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Old 08-28-2006, 02:50 PM
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406 race engine cam?

I'm going to build a 406 motor for dirt racing. It is going to be fairly stock with a stock cast crank, 5.7" aftermarket rods and hyperutectic dome pistons to give around 12:1 compression. Currently I have 461 stock heads. I plan on getting some aftermarket cast heads. Possibly even Vortec design heads. My question concerns the cam. I have designed a cam on some desktop dyno software. I come up with numbers for I @ 0.050 = 238 E = 250 with a LCA = 112. The lift is I = 0.510 E = 0.525. This is with a solid flat tappet cam. I am looking for heavy mid range torque. According to the software it will give me that. Was wondering if anybody has tried using a cam with similar specs? And if it would work? My understanding is that it will utilize a lot of dynamic compression because it does not have a lot of valve overlap. What sort of intake runner size would work best? I will be running straight methanol and have a heavilly modified holley 800 cfm carb. This will be in a car that weighs 2500lbs total with driver. I'm trying to keep this on the cheap side, but I don't want this thing to come appart on me either. RPM range will be from about 2500-6000. Peak power should be around 5500 and peak torque is 4500 but is strong from the bottom up.

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Old 08-28-2006, 03:15 PM
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If you haven't bought rods yet then get the 6". So you can lighten the piston. The lighter piston is easier on the stock crank.

Is this a modified? sounds like it with a 2500 pound rule.

If you buy the hypers. stick with a .125 dome max to keep piston weight down or even better, go with Dart 49cc heads and flat tops. If your gonna use the stock crank then keep your compression at 12:1 or less. You don't want to run over your own crank. I've done that. It hurt. A lot. Circle track engines are nothing like street engine because your on and off the throttle so much. With alky, you can't get a port big enough. 230 is the norm. Your program no doubt, is based on a gas cam. Your blowing all you torque out of the exhaust. You can't buy a book cam for alky either. Call comp and get a custom cam for 25$ more. Plan on going 7500rpm to be competitive in a mod. At least around here. Most mods are making 625 to 700 here.
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Old 08-28-2006, 05:08 PM
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That split duration ratio would be odd, it's too much, as would the 112 LCA, it's too wide. With the exception of the real small chamber Dart Iron Eagles most race applications will want a 106 or so LCA. For almost any head you look at to build power your going to be in the mid 250 duration at least, especially with that compression. Split will work out to be around 6-8 degrees with the better camshaft grinds out there. That's about the split I'd use on the Vortec as well. We will never, ever pick out a camshaft prior to selecting the head.
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