Mopar Action On-line – Tech Questions


Tech Question

Ron Stretch, Millville, NJ, 1968 Dodge Super Bee 383

That was a great article on using vacuum advance for a streetcar in the latest issue. My ’68 ‘Bee is street driven. It’s a 383,Torqueflite, stock converter, 750 Edelbrock and stock intake, 906’s with alittle work, and using stock exhaust manifolds. The cam is a MoparPerformance 284/484 hydraulic lifter P/N 4120235.

I’ve been trying to dosome tuning to get it to idle a little better for the street and improvethrottle response from idle. When I checked the vacuum it only had about 6in/hg (steady). I looked for a leak and couldn’t find anything wrong. Shotsome carb cleaner around the ports and carb base but it didn’t suck it inanywhere. From what I’ve read lately, it seems like a lot of people get thesame reading on vacuum. This cam is the older version of the 284/484 with 68degrees of overlap. I know Mopar Performance now sells this cam 56 degreesof overlap. I knew the idle would be choppy (who doesn’t love that?) but I’mgettin tired of the poor driveability.

I was thinkin’ about changing the camto either a stock cam or the Comp Cam 280. I also thought about trying a setof variable duration lifters like Rhodes or Johnson. Any experience withthose lifters or thoughts you can share?


Yes, there’s no doubt that the narrow lobe centerline is at the root of yourproblem. I get the gut feeling, from reading between the lines, that thissees mainly suburban street use and rarely revs high enough to where theoverall engine and the cam specs are happy together. Shame, this cam canmake some real HP, but, in a 383, it does need some RPM. No chance ofconvincing you to try a slightly “looser” converter? That would help a lot.

The carb may also need some tuning work, it can’t be expected to be spot-onout of the box. Maybe temporarily install a UEGO sensor / display deal andsee if it has a big lean spot, etc….?

The fast-bleeddown lifters do work, the only fly in the ointment is thatthere are so many variables that affect how well (or not well) they work forYOU. The main factors are valve spring pressure, oil viscosity, and temp.

Frankly, even the stock cam (originally designed for a 440 Magnum) was a bithairy for Granny, in fact, back in the day, there were a few guys atChrysler Engineering who though it was excessive. Of course, time (and timeslips!) and proved the naysayers wrong.



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