on with the one that says R cause it makes the tip of a sprocket tooth point straight up dead center, the A and 0 have it like in the middle of 2 teeth and somewhat in the middle..the crank is at TDC #1, i thought that when the motor is at that you want the lifters in #1 to both be at the very bottom of there cycle, and it appears that they are both at the very bottom with the cam sprocket gear dot facing straight up......the instructions didn't say much about this or how to get the dang chain on the gears, i have no idea how to do that and tried. last thing it doesn't say what to torque the 3 cam bolts to... thanks for the help
-Roger

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'69 SS, 355 9.7:1, ported twisted wedge allum. heads, .454/.480 cam, 9" rear 3.89 gears, 700r4, hooker mufflers (nothin sounds/flows better)

[This message has been edited by rogleete (edited 12-20-2001).]
 

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The A/R/0 designate Advanced/Retarded/0 or straight up timing. I believe you will need to use a Degree wheel to get that 106 degrees your looking for. Oh and if im not mistaken the Cam sprocket should have to Dot pointing straight down aligning it with the Crank sprocket dot. If you dont have a Degree wheel handy the rule of thumb is usually set it up at 0 degrees tdc.

[This message has been edited by Rsmith1969 (edited 12-21-2001).]

[This message has been edited by Rsmith1969 (edited 12-21-2001).]
 

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There should also be three marks on the outer diameter of the front face of the crank gear that correspond to the A/O/R markings near the keyway slots.

You are supposed to line of the appropriate matching letter on the face of the crank gear with the dot on the cam gear. Ex. You picked the R keyway on the crank gear, you need to align the R on the edge of the crank gear with the dot on the cam gear. The "R" on the crank gear and the dot on the cam gears should be aligned, with the cam gear dot below the cam centerline, and the "R" above the crank centerline.

If you lined up the two dots and used the R keyway your cam is installed about 120 degrees out of phase.

The R indicates the cam is will be 4 degrees (typical number) retarded in relation to the crank timing. Typical cams have an intake centerline around 106 degrees (check your cam card - this is not lobe separation). If you retarded it 4 degrees it now has an intake centerline timing of 110 degrees. typically this builds high RPM horsepower at the expense of low RPM torque.

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Mark Canning
1969 Indy Pace Car
350/300HP RPO Z11
My 69 L48 - 350/300HP Engine
 

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I believe the 106 degs is actually in refrence to when the cam is installed straight up (zero degrees advanced) the intake lobe will be at 106 degrees. You should call the cam manufactures help line and have them explain it better.



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...Dennis
"The '69, the '96 & the club"
 

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Intake centerline refers to the point where the intake valve is at its highest lift and it is in crankshaft degrees. It is associated with a specific cyinder, ex the number one intake valve is at its highest open point when the number one cylinder is 106 degrees after top dead center. If you take your total duration, 268 degrees in this case divide it in half (134 degrees) you can see that the intake valve lifts off of its seat 28 degrees before TDC for the associated cylinder. This is usually indicated on your cam card as (-28 ATDC). The valve closes 240 degrees ATDC refered to as 60 ABDC on the cam card. While the relationship to each cylinders top and bottom dead centers are the same, cylinder one is the only one you can relate to the TDC mark on the balancer. When you advance or retard a cam you are changing the location of the valves highest opening location (and opening and closing point)in relation to the pistons top and bottom dead center locations.


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Mark Canning
1969 Indy Pace Car
350/300HP RPO Z11
My 69 L48 - 350/300HP Engine
 

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Comp Cams grinds 4 degrees of advance into their cams. So if you install it "straight up" you will be right at the 106* mark they recommend. Do not use the "A" or "R", just use the round dots.

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68 Camaro, 383 small block with TH350 trans. 11.98's at 111mph and never trailered.
 
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