I'm looking at another firebird this will be the 9th always end up having to sell them. A new guy at work has a 82 that is sitting and he swears up and down it has a 400 out of a Caprice. Factory horsepower for this was 190hp and not may builds I am seeing are with the 400. I see tons of 355 and 383 build and crate motors. Is the 400 hard to work with and he also says it has about 400hp to the wheels but its been sitting and is in pretty bad shape. How hard would it be to build a 450hp 400sbc build, with a stock rebuild kit on one what is ball park out put it has a Edelbrock 770 on it. Sorry if questions are already on the forums been surfing around for awhile just not finding the answers im looking for.

I dropped a 1976 400 All stock except for cam into my 83Z with a beefed up 700R4 and 373 in the rear and was running 12.9 in the quarter. all the torque kicks it

He has the same gear in it. And the cam is for sure not stock. We been playing with getting it fired up, and the cam sounds like its nasty. The transmission I'm not sure what one other then Turbo350 I'm a manual guy so don't pay much attention to AT.

First thing to check would be the heads if they are orig 400 style change them out with some smaller cc heads, just drill some steam holes 3/16 use the head gasket for template. The 400 were always low compression motors bump it up and you can get all the torque and hp you want.

Nobody builds 400's for a couple of reasons. First of all, since they stopped producing them in 1979, finding one is getting harder and harder. When you build a 400, it's very common to have the block bored out .030" making it a 406. The 383 is more common to build however using the 400's parts to build a 383 takes a lot more work and aftermarket components to do the job are better and cheaper than using OEM stuff.

To build a 400+ SBC, the best way to do it is to start with an aftermarket block. You can then build a 434. Going more than 434 in a SBC gets a little expensive.

What the engine came out of and what it was rated at doesn't mean much if cam, heads, intake etc are all changed. The 2 bolt main blocks are more popular. A 4 bolt main 400 has weak webbing around the mains. A 2 bolt block with studs is stronger than the 4 bolt.

There's nothing wrong with building up a 400 if you can find one but be aware that it can be a lot cheaper and easier to just buy a crate engine.

When I bought my car, it had an old school 383 and after a head swap and a different transmission with a proper stall converter, I was able to push it into the high 11's before blowing it up. Cast pistons and stock rods with stock rod bolts don't like to spin to 7000 rpm very well. It had a lot of miles on it when I bought it and managed 200 1/4 mile passes before it failed.

Since it already has a 400 in the 82 Trans Am is only reason was wanting to make something out of it. In all the other firebirds I have had always wanted to go 355 or 383. Wanted to do a 450HP street build with maybe NoS for the track. This one just kind of fell into my hands, I just sold my 83 that I put a 2002 dash in. I wasn't by any means hunting down a 400 block.

Thanks for all the feedback thus far really giving me ideas on what I wanna do. As for redlining 200 runs on a stock bottom end I think that motor gave more than it should .

The factory built SBC 400 used a 5.565" connecting rod, where as the factory built SBC 350 used a 5.700" connecting rod. Depending on who does the engine building, many SBC 400 are performance built using the longer SBC 350 5.700" rod or even a 6.000" rod. The down side to using the longer rod is the added expense. SBC 400 pistons are expensive compared to a SBC 350. Depending on the performance goals, the SBC 372 ( 400 block/ 400 pistons / 350 crank / 350 rods) can work well for a budget build.

dave w

I built a 406 for my firebird. I used a 5.7 rod and a keith black 147 piston which has a 17cc dish. With a 64cc head its right at 10.7:1. I went with the 5.7 rod because it is "suppose" to give a better rod/stroke ratio, I think I said that right. I had the bottom end balanced since I changed so many things.

You can still find 400 blocks out there. Since the machine shop screwed mine up I am hunting a stock bore 2 bolt block and starting over.

An aftermarket 400 block would be nice but they start at 1400 bucks from DART and uses 350 mains(I guess you could have the 400 crank turned down but I don't know for sure)

i had a 2 400ci engines and were always over heating thats was a big problem with the 400

I used a stewart components water pump, griffin 31x19 radiator, high flo thermostat and dual SPAL fans. It ran about 180 all the time. I think with a stock cooling system it would be tough to keep one cool.

The only time my 400 overheated was when the lower radiator hose split open going down I-805.

No tougher than keeping an engine of comparable power output of any other displacement cool.

All this "400 overheating" stuff is way overblown.

i believe the walls are thinner and the head castings are way thinner but the big problem is when the steam holes get clogged with rust then they over heat faster then say a 350 engine

Not really. The only purpose of the steam holes is to prevent steam pockets in the water jacket so you won't get a hot spot on the cylinder wall (vapor doesn't pull heat away from the iron as well as liquid does). It doesn't affect overall cooling.

so then i can use standard 350 heads on a 400 with out drilling the steam holes... answer NO! why because it will over heat! thats what happens when the steam holes get blocked it over heats....