How to pick a cam

[firefighter3931]

The tight LSA cam profiles have a dirty idle....no way around it. As Craig (Flyinglow) explained above the problem is overlap...the longer the intake & exhaust valves are open simultaneously...the worse the smell @ idle. The longer duration just pushes the powerband upwards.  

For a cruiser type application you need a cam with short overlap, short duration and a wide LSA. Cams with wide lobe centers broaden the power curve, increase manifold vacuum and idle smoother. With a wider LSA you will loose some of that idle "rumble" but you will have a much cleaner running engine.  

Here is a brief explanation of cam timing & LSA : http://www.compcams.com/Pages/413/cam-timing-lobe-separation-angle.aspx

What you need is a cam with short duration and a wide LSA to increase manifold vacuum and spread the power out and clean up the idle. A cam swap is definitely in your future  



Ron

Ps. Here is the cam I would use :

Crower : 32240

Part Number
32240

Engine Make
Chrysler/Dodge/Mopar

Year
1958-1980

Part Class
Camshaft

Camshaft Name
Power Compu-Pro

Camshaft Series
Compu-Pro

Engine Type
V8

Engine Size
350, 361, 383, 400, 413, 426 & 440B

Product Type
Hydraulic Flat Tappet

Valve Lash
.000" intake and .000" exhaust

Lobe center
112

Advertised Duration: Intake / Exhaust
260 / 267

Duration @ .050" Lift: Intake / Exhaust
212 / 218

Lobe Lift: Intake / Exhaust
.304 / .318

Rocker Ratio: Intake / Exhaust
1.5 / 1.5

Gross Valve Lift: Intake / Exhaust
.456 / .477

CID
383

Performance Level
2

Low RPM
1500

Peak HP
4000

Redline
5500

Performance Description
Perfect combination of power and mileage. Provides excellent low end and mid-range power with extended rpm's for spirited driving.

Engine Application
Level 2 profiles are for individuals that require more power and an extended rpm range. Works well with stock and near-stock engines and drive trains. These camshafts provide excellent low end and mid-range power for spirited street, offroad driving and mild marine applications. Designed for lightly modified street engines.

Recommended Modifications
Small diameter tube headers, low restriction dual exhaust, aftermarket manifold, increased cfm carburetor, reworked or performance ignition and increased compression (9.5:1) for maximum output. Aftermarket torque converter with slightly higher stall speed or manual transmission. 

Product Characteristics
More power and an extended rpm range. Excellent low end and mid-range power

CID #2
413

Performance Level 2
2

Low RPM #2
1500

Peak HP #2
4000

Redline #2
5500

Performance Description 2
Perfect combination of power and mileage. Provides excellent low end and mid-range power with extended rpm's for spirited driving.

Engine Application 2
Level 2 profiles are for individuals that require more power and an extended rpm range. Works well with stock and near-stock engines and drive trains. These camshafts provide excellent low end and mid-range power for spirited street, offroad driving and mild marine applications. Designed for lightly modified street engines.

Recommended Modifications 2
Small diameter tube headers, low restriction dual exhaust, aftermarket manifold, increased cfm carburetor, reworked or performance ignition and increased compression (9.5:1) for maximum output. Aftermarket torque converter with slightly higher stall speed or manual transmission. 

Product Characteristics 2
More power and an extended rpm range. Excellent low end and mid-range power

Grind Number
260HDP

[Dino]

It sure is in my future!   

Thanks for the advice, I'm reading up on cams now.  Going from headers to hp manifolds would anything change?  Do I have an advantage running these headers the way I use this car?  My only beef with them would be the increased heat, but they can be coated and then still I haven't really had heat issues either.  The other negative would be the typical thin metal sound they make.  That's only noticeable at idle though and goes with the territory.  This is really nitpicking as they seem to work just fine as is.  If manifolds are more appropriate for my car then I can go that route to.  I have attic space to store the headers.   

A new exhaust is not yet needed but it would not be a waste either so I can go either way.

[firefighter3931]

Dirk,

The cam listed above is "manifold friendly" so you can use it with either headers or HP manifolds so it's a good choice for your application either way. 


Ron

[flyinlow]

An added advantage to the milder cam will become apparent down the road when you put an OD trans in. The '73 has .69 OD and the engine spends most of its time right around 2000 rpm.

Larger overlap ,longer duration ,smaller LSA Cams seam to be more sensitive to having a tuned low restriction exhaust.

Shorter overlap, shorter duration and larger LSA cams seam to tolerate manifolds and stock mufflers better.

They are a pain ,but with proper tuning, headers help any engine make the most power it can.

[Dino]

Dirk,

The cam listed above is "manifold friendly" so you can use it with either headers or HP manifolds so it's a good choice for your application either way. 


Ron

Excellent!!  Thanks Ron!   

An added advantage to the milder cam will become apparent down the road when you put an OD trans in. The '73 has .69 OD and the engine spends most of its time right around 2000 rpm.

Larger overlap ,longer duration ,smaller LSA Cams seam to be more sensitive to having a tuned low restriction exhaust.

Shorter overlap, shorter duration and larger LSA cams seam to tolerate manifolds and stock mufflers better.

They are a pain ,but with proper tuning, headers help any engine make the most power it can.

I don't dislike the headers.  They seem to fit pretty decent, no rubbing, nothing burning up from the heat.  They are old and rusty but that's just appearance.  The thin metal header sound will probably even diminish if I coat these.

Of course it's no fun installing or removing these but that's the price you pay.  I honestly wouldn't know what to expect from hp manifolds but people seem to like them.  The drop in temperature and the extra space would be nice but probably not needed.

I guess a good strategy would be to change one thing at a time, change the cam and keep the rest.  See how it does and improve where needed.

[moparsr2fast]

 The cam you are running now Dino is the old "hemi " grind. It is bigger then a stock magnum cam, but not by much. Imho, you might better accomplish your goals by going to an EFI system rather then swapping out the cam. That will eliminate your fuel smells, increase mileage and  reliability.   

[Dino]

The cam you are running now Dino is the old "hemi " grind. It is bigger then a stock magnum cam, but not by much. Imho, you might better accomplish your goals by going to an EFI system rather then swapping out the cam. That will eliminate your fuel smells, increase mileage and  reliability.   

I'd love to have efi.  I'd actually like to build my own system from parts available.  I was thinking of doing so when I no longer have to spend all my time on studies, just for fun.  It sure would help the smell!