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

[Greg Taylor <amundaza@xxxxxxxxx>]

Guys,
I don't think you'll need to fill the block for putting a 401 crank into a 343 or a 360, unless you're planning on some serious HIGH RPMs with the engine.  You're talking a difference between a 3.44 vs 3.68 stroke crank.  Also, the engine is going to need custom pistons anyhow, for use with the 401 crank & 343 bore, so why not use the aftermarket 401 H or I beam rods with the integral cap screws and you might not even have to clearance the bottoms of the cylinder bores (stock rods w/bolts would require clearancing).  When we stuffed the 390 crank into my 304 block, NO clearancing was needed with the after market 401 I-beam rods ... the cap screws allow about 1/4" more clearance, than the stock rod cap bolt/nut combo.

Sincerely, 
Greg Taylor 
Rochester Hills, MI
1989 Jeep Grand Wagoneer "TRMN8R2"
330-CID AMC Stroker V8

From: Frank Swygert <farna@xxxxxxx>
To: AMC List <amc-list@xxxxxxxxxxxx>
Sent: Thursday, July 28, 2011 6:47 PM
Subject: Re: [AMC-list] 401 Crank into a 343 how to sought

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
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