Need help to find cam

[69bananabeast]

I made the swap to big block about a year ago .   Ever since then the 440 has been running kind of rough no matter how much time I spent  tunning.  About a month ago the mechanic we go to told me it's because the Cam I have is for a "standard car"        Is there really a difference ?
   
   Mopar Performance
  Mechanical Flat Tappet, Advertised Duration 284/ 284, Lift .528/ .528, Mopar,  2,400-6,600 RPM   

If there is   I was hoping to be able bump up to a bigger cam   

Thanks in advance

[67_Dodge_Charger]

That is a short duration high lift cam which translates into a rough idle.  If you want a smoother idle look at something with a longer duration, around 290.  I think that Ron "Firefighter" mentioned this to me when I was looking at cams last month.  The comp solid cam with 290 intake, 298 exhaust (I can't remember the lift, but I believe it was around .545) would give you a smoother idle.

good luck
Robert

[69bananabeast]

also I forgot to mention that     I have to power brake when im at a stop so it wont die out .  I messed around with the tunning for awhile  but i can only get it to idle at a stop for 10 seconds or so if  I don't power brake.

[firefighter3931]

I made the swap to big block about a year ago .   Ever since then the 440 has been running kind of rough no matter how much time I spent  tunning.  About a month ago the mechanic we go to told me it's because the Cam I have is for a "standard car"        Is there really a difference ?
   
   Mopar Performance
  Mechanical Flat Tappet, Advertised Duration 284/ 284, Lift .528/ .528, Mopar,  2,400-6,600 RPM   

If there is   I was hoping to be able bump up to a bigger cam   

Thanks in advance

The MP528 solid is usually a smooth running cam in most big block applications. By running rough, what are you describing ? Idle quality ? hesitation/bog ? Need a better description.....

You probably just need to set up the carb and ignition with a little tuning.




Ron

[firefighter3931]

also I forgot to mention that     I have to power brake when im at a stop so it wont die out .  I messed around with the tunning for awhile  but i can only get it to idle at a stop for 10 seconds or so if  I don't power brake.

Where is your timing set ? How much advance at idle ? What carb are you using ? intake manifold ? Headers ?

Post a list of all the engine/trans and rear end specs....


Ron

[69bananabeast]

446   
10:1 Flat top  KB
Heads :  Indy  EZ  78cc  match port
Rockers:  1.5 Indy
Carb :  Holley   870  vac  2nd   Street
Intake:  MP Single  High Rise
Headers:  Hooker   1  7/8
Trans: TCI  727   
Rear:   8 3/4    3:73  Locker
Stall:  2500


Idle is bad  .  it'll  be around say 1200  and suddenly it will get stuck at say 1800 .   I have to turn the car off in D or R  so it wont diesel over.  Sometime when I try to get on it it will back fire .  Not sure what timing and advance are set at right now , believe it  was set around 30 something in the past .

[firefighter3931]

That is a pretty mellow combo. Vegas Mike has a bigger cam with more overlap and we had his idleing at 750rpm in gear. Basicly it's the same engine but with edelbrock heads.

Start with the ignition. You need at least 15* of advance at idle and plug off the vacuum advance and leave it plugged ! Map out the advance curve with the base timing set at 15* initial in 500rpm increments. We need to know where it stops advancing and at what rpm it stops advancing....and what the total advance is. Also get a vacuum guage on it to see how much vacuum it's pulling at idle. Check for vacuum leaks.

That carb isn't the best choice for your build, inmo. At the present time it has the engine idling on the main circuit....not the idle circuit like it should be. What it really needs is a holley HP or Proform race series double pumper in the 750cfm range.


Ron

[69bananabeast]

well the carb would be going out when i get some money . I've been wanting to go  the Intake EFI route .   I think I might have a 750   Street avenger somewhere , would tha tbe better for the time being?

[firefighter3931]

   I think I might have a 750   Street avenger somewhere , would tha tbe better for the time being?

Probably not. The issue is not the size of the carb.....it's the fuel metering at different throttle positions and at idle. Agressive cam profiles need agressive fuel curves or you will experience tuning issues.

Start with dialing in the ignition first before buying any new parts. You might be able to tune out the off idle stumble with a squirter and jetting changes. First things first....the ignition needs to be right before you move on to fuel delivery.


Ron

[jg68]

I agree with Ron 101%, MOST if not ALL carb related problems are do to a bad (or not up to par) ignition system or timing issues, start there first

[MOPARHOUND!]

What they said, and.............

Intake:  MP Single  High Rise

I'm assuming this is a "Single" plane intake (versus single 4 barrel).

You might consider a Holley Street Dominator intake (smaller plenum) or even a dual plane, given the combo you have.

[firefighter3931]

What they said, and.............

Intake:  MP Single  High Rise

I'm assuming this is a "Single" plane intake (versus single 4 barrel).

You might consider a Holley Street Dominator intake (smaller plenum) or even a dual plane, given the combo you have.

Hound brings up a good point.....the M1 single plane is more of a race manifold. The performer rpm high rise dual plane or street dominator are much better suited to your build. The large plenum M1 is hurting the intake velocity and throttle response will be soft/sluggish at lower engine speeds with this type of manifold.


Ron

[69bananabeast]

I'll try to mess with it this weekend and and see h ow it goes.