RE: VooDoo cams and the like: When doing DCR calculations for 10.5 to 1 in .060 over 350 it looks to me like the advertised duration numbers make the DCR higher than it should be.

Any idea what numbers should I use with 268/276 VooDoo cam for DCR calculations? How do I get those numbers for other VooDoo cams?

Can asymmetrical and agrressive lobe cams be used in DCR with "accurate" results?

Thanks in advance.

Jeff

The VooDoo cams are retarded at the seat by several degrees. I'll have to see the real numbers at work, but they are like they are a 4° longer cam at the seat. A 268 would open like a 264 and close like a 272, or even more different. You almost have to have the seat timing numbers to know what to use in calculationg DCR.
This is the way I've designed cams since 1977, and are not unique to the VooDoo line.

UDHarold

Harold, thanks for the reply.
Are the seat timing numbers top secret? I would be interested in knowing them them if possible.
If not, I'm sure others would also like a fudge factor to apply to DCR.

Harold, THANKS, I really dig all the theory and knowledge you share with us. I was amazed when I first used ultradyne cams (a very long time ago), and I still use your cams, and I'm still amazed.

Thanks.
Jeff

So it looks like you'll just add 2 degrees to the intake closing number that the DCR calc gives you.

Harold,

Please take this with a grain of salt, but I really figure it will be to you and Lunati's advantage to advertise the "dead-nuts on" intake valve opening and closing points. AND I'm also talking about lashed advertised duration for the VooDoo solid lifter cam line too.

B/c I figure there will be a bunch of guys just like me that will try to do their homework using the dynamic/effective compression ratio caculators that are out there and so will want to know just what they are buying for a particular compression ratio and that won't bother you guys to find out.

AND I'm really trying to help here too b/c the days of "black-magic" cam picking is almost totally out of date..... (Pun intended, he, he!!)

I learned how to calculate DCR back in school before we had computers BUT totally forgot about it b/c I have done it on my trusty slide-rule until I read Ed Staffel's great book and then got into Pat K's great site.. Now the guys and I have P/C's and program's like Pat K's to play with..

Think you got a winner on your hands...

pdq67

pdq67,

The VooDoo 256 has seat timings of:
IVO 20°BTDC IVC 56° ABDC EVO 64° BBDC EVC 18° ATDC
The others add 3 or 4 to each number.
VooDoo 262:
IVO 23°BTDC IVC 59° ABDC EVO 67° BBDC EVC 21° ATDC
VooDoo 268:
IVO 26°BTDC IVC 62° ABDC EVO 71° BBDC EVC 25° ATDC
VooDoo 276:
IVO 30°BTDC IVC 66° ABDC EVO 75° BBDC EVC 29° ATDC
VooDoo 284;
IVO 34°BTDC IVC 70° ABDC EVO 79° BBDC EVC 33° ATDC
Because neither Comp Cams or Lunati figure their seat durations at .004", the SAE standard, you can add 3° to the intake closing point to get the SAE closing point. This will give you an obviously lower DCR, and perhaps a truer number.
The VooDoo series of hydraulic cams, and the hydraulic rollers too, have gentle, almost stock seating velocity, closing ramps, for NOISE control. Their rated durations are for comparison with the Xtreme Energy line.

UDHarold

Harold, thanks for the info! Those numbers look great. I can't wait get it in and running. I'll report back when I do.
Which ones are coming out next?

Jeff

Thanks Harold!

I bet the guy's will chew on the numbers for a bit AND the orders will start coming right in!!

You might want to post this over at both the Team Camaro and Second Generation Camaro Owners Group sites too?? B/c I know the guys have been chatting about the VooDoo line a bit lately...

Just go right in and post, "Guy's, here's the numbers on the VooDoos", sorta deal...

pdq67

I ran Harold's seat times through the cam timing calcs and found that using 108º ICL, regardless of the LSA, gave the timings Harold provided. That is with 112º LSA using 108º LSA (4º adv) for the 3 smaller cam give the timings provided. For the 276 and 284, that have 110º LSA, using 108º ICL (2º adv) matches with Harold's numbers.

With these results, it looks like the two larger cams are more unsymmetrical than the smaller cams. This doesn't mean the cams should be installed with 2º advance. It means that if you want to calculate the seat times, you have to adjust the ICL just for the calculations. This is due to the limitations of the formula in that it assumes a symmetrical lobe.

Pat,OK!
Where's the DCR formula for asymmetrical lobes? Just kidding!
Thanks for the help!

Jeff

I just hate it when I make a mistake......
I forgot the 256 and 262 were on 112. Those numbers are for 110 LSA.....
The correct numbers for 112 LSA are:
VooDoo 256--
IVO 18°BTDC IVC 58° ABDC EVO 65° BBDC EVC 17° ATDC
VooDoo 262--
IVO 21°BTDC IVC 61° ABDC EVO 68° BBDC EVC 20° ATDC

Sorry for all the un-needed calculations. The extra 3° intake closing should still be added.

UDHarold