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How to build a motor for top end power ?

I will degree a 6.2 cam ,I think if any are different that would be the one.
 
EWC said:
Shop manual lists lobe lift @ 7.133 mm + or - 0.05 . That's .281 inches lobe lift multiplied by 1.5 rocker ratio = .421 . This would be easy to check , just mic the lobe and the base circle . That I can do on a stock cam .
Click to expand...


Would be nice to find somebody with a mostly complete engine that could check what teh actual rocker arm ratio is. I know GM lists many at 1.5:1, but in reality they are only 1.47:1. This can also lead to some confusion.
 
Measured the first 2 lobes after the fuel pump lobe and got : .273 , .278 . Damn , no wonder this thing didn't run , off by .008 !
 
The base circle is the " round part " and the majority of the lobe . The " ramps " are the parts leading to and away from the peak or tip which is of course max lift . Measure the base circle from 9 - 3 o'clock , with the lobe straight up at 12 o'clock , and that will be the base circle dimension . This is the diameter of a circle if the lobe was not there . Since this goes around the cam for at least 180 degrees , with the lobe at 12 o'clock , you can now measure from the bottom , 6 o'clock , to the 12 o'clock position . This dimension has the base circle dimension subtracted from it resulting in lobe lift . Think of it this way , put the lobe @ 12 , measure from 12-6 and 9-3 and subtract .
 
EWC said:
The base circle is the " round part " and the majority of the lobe . The " ramps " are the parts leading to and away from the peak or tip which is of course max lift . Measure the base circle from 9 - 3 o'clock , with the lobe straight up at 12 o'clock , and that will be the base circle dimension . This is the diameter of a circle if the lobe was not there . Since this goes around the cam for at least 180 degrees , with the lobe at 12 o'clock , you can now measure from the bottom , 6 o'clock , to the 12 o'clock position . This dimension has the base circle dimension subtracted from it resulting in lobe lift . Think of it this way , put the lobe @ 12 , measure from 12-6 and 9-3 and subtract .
Click to expand...

I would measure from a lifter installed in a lifter bore (with a dial indicator) with the assembly mocked up.

The motion that the cam imparts on the lifter is slightly different because of the change in rotational to linear motion. ESPECIALLY in flat tappet applications.
 
6.2 turbo said:
I just noticed today that my tach has a peg at 5000 rpms,but it kept revving higher,would guess around 5300 rpms. I would go solid lifters,before variable duration hydraulic. Or hydraulic with .002 lash.
Click to expand...

Wow, 5300 rpms! I'd like to see an engine be able to go to 5500 rpm and I think I'd be in the same boat building an engine needing top end power for pulling and the nature of the V8. I'm gonna have to spin that engine up pretty good to get the weight moving and would be nice if it wouldn't stop at just 4200-4400 rpm. All the Cummins spin 4000-5000 rpm in those higher classes...don't see why the 6.2 or 6.5 could go 5500. Sounds like a cam regrind is a great way to go and is not too costly either compared to having to buy one at $600...
 
Well I degreed a 6.2 cam. Everything seems about the same,except it apears retarded 2 degrees. Centerline was 104,instead of 102. It could be an error with my tdc also.
 
6.2 cam specs
Exhaust opening @.050 = 38 degrees
Exhaust lift .281
Exhaust duration @ .050 = 201
Exhaust closing @.050 = 16 degrees BTDC
Exhaust centerline 118 degrees BTDC
Intake opening @ .050 = 14 degrees ATDC
Intake lift .280
Intake centerline 104 degrees ATDC
Intake duration @ .050 = 178
Intake closure @ .050 = 12 degrees BTDC
LSA = 111
ground in advance 7 degrees
 
Tip off for me was the duration is the same as the stocker and the lift as well . The Crane is close on the exhaust but the intake is definately different . I also measured the base circle and they took off approx .030 . That tells me they moved the ramps around to get more lift and change the shape of the lobes .
 
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