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Which cam? *big ass picture*

Zeus33rd

Zeus33rd

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~WARNING- BIG PICTURE!

Which one looks best you guys? The only chages made were to the cam.
screenshot_dyno1.jpg


I think I like the lower right one because of the flat torque curve.

The upper right one I just threw in for shiits and giggles...Roller cams are too cool. :):bow:

Goin in an '83 K20, 465/208. 3.73's, max 35" tire.
:D
 
Last edited:
After a small lesson from 4x4High in cam specifics, and Desktop Dyno, I've found that the above screenshots aren't really accurate. I'm working on updated screenshots as we speak. :)
 
seat to seat is the worst way to look at a cam. you should be testing at .050 lift... just a note. Advertised duration is just that, its an ad campaign, .050" lift is more of a standardized way of reading a cam's duration.
 
I think I'd be looking at the lower right one as well.

After my engine build, I realized that although low end torque is great (gas engines here) you need some upper end if you like to get on it once in awhile. It's not as much fun if the engine ends up wheezing around 4000RPM.

I agree on the seat to seat, go with the .050 numbers. Where are you getting the cam numbers? Not sure what version that is, but I know DD2K had a cam "building" function where you put in a range of specs, let your computer run for a few hours, and it would spit out some cam suggestions.

Also, if using manufacturer data, don't limit yourself to just one company, comp, crane, edelbrock, whoever...in my experience one may offer a grind (or multiple) entirely different and better suited to your application than another.
 
Id go with the first one. 536 lbs at 2000rpm looks good to me. Thats where you will be spending most of your time right?
 
sled_dog said:
seat to seat is the worst way to look at a cam. you should be testing at .050 lift... just a note. Advertised duration is just that, its an ad campaign, .050" lift is more of a standardized way of reading a cam's duration.
Click to expand...

It was suggested to me to use the seat to seat specs so I could also use the IVO, IVC, EVO, EVC specs. I'm somewhat ignorant on the subject so I just went with that.

dyeager535 said:
I think I'd be looking at the lower right one as well.

After my engine build, I realized that although low end torque is great (gas engines here) you need some upper end if you like to get on it once in awhile. It's not as much fun if the engine ends up wheezing around 4000RPM.

I agree on the seat to seat, go with the .050 numbers. Where are you getting the cam numbers? Not sure what version that is, but I know DD2K had a cam "building" function where you put in a range of specs, let your computer run for a few hours, and it would spit out some cam suggestions.

Also, if using manufacturer data, don't limit yourself to just one company, comp, crane, edelbrock, whoever...in my experience one may offer a grind (or multiple) entirely different and better suited to your application than another.
Click to expand...

Cam #'s are coming from the Comp Cams website. Just went with comp cams becuase it was easy to get specs from. I'll do somemore testing tonight with other brands. And I'm with ya on needing some upper end oomph. I like to hammer down once in awhile. :D

neverendingproject said:
Id go with the first one. 536 lbs at 2000rpm looks good to me. Thats where you will be spending most of your time right?
Click to expand...

That was a roller cam I put in there just for shiits. I'd love to beable to afford it. :bow:
 
sled_dog said:
seat to seat is the worst way to look at a cam. you should be testing at .050 lift... just a note. Advertised duration is just that, its an ad campaign, .050" lift is more of a standardized way of reading a cam's duration.
Click to expand...

The only reason people use .050" spec is so they can compare cams between manufacturers because .050" has become a standard, not all cam company's give a seat to seat listing on the valve opening and closing specs. I am fairly certain that desk top dyno will only let you input the IVO, IVC, EVO, EVC if you use the seat to seat method. For this reason alone is the only reason i told him to do it that way. I agree that .050" would be a better method if it can be done on desk top dyno.
 
KidJethro said:
That was a roller cam I put in there just for shiits. I'd love to beable to afford it. :bow:
Click to expand...

If you can find the equipment, roller cams can be had fairly cheap from GM and most people that get roller cams in crate motors sell thiers on ebay. I found a roller cam for 50 bucks, and pulled the spider tray and the lifters out of a junkyard block.
 
KidJethro said:
That was a roller cam I put in there just for shiits. I'd love to beable to afford it. :bow:
Click to expand...

we've discussed it before and I think its commonly agreed, roller cam numbers are very skewed and inncorrect with desktop dyno. If you input a cam as a hydraulic cam, then switch it to roller, you gain like 50 ft lbs of torque. Yeah roller cams are nice, but not THAT nice.
 
sled_dog said:
we've discussed it before and I think its commonly agreed, roller cam numbers are very skewed and inncorrect with desktop dyno. If you input a cam as a hydraulic cam, then switch it to roller, you gain like 50 ft lbs of torque. Yeah roller cams are nice, but not THAT nice.
Click to expand...
Actually, there is more to a roller cam than meets the eye. The reason you get more torque with the same specs is only partially due to the less rolling resistance but more because of the much more aggressive opening and closing ramps of a roller cam. Go do some checking and you will find out for yourself. I'm only trying to say that the gains are real and the reason for it. :thumb:
 
4X4HIGH said:
Actually, there is more to a roller cam than meets the eye. The reason you get more torque with the same specs is only partially due to the less rolling resistance but more because of the much more aggressive opening and closing ramps of a roller cam. Go do some checking and you will find out for yourself. I'm only trying to say that the gains are real and the reason for it. :thumb:
Click to expand...

I understand all of that, I just built a roller 383, spent a good beat to keep it roller. But I don't believe for a second that its a good 50+ ft-lbs gain to go from flat tappet to roller. I would be interested in seeing two identical cams(spec wise), one roller, one non, dyno tested side by side. Should send a request or something to Chevy High Performance or GM High Tech.
 
graph.jpg


there is my engine setup(well very very close to it), in DD. Dyno one is my 383 with a LT4 Hot Cam(cam I have), but telling DD it is Hydraulic Flat Tappet lifters. Then Dyno 2 is the exact same setup(same specs on everything), except telling it that the cam is roller. You really believe that a roller setup is going to create a perfectly flat torque curve around 2k rpms that is something like 80 ft-lbs more than flat tappet?
 
How do you get mopre than one hp/tq curve going on one graph? I'd love to see them all on one screen.:D
 
sled_dog said:
graph.jpg


there is my engine setup(well very very close to it), in DD. Dyno one is my 383 with a LT4 Hot Cam(cam I have), but telling DD it is Hydraulic Flat Tappet lifters. Then Dyno 2 is the exact same setup(same specs on everything), except telling it that the cam is roller. You really believe that a roller setup is going to create a perfectly flat torque curve around 2k rpms that is something like 80 ft-lbs more than flat tappet?
Click to expand...

I absolutely do believe that a roller cam makes much more torque and HP than a flat tappet hydraulic cam does. I go over to my buddy's shop all the time that has a race engine shop with a dyno and have got to see many different engine combos ran on the dyno and YES, a roller cam does make a significant amount more torque and HP over a hydraulic cam with the same specs. Now keep in mind that the opening and closing degrees of the valves may be identical and the duration and lobe separation the same as well but a roller cam has a much more aggressive opening and closing rate than does a hydraulic flat tappet and THAT is why it makes the difference.
 
Hmm, missed the rest of this one yesterday apparently!

So seeing back to back identical cams, one hydraulic, one roller, have you seen the 20% increase in tq that DD2K shows above?

I've only known one person that used his track times to compare to what DD2K had spit out with his combo, and when he went back to flat tappet instead of roller, his DD2K numbers and track time calculated power numbers added up.

IMO 20% difference with the exact same setup is miraculous. I mean, seriously, what can you possibly swap in a normally aspirated engine that changes the torque by 20%. From TBI to Vortec heads I doubt you'd even see that sort of change.

Not trying to argue, I just find it difficult to believe roller cams are THAT much more efficient. I understand the reasons they are more efficient, I just don't see 20%. (as in the above example)
 
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