I am trying to learn a little about cams, not try to be an expert, just be a little more familiar with the concepts. So I figured that I would compare two cams, one that I have and one that I want to install.

I have this hydraulic cam installed:

@ .050 224/224 .450/.460 114/114

When I look at the specs for this cam the advertised duration is 291/287. Don't know where this is measured at, but I've read that for a hydraulic it is generally .004 or .006 off the seat. So, I plug in the advertised duration to a DCR calculator and it tells me that the "advertised" IVC is 79.5 ABDC. Now if I look at the .050 valve timing I get:

IVO -2 BTDC, IVC 46 ABDC, EVO 46 BBDC, EVC -2 ATDC

The difference between .050 and advertised is pretty big 46 vs 79.5.

Now I look at the solid cam that I want to run and it is:

@ .050 232/240 .490/.500 113/109

The advertised duration for this cam is 262/270, which is measured differently for a solid cam and for this one is at .020. I plug these numbers into the DCR calculator and it says that the "advertised" IVC is 60 ABDC. The .050 valve timing is:

IVO 7 BTDC, IVC 45 ABDC, EVO 57 BBDC, EVC 3 ATDC

The difference between .050 and advertised is not as big as the hydraulic 45 vs 60....maybe because .020 is closer to .050 than .006?


So at .050 these cams look pretty close, but the "advertised" IVC is far apart 60 vs 79.5. So I guess that means that the solid cam closes faster than the hydraulic, but can you compare them apples to apples when they are measured differently?

Also if I plug 60 IVC into a DCR calculator along with the other specs for my 383 the DCR comes out to be 8.740, but with the 79.5 from the hydraulic the DCR comes out to be 7.407. These cams don't look that far apart is there really that much difference in DCR between the two? Ugh...:confused:

OK!!

You have to run whatever advertised duration numbers you have w/ a hy-cam b/c that'a all you have to go with, imho!!

As for a solid lifter cam, I am of the opinion that it's lashed duration should be it's advertised duration b/c that's when the valves move!!

And for GM's number's they were out to lunch if you can even find advertised duration numbers b/c they used something off the wall like .001" lift at the lobe!!

This is why the great old Z-28 solid cam, the old 30-30 or -346 cam is rated at you guessed it, 346 advertised degrees duration!!

Have you read Pat Kelley's great DCR site??

http://cochise.uia.net/pkelley2/DynamicCR.html

I've read it three time's and more!!

I know it is a sim. program, but what is interesting is the trends that it's numbers will give you when you plug the results into another sim. program like D2k.......

Then input your power curve numbers into DRAG if you want to really have some fun!!

Again, just another sim. program that's still good to use to look at trends in combinations W/O buying parts!!

This stuff is a hoot to me!!

pdq67

I've read through it but it gets a little technical...maybe more technical than I want to know I guess.

The cam guy (Ultradyne) says that this solid cam should be no problem in my motor, I guess I'm just looking to get that little warm fuzzy feeling that he's right with some kind of calculator or someone's input. I just am not all that savvy about this kind of stuff, I'm trying to get in the ballpark but I don't know that I want to know every last detail. :o

I think I'll start with "the cam guy is right, it will work fine."

It's a problem trying to get repeatable results with a calculator when the numbers you punch in are referenced differently. You could run the numbers on 4 differnet hydraulic cams from the same manufacturer, and you would get meaningful info, because they all reference the same thing, are measured the same way.

Even comparing a, say comp solid to a comp hydraulic would still be pretty meaningful. While the hydraulic is spec'd at .006 and the solid at .020, remember you got .014 or so of lash to take up on the solid, so both are really spec'd at .006.

Paul is dead right tho, about the way GM ratede their cams. I think it was done by an advertising exec who didn't even know what a cam is. The stock cam in the L30 (-929) is advertised at something like 310 duration! ,050 numbers would be around 215!

To get a meaningful comparison, you'd really need to get out the degree wheel and dial indicator and run a real .006 duration.

The calculators are nice, and they are useful, but they are not 100% real, and garbage in = garbage out.

The solid cam you picked will run nice on pump gas in a 10:1 motor. It will idle fairly smooth at well under 1000 rpm and produce good vacaum.

I might be severely tempted to go another 10 degrees, and perhaps widen the LSA, particularly if the compression is closer to 11:1 than 10.

Either way, with efi, you'll be able to tune it so it runs nice.

Paul, Jim, Thanks!! :thumbsup:

This whole cam thing I just can't get my brain wrapped around. I can understand most things I guess, but cam logic just doesn't compute in my head.

So maybe one of the things killing me here is that I'm comparing a GM hyd grind (wacky advertised) to a solid???

My compression is about 10.5:1. Jim, you'd go with a .050 242/250 duration? Then I'd need a 3k stall, huh?

Jim, what numbers tell you "The solid cam you picked will run nice on pump gas in a 10:1 motor. It will idle fairly smooth at well under 1000 rpm and produce good vacaum."? Do the duration numbers tell you that? Sheesh, I feel so dumb about cams. :clonk:

The wider the lobes are separated, idle characteristics improve, meaning more vacuum is created because the valves are open together, read overlap, for less degrees of rotation - only if other characteristics of the cam design do not change.

Hypothetical example: Camshaft has the same lift & duration, and same intake centerline. Int opens at 10* BTDC, Exh closes at 10* ATDC, total overlap is 20* because lobes are ground at 114* about each lobe centerline. Now, lets shorten the LSA from 114* to 110*. Int opens at 14* BTDC, Exh closes at 14* ATDC, overlap total is 28*. Valves are staying open longer thus engine is creating less vacuum. Can't create vacuum if there is a big leak.

A book the size of Leo Tolstoy's War and Peace can be written, and probably has, about camshaft design and its effects if one item is changed over the others. Not to mention the higher the lift & longer the duration, the valve head diameter, the valve angle in the head, the piston design used, etc., etc., the valve could hit the piston head. This really sucks.

Paul, the .050 duration numbers tell you a lot about how a cam will run and idle, along with lobe sep and intake centerline.

VERY generally:
225 or less = pretty mild, just a step above stock
235 or less = compromise cam, highly recommended in most street cars
245 or less = max "street" idle getting radical, good top end power
more than 245 = getting poretty darned racy.

With 10:5 to one, and what I know about your combo, your original choice of a 232 solid is a good one. Forget the 10 degrees more!

OK,

"Overlap" = Intake and Exhaust valves both open, not creating vacuum.

"LSA" = the difference in degrees between the centerline of the intake lobe and the exhaust lobe...Like a "V" where the difference is measured in degrees across the top of the "V".

Higher LSA makes the "V" angle wider, so the valve on the left side of the "V" angle closes earlier so that there isn't as much overlap with the valve opening on the right side of the "V' angle. More vacuum and smoother idle.

Smaller LSA makes the "V" angle more narrow, creates more overlap making less vacuum and a choppier idle.


I like that little chart Jim, I'll keep that in mind....225 duration - step up from stock pretty mild , 235 duration next step up - between pretty mild and more racey. Those two ranges and below are probably where I'll stay with all of my cam choices. Below for stock restos and 230's would be about my max.


So then, the only other thing I guess is how do you "calculate" or know that the solid cam that I picked wont turn my 10.5:1 383 into a pinging/detonating mess? The DCR calculators that I've tried put the DCR pretty high, so what numbers say "Safe for pump gas"?

I have read a DCR number of 8:1 is safe for today's pump gasoline. So, you have to know the closing & opening points of the lobes to figure this, I'm sure you've read/seen it.

Wouldn't electronic solenoids in place of the camshaft & valve springs be alot easier? One could change cam by mere finger strokes of a laptop.......radicial to the mildest in seconds.

Wouldn't electronic solenoids in place of the camshaft & valve springs be alot easier? One could change cam by mere finger strokes of a laptop.......radicial to the mildest in seconds.

He, He, that would be something huh?!?!

Wouldn't electronic solenoids in place of the camshaft & valve springs be alot easier? One could change cam by mere finger strokes of a laptop.......radicial to the mildest in seconds.

I read about 3 years ago, Mercedes or some other European concern has it, sorta kinda... dual lobes or something. Mild to Wild flick of a switch.

Cat has it on diesels, I think on the injector valve only. 3406E. I'm not diesel so I'll quit there.

Fwiw, the old -929 cam is 195/202 duration at .050" lift.

And If you talked to UDHarold, and he gave you a cam spec to run, you have probably THE best cam pick going b/c he KNOW'S his stuff!!

Harold designed CC's great old 268HE for one cam, (and I don't know for sure, but I figure probably the CC Magnum line too), Lunati's new VooDoo line and his GREAT old Ultradyne cam line!! Since it was his company originally!! Where did you think the UD came from that's on the front of Harold in his handle...

Don't believe me, then just go over to Big Brother's site, (i.e., Team Chevelle) and ask the Chevelle guys what they think of Ultradyne cams!!

pdq67

Wouldn't electronic solenoids in place of the camshaft & valve springs be alot easier? One could change cam by mere finger strokes of a laptop.......radicial to the mildest in seconds.
A LONG LONG time ago, I saw a Smoky Yunick motor in a magazine that did just exactly that.

Don't know what happened to it, or why we've never seen it again. Also don't know how he made the valaves go up and down, this was long before computers, like in the '70's, man... It did run tho, and had truly variable valve timing.

Most of the new cars with variable valve timing are DOHC motors that use oil pressure to advance / retard the intake cam. BMW has had it for years, and even the inline six in my wife's trailblazer does it. Kinda weird, about 4000 rpm, the motor turns from a total dog to a screamer, and proceeds to wind itself up to 65k! Too bad it doesn't have the gearing to make it work, that 2000 rpm drop between first and second is a killer.

Paul, I'd have to check all your numbers to verify, but...

My 383 (9.7:1, 8.0:1 dcr) with a 270 adv / 224 @ 050 comp magnum cam (700 rpm idle @ 15" of vac) is happy on 89 octane, tho I usually run 93.

If I juggle the numbers to get 10.5:1 static, I get an 8.6:1 dcr (with my cam)
If I put yours in, I get 8.67:1.

If I add 10 degrees to the intake lobe, I get 8.36:1.

I'd go "up one" on your cam choice. It's still gonna be pretty mild in a 383. I've always been VERY conservative picking cams, but the one I got now isn't no where near enough.

Paul there are some things not considered in all these calculators. Ramp speeds are one of those things. For example comparing the two Chevrolet solid off road cams both are 112 cams. The second design however has slightly more lift and slightly more duration. On paper it looks to have an advantage. However if you see a graph showing the two cams ramp speeds the first design is much more agressive. It opens much more quickly and stays open longer, at least until around .100 lift where the first design cam has a steep ramp and closes quickly after that. The second design cam tapers off very gradually onto the base cirlce. So it looks good on paper, but isn't doing much for you at that point. If you ran 1.6 rockers like I do with a first design it's a better all around set up than the second design.

I don't recomend this cam unless you are trying to run high compression, short stroke, high rpm, and steep gears and you don't mind giving up low end torque. Most would not enjoy driving a car with this tyupe of camshaft. The intake closes very late, 92 ABDC @ .050. If you add in the 15 degrees the calculators want to adjust it closes at 107 degrees. This drops the SCR way, way down. My 11:1 4.155 x 3.48 SBC (377) will have a DCR of 5.2. Very soggy bottom end, but one reason the first design cam motors aren't as prone to detonation. But flat tops, small chamber aluminum heads, zero deck, 6 inch rod, .038 quench I think you can run pump gas with this cam, even with a SCR of 11:1. I've seen it work on 11:1 302 with domes so it ought to work on a FT 4.155 bore motor with the same CR.

Deleted what I wrote, was not thread related.

DCR isn't affected by ramp speed is it?
I just woke up, so maybe I'll need to delete later.
Line me out please

DCR isn't affected by ramp speed is it?No, DCR is a calculated ratio. Ramp speed has nothing to do with the calculation.

My 383 (9.7:1, 8.0:1 dcr) with a 270 adv / 224 @ 050 comp magnum cam (700 rpm idle @ 15" of vac) is happy on 89 octane, tho I usually run 93.

If I juggle the numbers to get 10.5:1 static, I get an 8.6:1 dcr (with my cam)
If I put yours in, I get 8.67:1.

If I add 10 degrees to the intake lobe, I get 8.36:1.

I'd go "up one" on your cam choice. It's still gonna be pretty mild in a 383. I've always been VERY conservative picking cams, but the one I got now isn't no where near enough.

Ya, this is EXACTLY my issue. I wan to run around a 230/240 on a 112 as that just feels like the "right" size as I am conservative, but the DCR calculator says PING CITY! Unless someone has some other input as to why the calculated DCR of 8.67 would work in my combo I'm going to have to go with the next size bigger for peace of mind:

@ .050 242/248 .482/.504 114/110 Advertised 274/282

http://www.crower.com/misc/cam_spec/cam_finder.php?part_num=00321&x=19&y=7

This comes in around 8.2 DCR which is a more comfortable number.

Or, have you ran it through D2k installed straight up??

112/112...................

I know the old -962 cam was like 115/114 or something like that! As well as the old 30-30 cam is 114/112.

And the newer LS- cams are like 117/115.5 or so...............

pdq67

uh oh... getting complicated again.

PAul's right, running the first cam straight up (4 degrees retarded) WOULD put the dcr right where it should be. Dunno what else it would do...

I do like the last one you linked tho.

GM 962
@ .050 224/224 .450/.460 114/114

**DCR 8.0

@ .050 230/236 .458/.468 112/112 (4 degrees retarded) Advertised 264/270
http://www.crower.com/misc/cam_spec/...00320&x=19&y=7

**DCR 8.4

@ .050 242/248 .482/.504 114/110 Advertised 274/282
http://www.crower.com/misc/cam_spec/...00321&x=19&y=7

**DCR 8.2

DD2k Comparisson with a Single Plane 900 CFM:
**I know my engine isn't making these kind of numbers but this will compare the cams using the same parameters.**

GM 962
2000--138--363
2500--181--379
3000--227--397
3500--280--421
4000--333--437
4500--380--444
5000--414--434
5500--419--400

Crower 00320
2000--151--397
2500--198--415
3000--249--435
3500--304--456
4000--358--470
4500--404--472
5000--436--458
5500--444--424

Crower 00321
2000--141--371
2500--187--393
3000--237--415
3500--295--442
4000--353--463
4500--405--473
5000--442--465
5500--455--435

oh boy...

I like your numbers on the lil crower. 8.4 DCR with EFI is do-able. Be sure to smooth every edge in your chambers and piston tops, and then smooth em and polish em. It won't ping.

What did DD say abpout the difference in that cam between "normal" and "straight up"?

I would NEVER trade 25 ft-lbs at 2000 rpm for 10 HP at 5500.

Crower 00320 Advanced 4 degrees
2000--153--403
2500--202--425
3000--255--446
3500--310--465
4000--361--473
4500--403--471
5000--428--450
5500--422--403

Jim, I don't need another 25 lbs of TQ at 2000, LOL!! Even with the 962 cam, off the line it melts the tires.

What I see that makes me happy is the comparison at 2000:

GM 962
2000--138--363

Crower 00321
2000--141--371

That means (if DD2K has any accuracy at all) that the 00321 cam should "feel" about the same off the line.

Tire melting is a good thing, hehe

Tire melting is a good thing, hehe

Especially with the wife in the car!! She gets all nervous and squeely...and about loses it when the car starts to drift sideways, LOL!!!! :D :D :D

Your wife will ride on your Camaro!

Guys my post wasn't meant to say that DCR is positively effected by ramp speeds. But I'm questioning how accurate they may really be when there is no consideration for how slowly a valve actually comes off the seat, or if it matters, maybe it doesn't. I find it odd that the calculators will ask for your intake closing point with no regards as to how agressive the ramp is. The second design off road cam is off the base for 35 degrees before it gets to .050 valve lift, same on the intake closing side. The first design only takes in about 15 degrees. I don't know how much effect it will have on the calculators, but it seems to me that a valve that opens or closes very, very slowly while just barely off it's seat will effect DCR differently than one that opens and closes quickly. The calculators just see this as being open even though it is literally off it's seat by only .010" for 10 or 15 degrees. Does that have the same effect as a ramp that opens .050" in the first 15 degrees? I don't know. You can argue that it is open longer with no regards to how far it is open, but my question is how much effect does it really have while on those very lazy ramps? But the DCR calculators don't seem to care, so maybe it doesn't matter. Or maybe this is the wrong thread for this discussion. Just trying to look at things from a different perspective and get evereyones input.

Think of it this way and tell me if I'm wrong. If two cams have the same timing of events (opening and closing points) but with vastly different ramps, one closing very quickly and the other taking 40 degrees to close the final .010" are we saying that the same amount of compression will be bled off the engine regardless of which cam is installed? I know you can move a lot more air through a large opening than a very, very small opening. The velocity and pressure are effected, but at some point the small opening won't be able to bleed off as much compression as a valve opened further using a quicker ramp? The calculators don't take this into consideration so maybe it isn't important, or maybe I'm just thinking about it too hard with the wrong side of my brain.

Dave I didn't mean to ignore your post, but as you can see from what I've posted about cams, valve timing, DCR, etc this stuff is not really my strong suit. Maybe somone else with more knowledge can give you some input.

I will agree though and say that DCR is not the final answer, just a gauge to get you in the ballpark. It's in the actual application that the final tolerances will be determined.

Paul I'm with you, there are a lot of variables to consider. I use the DCR calculator a lot lately myself while selecting my pistons for the new motor.

I'm just starting to read so much on the cam timing and events and it got me looking at GM cam graphs. I just noticed the vast difference in how quickly some of the cams come off and rejoin the base circle compared to others. That has me wondering how much effect some of the lazy ramp cams really have for those 30 or 40 degrees that the valve isn't quite closed at the closing of the intake compared to one that closes quickly. And how much the numbers really mean. To the DCR calculator it doesn't seem to care if the valve is taking 40 or 50 degrees to close the final .010" or if it does it in 10 degrees. To me it stands that not much is really happening on the lazy ramp cam at the end of the intake closing, but the DCR treats it just like a quick closing intake valve cam grind.

Guess I'm just wondering if the numbers can be skewed (spelling?) by a very lazy ramp. It would look like it's bleeding off a lot of compression, but if just barely off the seat how much is really being lost? Maybe I'm thinking way too hard about this.

I didn't mean to hijack your original thread you posted. Just had this idea in my head and wondered what everyone else thought about it or if it matters when looking at DCR.

OK...

Crower 00321
@ .050 242/248 .482/.504 114/110 Advertised 274/282 DCR 8.2

Comp Magnum 282S
@ .050 236/236 .495/.495 110/106 Advertised 282/282 DCR 8.2

Very similar advertised numbers, the comp cam is on a 110 though. DD2K numbers for the 282S are very similar to the crower 00320 but with a lower DCR. Thoughts?

lmao.... throwing another cam into the mix?

The 282s is an old school hot rod cam. A (big) magnum hydraulic on steroids. Everyone who has one loves them. You for sure know there is a CAMSHAFT thumping under that hood.

Not sure that's what you are looking for.

lmao.... throwing another cam into the mix?

The 282s is an old school hot rod cam. A (big) magnum hydraulic on steroids. Everyone who has one loves them. You for sure know there is a CAMSHAFT thumping under that hood.

Not sure that's what you are looking for.

It doesn't seem that big of a solid, it actually looks smaller than the crower. The 110 makes it lumpier I'm sure though....

You know, since the advertised numbers are so close I'm wondering if in reality these cams would be about the same. The .050 numbers are all I have to plug into DD2k so it can't tell the difference if they really close at very nearly the same point.

Check the DCR on both at lash!!

I bet lashed the Crower grows and the CC shrinks. In other words, I bet their advertised duration numbers become closer together.

And IF NOT then 274-242= 32! Vs 282-236= 46! Intensity numbers so the old CC will be easier on the valvetrain, imho...

pdq67

Makes sense Paul, I don't know where I'd get those numbers though.

Paul's hit it. That comp is an old school hot rod grind, where the crower is more modern and refined. I haven't heard the crower, but a car with a 282s sounds RADICAL. Again tho, the people who have them love them.

Ya, my buddy would just laugh if I installed a 110. 110 would be choppy I'm sure as the 114 would calm down a bit.