I called Mopar performance today

[sam z]

Gave them the low-down like I have done so many times here:
72 440 HP
484 cam, holley street dominator intake, auto, 3.91, OEM casting heads with
bigger valves and hemi springs.

So....went back to carb discussion and my obsession to get a new one. Currently has
holley 4779 DP. Mopar guy said go with a 770 street avenger, immediately replace power
valve with a 4.5 unit, stay with intake (but an EDDY RPM performer may be an upgrade
to consider). Also said to replace springs in distributor with a kit that he gave the part
number for. Said timing at idle 20 degrees with total advance of 38.

In summary told me that should be more drivable around town, will reduce bog / hesitation / fart
when you stand on it, should not run as rich with slightly less obnoxious emissions.

Chris, you usually add brilliantly to this stuff, so feel free now.

 

[mcmopar]

You can do a WHOLE lot better than the MP 484 cam these days. You'll also need to check your compression ratio to see what you have before swapping out cams, too.
The MP springs for the distributor are a bit light. You might be a bit better off going with the stock small spring for both distributor weights (the stock distributors had a small spring on one weight and a heavier spring on the other weight).
The Street dominator is a fine intake. No need to change it out.

 

[mac]

i agree about the 484 cam. that was my first cam and was only good on the top end of the rpm range. also agree about getting the timing curve set. lastly the value of the power valve should be determined per your cars vacuum. 4.5 may be a good starting point but needs to set to your car vacuum readings.

 

[sam z]

The recommendation to go with the 4.5 power valve was based upon knowing the car has low
vacuum readings. The car's compression is OEM at 8.2:1. The spring kit he recommended was
a Mr. Gasket part # for the distributor.

I told him I didn't have a big initiative to swap the cam out, as I don't feel like digging too deep on this
engine. I realize from many of you guys previously this cam is a dinosaur. My goal is to get the existing arrangement
running better / more drivability.

Thanks guys keep going if there is anything else.

 

[moparchris]

Gave them the low-down like I have done so many times here:
72 440 HP
484 cam, holley street dominator intake, auto, 3.91, OEM casting heads with
bigger valves and hemi springs.

So....went back to carb discussion and my obsession to get a new one. Currently has
holley 4779 DP.I would stick with this carb, it is a really great carb! Mopar guy said go with a 770 street avenger,Even though its of similar CFM it will be down on power. immediately replace power
valve with a 4.5 unit, Power valves are measured in vacuum (inches of mercury) a 4.5 will start to open at 4.5" of vacuum. A good rule of thumb is 1/2 of your vacuum reading at lowest idle will be your PV size. I.E. 7" vacuum at idle in gear you need a 3.5 power valve. stay with intake (but an EDDY RPM performer may be an upgrade
to consider). There will be no appreciable difference in power, a waste of money at this point. Also said to replace springs in distributor with a kit that he gave the part
number for.If its an automatic I would lock the distributor at full advance. Set the timing at 34 at idle and it will be that all the way through. The reason for this is that it will stabilize your idle speed and the amount of power your motor will make at idle, that will help with idle speed drop when you put it in gear. Said timing at idle 20 degrees with total advance of 38.

In summary told me that should be more drivable around town, will reduce bog / hesitation / fart
when you stand on it, should not run as rich with slightly less obnoxious emissions.The bog hesitation is from the carb being adjusted wrong and having the wrong power valve. The PV , when open, makes the primary jet 10 sizes bigger and will make the exhaust stink badly. The accelerator pump has quite a few adjustments and can be tailored to your liking without a doubt once you solve some of the other problems. Carbs are the first thing blamed when other fundamentals have issue. The 484 grind from Mopar is an old grind. They were made to have a very strong but narrow powerband for low compression motors, sadly they suck in the driveability department. A cam change would solve a lot of problems but its not necessary.