I would guess your 400 cam is the same. You might gain 10hp with that cam, another 10 with a 4bbl. Depends on what your goals are as to whether it makes sense to do.
Joined: Sun May 06 2007, 10:35AM
Location: State of Denial
Posts: 81
Are you sure? I would like to know specifically what that cam grind is .
I know that after 1972, OEM factories changed a lot of things regarding cam timing to meeting coming emissions standards. Cam duration and timing was one of them.
The cam I would like to use is the 383 Magnum cam which is similar to the 365hp 440 cam. I'm looking for a little more torque and to take advantage of the 4bbl that I've put on the engine with an Offenhauser Dual Port manifold for increased low end torque an fuel economy.
A dual exhaust is also a planned addition.
I don't want to go too wild with cam duration as wild cam duration can wreck a stock torque converter with its sharper power pulsations at idle and under acceleration.
Joined: Thu May 01 2008, 11:15AM
Location: Chicago,IL
Posts: 2868
am I sure, no. I don't have a new enough service manual to look up a 400. I can't imagine it's very much different. It's a smog 2bbl cam either way.
You'd see more benefit from pitching that Offy intake. Search hotrod.com for their 383 intake comparo, they dynoed 20 some intakes, that one did particularly poorly. Down on both torque and hp across the whole rev band. A stock 666 casting 383 4bbl intake would do you better even.
Joined: Sun May 06 2007, 10:35AM
Location: State of Denial
Posts: 81
I have that article from Hot Rod as well. My reasons for using the Offy are my own and I'm looking for improvements in mileage and intake mixture control.
Thank you for your input. I believe that the max duration that I can go with using the stock torque converter will be about 270 degrees intake and exhaust.
You can go with the factory 383HP cam (Mopar purple shaft 268/280 degree) or any other brand 268 degree cam without causing converter problems. I run a Comp Cams Extreme Energy 268H with no problems.
Since you're putting on a dual exhaust setup, track down a set of factory HP exhaust manifolds because they do make a noticable difference in torque/horsepower over the regular log manifolds.
In my opinion the 256-260 cam used in the 68-70 or 71 383's is a much better cam. You will notice most of the increased duration of the 260-268 cam is on the valve closing side which effectively retards the cam in the engine. Definitely a smog cam.
The valve lift for the 68 383 cam wasn't mentioned on furious70's post but it's .425 intake and .435 exhaust.