just looking for imput,i am putting my red 75 duster back on the road, after 10yrs, still playing with 76 duster drag car, i have the motor ready but after reading all the cam talk i was questioning wether to custom order a dual profile cam. i am going back to its street trim ,when it ran mid to low 15s. the engine is 0.030over ,decked 0.090, head planed 0.075,comp works out to 9.6/1,head has stock valves backcut and rework, the head is pocked,port match and chamber /port cleanup . intake is offy and 600vac carb. trans is 904 lockup with 274 first gear. rear is 8.25 with 3.91posi.when i ran this comb on street/race i had 276deg .490 mopar cam,i really liked the way it worked,would there be any advantage to ordering a custom grind with 276/.490 on the intake and 262/.470 on the exhaust. any imput would be appressated.thanks

The main idea behind using a "reverse dual pattern" cam with our 120 degree firing inline engine is to delay the exhaust opening event. You can do that with any lobe design but end-up with to much exhaust overlap (at exhaust closing) with longer duration lobes.

Using a shorter exhaust duration / profile allow us to position the exhaust event to open later (blowdown near 120 ATC) and also get the ex. valve closed while still close to TDC at overlap. (20 to 40 degrees ATDCex)

The intake valve has different considerations so you have more choices with that lobe. In general, a SL6 engine is more intake side limited, so adding more intake event helps, especially with the small carb set-ups.
As the intake side improves, this is less of a factor.

As for your proposed design, my guess is that you will get more low RPM responce and power with about the same high end. Basically you are working to find a cam that will give you a nice wide and flat power curve that is well centered in your engine's operating range. (ie: 2000 to 5500 RPM)
For $128.00 plus shipping for anything Erson has masters for, now is a good time to get some "special" cams made-up.
DD

thanks doug, i was talking to tom by e-mail and he can only ship to me here in newfoundland by courior and not ground frieght u.s post to canada post, last time i shipped that way to many hinded charges, so out of luck. but i can order through canada high performance, there comp brand custom cams are 280$can shipped. p.s. doug are you selling any harden oil pump gear if so how can i get a few.