Hi-performace engine advice?

Quicker spoolup=more streetability
I'm down with that
 
A stock cam is fine for stock RPM's... When you start going beyond the stock rpms things like heat start to build up faster, at higher than stock RPM's you would want that valve to remain open as long as you can to cram air into the cylinder, plus with aftermarket cams things like the rate of which the valve opens can be altered as well, so you have a cam that opens the valve at an earlier time, faster, and holds it open longer. Which show the qwicker spoolup and better driveability and lower EGT temps. So all that being said- why try and play at this level with a stock stick, when aftermarket sticks can show more benifits over stock sticks- 'on a modified' engine, turning rpm's that are higher than stock, with all that extra fuel being sent into there....

Sounds to me like you'd be limiting yourselves with the stock stick.....
 
Well... sure changing the cam timing can change the rpm where the motor is most volumetric efficient. Not saying I wouldn't mind turning more Rs and understand that a cam along with some valve train work would allow me to do that. That said I still would kill to get my big single to light at 1500 instead of 1700. Even if I had upgrade valvetrain I would not be wanting to drive around all day at high Rs so I could spool my turbo. I want low end... worry about the high end later. So... will a cam give you better spool down low and if so by how much?
 
Sure it would allow earlier spoolup as the valve lift rate is much earlier and faster and max lift is being held open longer. Allowing those bigger turbos to spoolup earlier.

By how much? Depends on the profile on the cam itself, and how much airflow is needed to get that turbo spooling.

That's why you have to carefully select the parts that you purchase to work in harmony with the the rest of the engine....
 
Which is what I'm trying to do lol :)

The question is who has tried a cam on a truck that is fueling heavily and using a large single? Which cam and specifically how did it affect your spool?
 
Good advice from the guys.... Get the right parts and do it once! A cam will and does make a difference. The wrong choice can hurt performance but the right one can sure make things come alive.....

Doug Smith
 
Guys, I appreciate your input but let's stop talking in platitudes. Be specific. You had what turbo, what level of fueling, and what cam, and... how did it affect spool? If you don't want to be specific with an rpm delta that is fine but rate the affect on a scale of 1 to 10 with 1 being it's hard to tell if my turbo spooled better at all and 10 being it is a night and day difference. It's a fair amount of effort install a cam and if it's going to give me 25rpm better spool I'll spend my money on beer instead lol.
 
Such an elusive answer lol.

If I had ever ran a cam on my truck I guarantee I could provide very specific findings in relationship to what it was before the swap. I'm pretty sure I could use those findings to sway others into buying one or maybe not buying one lol. I suppose if the results were short of spectacular I would probably get quiet when someone ask me for specifics :)

Still hoping for a reply...

PS ask me how my truck changed when I swap stock sticks for Mach2s... then 2's for 4's... then 4s for 6s. How about stock turbo to B1 and then B1 to II64. How about when I tightened up lash? How about Comp or no Comp and the various Comp settings? I can give you details until I put you to sleep. Why can't anyone do that when it comes to cams?
 
Last edited:
OK here ya go..... I have run the PDR cam, spoolup was better than stock (200 rpm or so). I moved my power band lower in the rpm range, max HP went fron 2700-3300 to 2450-3300. Egt's dropped about 150* on the topend and mpg went up about 1-1.5. This was on a 2001 running a B-1, Edge Drag Comp, Bully Dog 8's and nitrous. No power was added to max.

Jump forward 3 years, installed a Helix 3 cam in our shop truck. It had a Steroid B-1, Redline Box, Edge comp (for timing), Mach 8 injectors, and nitrous. This truck made 832 RWHP! The truck made about 28 HP more running the cam than pre-cam. The rpm range was extened up, max HP was lost pre-cam around 3300, after the cam I can hold onto max HP till over 3700 rpm. The bottum end HP was better (2650 vs. 2800). Egt's are down a ton on the topend, somewhere around 150-200* depending on the setup. Spoolup with this cam is somewhat better than stock but it is really designed for more rpm not down low grunt.

If there is anything else I can answer please let me know.

Doug Smith
 
duke1n said:
Such an elusive answer lol.
Why can't anyone do that when it comes to cams?
Click to expand...

LOL
You have to understand that the 'off the shelf' cam grinds that are out there
may work well for some engines, they have their different stage cams ( stage1-stage2 ect.) to choose from, which put you in the ballpark of a good combination. Generally speaking.

But not every engine is built the same- so one could fully maximize the potentials of power by going to an experienced diesel cam grinder, and discuss your engine mods and what your looking for. And then you will have a cam that is tailored to your engine, maximizing the Hp, where and when you want it.

Take 2 cams with the same max lift for an example-
Just by changing the ramp profile to open the valve faster, earlier, while keeping the same max.lift will change how and when the engine builds its power.....same goes for holding the valve open at max lift longer allows more air in to the cylinder.

Clear as mud?:ugh:LOL
 
Last edited:
Now that's what I'm talking about lol. There was a time back in high school I researched and studied cam profiles and timing and wrote a term paper on it. Could pretty much tell you everything there was to know about cams. Built a real nice running full roller, W2, 340 for my 70 Challenger. That was a long time ago. Being lazy now I just want someone to tell me that with my current setup, this cam will give you ~ this much better spool and boost. The way you describe the PDR cam sounds like what I'm after Doug. I'm not really chasing max hp #s. The truck now is around 600 on fuel and that is plenty. All I'm after now is better driving manners. Having the turbo come in 200 rpms sooner would be huge. Dropping EGTs 100 degrees would be icing on the cake. So, with this setup, which cam out there will give this to me?

02 ETC 5sp
Comp
II 64
Mach6s
5280 feet elevation
 
For what you are describing I would lean more towards a Helix 2 cam. I haven't personally run this cam in my truck but I have set up several customers trucks with them and they are awesome. Dyno sheets are showing the power band to be moved down about 500 rpm and the upper limit being extended about 100 rpm. Egt's are dropped about 200* and fuel economy improved about 1-2 mpg.

Don't get me wrong the PDR cam is nice its just that the Helix 2 is more of a better thing.

Doug
 
Jetpilot- how much a difference are the profiles between the Helix 2 vs Helix 3 ?
 
I am not allowed to give out specs.... I can give advice though on which cam works best for the application at hand. Basically though the 2 is the best all around cam where as the 3 is more for top end HP.
 
And you say this 800+ HP is used on the street. From what you're describing, one is better suited for drag racing and the other pulling. I thought this was about street HP. Somehow I don't think we're talking about the same thing here.
But, if the HP range for you engine is in the 3700 RPM bracket, you're out of the Cummins optimum operating range anyway. Keep these engine around 2800 and they pull the best. Yu know that.

I still think a cam is the last thing to consider, when money and time spent is for street power. The dragstrip is another story. There you gotta squeeze every power module you can, to be a winner.

..Bye now..

..Preston..
 
Let's stipulate that a cam is not going to bring you more peak hp if you plan on running in the stock rpm range. If you could gain 200rpm lower spool would not that be huge for a street driven truck with a large single? I don't even care that much about EGTs but if I could get even 100 rpm guaranteed better spool that would sell me in a heart beat. Since no one wants to make guarantees I end up asking lots and lots of questions in an effort to wade through the bs. Doug's response above is a good example of information that valuable when trying to make educated guesses at what works and what doesn't. Thanks Doug. Do you have direct experience with cams that you can share Preston?
 
Last edited:
200 RPM lower spool would be nice indeed on a larger single for street use, with a stick that would be the cat's meow indeed. I might have to look at this later on down the road.
 
turbothom said:
I still think a cam is the last thing to consider, when money and time spent is for street power.QUOTE]

Well a cam certainly is not one of the first things that most customers look at changing. But we are having a lot more guys change out their cams than before due to the better grinds that are available. Heck one guy put one in his pretty much stock truck just for mpg improvement. I didn't think this was practical but he had done the math and as a hotshotter it would pay for itself in about a year!

As for the 2800 rpm mark being optimum for the cummins, again that depends on how the engine is setup. The rpm can be moved either way by numerous factors one being the cam...... At some rpm point though the ability to efficiently burn the fuel becomes an issue and HP is diminished. Personally I think that head porting is one of the last things that needs to be done to a performance engine. A cam can help out the motor a lot more than porting, yet more guys port the head then install cams. The important thing is to set the truck up to give the customer what they are looking for.

Doug
Click to expand...
 
You must log in or register to reply here.
Back
Top