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Tech Question
Ron Stretch, Millville, NJ, 1968 Dodge Super Bee 383
That was a great article on using vacuum advance for a street car 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 a little work, and using stock exhaust manifolds. The cam is a Mopar Performance 284/484 hydraulic lifter P/N 4120235.
I've been trying to do some tuning to get it to idle a little better for the street and improve throttle response from idle. When I checked the vacuum it only had about 6 in/hg (steady). I looked for a leak and couldn't find anything wrong. Shot some carb cleaner around the ports and carb base but it didn't suck it in anywhere. From what I've read lately, it seems like a lot of people get the same reading on vacuum. This cam is the older version of the 284/484 with 68 degrees of overlap. I know Mopar Performance now sells this cam 56 degrees of overlap. I knew the idle would be choppy (who doesn't love that?) but I'm gettin tired of the poor driveability.
I was thinkin' about changing the cam to either a stock cam or the Comp Cam 280. I also thought about trying a set of variable duration lifters like Rhodes or Johnson. Any experience with those lifters or thoughts you can share?
Ron-
Yes, there's no doubt that the narrow lobe centerline is at the root of your problem. I get the gut feeling, from reading between the lines, that this sees mainly suburban street use and rarely revs high enough to where the overall engine and the cam specs are happy together. Shame, this cam can make some real HP, but, in a 383, it does need some RPM. No chance of convincing 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-on out of the box. Maybe temporarily install a UEGO sensor / display deal and see if it has a big lean spot, etc....?
The fast-bleeddown lifters do work, the only fly in the ointment is that there are so many variables that affect how well (or not well) they work for YOU. The main factors are valve spring pressure, oil viscosity, and temp.
Frankly, even the stock cam (originally designed for a 440 Magnum) was a bit hairy for Granny, in fact, back in the day, there were a few guys at Chrysler Engineering who though it was excessive. Of course, time (and time slips!) and proved the naysayers wrong.
Rick
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