Exhaust manifold crack again

[kookykrispy]

hard to beat a 350 with vortec heads and a properly matched cam

[108VanGuy]

Chassis Dyno

[ATTACH=CONFIG]40049[/ATTACH] here is a comparison of 2 different engines (not chevy) that shows how peak hp is misleading. the infinity has more hp but the bmw has much more all the way to 6k+. at 2k, where we drive, it is nearly double! the 'weaker' motor clearly wins in torque. peak horsepower gives you bragging rights while sitting on the bar stool, torque gets you off the line or up the mountain. I can not stress enough to ignore peak figures and focus on power where you need it. bone stock '70's 400 cid only made 265 hp but that was at 2400 rpm's! that 375 horse 383 may not reach 265 until well above 2400. regardless which engine you pick, get a cam with a range from idle to 4500 and a flat torque curve.

These torque curves look unusual to me. They should be much smoother if they are engine dyno runs. If they are chassis dyno runs then perhaps they are composite runs based on the engine speed. When making a power map dyno run, we would typically run the engine to near top RPM with no load and then slowly apply the load, stopping when we got close to idle. Gas engines would be loaded more quickly as they are more likely to overheat. A minimum of three runs are done for repeatability, but then most of my dyno experience is on large Diesel trucks not gasoline vehicles.
JRinaman makes a good point with the torque curve comparison and usable power band. IMHO, a good cruising speed is just above peak torque RPM. That way, your engine lugs down to peak torque requiring fewer gear changes. That is if your goal is a highway cruiser. JM2C
108VanGuy...

[jrinaman]

These torque curves look unusual to me. They should be much smoother if they are engine dyno runs.
108VanGuy...

didn't even look at that, it was the only one I found with 2 engines on one graph for simplified comparison. comp cams has several for their different small block chevy cams, much better info but not nearly as easy to make my point. joyrides cam is right about where he should be for more overall power without sacrificing low rpm power. even the 268 gives up a little where he needs it the most, I have always considered it a 'safe' cam for all around use but still too much for heavy loads up a mountain. back to kk's point, why not just swap the heads and cam? looking at these dyno charts, several good options for plenty of pulling power. http://www.compcams.com/Pages/401/dyno-sheets.aspx