Ralphbf

Just wondering......

Why would you build a 383 when you can have a 400?

Ralph

tfi racing

Try to find a good,used 400 block cheap.Then get back to us.

Indiancreek

They are getting hard to find that aren't beaten to death, or won't clean up anywhere near 0.030.

Aftermarket is an option, but the good one's are expensive.

Mark Riles

Aside from the difficulty finding a 400 block that's unmolested there are different end goals usually associated with theses engines. The 400 is something you might choose for low power band use like cruising and hauling *** away from a light. The 383 is a much happier high revving upper power band option. Aside from those differences, the 400 is how it starts, the 383 starts as a 350. The 350 can go in a lot of directions and they all have their advantages. It can be stroked and destroked to a lot of different cubic inch variations. If I were building a 400 for power I'd more than likely just step up to a BBC.

L88Plus

Come again???
They have the same stroke and will rev identically as long as the heads can feed 'em. A 400 will breathe better - as long as you have good heads on it - because the valves are further from the cylinder wall, less shrouding.
It's finding a good block that is the problem...

RobbSalzmann

I think the 383 evolved as a low cost way of upgrading the existing 350 engine by swapping out the crank and pistons.

A shadetree guy can buy a 383 rotating assembly with a slightly fatter cam and lifters, hone out the block, put it back together and have a big change in torque over a weekend. My buddies and I did this a few times back in the 19X0's

Edit: I forgot, you guys below reminded me. 350 bored .030 over with a 400 crank yeilds a 383.

bashcraft

This isn't true.

I too always asked why people would build a 383 instead of a 400. If you can swing an aftermarket block, the 400 is the way to go.

Indiancreek

383 started when the 400 mains were turned down to 350 and the first sbc 6 inch rods were converted Oldsmobile 6 inch rods (still have a set laying around here for some reason). Then all hell broke loose.

Ralphbf

So there is a guy here in town selling a 400 4 bolt main for $200.00.

So I should take it to a machine shop and have it checked out and
not worry about the 383?

billla

In the end, it's all about CID. Having a low(er) HP/CID ratio means a cheaper build overall...which is why BBCs are King. Costs are pretty reasonable right up to about 1.2 HP/CID...where they start to go geometric at 1.4 or so...

A 383 is the cheapest, easiest way to get CID in a GEN I. It's cheaper to buy a new, quality cast 383 crank than to have the existing crank turned, and most shops now clearance for a 383 (with stroker rods) as part of block prep VERY cheaply, with the cost a bit higher for stock rods due to the additional clearancing. If the power targets for a 400 block are beyond about 1.2 HP/CID, the stock caps are kinda marginal...lots of debate over this, but that's my perspective.

If an aftermarket block is involved, the there's no reason not to maximize the CID the combo is capable of. Bring money

Ralphbf

We kind of talked about this before, I'd be happy with an honest 400hp.

Ralph

Crepitus

That block will make a sweet 400hp build. Be sure the shop has a few stock block 400 builds under their belt. these blocks are notoriously thin. Have the shop check very carefully for cracks. Check decks and main webs very carefully Check the decks for cracks as well as flat and stock dimension. you dont want to deck or over bore very much at all, Deck less than .010 preferably 0 (pretty tuff with 30-40 year old blocks). No core shift or shift toward the thrust side is good. Over bore on a good block no more than .020.
Surprisingly the 4 bolt block is not the most popular choice. Of the stock blocks it goes somthin like this; 1; 2 bolt 509 with splayed caps, 2; 2 bolt, 3; factory 4 bolt. At 400 hp any of the blocks that dosent have a prob with core shift or cracking/warping will be fine. oh ya, Cylinder heads will need to be drilled for steam holes. The AFR web site has a good layout posted.

Good Luck!

Indiancreek

You can go .030 on the bore and hone. Few of them with many miles will make a .020. If your shop can sonic test and off set bore you might make size.
Sonic tested maybe a .040 but only with the sonic test. You can plumb coolant directly from the water pump to the center cylinders if cooling the center becomes an issue. After it's up and running, do some trmp. checks and see if the center cylinders are much warmer than the others.
On the other hand a 383 wouldn't come with all the extra work and costs.

Crepitus

On a mild build with a good block, ok Ill agree with .030. I dont really understand plumbing from the pump to the center cyls. Can you elaborate? My understanding is on the siamesed block there is a stagnate coolant area that is vented by the steam holes. An issue at low pump speeds. On hobby and street stocks we often dont drill the heads because pump speeds seem to wash things out just fine. Deck cracking in that area is so common I prefer to drill all stock block builds. Ive seen a lot of cooling ideas over the years for various reasons but I'm not sure Ive seen any huge results. Common cracking in that area could suggest a fix better than GMs steam holes is needed.

toddalin

If you want a fun engine, forget the 383 or 400. Find a 400 block and build a 377. That's a 400 bore with a 350 stroke that you can rev the snot out of!

hugie82

383 are easy to build and 400 are hard to find
But most who have a 383 wished they found a 400 IMHO

billla

Just a side note that in a performance build, generally the block is zero-decked - which requires a cut of .020 - .025 or more. There are zero issues with this, even on a 400 block.

Ralphbf

Don't the 350 and 400 have the same stroke?

350 - 4.030 and a stroke of 3.75 inches

400 - 4.125-inch bore and a 3.75-inch stroke

From Wikipedia

Ralph

How do you end up with a 427 small block?

bashcraft

Fixed that for ya.

hugie82

427=4.165 x 4.00 stroke