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  #1  
Old 03-05-2009, 11:20 AM
racerdave racerdave is offline
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Default which Cam? 440/4x4

Howdy folks, I am the new proud owner of a 1970 3/4 ton 4x4 440/727/HD44/Dana 60. I bought this truck to play with here in the desert. I plan on Bobbing the bed very short and adding lockers and 38" tires. My question is this-I want a "rumpy" cam that works good on the bottom. This truck will not see the hiway, I want it to idle rumpy and have a strong pull to about 4500-5000 rpm. Does any one have an opinion on what cam make or profile I sure look for?
Thanks in advance.
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  #2  
Old 03-06-2009, 09:34 AM
rampage_82 rampage_82 is offline
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well if the idle is the only thing you're looking for, you might look into one of the comp thumpr series... I have run the Lunati Bracket Master II cam, it had a thumpy idle, but it still pulled ok down low, however that was on a 440 with 11 to 1 compression, don't think it would have done so well on low compression... that's just my .02

Sounds like a neat truck.. I have a 1988 Ramcharger with a 440, 4sp, 205, Dana 60's, and 37x12.50x16.5 Hummer tires. It is a blast.. In my profile pic, you see my D50 with a 440, and I'm just starting on my wife's truck.. a 1984 W150 shortbed, I'm in the process of putting a 383, 727, np208, Dana 44 front, Ford 9" rear, 6" lift and 38x12.50x15 TSL's on/in it, I think it will make a fun little truck. Especially when I get the money to build the real engine for it.... hehehe
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  #3  
Old 03-06-2009, 11:16 AM
racerdave racerdave is offline
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Thanks Rampage. Yea, I'm looking forward to playing with it. I have a neat 82 bodied Ramcharger that is a Walker Evans clone, its got long travel suspension and a 360 small block. I got this 70 truck because it was a good deal and I got all the godies= good running big block, 8 lugs, 205, and that "classic" old school look for not much money. Hell the 205/ Dana 60 is worth what I paid for the whole truck! I need to build a truck that can go out and recover all my buddies broken Blazers!! This truck is a long bed so i plan on bobbing the frame and the bed. I have already mounted the swampers on it and it looks mean, its painted that 70 forest green sso she's called "mean green". I want a cam to make her sound like she looks! I have heard of the "thumper" series, is it the overlap that makes it rumble or is it duration?
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  #4  
Old 03-06-2009, 03:37 PM
Cudafever Cudafever is offline
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I would say both! more duration, usually creates more over lap.......

The longer the ext. valve stays open while the intake is opening( over lap) for the next syl..............the more previous burnt gasses travel backward into the piston and even past the intake valve and into the intake runners.

yeah over lap is the key when searching for a lumpy cam.
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  #5  
Old 03-06-2009, 05:09 PM
DonCarr DonCarr is offline
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Best cam would likely be a custom ground hydraulic roller $$$

Here's a link to something similar to a Thumper cam, talks about low compression.

http://www.hughesengines.com/Index/p...4&partid=25116
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  #6  
Old 03-06-2009, 06:27 PM
Cudafever Cudafever is offline
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http://www.hughesengines.com/Index/p...4&partid=25116

All I can say is, WOW!!!!!!!!

It's possible due to this cam making a much better DCR(Dynamic Compression Ratio)...........But WOW!!!!


It seams to dis prove my statement i made above as well...........Over lap is only 24.5*..........Thats way Way small
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  #7  
Old 03-06-2009, 09:04 PM
crisser crisser is offline
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Quote:
Originally Posted by Cudafever View Post
http://www.hughesengines.com/Index/p...4&partid=25116





It seams to dis prove my statement i made above as well...........Over lap is only 24.5*..........Thats way Way small

Those figures are at 050. Need to get the figures at 006.
That big engine wouldn`t want to run at any kind of speed with 25 degrees of total overlap.
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  #8  
Old 03-07-2009, 05:17 PM
Cudafever Cudafever is offline
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I have been doing a little bit more digging of info and comparisons of that cam with others....................to old saying,:You can have you cake and eat it Two".....

racerdave, With that Cam, I thing you can!!!!!!!

DonCarr, Thank for the link
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  #9  
Old 03-07-2009, 05:44 PM
valiant64 valiant64 is offline
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...Maybe something like the Isky .280 (.232 @ .050) .485 & 108 deg. lobe center Megacam. Needs 9.5 to 10.5:1 compression. Lotsa other choices, but I've used this cam in a C-body with a 383, and torque wasn't lacking w/ 2500 stall & 3.91 gears, plus it had a nice lopey idle & still had enough vacuum for power brakes & the a.c. still worked fine as well.
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  #10  
Old 03-08-2009, 11:05 AM
rampage_82 rampage_82 is offline
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I used that Isky 280 Megacam as well in a 383, It ran extremely hard, however was a little soggy on the bottom, however it might be perfect in a 440.
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  #11  
Old 03-11-2009, 11:13 AM
Dr. Righteous Dr. Righteous is offline
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Quote:
Originally Posted by racerdave View Post
Howdy folks, I am the new proud owner of a 1970 3/4 ton 4x4 440/727/HD44/Dana 60. I bought this truck to play with here in the desert. I plan on Bobbing the bed very short and adding lockers and 38" tires. My question is this-I want a "rumpy" cam that works good on the bottom. This truck will not see the hiway, I want it to idle rumpy and have a strong pull to about 4500-5000 rpm. Does any one have an opinion on what cam make or profile I sure look for?
Thanks in advance.
Hmm, considering the vehicle the selection of a high overlap (rumpty idle) cam seems to be a mis-match unless what you are building is a pure race vehicle (sand drags, mud bogging) and not a 4x4 that will see trail duty, where the most importance is off idle, low RPM torque and not full throttle blasts.

Consider the vehicle. A HEAVY 3/4 ton truck with LARGE tires. A large overlap cam bleeds off compression at low RPM. This is the OPPOSITE of what you need in this vehicle. There are plenty of 4x4 and "RV" cams available that would seem better suited for your application unless you are truly building a off road race vehicle.
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  #12  
Old 03-11-2009, 12:32 PM
Cudafever Cudafever is offline
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Quote:
Originally Posted by Dr. Righteous View Post
Hmm, considering the vehicle the selection of a high overlap (rumpty idle) cam seems to be a mis-match unless what you are building is a pure race vehicle (sand drags, mud bogging) and not a 4x4 that will see trail duty, where the most importance is off idle, low RPM torque and not full throttle blasts.

Consider the vehicle. A HEAVY 3/4 ton truck with LARGE tires. A large overlap cam bleeds off compression at low RPM. This is the OPPOSITE of what you need in this vehicle. There are plenty of 4x4 and "RV" cams available that would seem better suited for your application unless you are truly building a off road race vehicle.

Al tho i completely agree that the best bottom end cam is a smooth idling cam. And a top end (rpm) cam will inherently have rumpty idle...................

You should go check out them cam spec's
http://www.hughesengines.com/Index/p...4&partid=25116
Basically they closed the intake valve sooner(Better D.C.R.) then left the exh valve open longer(Has lumpity idle, do to still having a good amount of overlap) Basically you loose a little bottom end, loose a little top end............and have a torque curve you can lay a shoe string on.

Not the best of either end of the scale..............but better then wanting a rumty idle and hating the every thing else bought the cam(To Big)
Which most of us have done and lost performance
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  #13  
Old 03-11-2009, 12:47 PM
DonCarr DonCarr is offline
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Narrow lobe separations (high overlaps) increase the cranking compression while dropping vacuum. So the power at idle is good, it's just very shaky. Likely why it's recommended for mismatched compression ratios, ie too low a compression for given cam lobe, like in this trucks case.

One needs to look at how much the exhaust valve is open at the bottom of the stroke (BDC- while the intake stroke is occurring)) - ie a 3.31 inch stroke may only compress for 3 inches due to open exhaust valve. The tighter lobe separation may compress for 3.1 inches (say).

Seems backwards, but there are bigger low rpm gains for tight lobe separations due to the bottom of the stroke, than losses at the top due to overlap. See lobe lift duration chart, like the letter m. Increasing overlap at the middle of the 'm' brings the sides of the 'm' in. Look where they cross BDC.

These rat-a-tat-tat cams make more low end power, sounds backwards but that's what the article says. I'm trying to figure this out too.

High intensity roller cams etc make the best of both worlds.

http://www.popularhotrodding.com/tec.../photo_04.html

http://www.popularhotrodding.com/tec.../photo_06.html

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  #14  
Old 03-11-2009, 01:58 PM
Dr. Righteous Dr. Righteous is offline
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Quote:
Originally Posted by DonCarr View Post
Narrow lobe separations (high overlaps) increase the cranking compression while dropping vacuum. So the power at idle is good, it's just very shaky. Likely why it's recommended for mismatched compression ratios, ie too low a compression for given cam lobe, like in this trucks case.
I don't agree. This is contrary to everything I have read and to my personal experience.
High overlap cams DECREASE compression at low RPM because of the "overlap" of both valves being open at the same time. The only increase in compression is seen dynamically because of the scavenging effect that overlap can produce. At low RPM the exhaust gas velocity is insufficient to take advantage of it.
This is why a "race cam" in a smogger low compression engine will KILL torque. Also the drop in vacuum is because of the drop in engine efficiency at low RPM. For a high over lap cam to really work you need an increase in the static compression ratio of the engine. Because the fact that low end efficiency are lost, more static compression can compensate.
The combination is dialed-in with the timing advance curve for max power.

Quote:
Originally Posted by DonCarr View Post

One needs to look at how much the exhaust valve is open at the bottom of the stroke (BDC- while the intake stroke is occurring)) - ie a 3.31 inch stroke may only compress for 3 inches due to open exhaust valve. The tighter lobe separation may compress for 3.1 inches (say).

Seems backwards, but there are bigger low rpm gains for tight lobe separations due to the bottom of the stroke, than losses at the top due to overlap. See lobe lift duration chart, like the letter m. Increasing overlap at the middle of the 'm' brings the sides of the 'm' in. Look where they cross BDC.
The power is in the right combination of parts and mods. The more cubes, the more torque an engine will make with a high overlap cam.
The single biggest boon to cam selection is the "mainstreaming" of roller cams.
A roller cam engine from the factory (Magnum) opens up a would of power making cam profiles that a flat tappet engine will need big money invested in valvetain mods to run.
Unless he is planning on investing in a roller cam setup for his 440, I would discourage a "rumpty rumpty" cam for a 4x4 truck. I'm not saying it is stupid, but like I said, unless he is building something for sand drags, or hill climbing, a cam that yields the best torque at low RPM is what you want in a 4x4.
Off road trail riding requires finesse and light throttle to ease through situations. High RPM blasts ending up breaking parts (or otherwise wrecking) your rig.
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  #15  
Old 03-11-2009, 02:27 PM
DonCarr DonCarr is offline
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Trying to visualize how camshafts work gives me a headache, but I'm trying to visualize whats' going on. The above info is what I grasp from articles I've read. I still don't quite "get it"

David Vizard speaks on lobe separation too. Looks like his diagrams in the popular hotrodding article. Vizard claims few people understand cam selection. He says most people throw torque away for the idle and vacuum benefits of a wide lobe center. A 350 likes about 108 degrees, however many cams are in the 112 degree territory. (but then the 112 cam may tolerate an extra 10 points of compression). Delicate tradeoffs.

Rough idle is from charge dilution, not a decrease in cranking compression. Some people use special valve seat preparations and heart shaped combustion chambers to reduce charge dilutions (@ overlap). This improves idle quality.

My personal opinion is that it's likely best to pay a few extra bucks to a company like Hughes to pick the cam. They know what's going on - but of course will lead people to their high intensity profiles which may not be the best (cheapest) choice.



ps; that popular hotrodding article is by Vizard. http://www.popularhotrodding.com/tec...ics/index.html
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  #16  
Old 03-11-2009, 03:06 PM
Cudafever Cudafever is offline
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I'm no Cam expert, Sorry if i sound like i am one


Basically we are taking about two different events happening here.

The first event is on the exh stroke were the timing of the int "Opening", and the exh Closing give us are over-lap 40* 60 *80* exc........The hire the number the more exh gasses back up and re enter the piston before the exh valve closes.(at low rpm) causing the lumpy idle(This is not always bad for emissions, and its doing the same thing a EGR Valve would do)

On the Compression stroke, the amount of D.C.R.(the actual compression the eng see's when it running) is determined by when the intake valve close(compression can not begin to build until both valves are closed.

(Just trying explain that when the int valve close, on the compression stroke make a big difference on DCR or what the eng see's)
which means you could have a 11.1 compression motor that only had 140 psi when you check you compression with a compression gauge.
AND had a 9.1 motor with a int valve closing much sooner on the compression stroke............Giving you 140 psi cranking pressure.
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