How to pick a cam

[Dino]

First of let me say I am not swapping my cam just yet because I've never done it and I really don't want to pull my engine.  That said I will eventually have to bite the bullet and do this because the purple cam that's in there now is all wrong for my purposes.

Here's the deal, I know very little about this engine and I know that's a problem when you need to pick a cam.  All I know is that it's a 71 HP block from a squad car.  It has six pack rods and TRW pistons.  Compression is supposedly above 10 but I cannot confirm this.  The 727 came out of the squad car as well and I don't know what converter it has. 

The previous owner used this cam with 3:55 gears, and an Edelbrock performer intake manifold and 1407 carb.  The carb was crap so I removed it and installed a Thermoquad which was a huge improvement.  I removed the 3:55's and installed 2:96 gears and 28" tall tires.  If ever I get a 6 speed installed I'll get another gear to match it up but as long as I'm running a 3 speed, the gears are staying.  It also has headers but I have no clue what brand.  They fit and seem to be without leaks though.

I use the car as a daily driver, although I have another for that.  Most of my trips are in the 30 minute range going to school or work, travelling through towns and on 55 mph country roads.  However, when the car runs as I want it to, I hope to take it on much longer trips.

The longest so far was driving for around 5-6 hours which it is happy to do, but I won't do it anymore because there's always something smelling with this thing, be it fuel or exhaust or burning oil on the headers as is happening now, I need to fix this somehow.  The most fun I can have with this car is going on long trips with my wife, but because of the smell she no longer is anxious to do so just like me.  Can my cam be part of the reason why it smells?  Anyway, that's another issue altogether. 

I never race the car and have no desire to do so.  I don't WANT to give up power, but if I can't have my cake and eat it then I need it tuned for what it is used for most which is cruising.  With the gears I have it's pretty hard to roast the tires, it seems most of the power is at higher rpm where I do not need it as much.  I need as much low end power as I can get since I'm usually running below 3000 rpm.

I guess I can just get a stock cam but I figured I'd let the pros tell me what's the better one to get. 

One thing I'll miss is the sound it makes at idle. I'll be very happy to have a more stable idle, but I do want the car to sound good (don't we all). 

So with this information is there something that may work for my application?  Also I'm assuming it would be a good time to change the timing chain at the same time no?

[flyinlow]

Dino,

You can change the cam with the engine in the car.

I am a fan of the plastic fantastic (TQ) but they don't seam to work well with bigger cams. I have a Lunati Voodoo 60303 (1800-6200 rpm) in my mild build 446. The TQ worked Ok with it.

Lots of newer designed cams out there. A few are even designed to give that raspy idle while still having good street manners. Send an email to Comp cams, Lunati, and Hughes, tell them what you have and want and see what they recommend.

Our Chargers are big gals so over all mid range torque is the target .   

[don duick]

wow 2.96 gears with 28 inch tyres ? great setup if you like driving downhill on a long highway. I would use the smallest cam available from the big name companies. eg comp cams smallest cam has 206 degrees duration @ 50. I had a 212 @50 in my low compression 440, that ran well, smooth idle good power down low and still made power up to about 4000 but had really bad valve bounce with the stock springs. I also had a mopar purple shaft 284 advertised duration with .484 lift. That cam was totally useless. I noticed a huge improvement with the comp 212 @50 cam. My gears are 3.23 with 25.5 inch tyres. When you install the 6 speed you might want to change the cam and diff gears again.

[Dino]

I know it seems like I'm trying to take away performance but I'm not, I just don't have use for power in the high range so I need to tune it for my needs.  When I have a 6 speed and lower gears in the back then I have some more to play with, but with a stock 727 I'm a bit limited.  It would be nice to keep the same cam but when that time comes I'll likely pull the engine anyway.
Fact is that I really hate running high rpm's in a street car.  When I drive this car now it is super smooth but the power band is not where I need it to be.  When I first got the car it was pretty fast off the line, but when you don't race it's a bit of a moot point.  All my driving is in towns so closer to stock is more applicable for me.  If it was a Sunday driver I'd leave it alone but I do take it out a lot.

I have heard from others that any stock-ish cam will be a great improvement over the purple cam.  I'll email those companies and see what they say.  I'm looking for an old message from Ron where he gave me the name of one to look into as well.

What all needs to be removed to do this swap without pulling the engine?  Do the grille and a/c condenser have to come out?

[flyinlow]

To remove to cam ( I am looking at a '70 ,440)  remove fan,shroud, radiator, waterpump housing, fuel pump, timing chain cover,valve covers,intake manifold ,valley cover and waterpump/ps pump as necessary.

A/c condenser ? not sure if you can move far enough forward by unbolting.(probably not) the condenser is missing from the '70. I did some quick measurements ,using 24" for the cam and you would have to remove the condenser and the center bracket for the hood latch which is bolted in.

If you have a functioning R12 system you will need someone with a refrigeration capturing machine.

[flyinlow]

Not sure which purple stripe cam you have. If its a mild one you might check the cam timing and possibly advance it a few degrees picking up bottom end power. You would not have to mess with the intake or A/C to do this. (or buy and breaking in a new cam) 

[don duick]

to do cam swap - you do not need to remove the grill. turn engine to top dead centre on firing stroke.

remove -

radiator, alternator (disconnect battery),  power steering pump, water pump, fuel pump, crankshaft pulley, balancer, timing case cover, rocker covers, rocker shafts, pushrods, distributor and leads, (remember direction rotor button is pointed), inlet manifold, lifters, cam sprocket, before you remove the sprockets note the position of the dots.

now you are ready to pull the cam out. try and find a long bolt to screw into cam to use as a handle, this will make it a lot easier to handle as you have to be really careful pulling out the cam as you have to avoid scratching the cam bearings with the cam lobes.

when installing new cam you need  a rule to  line up the dots  

[don duick]

sorry I forgot about air, not sure never seen air condenser on a big block.

[Dino]

Thanks guys!   

The A/C is not charged at this time, I only just got the car running so I planned on charging it in a day or two when it's a bit less hot outside.  It's a R134a system. 

I'll have to think this all through a bit.

[Roadrunner]

Well with out knowing what the heads are & if anything has been done to them, you will still be guessing. as for carb. a Holley 780 is all around good choice, a look at your converter will be in the mix also & lower gears are going to get you out of the gate quicker. As for the cam its self no matter which one comp suggests & there good at knowing, get a degree wheel & use the cam card they give you. Then if by chance you want more or less you know where you are ( keep records) I my self would build a complete new motor & keep that old one as back up. Then you know what you have. Good luck with your choices & your build

[Dino]

Well with out knowing what the heads are & if anything has been done to them, you will still be guessing. as for carb. a Holley 780 is all around good choice, a look at your converter will be in the mix also & lower gears are going to get you out of the gate quicker. As for the cam its self no matter which one comp suggests & there good at knowing, get a degree wheel & use the cam card they give you. Then if by chance you want more or less you know where you are ( keep records) I my self would build a complete new motor & keep that old one as back up. Then you know what you have. Good luck with your choices & your build

Thanks for the tips but I'm not trying to get out of the gate quicker, I'm going the other way.   

The tall gears and Thermoquad are staying.  When I have the 6 speed then I'll change the gears for something lower.  The carb stays until I have the time to build a modern efi setup...or the carb dies for some reason.  Those small primaries are perfect for my driving and the car still moves more than plenty when the secondaries open.  Unfortunately all the power is in the higher rpm range so I rarely get to use it. 

If I had the funds and the space, starting fresh would be a very good idea.  I don't like not knowing what's in the engine but it does run really well, never had an issue with that engine so I'll just have to change some parts and hope for the best.

Thanks for reminding me of the degree wheel, I need to read up on all that stuff.

I am glad to hear the grille can stay in place, I was reluctant to try to loosen those bolts! 

[flyinlow]

What kind of vacuum readings do you have at idle and cruising at freeway speeds?

Maybe you can work on tuning what you have. You said the engine makes good power at WOT, good oil pressure and no noises.

One disadvantage to the thermoquad is its small primarys. They atomize fuel well but they make the car feel lazy. Lets say you push the gas petal down 1 inch, a thermoquad will flow less air than say 750 holley with its bigger primarys even though at wide open throttle the TQ would flow more.

[Dino]

What kind of vacuum readings do you have at idle and cruising at freeway speeds?

Maybe you can work on tuning what you have. You said the engine makes good power at WOT, good oil pressure and no noises.

One disadvantage to the thermoquad is its small primarys. They atomize fuel well but they make the car feel lazy. Lets say you push the gas petal down 1 inch, a thermoquad will flow less air than say 750 holley with its bigger primarys even though at wide open throttle the TQ would flow more.

Very true, the Edelbrock 750 required less throttle to move.  However the TQ runs so much better that I can live with that.  I always had a bog with the Eddy and it always ran real rich at idle and lean at WOT.  The TQ fixed all of that.  It is super responsive in that it behaves like an EFI car.  Except the cold start with no choke, that's pretty terrible! 

Imagine driving a car, any car, on a 55 mph rural road with plenty stops.  Now imagine how little you really depress the go pedal.  If my 4 banger Honda can keep up then the beast can surely do much better, and it does.  The power it has now is more than adequate, but I can feel the cam is way out of place.  A bone stock cam would really wake up the low end I think so if I go a tiny bit hotter than that it may be ideal.

The engine is indeed tip top, no noises, no ticking, no surging or anything out of the ordinary.  Stock gauge, calibrated by yours truly, shows 40 psi under light load.  The first thing people say when they ride shotgun is how smooth it is, and it really is.  I think that once the cam has been replaced it'll feel more like an Imperial than a Charger.   

[Dino]

Not sure which purple stripe cam you have. If its a mild one you might check the cam timing and possibly advance it a few degrees picking up bottom end power. You would not have to mess with the intake or A/C to do this. (or buy and breaking in a new cam) 

The only thing the previous owner could tell me was that it has 0.474" lift, 283 degree duration and that he could be off a bit, he couldn't find the paperwork for it.  He also believed it was a purple cam but again no certainty here.

Unless I install way lower gears and maybe replace the intake and carb with something bigger, this cam is not going to be happy.  And since I don't want to do any of those things, the cam will have to go.  The thing is, I just got this car back together and on the road after a very long year.  I have only put 80 or so miles on it since I finished it and I'm a wee bit reluctant to start a job this big, one I have never before attempted.

I have put thousands of miles on it so a few more in its current configuration will have to do.  At least the car runs great and all the electrical issues are solved.  I just need to have the timing reset and those pesky small valve cover leaks fixed and it'll be in its best shape in a few decades.   

One thing I really want to know though...can the cam be partly responsible for creating fuel or exhaust smell when I punch it or will a stock cam do this as well?

[71 SE3834V]

Dino, I would be happy to help you with replacing your cam if we could work it out. It's a lot easier working with someone who has done it before. If it could be worked out you might want to do it at my little shop. You might be tickled to see all the equipment I have here. Once you see how easy it is to time your engine you won't be taking it in to the shop everytime it needs to be done.
Drive your car for awhile until I get mine done and out of the way. Part of the reason mine is taking so long is every part needs years of crap cleaned off of it and painting.
Oh, and the a/c comp. has to come off. It's bolted to the water pump housing on '71's. If I remember right yours was located in the same location as mine.

In looking at the MP "Purple Shafts" I see a lot of different ones offered w/different specs. Unless yours is measured you won't know which way to go with a new one. FSM lists the stock one as being Intake 268*, Ex 284* for '71 383HP & 440. 213/225 @ 0.50, .450/.458 lift.

[don duick]

cam has nothing to do with fuel or exhaust smells.

maybe  weak ignition not burning properly,

   or

tall gears, when you accelerate the car wont respond  and fuel is wasted. I got better economy from 3.23 gears than 2.76 I previously had.

[BSB67]

cam has nothing to do with fuel or exhaust smells.

maybe  weak ignition not burning properly,

   or

tall gears, when you accelerate the car wont respond  and fuel is wasted. I got better economy from 3.23 gears than 2.76 I previously had.

Tightening up overlap will help the fuel smell

[Dino]

The worst of the smell is when I push the go pedal.  I literally come home smelling like exhaust after a 20 minute ride, where I mash the pedal once or twice leaving a stop.  I didn't think all of it would be the cam's fault but a small part of the problem.  Maybe I need a different kind of air filter housing.  I have a dual snorkel hanging around somewhere, maybe that'll work better?

[don duick]

is it running rich ? check a spark plug see if it is black,

air filter clean?

check overflow tube on your filler neck inside the trunk

fuel leaks on carby?

exhaust exit past the rear bumper ? and not under the car 

[Dino]

is it running rich ? check a spark plug see if it is black,

No it's running as it should but that's not to say it can't be tweaked better.  I need to reset timing before I touch the carb but no issues there, plugs look fine.

air filter clean?

Yep, K&N with less than 1000 miles on it.

check overflow tube on your filler neck inside the trunk

Will do   

fuel leaks on carby?

None

exhaust exit past the rear bumper ? and not under the car 

Yes it does

[don duick]

did you have the problem of fuel and exhaust smells with the edelbrock carb and 3.55 gears ? and what was wrong with the edelbrock carb?

[Dino]

did you have the problem of fuel and exhaust smells with the edelbrock carb and 3.55 gears ? and what was wrong with the edelbrock carb?

Yes, same problem.  The carb always had a bog no matter how it was tuned.  Different jets made it better but I could never get it to be smooth.  Seems to be a thing with these carbs and engine combo.  I was going to buy a new carb but decided to give the TQ a try since I had it.  It made everything better but I couldn't get rid of much of the smell.   

I removed the 3:55 in the first week I had the car and at the time it had a driver's side header leak so that made it all much worse.  Once that was fixed it got better.

[flyinlow]

A .474 / 283 total duration is not that wild of a cam depending on overlap and centerline numbers and of course your Compression ratio.

A higher RPM cam will tend to have more valve overlap meaning the number of degrees of crankshaft rotation that both intake and exhaust valves are not fully closed. This will let some unburned air /fuel mix go right from the intake manifold into the exhaust. It makes your eyes burn if you stand behind the car at idle. As the rpm increases and the cam gets into it's rpm range their is less time for this combustion camber bypass to occur. The engine smooths out and the exhaust becomes less annoying.

There are more knowledgeable folks here to steer you to a good cam for your car. i have only done a handful of BB Mopars, but I did stay at a Holiday Inn Express last week.

Do you have an exhaust leak? or body panel plug missing? I only notice the exhaust smell of my Chargers at idle near the back of the car, not under acceleration driving it.
I carry a battery powered CO2 detector in my car. It started chirping once,not a steady alarm, on cold day. Loose header collector bolt.  

[Dino]

I didn't think I had an exhaust leak.  It doesn't look or sound like it does but something has to be wrong.  I don't see how else I could be smelling of exhaust fumes when I was driving it so I'll double check everything.  The exhaust when cold does have raw fuel in it.  Once the TQ was on it got to be quite a bit less than the eddy but that carb always ran rich at idle as well so that didn't help.  The TQ runs leaner at idle.   

The idle, stable as it is, sounds rough.  Of course that's half of the attraction because the rough idle actually sounds pretty damn good, but you can tell it's not running at peak efficiency.   

As an experiment I hooked up the vacuum advance to full manifold vacuum and installed a dual snorkel filter to see if that would improve anything.  Now I should never change two things at a time because then I don't know what made the change, but I did.  The car smelled so bad of fuel and exhaust that I had to turn back home.  I put my simple MP air cleaner back on and changed vacuum advance to ported and it the smell was much better.  Still enough to make my clothes smell but at least I didn't taste it anymore.

I'll install that Percy gasket on the passenger side header, it won't hurt.  The old gasket is probably oil soaked by now anyway.  Timing is pretty damn close now but I'll have it checked again.  Is there a good exhaust leak check product I can use?

Hopefully I can get rid of most of the stink without  changing the cam, I'd like to not do major surgery on this car for a while.   

[Dino]

I missed half your question again, I'm a bit exhausted myself.   

There are no body plugs missing and the floor is nicely sealed up and insulated.  Very little heat comes through, even right on top of the collectors.  The previous owner was an engineer and he coated the front floor boards with some sort of thin epoxy and boy does that stuff insulate! 

I'm thinking of holes in the firewall and there are some unused screw holes but no big holes.  Heater valve is on and sealed properly as well. 

This is likely just a combination of old technology with minor leaks up front and a bigger overlap to cause some stink at idle.  If we didn't have asthma we probably would just accept it, but we can't. 

I'll tune it as best as possible and will make sure there are no more leaks.  That spot on the header is a mystery to me.

71 I'd love to take you up on that, but let's get your car done first.  Let me know when you need a hand.  I'll yank that trans if you can check my timing, I have springs and instructions now!   

I think a cam swap will be a good thing, even keeping in mind that I will have a 6 speed later down the road.  But far down the road.  If I make a good choice I should be happy with the same cam, all I'd have to do is swap the rear end gears for something lower.  Maybe the 3:55 will be perfect for that setup.  After just reassembling this car though, I'm reluctant to take it back apart. 

[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!