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Old 09-24-2005, 11:12 AM
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383 flywheel choice question

Hi, I'm installing a 383 into my '79 CJ5 Jeep, and am hoping someone here can help me with advice about what to use for a flywheel/clutch, etc. My step-brother started the restoration, but got moved out of state, so I'm trying to finish things up. I should point out that while I've got some very mechanical friends helping, I'm NOT a mechanic, and they all specialize in other makes (BMW's and ricers). So I'll try and be as knowledgeable and specific as I can be.
The engine is a 383, and built to be a "stump-puller" as I've read it described elsewhere in this site. I understand that it uses a 400 crank. I was told the red-line would be very low - mid-4k or so, and to be expecting somewhere around 400hp. I'm running it into an SM-465 Chevy truck trans.
I've read that the 400 engine uses an externally balanced flywheel, while the 350 uses an internally balanced flywheel. Is there a simple answer as to which I should use?
Please feel free to bring up any related questions or offer any advice. Thanks, Paul

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Old 09-24-2005, 12:20 PM
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You got a leaky spark tube...
 
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Seems like 400 hp at 4500 rpm for a small block would be kinda hard to do without the power continuing to climb well into the 5500 rpm or higher range. But I dont know, I dont have much experience with high hp engines.

I dont know what the factory flywheels in the pickups weighed but Summit does list some 33 lb flywheels on their site. I dont see why you couldnt just find a good used one. Clean it up and go with it. Get yourself a good clutch from Centerforce or Hays and be done with it.
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Old 09-24-2005, 03:15 PM
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If the 383 was built with a 400 crank AND it was NOT balanced by drilling in pouring, then you must use a 400 harmonic balancer and fly wheel, not just any old SBC fly wheel and harmonic balancer.

Trees
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Old 09-24-2005, 10:30 PM
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You'll need a 400 flywheel and balancer if the rotating assembly was externally balanced. Assuming the assembly was balanced . If you've got an old 400 flexplate you can drill out the spotwelds holding the weight on and then transfer the weight onto a 350 flywheel in the proper location. Set the old flexplate over the 350 flywheel and mark where the weight needs to go then have it welded on. This is a backyard type down and dirty way to turn a 350 flywheel into a weighted 400 style and I've had to do it a few times when I didn't want to wait for a 400 flywheel to get shipped in. It works fine for a street type motor no problem.
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Old 09-25-2005, 05:06 AM
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If you do buy a new flywheel get one is as heavy as possible. This will let you just ease out of the clutch while easing off the brake while starting on a steep climb...obviously low axle gears help to.
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Old 09-25-2005, 07:18 AM
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Easy answer is no simple answer, huh?

As I understood things, the engine WAS built with a 400 crank. I had a previous engine balanced (351C) while it was built, but I'm not really sure what is meant by internally vs. externally balanced. Does this refer only to the crankshaft's balance? If it only refers to the crank, is there a way to determine whether it was balanced (removing oil pan and inspecting?) or not?
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Old 09-25-2005, 03:46 PM
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You got a leaky spark tube...
 
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You can start by asking the person/shop that built the engine if it was balanced and if they say it was then they should have a balance sheet with all of the balancing info on it. Every time Ive had a crank balanced Ive always gotten a balance sheet with some kind of info back.

If you pull the oil pan you can look for areas there may have been (hopefully) small amounts of material added or removed from the crankshaft counterweights.

And possibly the damper and flywheel/flexplate???
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Old 09-26-2005, 06:32 AM
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Thanks for everyone's input. I'll check and see what I can find out. Paul
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