[mike76]

Looking at the cam card it says " 281/289 " as the advertised duration. That's a bit more than what's listed on their site. Wondering if that's being recorded at a lower tappet lift ? Why would they do that? Also thinking on maybe using Rhoads v max in my 428. Thoughts would be appreciated. Thx, Mike

PS: Their site says " 276/284 " .

[pastry_chef]

Originally Posted by mike76

Looking at the cam card it says " 281/289 " as the advertised duration. That's a bit more than what's listed on their site. Wondering if that's being recorded at a lower tappet lift ? Why would they do that? Also thinking on maybe using Rhoads v max in my 428. Thoughts would be appreciated. Thx, Mike

PS: Their site says " 276/284 " .

Nice cam!
The 281/289 is probably at .006 tappet lift
All good man, here is the word from the designer.
You are fine to use the V-Max if you want.

Originally Posted by UDHarold

First of all, Lunati/Holley kept the computer and the printouts, so I cannot go back and reference what the actual numbers were.
When the VooDoos were first designed, several Sales Managers and a different owner ago, Lunati decided that they would compete directly with the Xtreme Energy cams at seat duration. I believe the actual ramp height was around .0068"-.0070" high.
The .050s were .050", the .200s were .200", as expected.
My designs are more unsymmetrical, with more offset, and so a later intake closing point, on the same LSA/ICL. Our shorter cams were on 112 LSA, instead of the 'One Size fits All' of the CC 110 LSA.
Oddly enough, even with the much later intake closing point, our VooDoos made much more bottem end at 2500, where the dyno tests started.
It is not where you close the intake valve that matters, but instead how much air and fuel is in the cylinder when you close the intake valve.
Closing the intake valve is the very last thing you do in the cycle. Everything else has more effect on the air/fuel charge.

UDHarold

Here is a bit more duration info.

VooDoo-----.100"---.200"---.300"
276----------203.9---146.4---74.8
284----------211.9----154.4---88.0

[STEELCITYFIREBIRD]

I see no reason not to.
The adjust ability of the design allows you none to some.. and more, and intake differ from exhaust..... I like adjust ability. And likely the highest quality Pontiac HFT your going to buy.

THe 0.050 duration is where to compare, the advertised #'s are just that...advertising.

[Steve C.]

Stated- "the advertised #'s are just that...advertising."

There is more to the seat duration than advertising.

One example:

http://www.wallaceracing.com/overlap-calc.php

Also.....

"When comparing two different cams, if both profiles rate the advertised duration at the same lift, the cam with the shorter advertised duration in comparison to the 0.050 duration has more aggressive ramp. Providing it maintains stable valve motion, the aggressive profile yields better vacuum, increased responsiveness, a broader torque range, and other driveability improvements because it effectively has the opening and closing points of a smaller cam combined with the area under the lift curve of a larger cam."
Billy Godbold at Competition Cams


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[ponchjoe]

I don’t speak cam specs but my thoughts are that cam will be killer in a 428. What’s the rest of the build?

[Steve C.]

This from the Comp catalog....

"When it comes to ordering a roller cam, there are two things that need to
be considered: journal diameter and roller lifter wheel diameter. Journal
size and wheel diameter are very important in making sure the lobe is
performing to the specifications you require.
For example, if you were selecting lobes for a custom grind Big Block Chevrolet
cam then you would need to make sure the lobes were designed for a
Big Block Chevrolet journal diameter (1.948"). If Small Block Chevrolet lobes
were used instead, the specifications of the cam would be inaccurate. The
journal diameter of a Small Block Chevrolet is 1.868". The lobes on the big
block cam would "grow" approximately 2° if ground using small block lobe
designs. The same principle applies to various roller lifter wheel diameters."

This is why when you order a Comp Pontiac cam with a "B" suffix code the seat duration is often, but not always, different.
Comp masters are based on a Small Block Chevy core and the Pontiac core is a different size.

I've had a similar situation with Bullet Racing Cams. When I ordered a custom cam from them they forgot to allow for the difference in the Pontiac core size and the seat duration was 2 degrees off than what was ordered. This was found when my engine builder was degreeing the cam. They offered to do it over but it was already installed and to me it would make little difference.

This may not be the situation here, but food for thought. Call Lunati on the subject ?


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[mike76]

Originally Posted by ponchjoe

I don’t speak cam specs but my thoughts are that cam will be killer in a 428. What’s the rest of the build?

Ported#62 heads ;9.8 compression ;4 speed ;3.42 rear.
All good info here and I appreciate it. I just wondered why Lunati advertises a certain seat timing for a cam while the cam card shows a different number that's all. I think it should be consistant since this is suppose to be an off the shelf grind

[pastry_chef]

Originally Posted by mike76

I just wondered why Lunati advertises a certain seat timing for a cam

A marketing decision a long time ago.
Many important numbers don't show on a cam card either.
Voodoo are very asymmetrical lobes, designed by one of the top cam guys the world ever had.

[gtofreek]

I have a cam card here for the 704 and it shows 276/284 advertised. It was from a few years ago. Oddly though, I also have a cam card here for the 703, and it shows 275/281 advertised[not so long ago]. Not sure why, but I do see them vary by a degree or so from whats advertised at .050" but this is quite a bit. The only thing I can think of that's different is years ago[from when this 704 cam card I found here is] Lunati ground their own cams. Now, since Comp and Lunati are owned by the same people, the Lunati cams are now ground at Comp, so maybe there is something different with the way they are reading the cams. Here is a sound clip of a 428 with the 704 cam, and standard lifters. It has 10.8:1 compression though. Makes around 11" vacuum.
https://www.youtube.com/watch?v=bO9SShvaKUo