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I would love to chime in, but all I get from your links is some BS about vigilink.
Let me warn you about the flexplate. Most everybody is using flexplates from an offshore source (read China) and the thin material will not hold up. Buy an SFI certified flexplate that was meant for drag racing (SFI 29.1) and sidestep the problem.
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Thank you Denny.
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I probably should add this as well. You didn't say what your rear gears were in the initial post. Both of the engines you listed will be happiest with at least a 3.5 rear gear. More would be better. 3.73 or higher would be a good choice depending on tire diameter.
That's the problem with increasing cam duration. Contact ATK to find out what cruise RPM's at 60 MPH they recommend. I'm going to guess around 2500.
I'm not sure about the gear ratio, I think they might be 3.23s if I remember correctlyQuote:
Originally Posted by Hotrod46
Without the correct gearing, you will not get the benefit of all that advertised HP. If the engine is forced to lug around at low RPM, you will be worse off than with a stock engine. It will feel very sluggish and fuel economy will be terrible. ATK also recommends a higher stall converter than stock. If you don't want to change the gears and converter, you would be better off with a milder engine.
Depending on your tire size, you might get by with the 3.23's. The cams in both engines are for building power and torque in the midrange to high RPM's. The cam I had in my 383 was milder than the one in the ATK and I barely got by with 3.23's. The 383 is good at making torque, but the cam still programs the power characteristics of the engine.
Sorry if this sets you back, but you need all the info before spending all your hard earned cash.