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Author Topic:   sb 400 rpm's?
posted July 08, 2003 10:53 PM
I've never messed with a 400 before and I'm trying to get my modified on the track this season. A friend gave me a 400 short block that I'm putting a set of rings and bearings in and reusing the cast pistons and stock rods. My question is what kind of rpms can I safely spin this thing and how long can I expect it to last. The block is allready .060 over so I don't want to invest much money and I'm running out of time. Thanks for any help.

posted July 08, 2003 11:59 PM
Are you changing rod bolts? I wouldnt go over 5500 to 6000 and expect it to last very long if you do....Good Luck...Towman

posted July 09, 2003 01:15 AM
I would NOT use the stock rods at all,a least run a good set of stock 5.7 rod or 6" rods would even be better.
400's make excellent torque so you do not have to turn them a whole lot of RPM's
Just my 2cents

[This message has been edited by eighty (edited July 09, 2003).]

machine for speed
posted July 09, 2003 01:44 AM
Good Luck, .060 on a 400 is marginal at best. Expect to have problems, My guess is that if you have very much chassis flex you will crack a cylinder wall.

posted July 09, 2003 11:09 AM
Keep it under 6000 rpm's ,don't forget the extra cooling holes for the heads ,Keep it cool.
Friend had one in a super stock for 3 years and pulled everyone out of the corners .
I would say use it till you have another motor built cause it would make a good spare.

Tim Weiss
posted July 09, 2003 11:44 AM
been running 400`s for years all we ever run x rods stock crank forged pistons balanced run it 6500 to 7000 every week 2 years since rebuild it is just now starting to smoke a little though still lots of power

posted July 09, 2003 11:55 AM
I built a 400 small block last season 30 over decked.I ran the Wiesco flat tops the Eagle 6" 3D H beam rods with a 3.75 stroke steel crank,with Vortech heads in a 77 Monte Carlo Hobby Stock.I sold the car last season after I built it and the fellas who bought it are amazed at how tough that engine is.

I turned it 7800 rpm`s and they run it around 6800 since changing gears and will it fly.Our hobby`s can run a 400 small block in the larger frame cars and it eats the chevy metric 350 small blocks for lunch.

Good luck though on the 60 over 400 me myself would trash it because it isnt gonna run long.Its going to be more trouble than its worth.


posted July 09, 2003 11:22 PM
Thanks for the answers it pretty much confirms what I thought. I don't expect it to last long just to get a couple races on the car before winter when I can build a decent one.

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