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great find, Chevy 400 Small block

57K views 15 replies 9 participants last post by  TroyBoy 
#1 ·
Finally got my truck and opened the hood to find a Chevy 400 Small block! Next question is, I have read about 50/50 split on likes and dislikes, anyone with experience please weigh in. I also heard about cooling problems with the siamesed heads, but also heard that it is solved by having heads with steam holes drilled. Any experiences there? Thanks!
Zak

This is what I found on the net:
BLOCK # 330817
4.125 in bore family (1970–1980)
400

The only block of this family, 400 cu in (6.6 L) small-block, was introduced in 1970 and produced for 10 years. It was loosely based on the medium journal 350 and had a 4.125-inch (104.8 mm) bore and a 3.75-inch (95.3 mm) stroke. The 400 differed from other small blocks in that the cylinders were siamesed, used a 2.65” large journal, and oftentimes had one more freeze plug on both the left and right sides of the block. Initial output was 265 hp (198 kW) and was only available equipped with a 2-barrel carburetor. In 1974 a 4-barrel version of the 400 was introduced, while the 2-barrel version stopped production in 1975. 1976 was the last year that the 400 was used in a Chevrolet Passenger car, available in both A-Body and B-Body lines. While popular with circle-track racers and drag racers, the engine was prone to cooling troubles if cylinder heads without steam holes were used.
 
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#4 ·
Would like info from those experienced with a chevy 400 small block

sorry if I wasnt clear in the first post. I would like to know from those who worked/drove with a chevy 400 small block if there are cooling problems, or if that is a myth. Also wanting to know how they are overall as a motor. The info I posted first was all I could really find on a small block 400, the rest of the stuff I found on the net is split 50/50 like/dislike. Any opinions/experiences would be welcome. Thanks!
 
#5 ·
Any SBC head including the Vortec head can be used on a 400SBC engine as long as the gasket matches the block and the head has the proper holes for the "steam holes", which actually allow coolant to circulate through that area, preventing steam buildup and hot spots.

I have found if mated with sufficiently sized radiator and other cooling components, the 400 is no harder to keep cool than any other SBC.

Properly built the 400SBC can be a real performer, for not much $$.

If you have it bored, bore it only enough to clean it up and make sure the shop uses a plate for boring and for final hone also.
 
#9 ·
Overdriv said:
Any SBC head including the Vortec head can be used on a 400SBC engine as long as the gasket matches the block and the head has the proper holes for the "steam holes", which actually allow coolant to circulate through that area, preventing steam buildup and hot spots.

I have found if mated with sufficiently sized radiator and other cooling components, the 400 is no harder to keep cool than any other SBC.

Properly built the 400SBC can be a real performer, for not much $$.

If you have it bored, bore it only enough to clean it up and make sure the shop uses a plate for boring and for final hone also.
Overdrive, I'm a first time hotrodder. What work would you suggest? It isnt bored or anything. Far as I know, it is still factory spec.
 
#10 ·
I run a 406 in my Z-28 that is a 75 block. I took the short block to a local speed shop and had them take care of cleaning, machining, and assembly of the short block. I had the steam holes drilled in the Dart Pro 1 heads and I run right at 10:5:1 compression with a full roller valve train. I run a Griffin aluminum radiator with a set of electrical fans out of a 4th gen Z-28 using a Flexalite fan controller. I have no heating issues at all, no matter the temp or even sitting at an idle in traffic. You will absolutely love the power and torque these engines make. Have fun!!! :D
 
#11 ·
sb 400

the sb 400 is a fine motor !! with plenty of snort when you want it !!a bit of cam will wake it up along with a little open exhaust !! never experienced any cooling probs!! but when this motor came out was a replacement for big block so had plenty of radiator !! haven't wrenched for a living ror about 20 years so am off pace on all teck data!
 
#12 ·
JMSTOY said:
Overdrive, I'm a first time hotrodder. What work would you suggest? It isnt bored or anything. Far as I know, it is still factory spec.
Whoaaa, you first got to tell us, and show us, pics would be nice, what you are going to do with it and what you want out of the whole combination.

Nothing wrong with being a first time rodder, it is a sickness you know. Few ever recover.

Details??
 
#13 ·
Well, not sure what I am going to do with it, end product. But my hope is to have a daily driver, fun when I want it, but good enough to go to work every day. I want more than 5 mpg, but i also want to put a few rice burners in their place! :)That may be bi-polar, sorry. It is going in a heavily modded, chopped, 54 chevy truck. It already has a 12in rear in it, and a chevy muncie 4 speed transmission. I just got it and have not even looked inside, just exterior. Engine is not currently running, need gas tank, drive shaft, engine mounts, etc. I am going to take it to a local speed shop to get it cleaned, inspected, and ready to run, but dont know what to tell them to do with it! Bored over, heads, kinda lost here and trying to understand what I truly need. Thanks for helping a newbie out! Pics to follow
 
#15 ·
Well, without knowing the history of the engine, I'd have it completely overhauled. Minimum cleaned and sonic tested, heads checked for cracks. If everything checks out good the machinist will tell you how much it will need bored to clean up. That is what I'd go with, no more no less.

New bearings, rings, pistons and have the connecting rods resized. If you have access to a set of 350SBC rods I'd use them. You will need to decide on what heads you are going to use so you can tell the machinist what size the combution chamber is, so he can get the correct pistons.

If you are going to use iron heads try to keep the compression around 9:1, if using aluminum heads, you can probably up that to around 10:1, again depending on your head/piston/cam combination. Educate yourself on the proper quench needed, and what it means, then ask the machine shop if they know about quench. If they don't, find one that does. Make sure they always bore and hone with a torque plate.

A popular combination is a "D" shaped cupped piston and a vortec type head. Whether a set of GM vortecs or an aftermarket set of aluminum vortec clones, it makes a very good combination for the street/strip type application. Lots of torque to get that heavy truck moving. There are guys on here that can be very specific as to the correct parts combos and I'm sure they will post. But you need to search this board for SBC 400 builds etc., there have been numerous threads with just the info you need.

From the git-go, you need to decide on a budget and level of performance you want or can afford. If this is your first time, as you stated, be conservative and focus on the whole vehicle. If makes no sense to put all your money and effort into an engine and the rest of the truck be poorly outfitted to handle the power.

BTW, a noble cause indeed, to want to smoke the ricers, but you better have some deep pockets as some ricers are the real deal, do not underestimate them.
Good luck and have fun learning.
 
#16 ·
Have a 509 block that came out of a 69 Chevy pu. I got the truck from a buddy who had taken the engine out of his Monte Carlo. He thought it was a 350,lol. Best 350 I ever had,lol. I used to tow cars and stuff with that truck and it never overheated or anything else bad. The truck just had a plain jane radiator and shroud,nothing out of the ordinary. They are great engines and I wish you the best with your project.
 
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