Re: [AMC-list] 401 Crank into a 343 how to sought

[Frank Swygert <farna@xxxxxxx>]

When stuffing a 390/401 crank in a 343/360 block four bolt mains aren't 
necessary. They aren't necessary in the 390/401 block either. Helps for 
really high rpm use though. The bottoms of the bores need to be notched 
a bit to clear the rod bolts for the longer throw crank. The 343/360 
block isn't quite as stiff as the larger block, so limit rpm to 6000 at 
the most (5500 would be safer). I'd build the engine to take advantage 
of the extra leverage of the longer stroke -- a low rpm torque monster, 
out of cam by 5000-5500 rpm. The one or two guys I heard of doing this 
for high rpm drag engines filled the block to the bottom edge of the 
welch plugs (freeze plugs) for added strength. There should still be 
plenty water jacket to even drive it on the street filled like that, but 
make sure you have a good cooling system and a temp gauge.

--
Frank Swygert
Publisher, "American Motors Cars"
Magazine (AMC)
For all AMC enthusiasts
http://www.amc-mag.com
(free download available!)

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