[John Milner]

I am going to be installing a 704 Lunati Voodoo camshaft in my 455. The specs on the cam are (233 241 .504 .525 110). My heads are some 6X4's with the stock length valves. Normally, I run Crower 68404 springs with stock length valves. They are usually about 115 lbs at 1.6 height. I have read up on the Lunati cams some and I have read that they like a spring that is about 130 pounds closed. What spring is everyone running with this camshaft? I am not sure what Lunati recommends for it. They do not have that listed on their website.

[steve25]

The average D port valve spring installed height is 1.560" to 1.580"

The average retainer to guide clearance is .480" to .500"

If the heads have had a valve job then these numbers could grow by.020" to .035" unless you had a very beat up seat in which case the amount the valve could sink may be even .050"

In any case to run a Cam lift of .525" you will need to cut the valve guides down and during that process cut them to accept positive valves seals in a .530" size assuming the guides have not been replaced with solid 1/2" OD guides in which case will need to run .500" seals.

On average cutting the guides for seals will pick you up .060" in retainer to seal / guide clearance.

If your heads are apart and you have the bucks then new valves in the stock high comp lenght will ease your valve spring choice 's and give you more room for added valve lift down the road should you go with 1.65 rockers.

[1967Tempest]

Originally Posted by John Milner

I am going to be installing a 704 Lunati Voodoo camshaft in my 455. The specs on the cam are (233 241 .504 .525 110). My heads are some 6X4's with the stock length valves. Normally, I run Crower 68404 springs with stock length valves. They are usually about 115 lbs at 1.6 height. I have read up on the Lunati cams some and I have read that they like a spring that is about 130 pounds closed. What spring is everyone running with this camshaft? I am not sure what Lunati recommends for it. They do not have that listed on their website.

Running the same cam and heads and springs. Haven't had an issue at all. The 68404 has performed fine. Geometry with stock valve height and pushrod is spot on. I spoke to Lunati when selecting that cam and they said no issues.

[1967Tempest]

Originally Posted by steve25

The average D port valve spring installed height is 1.560" to 1.580"

The average retainer to guide clearance is .480" to .500"

If the heads have had a valve job then these numbers could grow by.020" to .035" unless you had a very beat up seat in which case the amount the valve could sink may be even .050"

In any case to run a Cam lift of .525" you will need to cut the valve guides down and during that process cut them to accept positive valves seals in a .530" size assuming the guides have not been replaced with solid 1/2" OD guides in which case will need to run .500" seals.

On average cutting the guides for seals will pick you up .060" in retainer to seal / guide clearance.

If your heads are apart and you have the bucks then new valves in the stock high comp lenght will ease your valve spring choice 's and give you more room for added valve lift down the road should you go with 1.65 rockers.

I also have the above performed as well.

[Steve C.]

" I spoke to Lunati when selecting that cam and they said no issues "

More often than not calling Lunati is similar to calling Comp Cams tech. Depending on the cubicle your phone call is routed to Comp often just regurgitates the use of their 995 valve spring. Similar to Lunati with almost all their hydraulic cams, including the Voodoo line, they say to use their 73949 valve spring.

From Jegs....

Lunati 73949 Dual Valve Springs
OD: 1.440"
Inner ID: .750"
Seat Load: 120 lbs/in @ 1.650
Open Load: 319 lbs/in @ 1.250
Coil Bind: .950"
Rate: 363 lbs/in

https://www.jegs.com/VendorInfo/Luna...ti-catalog.pdf

.

[1967Tempest]

Originally Posted by Steve C.

More often than not calling Lunati is similar to calling Comp Cams tech. Depending on the cubicle your phone call is routed Comp often just regurgitates the use of the 995 valve spring. Similar to Lunati with almost all their hydraulic cams, including the Voodoo line, they say to use their 73949 valve spring.

Interesting... I guess thats why I always seem to see the 995 mentioned. Tech Support Urban Legend.

[Formulajones]

Paul has quite a bit of experience with these voodoo lobes, both custom and off the shelf stuff and has hours of dyno testing them.

I'm pretty sure I've heard him say on more than one occasion these lobes really like about 130-135 lbs. seat pressure to properly control the valve on the flat tappet versions based on his dyno testing. I don't think there is any one particular spring he uses to accomplish this, because there are so many other variables at play like valve length, retainers used, etc...

The last cam setup I did from Paul it really took some digging to find a proper spring because the inner springs were not fitting the retainers properly and we didn't want the inner spring dancing around.

It's just one example of why tossing these engines together isn't just a simple "out of the box" deal anymore and difficult to recommend something if you really sweat the details, and why machinists like Paul are so successful at what they do.

[Cliff R]

If you are using the light factory retainers and 1.6" installed height the 68404's will be fine. Been using them for decades w/o issue with lower lift cams in mild applications.

They will spec out heavier than what is listed on the website or supplied information with them. I would imagine this happens to some extent due to the step in the retainer for the inner spring.

We used a set of 68404's on a pretty "hefty" Crower cam on a set of #48 heads with stock hardware for at least 10 years, street and considerable track time, zero issues and that engine saw past 5500rpms frequently. I'd add here that if you are going to use stock retainers some material can be removed from them where they seal off the factory "O" rings. This assumes that PC seals are going to be used instead. This gains the extra room needed to run well over .500" lift with the stock parts.......Cliff

[John Milner]

Thanks for the replies everyone. Thanks Cliff for the information on the stock retainers. I have a set and like to save a dollar when I can. I will go with the 68404's.

[Steve C.]

Quite a bit of difference between 113-115 lbs compared to Paul Carters actual experience, including his dyno testing !


.

[Steve C.]

"I'll just be running stock retainers with the crower 68404 springs. Should those work ok with the lunati camshaft? My current rockers are 1.5's."
John Milner

"They will be a little weak. You need to shoot for 125-130 lbs. on the seat, and over 300 open with the 30° intake seat. Otherwise you might experience valve bounce from the flat seat angle. The Voodoo cam has a very gentle closing ramp, but still the 30° seat needs pressure."
Paul Carter


https://forums.maxperformanceinc.com...ght=Voodoo+704

Using fresh new valve springs that have been tested to verify their actual pressure ? Or using springs that have had some running time and may have lost some pressure with use ?
I'll suggest Paul also keeps in mind with his suggestions that is as installed and before they might lose some initial pressure with run in !

.

[John Milner]

So are you saying that the Lunati springs would be the way to go? I really don't want to buy new valves. They should set up pretty close to 1.6 without any shimming and factory style retainers as they are. I can order the Lunati retainers but I would imagine that they would set up pretty close to what the stock retainers ones do. I have the 68404 springs on the shelf. I'll buy the Lunati spring if it is necessary.

[Steve C.]

Personally I'm not suggesting any specific make or part number valve spring. However related I'll refer you to the good information in post number 7 and specifically the comment made regarding digging to find a proper spring. Every situation will be different.

And I will offer this.......

"Always run enough seat pressure to control the valve action as it returns to the seat. Heavier valves require more seat pressure. Strong, lightweight valves require less seat pressure. When in doubt, run slightly more seat pressure . . . not less."
Crane Cams

That is not meant to suggest you have either "heavy" or "light" valves, only to suggest that I would support running a little higher pressure as suggested within this thread.

Finally this.....

From a valve spring catalog.... "Note: spring tensions often vary measurably within the same production runs; therefore it is recommended that EACH SPRING be tested on an accurate spring tester and the springs installed at the recommended SEAT PRESSURE."

And test them with their actual retainer installed at the measured and verified installed height.

"Never trust catalog stated pressures, they can and do vary"

And very important springs can lose pressure after run in and over time.

.

[Steve C.]

Today we are seeing many builders using higher spring pressure to control many of today's lobe designs. And related to this fact I have previously made the statement below a few years ago, and I'll repeat it here......

"We still have many who feel increasing pressure even with today's more aggressive lobes puts more stress on all the related components and robs some power. It would be of interest to know how many thousands of people out there in the up to date modern Hot Rod land that are using a bit more spring pressure to control things without any issues at all with longevity. Personally I have spoken with two popular engine builders featured in the back of Jim Hand's book about this VERY subject, along with numerous well known engine builders outside our community about it. Many have little qualms about it."


.

[John Milner]

That’s interesting, thank you for your input. I might need to think about running more pressure with this particular cam.

[steve25]

A fact that should not be over looked here in terms of iron head is that since most of them use a 30 degree Intake seat is that they tend to bounce more when reaching closure due to no wedging action that a 45 seat has some of.

In sort our big 1.96" or 2.11" valves need more seat pressure and more open pressure then you think when using aftermarket Cams.

If you look at the factory springs in the GM parts books that Cam on the RA4 motors since Pontiac used a computer to design the gentle lobes that it uses the engeneer's where able to use a spring with less seat pressure then what most of the low compression 4 bbl Heads came with!