I am currently running a 400 with the following specs
bored 40 over
stock pistons
comp cam 265deh
balanced
heads shaved 20 thou
edelbrock intake
600 edelbrock carb
msd dizzy and 6a box
headers 2.5 inch exhaust
2500 stall convertor
np205 t case
44 inch tires
4.56 gears
The motor runs good but I need more power and torque
I am trying to decide between flat top pistons port stock heads, Aussie heads, or just start with a 460. What can be gained by staying with the 400 and upgrading parts? I do not mind if I have to run race fuel.

 

TMeyer, Inc. Precision Automotive Machining Check this site,as this guy is a 400 guru.Lots of aftermarket parts,and built projects to check out.He is also a member/sponsor on this site.

 

If I replace my stock dish pistons with new flat top pistons will I have proper clearance in the cylinder walls and will I have to rebalance the rotating assembly?

 

The hot setup for the 351m is convert it to a 400.You will need a 400 crankshaft and a set of pistons with a 400 compression heigth.The 400 is a longer stroke design at 4.0".The connecting rods are the same length.351m high compression pistom designs are almost non-exsistent.Plenty of 400 aftermarket design aftermarket parts and such for the 400.Look over the Cleveland section of Tim Myer's website.Many different arrangements to decide on..He sells a complete balanced and ready to use rotating assembly for $1200.00 for a 400 platform.Or cruise the junkyards and find a 400 complete engine and make the modifications yourself.Call him up,and tell him what you are wanting to build.And don't forget to get a new aftermarket timing chain drive gear conversion set.Hope this helps,and let us know how it works for you.

 

I suggest the same as above, but with differant heads. The 2v 400 heads are prone to detonation, and there are better designs out there. Also since this motor makes so much power in the bottom end, I suggest losing the 2500 stall, even though it probubly doesn't stall that high. Stock convertor, or maybe the slightest size bigger is all I would ever do. I know 2500 seams small, but trust me this motor doesn't need one and definately not with a 4x4.

 

get a bigger carb, these 400's run so much better with a good sized carb, for you a 750 would be about perfect (I run a 1050 dominator on mine , but then again it's not entirely stock lol). if you're going to go internal, ported Aussie heads and zero deck pistons will make a big difference, also a jump in cam size will give big gains too. depends on how much you want to spend, but I'd for sure get a bigger carb on there (and don't get a truck avenger, they're good when new, but quickly loose reliability after some use)

 

Funny you said that about the truck avenger because I had one on this motor and it ran great for a couple of years but now I cant get it to run right at all.

 

been running www.quickfuel.com carbs and had very good reliability and tunability. 750 cfm for sure. My next question is what is your long term plan for your truck. 400 good engine but if planning on bigger expectations big block might be the way to go. stroked big block is hard to beat but depends on your situation. stroked 400 stout contender also. But once you go big cubic inch parts reliability is your next problem. chromoly everything and tranny upgrades and drivetrain issues. Its all good, just money. catch you later!

 

yeah truck avengers do that dunno why, something happens and then they go all to crap, and don't improve no matter how many time you rebuild them. (predators do the same thing after a couple rebuilds too).

 

If your engine runs good i would recommend 5.13 gears or higher(numerically) in your axles you would be suprised on the difference gears can make. some trucks came stock with 4.10 or 4.56 gears and around 30" tires. just something to think about

 

Edelbrock heads should give you more torque. Plus they are bolt on and ready to run.

I hear there about as cheap as aussie heads all said and done.

 

I run a 77 ford with 40" hawgs with 4.56. this is border line gearing. your motor will have some problems with 44's and 4.56 gears. 5.13 is the way to go. catch you later. one of the things I forgot is once you start making power is you'll blow/burn up you stator out of your torque converter. I've had this happen twice with 40" hawgs and 4.56, TCI converters didn't do so well even upgraded converters. I've upgraded to a hughes torque converter xtm43 is the part number if I'm correct lower stall. If running a c-6 your gonna need a 5.13 gear ratio. In my c-6 I have a low gear kit and the best planetary gearz available. spent some money on c-6 to live in a part time daily driver application and toy truck. any questions drop a note.