Don't understand cams

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Cudafever said:
Thanks again RRR for the links.........but as alway, reading and learning, cause desire for even more understanding.
Ok here is my question. It has to do with overlap. I had this all figured out long ago but, NO.

My 340 had a MPP cam .474/280* cam with a 60* of overlap. My new cam to match my new 408 motor has a Hyd Roller Cam that is much larger.562/.550 lift 243/247 duration @.050". Gross(@.006") duration of 294/297)
So this cam by Comp, does not have a Overlap spec but by using the cam card i see that the intake close and exhaust open spec's it can be figured out. or so i though...........
so Intake opens at 19* btdc and exh close at 13 atdc. so my math says that i only have 32* of overlap. Now these ## are a @.050"
I realise that i'm comparing apples to oranges here but, that is only half of the overlap, of my smaller cam.
Now i'm sure that they differ because of the gross and @.050" But over 30+ degrees.....less???
Click to expand...
I don't get it.
Overlap = the two durations averaged and subtract double the LDA
You didn't give the LDA but if I assume 106*, the formula looks like this;
(294 + 297)/2 less (106 x 2)= 295.5 less 212 = 83.5

If the LDA was a 110* it would look like this;
(294 + 297)/2 less (110 x 2) = 295.5 less 220 =75.5

If the LDA was 114* it would look like this;
(294 + 297)/2 less (114 x 2) = 295.5 less 228 =67.5
These are quite different cams with very different idles, for sure.And the ICAs are 4* apart depending on install,therefore different compression requirements for street use, and probably will want different TCs and maybe gears.
To make an 8.0Dcr and about 162psi,in a 408, the Static CRs would need to be 11.5,11.1,10.7, or about .4 point change in SCR for each change in listed LDAs.
EDIT; ICA is Intake Closing Angle, LDA is Lobe Displacement Angle,Dcr is Dynamic compression ratio, Scr is Static compression ratio
 
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AJ/FormS said:
I don't get it.
Overlap = the two durations averaged and subtract double the LDA
You didn't give the LDA but if I assume 106*, the formula looks like this;
(294 + 297)/2 less (106 x 2)= 295.5 less 212 = 83.5

If the LDA was a 110* it would look like this;
(294 + 297)/2 less (110 x 2) = 295.5 less 220 =75.5

If the LDA was 114* it would look like this;
(294 + 297)/2 less (114 x 2) = 295.5 less 228 =67.5
These are quite different cams with very different idles, for sure.And the ICAs are 4* apart depending on install,therefore different compression requirements for street use, and probably will want different TCs and maybe gears.
To make an 8.0Dcr and about 162psi,in a 408, the Static CRs would need to be 11.5,11.1,10.7, or about .4 point change in SCR for each change in listed LDAs.
Click to expand...

Thanks Aj, will studying this a bit before commenting. Yes it is 106 LSA and 12.8 compression.
I'm assuming that" IDA" is the same as lsa(lobe separation angle)
 
I would say that 83.5 overlap is vary close. 58 more cubes, 4 more points of compression than before,... and it lopes harder than before.(overlap raised from 60 to 83.5) Had to do some tweaking to get it to idle below 1000 rpm with my little old 600 carb. My 850 it lined right out!(already had holes drilled in butterflies.)
Thanks for the MATH HELP Guys!!!
 
post edited to be American friendly

Some cams are measured from .008,to make the advertised numbers;like Hughes. This makes their "small cams" behave like bigger cams. This is no big deal if you know about it, but there can be several degrees between .008 and .006 where other (most) manufacturers may have measured theirs. So it is possible for a Hughes cam to perform like the next bigger non-Hughes cam, and they love to mention this.On the flip side, it is possible, when buying a Hughes cam to buy one that is one or maybe 1.5 sizes smaller and not loose performance. So it's in the details. The .050 specs may be very similar, and really that's what counts. However, since compression cannot start until the intake is closed,you may experience idle changes when switching from one manufacturer to another because of the advertised figure differences.
IMO this is an unfair practice,on account of a Hughes 262* cam measured at .008, may be closer to another manufacturer's 268* cam measured at .006. So are you getting more cam for your dollar? or are you getting more cam than you wanted? And is it gonna upset you after it's installed and you have a lil more trouble tuning it than you expected?
And there is one other thing. A Hughes cam measured at .008 will appear to have a faster rate of lift from advertised to .050,than another manufacturers that is measured from .006 to .050,. And this kindof tics me.
 
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norton said:
Please don't make assumptions. As far as I'm concerned, my question wasn't vague at all. I have nothing to contribute, because I'm more lost now then when I asked for the advice in the first place. Because I know nothing about cams I asked a simple question. Would the cam that I have work in a stock engine, Hell I, even posted a picture of the specs. if not what should I look for that either stock or close to it. But like most threads here, things started going south real fast. I do thank those of you that took the time to steer me in the direction, that I wanted to go. For the rest of you, keep the pissing match up, I'm not learning anything but it's good entertainment just the same. But don't expect me to contribute to something that I know nothing about.
Click to expand...
Agreed, you needed yes or no, a definite NO for that. The easy advice is your stk. valvetrain is ok into the 280's of duration w/o any problem. You only need to make sure your
valve spring retainer to guide clearance is sufficient incl. room for whatever seals you're using,& that the springs are appropriate for the cam. That's the shortest ans. I got 4 Ya.
 
AJ/FormS said:
post edited to be American friendly
Click to expand...
Feel free to rag on me any time AJ LOL. All in fun.... Some clues fer ya: red neck, Appalachian, those round things on the car are 'tars'..... should be plenty of fodder there LOL
AJ/FormS said:
And there is one other thing. A Hughes cam measured at .008 will appear to have a faster rate of lift from advertised to .050,than another manufacturers that is measured from .006 to .050,. And this kindof tics me.
Click to expand...
Yes I have noticed this; makes it look fast on the ramps, or behave like a 'bigger' cam, like you say. On the other hand, some Cranes have advertised duration spec'd at .004" so the ramps look long, and you may get less .050" duration if you go by advertised only. And some of their lobe profiles for solids are measured at something much larger....like .010" or more IIRC.

You gotta look at it all.
 
Hyup, the devil is in the details.
As to the invisible line, YR, from your side it might be that, but from my side, they are making it harder and harder for us to crossover, so I just stay home.And as for taste in beer, I like yours just fine. I can drink it all day long and not stagger to bed.........
And as to ribbing me,everybody, bring it on. I like your southern humor too.
And if I preach an error, call me on it. Like right away before somebody suffers for it. Some of you fellows are possibly a little gentle. And I like that too. But sometimes the innuendo is a little vague, and it's hard to tell who it was directed at. If I'm wrong about something I'd like to know.I'm not too old or too smart or too thin skinned to respond to correction.I'm just an old guy. Soon I will forget all that I have learned, and one day the spark will go out, and they will bury a worthless decrepit old carcass. I'd like to think I helped someone somewhere sometime, before that day comes. Peace, out.
 
Ok so here is some of the more valuable post from the OP!
norton said:
Is this cam good to use in a 72- 340 with factory style rockers, lifters and push rods ?
Also, will this make my engine have a real lumpy idle ?
Sorry for a stupid question, but I've never understood camshaft, lifts and durations.
What would factory specs be for a 1972- 340 engine?View attachment 1714985708
Click to expand...

norton said:
My car right now has a 340 out of a 1970,that is 30 over, with a street thumper cam, J heads with 2.02 intake and 1.94 exhaust valves, an RPM, Dual plane intake and a 600 Holley. The trans is a 727, with a B&M 2800 Stall torque and a reverse valve body. The limited slip rear has 355s.
I bought the numbers matching 340 engine and would like to rebuild it to stock, install it back in the car, but not change anything else. This why I'm trying to match a cam to stock specs.
Click to expand...

norton said:
I really like the car the way that I, have it now, plenty of get up and go. However I want to drive it across Canada and back next year, about 6000-7000 kms or about 4500-5000 miles. Right now I'm getting 6 miles to a US. gallon. So build a factory spec engine and hopefully get 14-15 miles to a US. gallon.
Click to expand...
So first let's lay out what OP Has and Wants!
Stock 72 340 eng(low compression) stock except for over bore and cam.
Quote:My car right now has a 340 out of a 1970,that is 30 over, with a Street thumper cam, J heads with 2.02 intake and 1.94 exhaust valves, an RPM, Dual plane intake and a 600 Holley. The trans is a 727, with a B&M 2800 Stall torque and a reverse valve body. The limited slip rear has 355s.
That took over 90 post to get out of you. Sooo compression is around 8.8-9.4 depending on what piston are in there.

Now you can't have you cake and eat it too. (a GV would help! $$$$) but here i go!

Fuel economy. The mother F'ing cam (street thumper cam) is just a pretend cam and does nothing for fuel economy.(pretends to be a big cam but don't get the milage of a smaller cam that it is!) Get a cam that idles smooth as glass(talk to a cam company) get rid of the 3.55s for 2.76s and i would keep the converter, but a tighter one would help milage.

Power............ You said, you like the power you have but needs more than 6 mile to the gal
keep converter, keep gears buy a "torque cam" (Talk to cam manufacture)
And then you will need to learn how to" tune it" to get the gas milage. I say this because the combo that you have, "tuned", would get better milage then 6 mpg!!!!

Fuel Economy cam..... 10200700LK


Power cam............... 10200701LK

If you hadn't put the long trip, with the milage i would have recommended this cam. but it would have required a valve spring change and spring retainer to guide checked/clearanced......at this point you might as well put guides, valves, exc. Aks rebuild the cyl head!($$$)
Most power for you combo in my opinion.
Power +.................... 10200703LK


O, and i'm sure you're exhaust valve is not a 1.94(translation, it's 1.60 exh valve)

HERE IS THE LINK SO YOU CAN READ UP ON THE SPEC'S OF EACH CAM, THE SAME WAY AS I HAVE.

Voodoo - Hydraulic Flat Tappet - Lunati Power
 
Cudafever said:
So first let's lay out what OP Has and Wants!
Stock 72 340 eng(low compression) stock except for over bore and cam.
Quote:My car right now has a 340 out of a 1970,that is 30 over, with a Street thumper cam, J heads with 2.02 intake and 1.94 exhaust valves, an RPM, Dual plane intake and a 600 Holley. The trans is a 727, with a B&M 2800 Stall torque and a reverse valve body. The limited slip rear has 355s.
That took over 90 post to get out of you. Sooo compression is around 8.8-9.4 depending on what piston are in there.

Now you can't have you cake and eat it too. (a GV would help! $$$$) but here i go!

Fuel economy. The mother F'ing cam (street thumper cam) is just a pretend cam and does nothing for fuel economy.(pretends to be a big cam but don't get the milage of a smaller cam that it is!) Get a cam that idles smooth as glass(talk to a cam company) get rid of the 3.55s for 2.76s and i would keep the converter, but a tighter one would help milage.

Power............ You said, you like the power you have but needs more than 6 mile to the gal
keep converter, keep gears buy a "torque cam" (Talk to cam manufacture)
And then you will need to learn how to" tune it" to get the gas milage. I say this because the combo that you have, "tuned", would get better milage then 6 mpg!!!!
Click to expand...

Obviously I, didn't make myself very clear or you just read what you felt like reading.
I want to build a completely stock 1972-340 Engine, and asked about putting the cam in my 1st post in it.
Now I didn't go back and check which post that I put the other information in.
BUT, That information was just to say what's in the car now ( I no longer want) as apposed to what I want to put in it.
 
If all you wanted was a stock cam you would NOT have posted the cam spec in your first post!

Like i have said before, YOU CAN LEAD A HORSE TO WATER, BUT CAN'T MAKE HIM DRINK!!!!

Ok i digress. If you think i misrepresented you. then by all means, explain what you would like out of the build of this eng...................... when you rebuild the motor........what do you expect out of it...................
 
Cudafever said:
If all you wanted was a stock cam you would NOT have posted the cam spec in your first post!

Like i have said before, YOU CAN LEAD A HORSE TO WATER, BUT CAN'T MAKE HIM DRINK!!!!

Ok i digress. If you think i misrepresented you. then by all means, explain what you would like out of the build of this eng...................... when you rebuild the motor........what do you expect out of it...................
Click to expand...

All I wanted was a stock cam, I posted the picture of the specs of a cam that someone was trying to sell me. And as the title says, I DON'T UNDERSTAND CAMS, meaning I know diddley squat about them. For all I know or knew , that cam could have been stock or it could have been for a rocket ship.
This is a good reason that more people don't ask questions on these forms.
BECAUSE, ALL OF THE KNOW IT ALLS HERE, TREAT THEM STUPID.
I'm done with this thread.

RRR, said it not anyone's job here to teach me about cams and I get that. I should learn this from reading literature and hope in the end that I understand what I'm reading. After all the knowledge that all you guys claim to know Should go to your Graves with you.
 
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norton said:
All I wanted was a stock cam, I posted the picture of the specs of a cam that someone was trying to sell me. And as the title says, I DON'T UNDERSTAND CAMS, meaning I know diddley squat about them. For all I know or knew , that cam could have been stock or it could have been for a rocket ship.
This is a good reason that more people don't ask questions on these forms.
BECAUSE, ALL OF THE KNOW IT ALLS HERE, TREAT THEM STUPID.
I'm done with this thread.

RRR, said it not anyone's job here to teach me about cams and I get that. I should learn this from reading literature and hope in the end that I understand what I'm reading. After all the knowledge that all you guys claim to know Should go to your Graves with you.
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No ****?? You were treated stupid? WTF is wrong with you? While I don't agree with some of what was posted in this thread, you got some damn good advice, FOR FREE. You ain't paying me **** for nothing.

It was posted early on that was not the cam for YOU. Some of us went onto discuss WHY, because maybe, just MAYBE, someone will come along and actually READ what was posted and LEARN something. It's not our job to educate you. It's taken me decades to learn what I know, and I paid an assload to learn what I know.


RRR posted 3 (THREE) exellent, easy to read and understand links. I know. I read them all. Education, specifically self education, is time consuming. It takes a lifetime. And it's expensive. Whether others agree with me or not, I hope to save someone time, money, grief and parts. I believe that every single guy who posted in THIS thread had the exact same goal in mind, regardless if we all agree.



It pisses me off to no end when someone is ungrateful when you are given information that costs MONEY to learn for free. YOU have to do the WORK. YOU have to do the THINKING. YOU have to do the LEARNING.


Don't get pissy with us, because you won't or can't learn.

You have been give a bunch of free information. Instead of bitching about your feelings getting hurt, throwing a temper tantrum and acting the ***, read and learn.

Later dude.
 
yellow rose said:
No ****?? You were treated stupid? WTF is wrong with you? While I don't agree with some of what was posted in this thread, you got some damn good advice, FOR FREE. You ain't paying me **** for nothing.
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So tell me, who's advice was good yours or the person you claim was wrong. DUDE
I'm sorry that I wasted your time, asking for free advice, but if you don't want to share what you had to pay for, then why bother responding. I guess its like my poor old deceased Daddy used to say,
Advice is only as good as you pay for it.
 
Norton, I didn't say that trying to be an ***. I said that because there are so many different opinions on camshafts. It's a pandora's box. All I meant was, read the info for yourself and create your own, educated opinion. That's all.

norton said:
All I wanted was a stock cam, I posted the picture of the specs of a cam that someone was trying to sell me. And as the title says, I DON'T UNDERSTAND CAMS, meaning I know diddley squat about them. For all I know or knew , that cam could have been stock or it could have been for a rocket ship.
This is a good reason that more people don't ask questions on these forms.
BECAUSE, ALL OF THE KNOW IT ALLS HERE, TREAT THEM STUPID.
I'm done with this thread.

RRR, said it not anyone's job here to teach me about cams and I get that. I should learn this from reading literature and hope in the end that I understand what I'm reading. After all the knowledge that all you guys claim to know Should go to your Graves with you.
Click to expand...
 
norton said:
So tell me, who's advice was good yours or the person you claim was wrong. DUDE
I'm sorry that I wasted your time, asking for free advice, but if you don't want to share what you had to pay for, then why bother responding. I guess its like my poor old deceased Daddy used to say,
Advice is only as good as you pay for it.
Click to expand...

Because while we can throw you a fish, it would be more beneficial to you if we showed you how to learn to fish instead.
 
Wow, really, you think that all of us have just been PIssINg in your cheerios WOW!!!
Like i said before
"YOU CAN LEAD A HORSE TO WATER, BUT CAN'T MAKE HIM DRINK!!!!"
 
norton said:
So tell me, who's advice was good yours or the person you claim was wrong. DUDE
I'm sorry that I wasted your time, asking for free advice, but if you don't want to share what you had to pay for, then why bother responding. I guess its like my poor old deceased Daddy used to say,
Advice is only as good as you pay for it.
Click to expand...

And appinions are like *** holes, EVERY BODY HAS ONE...............I guess you had better NOT call a cam manufacture either. THERE GIVING FREE ADVICE AS WELL!!!! :BangHead:
 
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