Helix cams

[Matt400]

Don told me he has seen stock valves float on a stock to mildly fueled truck. So, the springs would be a good upgrade no matter what you are doing.

Hey Dave, did Don say what RPM he has seen them float?

 

[Fishin Guide]

Hey Dave, did Don say what RPM he has seen them float?

Unfortunately, I do not recall. Don hit me with so much technical info, I was just trying to get the job at hand done. :-laf



The parts of our valve trains are so heavy, it's a wonder that we all do not have more issues with the valves. But in a stock configuration with less lift, there is only so much energy that has to be absorbed by the spring. jack up the lift, and it has a harder time controlling that movement witht he remaining coil area.



Titanium keepers would help. As would anything to lighten the mass of the valve train. Unfortunately, this is a delicate balancing act as everything in these engines is heavy duty. So, some compromise is acceptable to many for mild performance gains, a lot of compromise is only worth it to a very small percentage of the owners out there.



Don has ceramic tappets and I am sure that he is working on more and more trick parts to enhance simple effencies in the motor. Time will tell.



Congrats to Doug and Don for pushing a VP truck over 800HP! That's quite the acclompishment! And to be looking to 900HP in the future shows that you aren't going to rest until you find the true limitations of a VP truck!! Oo.



Dave

 

[R-N-R]

So, how can you tell when the valves are floating? Sorry to ask such a rudimentry question, but I am genuinely curious.

 

[Vaughn MacKenzie]

Thanks for your comments Fishing Guide, they make sense.



As far as the valvetrain the pushrods sure weigh a lot. Could they be made hollow without sacrificing strength?

 

[Matt400]

So, how can you tell when the valves are floating? Sorry to ask such a rudimentry question, but I am genuinely curious.

I would bet if you stay under the factory redline you wouldn't see that condition.

More on valve float here:

http://www.hotrod.com/techarticles/113_0209_cam/index3.html

 

[Fishin Guide]

When it comes to floating valves on forced induction engines, the best way to determine this is on a dyno. The problem is exaggerated by big psi and high rpm.



Basically, some of the air charge is being forced back into the intake. In our application, this means small divits in our power due to a momentary loss of compression. On supercharged vehicles, this usually follows a set number of valve actuations per rpm. Don't know why, but it does. Kind of like a resonance with weight being a factor.



The stronger spring helps control all that weight in motion. And, it helps to decerate the valve and help it ride the closing ramp back down. There is as much to this as total spring strength coupled with spring rate.



While a stock truck probably won't have this issue, it does not take much fuel to add pressure and add some rpm... . you are now working the springs, and everything else, much harder.



I would definately recommend the springs to anyone doing a cam swap. While not required on the Helix 1, I would think the added lift and lobe profile of the Helix 2 would be a good idea. I have not seen a 1 or 3, so I can't comment on profiles. I did, however, completely check out my cam in the engine to be sure it was dialed. This is after Don M did the same thing with a dummy block in his shop.



As far as your question Vaughn, simple answer is I do not know. It would require somene that has an better understanding of the materials, stress points, work load and system dynamics to answer that question.



My gut says that there are ways to lighten the valve train to gain efficency, but I think that would be mostly a lost cause on the vast majority of street trucks. high RPM race and sled pullers with hardened billet cams would get the most benefit. For the rest of us, I think the springs are a prudent and logical upgrade when doing a cam.



JMO.



Dave

 

[Jetpilot]

I have seen many trucks that are having valve float at stock rpm. I am amazed again and again by the trucks I pull the heads off of to replace headgaskets (etc. ) that have marked up pistons..... I would go so far and say anyone pushing over 35 psi boost should consider them and anyone over 50 I really recommend them. The twinned trucks and trucks running cams with close valve -to-piston clearnaces are again folks who should really change out their springs.



Doug

 

[Fishin Guide]

I have seen many trucks that are having valve float at stock rpm. I am amazed again and again by the trucks I pull the heads off of to replace headgaskets (etc. ) that have marked up pistons..... I would go so far and say anyone pushing over 35 psi boost should consider them and anyone over 50 I really recommend them. The twinned trucks and trucks running cams with close valve -to-piston clearnaces are again folks who should really change out their springs.



Doug

Good info Doug!



Dave

 

[Matt400]

I have done springs on gassers without pulling the head but I suppose on these you would need to pull the head to do springs correct?

 

[Jetpilot]

Cummins makes a neat little tool (reatils for around $40) that allows you to change the springs with the head in place.



Doug

 

[Matt400]

Well then. . sudenly springs along with the #2 grind is looking better.

I would like to compare specs on the #2 against a new PDR custom grind to decide whats best for my use but I may have to settle with just knowing either one is better than stock.



Do I understand correctly the Helix 2 has more potential for mpg and spool up than the #1?

 

[DHayden]

I've wanted a cam forever but I don't have the tools or facilities to accomplish this job. A little over $1,000 is the cheapest I've found to have it installed by a shop. Anyone have a better bid ?

 

[Jetpilot]

Wanna drive up here? I normally get a good 25% less than your quote.



Doug

 

[R-N-R]

Don't you have to strip the motor down to the block to swap the cam? Something about the lifters being a pita to keep from dropping into the pan?

 

[lmills]

If you aren't careful, a lifter can fall down. However in most cases if you watch what you are doing you can do them without stripping it down.

 

[justinp20012500]

I have seen many trucks that are having valve float at stock rpm. I am amazed again and again by the trucks I pull the heads off of to replace headgaskets (etc. ) that have marked up pistons..... I would go so far and say anyone pushing over 35 psi boost should consider them and anyone over 50 I really recommend them. The twinned trucks and trucks running cams with close valve -to-piston clearnaces are again folks who should really change out their springs.



Doug

I ran 60+psi for 12k. Also had 6 thou shaved off the head with fire rings. I pulled the head when I sold the truck and the pistons showed no sign of contact.



I tested the factory springs at installed height and they all came out to about 70 lbs.



Is that unusual?

 

[Jetpilot]

There are exceptions both ways... . Your is to the good but there are many that are the other way. It seems to be a quality issue with the springs, some a better than others. Like I mentioned above I have seen pistons marked up in trucks pushing mild boost numbers with no rpm limit increase, while other trucks pushed much harder are fine. I have also seen a wide variance is spring seat pressures.....



Doug

 

[Idaho CTD]

When I had my head 0-ringed prior to twins (I was running a HX40, DD2's, and a Drag comp) there were intake valve marks on 3 or 4 pistons. The valve closest to the front of the motor on all cylinders that made contact were the most pronounced.

 

[SHobbs]

Wondering how a 24v acts with a mech. LP. I would like to get away from the elec. one. Is it as simple as unplugging the elec. LP and replacing with a mech. and taking off with no problems. Maybe a silly question but the only dumb question is the one not asked, lol.

 

[SRadke]

Is the 12 valve lift pump and option on a common rail?