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Discussion Starter · #1 · (Edited)
i want to look at building a 421 out of a 400 i was wondering if there will be any clearance problems with the 3.875 crank or should i go with the 4in crank and make a 434 once again is there gonna be clearance issues thanks
 

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you might as well go with the 434. the cranks cost the same & more than likely your going to have to clearance either one. most likely it will need clearanced at the pan rails, & the bottom of the cylinder bores. a lot of it will depend on the rods that you use too.
 

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Even with an aftermarket block, and a raised cam journal, you are probably going to have to clearance lots of stuff. You will need an aftermarket block and if you're going to do that you might as well go all the way out to 434, if you have it in your budget you can even go as big as 454 (big cubes in a small block package)
 

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I am wondering the same thing also. I am not going to but an aftermarket block because i already have a good 400 block. i was thinking of a 427 or 434. Both will need a small base circle cam also, I think! correct me if I am wrong. I want a larger cube small block, I had great results with a 383. Now I want some more..
 

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This shows the usual places. >> http://www.chevytech.com/2c42o17.html also the pan rail area. When you look at your block you should see where it's had clearancing done from the factory and will need more. I recommend using I-beam Rods with Capscrews instead of Rods with bolts & nuts. Like these >> http://www.competitionproducts.com/prodinfo.asp?number=SCR6A7 these are semi stroker clearanced. Better prices here >> http://www.cnc-motorsports.com/product.asp?ProdID=1125&CtgID=21452
Complete rotating assembly will probably be cheaper than buying individual parts.
 
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