[dana44]

73_duster, on Sep 18 2008, 10:49 PM, said:

I will give you every single important detail I can think of so I can stop argument to myself about a Camshaft size.

I have a 73 Plymouth duster.
Weight: The car is roughly 3150lbs
Engine: 360ci bored .30.
Intake: Holley 670CFM 4bbl. carb, secondary vacuums. Edelbrock Performer RPM AirGap manifold (port matched).
Cylinder heads: rebuilt 340 "J" Heads, Fully ported.
Camshaft: 218/218 dur. .454/.454 lift. W hydraulic tappets.
Rocker arms: stock (I believe the standard 1.5).
Pistons: 9.3:1CR flat top with valve reliefs.
Crankshaft: Stock cast iron (would be shifting about 5600rpm). It was properly machined.
Exhaust: Hedman long tube headers, 2.5in X-Pipe, dual flowmaster
Ignition: MSD 6A Ignition and Blaster 2 High-performance coil.
Transmission: 727 torqflite with stock torque converter (came out of 76 dodge 1 ton van)
Axle: 3.33 Pumpkin
Tires: 15" rims

I was considering buying a higher ratio rocker arm for more lift and dur. But a PC program called "DynoBasic" is saying that a camshaft with around .550 lift would only have more power than the current camshaft anywhere above 5000rpm. What the heck?

So I am a bit confused and need your opinion about what to do. The car will be driven on the street and strip sometimes. I would like a boost in power but DynoBasic says I can't acheive it at that RPM.
And if you do choose the higher rocker arm ratio, what would be a good brand and ratio?

You have two scenarios here. One is strip, one is dual purpose.

For strip, in order to get a .550 lift camshaft, chances are good it would be a duration in the neighborhood 0f 225 at .050 lift (around a 300degree duration cam) and really wouldn't do much on the low rpm range, but higher compression would be wanted, even though you have decent compression now. You would want a 2500rpm stall converter to loosen the bottom end up, your 3.33s will work with that, 2500rpm is around 55-60mph so it wouldn't be too loose on the highway and would work.

For dual purpose, you want to stay in the .485-.500 and no more. Ported heads (if done properly) and with matching intake ports, with a duration listed, will produce more usable power, whereas an 1800rpm stall would still be better, it is an 11inch torque converter that is stock (police application) and would give you better overall drivability. The shorter duration also gives you more bottom end torque, the 218 is about a 275-280degree duration overall, brand depending, which is just at the top end of being midrange performance with tight torque converter and 3.33 gearing and the 9.3 compression, so overall, your cam right now with 1.6 rockers will get you there better, faster, and cheaper than changing the cam out and still not having adjustable rockers and anti-pump-up lifters to rev as high as you want without the springs floating or lifters pumping up and floating the valves.

Remember, properly ported heads will do more with a small cam than a larger cam in unported heads every single time. Essentially you can get as much out of the hot stock cam with ported heads than a .550 cam in stock heads, so use the flow and appreciate the breathing ability of those heads.

[dana44]

73_duster, on Sep 19 2008, 03:47 AM, said:

You dual purpose answer sounds like a great plan to me, I checked Ebay and I can pick up a torque converter that size pretty cheap (Can't find a decent scrap yard). And about the rocker arms, I was looking through summitracing and was focusing on prices. Crane seemed to have pretty decent priced rocker arm sets, I found two different sets for about $260. Would it be safe to go the cheaper route? Or just save up for a pair of nice rockers? And what is a company you would recommend?

Aluminum are good, but steel is better for longevity over the long run, and pushrods aren't that expensive to match the adjustable rockers, and the advantage is the anti-pump-up rockers set at zero lash don't float the valves at 5500rpm, so if you can get steel ones for $260 and 1.6 ratio, great, and brandwise, Crane or Comp are both very reliable brands.