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Old 06-12-2006, 09:42 PM
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383 or 400??

I have a 71 chevelle and the mildly built 350 just doesn't have enough power. When I stomp on the gas, I want to be able to see the gas gauge needle drop. So for my future gas guzzling car, what's a better power plant? Stroking my 350 to 383 or just dropping in a 400 ( my friend has a 400 he said I can have for 200). I have heard the 400 block had some bore problems but i have also heard that is a great motor. Since the 383 is going to have the same stroke as the 400, I'm assuming the 400 is going to produce better torque since it has more displacement, right? Did the 400 have any major problems? and would the 400 bolt up to a 1971 turbo 350 without any problems?

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Old 06-12-2006, 09:50 PM
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Do a search, there have been literallly hundreds of threads over which one is better.

The 400 will bolt up to your pulleys' and tranny the same as your 350 did. Just make sure that whatever heads you use have the steamholes drilled in them.


Brad
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Old 06-12-2006, 10:27 PM
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If you can get the 400 and the block is in good shape then go that route. Would you want to take apart a perfectly good 400 just to build a 383? I actually had somebody try to tell me that was the better way to go. Hmm, more cubes? Bigger bore? I'll stick with the 400...

Make sure whatever head you use on the 400 you drill them (or have a machine shop do it) for the steam holes.
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Old 06-12-2006, 11:37 PM
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I support the no replacement for displacement but. Seeing you asked the debate is about the rod angle. The 400 had shorter rods so with the same stroke the angle the rod ends up at as the piston is halfway down the bore is greater than the 383 with the same stroke but longer 350 rods. In an all out racing engine the greater rod angle puts more sideways pressure on the piston and that increases friction and lost horsepower.Not to mention stress on the rods. Keep in mind motorhomes from the 70's saw countless 400's blasting up mountain passes for hours with no reputation for problems. I'd build the most cost effective method
that produces the engine suited for what your doing.

Jusy my two bits
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Old 06-13-2006, 12:26 AM
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my frined used to have a stock 350 in his 86 chevy 4x4 and you could watch the gas needle dropping if he got on it.....i think his gas guage moved faster than his speedometer
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Old 06-13-2006, 12:28 AM
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o yah, i just thought i would say that building something to intentionally get bad gas mileage is stupid.....a well tuned built engine can get just as good mileage as a stock engine because usually they are more efficient
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Old 06-13-2006, 06:03 AM
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Quote:
Originally Posted by DougGass87
my frined used to have a stock 350 in his 86 chevy 4x4 and you could watch the gas needle dropping if he got on it.....
I would have to imagine that is probably that gas moving to the back of the tank and away from the fuel level sender, making it appear that the fuel level drops when you floor it. I cant imagine a 350 using that much gas that quickly, unless he's got a 3 gallon tank or something...
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Old 06-13-2006, 06:45 AM
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I would have to agree with that earlier post about rod angle. If you plan to wine it up a lot it will ware much faster with 5.7" rods. Parts for the 383 will be cheaper like pistons and most import blocks. I have a 383 vortec where I ran 5.7" rods and after 20,000 hard miles I had oval pistons (hypereutectic) and oval cylinder boars. Now I've been running an internally balanced 383 with forged crank pistons and 6 inch rods. After 40,000 miles the pistons show virtually no ware and the cylinder boars are in much better shape. So in my case all you need for a fresh rebuild is rings and a fresh 350 block, no balancing required (probably cam and lifters too) pretty cheap. Anyways your talking 23ci difference in the engines, meaning you will make about 23 more HP and TQ with the same internals. 400's are getting scarce and many that are still around are not always in the best shape. If you do go for the 400 (same with 350's) make sure it doesn't have any core shift issues or you will eat up high lift cams (especially dual patterns).

Ross
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