Is a 400 a good motor ive had some.... but not much exp with one. In terms of good I mean power torq ecomony

The one I had was i a 1979 bronco.

 

they are great motors and don't be afraid to build one up.

the cylinder head design is advanced compared to a small block or FE. the 400 enjoys the canted valve arrangement of the 429-460 and big block Chevy 396-427-454. This unshrouds the valves for more airflow with the same size port. Also the 400 has built into it a "swirl combustion", if you look at the top of a 400 piston you will see 2 little tails near each valve relief, this causes the mixture to swirl as the piston goes down on power stroke, for a much more efficient burn.

the engine was about 20 years ahead of its time, really. most other makes just had flat tops with valve reliefs, domes, or dished back in 1970

with the 4" stroke and 3" main bearing, you can really rev it too with the right cam. The 429 BOSS also had a 3" main bearing and that engine would rev to 9000 rpm, and went heads up with the hemi. think of the 400 as a little 460 with a longer stroke.

people who think the bottom end of a 400 is "weak" are mistaken, it's bulletproof compared to a small block Ford or Chevy, and look at the power guys make with those small blocks.

I wouldn't bore a 400 beyond .030" without sonic testing, or you'll have cylinders with only about .095" thickness, which will run hot, and maybe crack if raced hard.

 

Swirl combustion features act on the movement of the intake charge as it enters the cylinder, prior to ignition.

Swirl combustion features are usually incorporated in the intake port design and/or combustion chamber design. Some diesel engines with swirl combustion use pistons with a "re-entrant bowl," on which the upper edge of the bowl is narrower than the lower part.

Is this what you're calling a "tail?"



That's just the shape of the valve relief required because the edge of the valve is so close to the cylinder wall. It is common to all pistons used in 335-series engines, which require the deepest point of the valve relief to extend all the way to the edge of the piston top.

 

that tail has a lot more to do with swirl than valve relief. if you look at the entire piston, and the tail on the bottom also, you'd see those valve reliefs are not directly lined up with the valves. hmmmm......

there is a patent on that piston top with the US patent office, and swirl was one of the best kept secrets in the automotive world. The name on the patent is "swirl combustion"

yes, it's a valve relief, but it also makes the mixture turn counterclockwise as the piston recedes. The entire head/chamber/valve/piston top is designed to work together.

a test engine with a glass cylinder was built, and the engine was run on low octane fuel at low rpm, and watched to see how the flame front reacted. that led to the development of the swirl piston top and chamber, which the 335 series has.

The Cleveland 4V heads with small chamber were the pinnacle of the design. That chamber also has major swirl characteristics, the large chamber less so

This is 20-30 year old technology, so I won't spend much time trying to convince people that it exists...that piston top could be flat and the valves still wouldn't hit with a .400 lift stock cam.

I've researched it heavily, read all the patent material and drawings, and the swirl design was used heavily in Bob Glidden's 351C ProStock NHRA drag racer, and Bill Elliot's NASCAR engine in the late 1970's-early 1980's. That's why they dominated with Cleveland engines and won many races and championships in a row.

Now the design is used by Chevy-Ford-Mopar also, even the ricers use it, it's no big secret anymore. Even my Briggs and Stratton 5HP tiller has a swirl valve in the carb, a bent piece of metal to get the mixture turning as it enters the port.