According to the comp cams website, the specs on my magnum 270 hydraulic cam are

270/270 duration @ .006

Intake 29 open, 61 close @ .006
Exhaust 69 open, 21 close @ .006

Intake 6 open, 38 close @ .050
Exhaust 46 open, 2- close @ .050

106 centerline
110 lobe separation

I tried degreeing my cam this afternoon but I wan't sure which method was more accurate so I did it both ways.

The FIRST set looked like this...

.006 = 38 btdc, 123 atdc
.050 = 11 btdc, 148 btdc

center line method - 66 & 136 = 101 centerline

I moved the crank gear ton another notch and redid the degreeing.

SECOND SET

.006 = 29 btdc, 116 atdc
.050 = 3 btdc, 140 atdc

centerline method - 74 & 144 = 109 centerline

Now I'm trying to zone in the proper timing and I'm not sure which is more accurate. I have an intermediate setting on my crank gear which will put my centerline where it should be however, my timing per the .006 measurements is matching up with the card.

So which do you recommend I go by? This is in a 402 .060" over motor that will run 10:1 compression. Thanks.

Dave

Dave, did you check it a few times to check the repeatability of your measuring setup?

If so, the second set of numbers is good.

Yep. Double, triple checked 'em. The measurements @ .050 are off as well....

Dave

are you using a solid lifter to do the checking?

I'm using the edge of a hydraulic lifter. Look, for the sake of argument here, lets assume my method is correct and focus on the data. If the data does not make sense, then just say so.

What do you guys recommend? Do I line this cam straight up or add some advance? How much advance or retard? Why? What is optimal for my setup? What readings are the best to go by? Centerline method? .050" method? If the centerline isn't matching up with the .050 numbers then do I have a misreading somewhere or is the cam slightly out of phase?

??????

Dave

Well, I went ahead and adjusted my lobe centerline to match up the cam spec.

Here's my results...

4 measurements of the centerline = 107, 107, 105, and 106.

Intake Valve
@ 0.006 = 32 btdc, 118 atdc
@ 0.050 = 7 btdc, 143 atdc


Good enough or was the previous setting was better?

Dave

Originally posted by ScoobyDoo:
Well, I went ahead and adjusted my lobe centerline to match up the cam spec.

Here's my results...

4 measurements of the centerline = 107, 107, 105, and 106.

Intake Valve
@ 0.006 = 32 btdc, 118 atdc
@ 0.050 = 7 btdc, 143 atdc


Good enough or was the previous setting was better?

Dave =
Dave,
Your 7 btdc number gives you a 107 icl but I don't understand your 143 atdc number??
I am assuming it is actually 143 btdc or 37 abdc.

The closing point should be 37 abdc.
It works like this. 224-7 =217, 217-180 = 37. The 180 is the distance from TDC to BDC. The 224 is your duration at .050.
In any event it looks like you are where you should be ;)

Only way to dial it in any closer would be to use an offset bushing in the pin bore.

Thanks for the clarification. I'm using a poor man's degree wheel and I was just reading the numbers off directly but yes, your right.

It looks like my first set was advanced quite a bit. What would have happened if I had not degreed the cam in and left it at ~101 centerline?

Thanks!

Dave