383 or 400?

iv got about 1200 to spend on my bottom end not counting cam ect, i have a .040 over 4bolt 350 block and a std 509 400 block im building a track only car, the haeds im gonna use are 462 hump heads they are freshly built but only have 1.94in 1.50 ex but my ? is which of the two short blocks should i go with and if i use the 350 block it will be a 383, i dont plan to rev over 5500 and probaly will never use nitrous but would like to havw forged sluge incase i get a wild hair this motor is going in a mustang with a th350 and 3500 converter so any suggestins would be helpful thank you


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400, All the way. the 509 is a excellant block. Not only is it 50 cubic inches bigger, but the power it makes over a 350 due to the larger bore and longer stroke make it one of the most sought after now. We tried them all, 350, 372, 383, then finally 400, once we went 400 we never went back. I wouldn`t waste my time on hump heads, get some good heads for it and really wake it up. We did the same thing, we went from hump heads to dart II`s and really found what it could do. Make sure you get good rods for it.

I'd say 400. I'd also say you have to little head and too much convertor. Should 60' good!

You mention both blocks and shortblocks - are they bare blocks or do either have the rotating assembly?

Reason I ask, is the piston type will dictate in part how the deal comes together.

Those particular heads will work better, RPM-wise, on a smaller engine than a bigger engine. The bigger the CID, the less RPM it'll turn before peaking. You need to keep this in mind when you cam and gear it.

If it were me, I would build a 383, pocket port (at least) the heads, use a dual plane intake and a 750 CFM carb, headers, etc., as per how the usual SBC build drill goes.

MODS- this same thread has posted twice, answers on both.

Do you think it'd be a good idea to combine them? The earlier thread is HERE.

Thanks.

is it a 4 bolt 400 or a 2 bolt, is it a 2 bolt 350 or a 4 bolt. the stroke would be the same between the 400 and 383, just the bore size would change. what kind of track are you going to be running on? I have a 383 but I would have built a 400 if I could have found a good block. If you have a good 400 2 BOLT MAIN block go for it, most of the 4 bolts have some pretty bad casting. Good luck

Budget the lower end and build the snot out of the top end

Okay Cobalt, lets go round two. From a power perspective why would you choose a 383 over a 400 in this case?

400 with out a doubt!
if your racing it then make sure you fill block up to freeze plugs with block filler and a crank girdle is a great idea aswell.
I got a 509 block and bored .030 now 406 cu inch and nothing can catch it off the line.
yeah nice to have big block power in a small block!
dont skimp on heads the 400s like to breath and big port heads are a must for racing.
im using brodix -10 heads and super victor intake.
so you get the idea of how big you can go

So the dish in the piston would be smaller, of course! LOL

build the bigger engine.

use hyper pistons. no need for forged.

save money on the block and spend it on some better heads. Even a set of votecs would be much better than 462's. The 462 heads will be a bottle neck.

I would use a set of 200cc dart iron eagles.

LOL, touche good sir.

Seriously though, for streetable power below 5500 RPM NA there is no reason to not use the 400 block- unless you have to go more than .030 over. 400 blocks have a bad reputation for bore distortion, especailly when overbored.

Also, since you are chasing low RPM poser the heads will not be that bad. If you're running a hyd. flat tappet cam then you can do a valve job and mild port clean up that will give you all the low lift flow you'll need. Concentrate on flow around .300" lift with mild lobe profiles and limited duration that's where its going to count. Vortec's would be a little better, but not enough to worry about IMO.

I'd still build the 383. All part of my evil plot, you see.

First, you build the 383 with “claimer” parts- budget means a lot in this circumstance, but not at the expense of reasonable durability and performance.

Then, you talk the engine up (stroker, fulie, torque that rotates the world beneath your tires, awesome top end charge, great MPG, even- that is, if you can keep a straight face); give it “street cred” and a Bad-A rep.

Then, foist it off upon that one deserving dude. You know the one: big-mouth, know-it-all professional student with all daddy's money but no street-smarts.

Take that scroat’s money, put it into a tough bottom end and a killer set of heads for the 400 and never look back! Ha.

But seriously, the 400 will out torque the 383, but the 400 will be out of breath very early. A build somewhat like these two engines (heads were 441's w/2.02 X 1.60 valves) HERE shows the 383 out HP'ing the 400 when cammed the same, or nearly so, but having it's A handed to it when it comes to torque. The builds aren't together, so will take a little searching to find them both.

The 383 would extend the power band some, a 350 (which those heads barely feed w/the stock ports and valve sizes ) would rev higher still and still be making some power.

As I said in my first post: "If it were me, I would build a 383". YMMV.

I've heard 20 HP w/just the swap to Vortecs from fulies- not exactly chump-change, IMO.

But here we have a lightweight car w/a 3000 stall converter.

Working within these confines, I'd want something with a little top-end to it.

462 heads
0.300" lift = 167/121 cfm
0.400" lift = 198/134 cfm

vortecs
0.300" lift = 190/137 cfm
0.400" lift = 227/151 cfm

not enough to worry about?


http://www.purplesagetradingpost.co...1.html#GM%20462

I would much rather have a 350 with good heads then a 383 or 406 with sucky heads.

To make power, spend the money on the top end. Build the 400 to stock specs (cheap) but set compression ratio to match the cam.