Im undicided,Don't know If I should just stroke it or just build more Cubic inches.I have two blocks one 400 sbc 2 bolt main and a 350 4 bolt main.I will be using a 3.800 Scat crank.What do you think?

 

406!!!

 

How deep are your pockets? What do you want the engine to do?
IMO, you need to answer those questions first.

If you are looking to make a 500 hp or lb-ft engine (flywheel), converting the 400 2-bolt to good 4-bolt steel mains is costly. The 350 4-bolt with studs should be strong enough, and cheaper to prepare.

What heads? Motown or Dart 220's might be a reasonable choice.
GM FastBurn also.

BTW, .030 over a 400 with a 3.80 arm makes a 412, not a 406.
The +.030 350 with the 3.80 is a 388. +.060 gives you the 393.

 

You do not need to convert your 2 bolt to a 4 bolt to run 500 +hp or torque. I have been running my 400 2 bolt block for several years making nearly 600 hp and have had no problems. But if you do have the money you can spend it and convert it to a 4 bolt, but I'd spend it on other go fast parts.

 

406 and use the best main bolt or studs

 

Im looking into a low Compression motor.I will be using a fair amount of nos.I also heard that the 400 4 bolt main is weaker than the 2 bolt main.Is this true?Something about the mains.

 

Great I think Im leaning towards the 400 sbc +60 over. Im really trying to get as much cubes.

 

The two bolt 400 block is stronger than the four bolt. As far as going 60 over, I wouldn't recommend that for a street driven machine. 30 over is about the most I personnally would go on anything that sees regular street type conditions.

 

Build the 406.
Stud the mains, get top notch machine work a good set of cylinder heads and it'll take all the abuse you could muster. Anytime you get the choice, "bigger bore motor or smaller bore motor", take the bigger bore. It'll flat out make more power.

-Mindgame

 

Don't skimp on cooling, cylinder heads or proper cam timing. Keep rpm below 6500 most the time and stock bottom end can hold up...

 

If you are going to convert the 2 bolt main motor to a 4 bolt then the best way to do it is to get some billit splayed main caps. They are much stronger than the factory straight bolt, 4 bolt main caps.

The 2 bolt main 400 blocks are stronger than the 4 bolt version because the webbing in the block is differant makeing them much more prone to crack. Your best bet is, as I already said, is to use the 2 bolt block and put some billit splayed main caps on it. It is more expencive but is well worth it in the long run. Also run as long a rod as you can. 400's have a terrable rod to stroke ratio which puts alot of undo stress on the sidewall of the bores. creating more drag, wears the cylinder quicker, and limits your RPM capability. You run a longer rod and it will take care of all of those problems.

 

I would recommend the 406 I run a stock 2 bolt block .030" over 13.6:1 it has main studs and a good align hone. I have well over 600 1/4 mile passes on this block (low 10s in a 3400lb car 7100rpm in the traps)I ran a stock cast crank for the first year until an oil pickup disentegrated wich sent metal through and tore up bearings and the journals. I now run a cola crank. Like LT said rod ratio is a problem with stock 400 rods I run 6" eagle rods. Another problem worth noting is cam to rod clearance you will most likley need to use a small base circle cam. If you plan to make more than 650hp total either NA or on spray I would cut to the chase and step up to a quality aftermarket block. The cost to benifit ratio of upgrading a stock block to billet splayed caps isnt worth it...... in my opinion if you make enough power to need splayed caps then there are other durabillity issues with the stock block that would need to be addressed such as deck thickness and cyl wall thickness. Both of wich are better in the aftermarket blocks. Just my .02

Craig

 

Well in a above post they said that im actually building a 412 not a 406.Im still undicided if I should Go .30 or .60 over with a 3.800 Scat crank.Tempature isn't that much of a concern to me.I think I can take car of of that With a 3 core Aluminum Radiator.Well Atleast thats what I think.I really dont want to run that much of a high compression.As far as the rods,Which Ones to get.Forged or billet?

 

Now that all the guys who own 406's have replied..... ahhh just kidding. I have a 383 in my drag car, but if I had to start all over and I had a 400 block and a 350 block kicking around my shop, I'd build the the 406. The old axiom of "There's no replacement for displacement" still stands. Tuned properly, and with the right cam, a 406 will make more torque, and at least equal horsepower as a 383.

 

...One more thing, the next engine I build for my car will be a 409 (.040 over 400).