Advice on rv cam

[benrunner]

How about an rv cam in my low comp 383? Will it wake up a little?

 

[Stewsta]

Hughes seems to be very popular for low compression cams

 

[benrunner]

What specs do I need?

 

[MLB12]

How about an rv cam in my low comp 383? Will it wake up a little?View attachment 216062

An RV cam is a great way to go on the low comp motors. You'll see considerable gains in the bottom end through mid-range, so driveability is vastly improved.

Check with your local MOPAR Performance dealer to see if they still have a current part number for one.

I used them quite a bit many moons ago, but now with the 426 it's not an issue.

 

[benrunner]

Great thank ya much mlb12

 

[Cranky]

Cams with a late intake opening (like 5* BTDC @ .050 lift) and closing usually work well. They produce a lot of vacuum and with a late closing, the air/fuel column keeps on rushing in even as the piston is at BDC. I'm not an expert in this so you might want to talk to someone who is so you can get something that won't cause ping issues. My last go round with one was in a 400 ci engine in a 3/4 ton pickup with 3.55 gears and 29" tires. It ran a 15.40 1/4 miles which isn't a ball of fire but it wasn't too shabby for a pretty heavy vehicle. Intake was a stocker from a 69 383 magnum, 650 Holley DP carb and headers were the only other mods.

 

[Herr_Poopschitz]

1/4 race cam

 

[Meep-Meep]

The right cam will do wonders. My low compression 455 Olds in my Tahiti jet boat got real happy with the addition of this Crane cam http://www.summitracing.com/parts/crn-803902 Something along these lines will work well for you. Just remember to keep your low compression ratio in mind when making a selection.

 

[super-bee_ski]

1/4 race cam

WTF is a 1/4 race cam?

Is this a joke?

I'm almost 61 now...I remember hearing that "talk" in the 60s....

But, this day and age...DATA and specifically Good Data is best.
Terms like:
Lobe seperation Angle: (Lobe separation is the angle in camshaft degrees between the maximum lift points of the intake and exhaust valves. It is the result of the placement of the intake and exhaust lobes on the camshaft)
Duration: (Duration is the angle in crankshaft degrees that the valve stays off its seat during the lifting cycle of the cam lobe)
Lift (Maximum valve lift can be calculated by multiplying the maximum lobe lift times the rocker ratio. For example, a 0.310" lobe lift cam yields 0.496" of valve lift when using a 1.6 ratio rocker arm.)
-Formula: valve lift = lobe lift x rocker ratio
Overlap:(Overlap is the angle in crankshaft degrees that both the intake and exhaust valves are open. This occurs at the end of the exhaust stroke and the beginning of the intake stroke. Increasing lift duration and/or decreasing lobe separation increases overlap.

 

[Meep-Meep]

Normally it's a "3/4 race cam." The 1/4 is probably a typo, unless he came up with a milder version of that infamous 3/4 race cam.

 

[super-bee_ski]

Yup,
But again, benrunner is asking for help...
Hypothetical: He goes to a place, asks for a 1/4 Race Cam....
HUH?

That jargon was used in the old days....

I always speak to the CAM company
Lunati
Crane
Comp
The techs know how to help.
Usually "Good" customer service
Cuz you all know, installing the wrong CAM sure can make for a bad day.....

benrunner, build for torque...

 

[benrunner]

Duration 268/268 @ .050 218/218 valve lift 457/457 rpm 1200-5500

 

[Cranky]

What's the valve events? First thing I look at is when the intake opens 2nd when it closes before looking at anything else. Also, use a degree wheel when you install it. The 'dot' method can have too many variables and machining tolerances on the sprockets can be way off. When you degree it in, all doubt is erased.

 

[super-bee_ski]

That seems "tame" enough....

 

[Cranky]

That seems "tame" enough....

Yup it does but how can you tell how much cylinder pressure it'll produce without knowing the valve events? You can still produce a ton of psi with a low static compression ratio.

 

[Hemi 354]

Back in the early 60s, we referred to a 3/4 cam as one that had ~.500 lift

 

[super-bee_ski]

Cranky's quote: "Yup it does but how can you tell how much cylinder pressure it'll produce without knowing the valve events? You can still produce a ton of psi with a low static compression ratio. "

Yeah,
I "LEARNT" a bit on that last post about Valve event...
I still never understood the whole process...

It is technical and dynamic, depending on many factors...
Why is Valve Event so important and yet the CAM manufacturers neve discuss it?

So the DEGREE WHEEL procedure is best....
It allows for "your" specific purpose/build?

 

[Herr_Poopschitz]

Normally it's a "3/4 race cam." The 1/4 is probably a typo, unless he came up with a milder version of that infamous 3/4 race cam.

Haha...yeah, joke. Meh, I thought it was funny.

Hell, 'purple shaft/stripe' is old jargon. Same as 'rv' cam.

- - - Updated - - -

Why is Valve Event so important and yet the CAM manufacturers neve discuss it?

They don't? All the variables you listed earlier are results of them...?

Fill out a cam request form at Crower or Bullet if you want the 'right' cam.

 

[Cranky]

Every cam card I've seen has all the info on the valve events. Opening and closing of both intake and exhaust in degrees when it's set at the recommended setting is listed. You can deviate the setting by a few degrees and then chart the events on a degree wheel and can chart out the events if the card is missing. Some cams respond very favorably to being advance a few degrees while others don't. Engine builders with lots of experience can pretty much tell you what a certain cam will do when it's moved a bit either way but man, it takes a lot of experience. Some can tell you based on the numbers what a cam might do in a certain combination but the best way to find out is by testing. Dynos tell a lot but on track testing is the best imo. I've had a good deal of experience with the old Mopar 284/484 cam in 440's and they seem to work pretty well in a mild build advanced 4 degrees for one example.....

 

[super-bee_ski]

Thanks "Herr_Poopschitz" & Cranky...

To me, CAM EVENT is a mystery...
But you guys helped clear it up (AGAIN)

KOOL..CAM CARD...