NJStingray

Just last week I picked up a '74 that has a 400 short block swapped in for the stock 350. I can't find all that much info about the 400 other than GM used it primarily on light and medium duty pick-ups. I also tried searching the forums to see if anyone else had a 400 short block to no avail.

Does anyone have a 400 short block? Is there anything performance wise I can do with the engine or would it be better to hold and swap in a 383 down the road? I appreciate any help/opinions/advice!

bashcraft

A short block is nothing more than an engine before the heads and intake have been bolted to it.

NJStingray

My understanding is that for the 400 short blocks, Chevy had to put steam holes to reduce hot spots. It's specific items like this that have me looking for more info, what I could do with the engine, and if there are other things I should be aware of.

bashcraft

You don't have a short block, you have a complete engine, correct?

Are you going to replace the heads? If so, you can have the new heads drilled, though it's debatable whether or not that's even necessary.

NJStingray

Ahhh, I see the confusion now! Sorry, yes - I should have clarified - I have a complete engine in my C3 currently and it is running. I just know it is not the stock 350 that was in it originally.

To answer your second question, I'm not sure what I can/can't do with the 400 (the 350 is obviously well documented here) and altering an engine is new to me (my mechanical experience has been limited to troubleshooting/fixing existing set-ups on more modern vehicles).

bashcraft

A 400 only has a longer stroke and a bigger bore, so most anything that can be done to a 350, can also be done to a 400.

bluedawg

You'd want to have good documentation of what's been done to the block and bottom end to know what you can get away with doing for more power. With out knowING at least wall thickness and information about the eternal it's a crap shoot. There was a thread not to long ago were a forum member put some money into a used 400" short block that made 500 miles before it exploded.

hugie82

I have a sb400 on the stand now and have had a few over the years. They run good but in stock form, they have no compression = no power. So if you are looking for a strong runner, start with a good set of heads since you have a short block. The heads must have the stream holes drilled if they are not present! The bottom ends are very strong up to 6000rpm. After that ARP studs are needed on the mains. Forged Pistons are advised.

NJStingray

Ah! Now that's some great info! Any heads you would recommend?

Also, I see you're from Bridgewater, NJ...I'm just 10mi down 78W in Clinton, Twp near the Round Valley Reservoir.

ShadowLands

Just about any aftermarket head will have the appropriate steam holes present for your block. Edelbrock, Air Flow Research, Dart, World Products, etc, etc, etc. You need to establish your goals for the engine/car in order to decide which heads will be a good fit for the application. Then you can pick and choose based on your parameters and price.

The Money Pit

I have been running a 400 for years and have learned a bit along the way. They are great power makers,...and heart breakers. Depending on the level of power you are after will dictate how often the heart breaks come.

If I were you, and the car is running OK now, I'd leave it well enough alone. Spend some time fixing other items first, then when you really want to raise the bar.....get into the 400.

FWIW....Mine runs about 540 hp, and has cost me three transmissions, two rears, required upgraded cooling and fuel systems. It runs like a Swiss watch to 7000 rpms now.....But the whole time I was sitting on worn out seats and driving with no radio.....If I could turn back the hands of time,....I would have done the interior, radio, etc .....first.

dugsgms74

Main advantage of a 400 block is the siamesed cylinders(which is the reason for the steam holes as well), because of the siamesed cylinders they can handle more bore. Keep in mind that they also have a larger main journal diameter than a 350.

BKbroiler

I'm even closer to you, in Lebanon Township (not Borough) near Califon.

74modified

I would check to see exactly what you have, because you didn't do the work. An original 400 will have a place for 3 freeze plugs on each side of the block. A regular SBC has only 2. So if it is a regular bock, they may have used a stroker crank to up the displacement to "400". If it is an original 400, they are a little different in that they are externally balanced and use special flywheels/flexplates. They are good engines, I ran one for years. 350 or other heads can be drilled with 6 small holes to match up with the 400 block. Good Luck

keithl1967

I built a 406 (the 400, bored .030 over) for my camaro...

Great runner...I used a stock cast crank, with Scat forged rods and Speed pro Hyper pistons...Couple with Dart Iron Eagle heads (64cc chamber, and 200cc intake runners), made for a 10.03:1 compression ratio. Put a comp cams hydraulic retro roller kit in it (K12-432-8), and according to desktop dyno (have not had it on an actual dyne), shoudl make around 460 HP and 515ft/lbs...

Bottom line is--the 400 is a great motor, if you build it right.

as an aside, I did have my heads drilled for steam holes--likely did not need to, but I did it for peace of mind--I'm a believer in "If GM did it..."

Gale Banks 80'

Many a Station Wagon came with 400's in them as well. 25 or was that 30 years ago the 400's were the rage for performance engine builds. To the point where junkyards were running out of used 400 blocks to build. This shortage could even be in some small part one of the factors the 383 was born. Put a 400 Crank in a 350 block and You have a 383. A lot of people were afraid of the 400 blocks with there Siamesed Cylinder Bores. Overheating, Blown Gaskets, Shifted Cores and weak Cylinder Bores were the concerns. People who knew Small Block Chevys couldn't deal with the differences of a 400. In addition to the above a larger Main Bearing diameter, externally balanced Crank, Steam Holes, short Rods ... However using the rule of there is no better substitute for cubic inches, the 400 still makes an excellent platform to build. The larger Bore un shrouds the Valves making more HP, the longer stroke makes more Torque.
The Blocks came in 2 and 4 bolt Main. Most Cranks were Cast. They make great Mild Street engines.

NJStingray

Right now that's the plan of attack. I'm just looking for info so that, when I get to this point, I know what I'm in for and whether it would be better to ditch the 400 or modify it.

I actually live in Lebanon Borough...not far at all. The boro is so small I'd easily know if there was another C3 residing in it

Thanks. My initial goal would be to add a little more "oomph" to it but am not looking for a monster 500+HP or anything.

I'm assuming you also put a different trans in with that kind of power and torque?

bluedawg

Read this thread. I'm not saying your 400" is in bad shape, but you might want to spend the extra time and money to have it checked out.


https://www.corvetteforum.com/forums...24-400-ci.html

terrys6t8roadster

I put together a 427SBC out of a 400 block. Used 6" rods, fully forged rotating mass, with a roller valve train. It's a torque monster, even with 3.08 rear gears it smokes the tires. Now the 9-car has a decent engine in it as in comparison to the anemic L-48 that it came with that had a hard time getting out of its own way. T

L88Plus

Early 400's only had 2 core plugs on each side, my "509"casting being one.
Tear it down and have the block sonic checked and magged before you decide what you're going to do with it. Don't buy heads, etc. - anything - until you're sure you have a block worth working with.