this is what I used

http://hometown.aol.com/ffastcbr/caminfo.htm

 

Grippy

It seems to be confused by the terminology used:
so valve open = -8.1 BTDC ; really means 8.1 ATDC

and valve close = -10.4 ATDC ; really means 10.4 BTDC

Then your formulas will work if you enter these figures in as negative numbers.

Overlap: -18.50 degrees
Intake Duration: 205.00 degrees
Exhaust Duration: 212.40 degrees
Intake Installed Centerline of 110.60 degrees ATDC.
Exhaust Installed Centerline of 116.60 degrees BTDC.

 

Here's what my cam card says,gross lift .588/.598,duration @.006 277/283,valve timing @.050 Int:3 BTDC 45 ABDC Exh:56 BBDC 2- ATDC@111.0 intake center line,duration@.050 int:228 exh:234,lobe lift .3460/.3520,lobe separation 115.0

 

-2 ATDC is the same as +2 BTDC. So Intake opens at 3* before TDC and exhaust closes at 2* BTDC. Thats 1* of overlap at .050 lift.

On a big cube motor, I cant say what size cam I'd use with a blower. I do know that Dennis (427 LS1) swapped in several cams in his truck last year. It had a 427 with a radix. I remember him saying he thought the 224 duration cam he had felt stronger than the larger ones he used. But that may be because the radix is undersized for that combo, so the cmaller cam created more dynamic compression and kept rpms down.

 

I entered in the values just as you said, came out the same 18.5 degrees overlap.

Am I missing something? check out the calculator I'm using


http://hometown.aol.com/ffastcbr/caminfo.htm

 

Grip use this

http://users3.ev1.net/~black_ops/cam...calculator.xls

 

can't, don't have excel.

are you showing something different? This Calculator I've been using has been accurate so far.

why would you figure overlap at .050?

isn't the correct way at .006?

 

Ah. Your's sorta works backwards where you need the ve's to find the duration and timing.


Go to proracingsim.com

Download the demo.

You can do some easier figuring. Most of the time your going to see X camshaft and wonder what the valve events are.

 

Overlap: -18.50 degrees
Intake Duration: 205.00 degrees
Exhaust Duration: 212.40 degrees
Intake Installed Centerline of 110.60 degrees ATDC.
Exhaust Installed Centerline of 116.60 degrees BTDC.

That's what I get using your calculator and filling it in w/ Nakid's camshaft. Make sure if you have a negative IVO or EVC for .05, to type it in negative.

 

Yup the overlap is still -18.5 degrees but the Intake Duration, Exhaust Duration and Intake and Exhaust Installed Centerlines are not correct unless you enter the IVO and EVC as negative numbers for Nakid's cam profile.