destroking a 400
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Elder User
Joined: Apr 2003
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From: Normal, IL
destroking a 400
hey guys. i was wondering what ur opinion is on destroking a 400 with a 3.85 inch stroke crank. it would be a long rod, high rpm engine and i was curious as to what u guys think of it. thanx in advance 4 ur input.
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Elder User
Joined: Apr 2003
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From: Normal, IL
destroking a 400
i disagree. a big block has a deck height very close to the 400's (within .025 inches) and people constantly turn 6000 and more. i beleive it can be done, just nobody's attempted it.
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Joined: Sep 2001
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From: Jax FL
destroking a 400
i think him and shazam need to talk. it sounds interesting, but i dont think it will happen for the price he is looking for.
it is doable
it is doable
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Elder User
Joined: Apr 2003
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From: Normal, IL
destroking a 400
my fathers 3.85 inch stroked 460 turns in excess of 6000 rpm and its only limitation is the small camshaft. and for this planned build, we plan on using 6.8 inch rods, and a piston with a compression height of 1.28 inches. this engine will also use a solid roller camshaft.
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Joined: Oct 2002
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destroking a 400
I don't see anything wrong with destroking this thing a little. Just look at the success that the 390 FE had with very similar specs. Besides if you want to buzz one up that high, a 4" stroke is wasting lots of friction in piston speed and crank rotation waiting for the rod to finish it's cycle to go back the other direction.
Posting Legend
Joined: Sep 2001
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destroking a 400
My 390+6FE would turn 9000 rpm, but it did have shaft mounted rockers and solid lifters. It was balanced and blueprinted also. It should be possible to turn the 400 at high rpm's also, but it will suck gas like a fiend. I was running my 396FE back when gas was $.25/US-gallon. I got 8mpg when she was running right, 4 when not.
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From: PacNW
destroking a 400
What am I missing here? I'm aware of the high RPM potential of 'oversquare' engines due to reduced piston speeds but look at the motors shazam has been building & running at 8000 RPM. In addition I have a friend of mine who used to run a warmed up 400 with basically stock parts at 7000 RPM consistently. In shazam's case he's running a significantly 'undersquare' engine at 8K and my buddy was running his 'square' engine at 7K with no problems.
I just don't see anything 'magical' about the 3.85" stroke of the 460. If you want to increase the acceleration on an IC engine, you need to lighten the reciprocating assembly. If I'm going to spend the money then I'd get some lightweight custom pistons, an aluminum flywheel & racing balancer and start doing some serious grinding & rebalancing of the crank & rods or go out and buy a custom forged steel unit with the appropriate weight modifications.
A mildly built 400 will turn 6K easily with the proper induction systems in place. A 4V manifold & carb and good quality headers combined with the proper camshaft will make a huge difference in the engine.
I just don't see anything 'magical' about the 3.85" stroke of the 460. If you want to increase the acceleration on an IC engine, you need to lighten the reciprocating assembly. If I'm going to spend the money then I'd get some lightweight custom pistons, an aluminum flywheel & racing balancer and start doing some serious grinding & rebalancing of the crank & rods or go out and buy a custom forged steel unit with the appropriate weight modifications.
A mildly built 400 will turn 6K easily with the proper induction systems in place. A 4V manifold & carb and good quality headers combined with the proper camshaft will make a huge difference in the engine.
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destroking a 400
Remember Ford's first V8 engine, the good old flat heads. Small bore, long stroke. What they lacked in horsepower was made up in torque.
Now look at the 5.4 and 6.8 modulars. 4.17" stroke, 6.66" rods, 10.08 deck, and a 3.55 bore. You can rev the snot out of them because the internals are very light plus the long stroke makes great low end torque. They are a win-win combo.
Stroke all your street motors.
Save the destroking for race motors.
Now look at the 5.4 and 6.8 modulars. 4.17" stroke, 6.66" rods, 10.08 deck, and a 3.55 bore. You can rev the snot out of them because the internals are very light plus the long stroke makes great low end torque. They are a win-win combo.
Stroke all your street motors.
Save the destroking for race motors.