CSB 400, best set up?

Car1 · Apr 11, 2019

I´ve been offered a pretty much untouched 400, casting#3951511, and don´t want to pass this opportunity up. I understand the heads #3973493 are rubbish, but that the engine should be a great start for a 400-450 hp/great torque, street engine. How would you set this up to deliver 400-450 hp still with nice torque? Engine would eventually land in a cruise/street car, not yet purchased.
Thanks/Car1

DZAUTO · Apr 11, 2019

I am a BIG, BIG time fan of the SB400.
There are WAY too many old wives tales about the inferiority of the SB400 ------------------- most, if not all, are unfounded.
Since about 1972, I personally have built about 25 SB400s ------------------- ZERO issues with any of them!

Let me touch on STOCK GM/Chevy heads first. Up through the 1974 models, Chevy made good heads. Then in 1975, they began cutting corners. The castings were lighter, metal was eliminated in some areas and 75-later heads had TWO exhaust cross over passages. This created more heat in the center of the head as well as increased the potential for cracks to develop. Thus, I avoid 75-later heads like the plague.
The heads, 3973493, on the engine you are looking at, are 1971-72 castings --------------- GOOD castings in my book (for stock Chevy heads). Those heads were built with 1.94/1.5 valves. After having heads like those inspected and magnafluxed, I like to use them. I have my machinist open them up to 2.02/1.6 valves and use stainless valves. I also have the heads modified for guide plates and screw-in studs as well as have the intake runners and bowles smoothed out (NOT a full port and polish). These heads already have the added holes for allowing steam to escape and with a flat top piston with 4 valve reliefs, compression is about 9.5:1.

All the SB400s I've built had the GM cast cranks and I use the longer 350 (5.7in) rods. Aftermarket pistons for this combination are readily available.
Oh ya, when using 350 style rods, a very slight amount of clearancing of the head of the rod bolt, which faces the cam lobe, needs to be done----------------to easy to do!

The 70-72 511 blocks had 4-bolt caps and the 73 511 blocks had 2 bolt caps. For a 2-bolt block, I prefer to use studs for the main caps instead of bolts and I install a windage tray in ALLLLLLLLL my engines.

A 400 cubic inch engine will tolerate a much bigger cam profile than a 283-327-350, so I like to use a cam with something in the .500in lift range.

topdog · Apr 11, 2019

The 400 cid engine is a truck motor with lots of low end torque. I run one in my 55. It is bored to a 406 engine, dual quads and double hump heads that are ported. To get some real horsepower you need to look at modern aluminum heads that flow nicely. Also a 750 single carb is actually better than my dual quads but I went for bling. I also have a flat tappet cam for lots of rump rump. Estimate at 425 HP. If I had to do it again the walls are too thin and engine runs very hot. In addition I would not use a flat tappet cam.

The 400 also is an externally balanced engine

topdog · Apr 11, 2019

My 406

Forgot to attach picture - oversize studs for rocker arms

Car1 · Apr 11, 2019

Thanks guys. I had a hunch this topic would render a few enthusiasts and recepies, hope there are more of them on the forum.
I´ve read posts on other forums about this engine, and many of them refers to problems with overheating. From what I understand, this has something to do with deleted water channels? In order to gain 400 ci I guess something had to go. Anyone got more info about this, and how to avoid heating issues?
/Car1

topdog · Apr 11, 2019

Car1 said:
Thanks guys. I had a hunch this topic would render a few enthusiasts and recepies, hope there are more of them on the forum.
I´ve read posts on other forums about this engine, and many of them refers to problems with overheating. From what I understand, this has something to do with deleted water channels? In order to gain 400 ci I guess something had to go. Anyone got more info about this, and how to avoid heating issues?
/Car1

Steam holes drilled in the heads is supposed to help. Just not enough meat between the cylinders to dissipate the heat. You are OK with a large cross flow radiator and no A/C . Running at 206 degrees is normal for that engine

bigblock261 · Apr 11, 2019

Corvette?

topdog said:
The 400 cid engine is a truck motor with lots of low end torque.

Speaking strictly in terms of the Gen I SBC era, I know Chevrolet offered the SBC 400 in Impala station wagons and pickups, but in my recollection not in Chevelles, Camaros, or Corvettes.

I also recall a huge following from the torque crowd, and as has been indicated, many 400s were built, by hot rodders, with needed improvements.

Back then, when pondering my next build, I weighed the costs, and just spent the same amount of cash on a screamin' 350. Nowadays, there is much ho-hum, another 350, really?

Let's just say I'm not burned out on 350s. Kinda like Chevy was with Chevelles, Camaros, and Corvettes.

JMO

mr55/56 · Apr 11, 2019

bigblock261 said:
Speaking strictly in terms of the Gen I SBC era, I know Chevrolet offered the SBC 400 in Impala station wagons and pickups, but in my recollection not in Chevelles, Camaros, or Corvettes.

I also recall a huge following from the torque crowd, and as has been indicated, many 400s were built, by hot rodders, with needed improvements.

Back then, when pondering my next build, I weighed the costs, and just spent the same amount of cash on a screamin' 350. Nowadays, there is much ho-hum, another 350, really?

Let's just say I'm not burned out on 350s. Kinda like Chevy was with Chevelles, Camaros, and Corvettes.

JMO

Chevelles starting in 73 got the 400 option. I too am burned out on 350s and add to that 383 crate motors and 400s. What's cool now a small journal SBC like a 283 or 327. The only stock block 400 I ever considered building was the 509 Casting.

DZAUTO · Apr 11, 2019

The SB400 was first used in 70 model full size cars and trucks and Monte Carlos.
Chevelles/Malibus/El Caminos got the 400 in 73.
The LAST year for the 400 was 1976 for cars and Monte Carlo.
Trucks continued to use the SB400 to its end in 1980.

Properly built and with a good cooling system, SB400s do NOT, repeat, NOT typically over heat.

The SB400 was used in trucks from 70 to 80 --------------- but it is NOT specifically a truck engine. That's like the old myth of the 348 originally being intended as a truck engine-------------NOT SO!

Oh ya, and MANY, MANY, MANY, MANY of the vehicles that were built with a SB400 also had air cond.

The 70-74 SB400s were 2bl carb engines. A 4bl (Q-jet) SB400 became available in 75.

ALL 70-72 SB400 blocks were 4bolt main ONLY. The 73-80 SB400 blocks were 2bolt ONLY.
Everyone has always believed that a 4bolt block was more desirable. BUT, time and experience has shown that the SB400 2bolt block was actually stronger---------------especially if studs were used instead of bolts for the main caps. The reasoning for a 2bolt 400 block being stronger is because the hole spacing for the main cap bolts is wider and the outer bolt holes go into a thinner/weaker part of the main webbing. And when the webbing is drilled/tapped for the outer bolts, it weakens the webbing. That's what all the SB400 gurus have projected. WELL, Tom Parsons has NEVER seen a 4bolt SB400 come apart in the main webbing. Sometimes I turn the 4bolt SB400 in my 56 Vette 6600rpm--------------been in that car for 20yrs. And here, I might add, all the 400 gurus recommend keeping the rpms below 6000 on a SB400 (I kind of have to agree with that philosophy, but I don't always adhere to that).

So, my bottom line opinion is, do not be so quick to avoid, or criticize, a SB400. It is a natural as a drop-in, bolt-in, hi-perf (or granny grocery getter) engine for replacing an original 265-283-327-350 small block.

Now, here is my only caution. When building a very healthy SB400, it is possible------------REAL QUICK-----------to get into the price range of what a nice BB, such as a 454, can cost. Shop around for parts and machine work, do as much of the misc engine work yourself, and make sure just what you really expect to achieve regarding torque/power.

mr55/56 · Apr 11, 2019

DZAUTO said:
The SB400 was first used in 70 model full size cars and trucks and Monte Carlos.
Chevelles/Malibus/El Caminos got the 400 in 73.
The LAST year for the 400 was 1976 for cars and Monte Carlo.
Trucks continued to use the SB400 to its end in 1980.

Properly built and with a good cooling system, SB400s do NOT, repeat, NOT typically over heat.

The SB400 was used in trucks from 70 to 80 --------------- but it is NOT specifically a truck engine. That's like the old myth of the 348 originally being intended as a truck engine-------------NOT SO!

Oh ya, and MANY, MANY, MANY, MANY of the vehicles that were built with a SB400 also had air cond.

The 70-74 SB400s were 2bl carb engines. A 4bl (Q-jet) SB400 became available in 75.

ALL 70-72 SB400 blocks were 4bolt main ONLY. The 73-80 SB400 blocks were 2bolt ONLY.
Everyone has always believed that a 4bolt block was more desirable. BUT, time and experience has shown that the SB400 2bolt block was actually stronger---------------especially if studs were used instead of bolts for the main caps. The reasoning for a 2bolt 400 block being stronger is because the hole spacing for the main cap bolts is wider and the outer bolt holes go into a thinner/weaker part of the main webbing. And when the webbing is drilled/tapped for the outer bolts, it weakens the webbing. That's what all the SB400 gurus have projected. WELL, Tom Parsons has NEVER seen a 4bolt SB400 come apart in the main webbing. Sometimes I turn the 4bolt SB400 in my 56 Vette 6600rpm--------------been in that car for 20yrs. And here, I might add, all the 400 gurus recommend keeping the rpms below 6000 on a SB400 (I kind of have to agree with that philosophy, but I don't always adhere to that).

So, my bottom line opinion is, do not be so quick to avoid, or criticize, a SB400. It is a natural as a drop-in, bolt-in, hi-perf (or granny grocery getter) engine for replacing an original 265-283-327-350 small block.

Now, here is my only caution. When building a very healthy SB400, it is possible------------REAL QUICK-----------to get into the price range of what a nice BB, such as a 454, can cost. Shop around for parts and machine work, do as much of the misc engine work yourself, and make sure just what you really expect to achieve regarding torque/power.

About the only thing I will dispute here is the availability of a 400 SBCs in maybe 70-72 Monte Carlos and never in 70-72 and trucks.

DZAUTO · Apr 11, 2019

mr55/56 said:
About the only thing I will dispute here is the availability of a 400 SBCs in maybe 70-72 Monte Carlos and never in 70-72 and trucks.

Yep, the Turbo Fire 400 with 2bl carb, rated at 265hp, was available in the 70-72 Monte Carlo. I have never personally seen an example, but they were also available with a 4sp.

mr55/56 · Apr 11, 2019

DZAUTO said:
Yep, the Turbo Fire 400 with 2bl carb, rated at 265hp, was available in the 70-72 Monte Carlo. I have never personally seen an example, but they were also available with a 4sp.

Me either, but never liked them other than to part them. Never in a truck, 72 service manual list v8 options as 307, 350, and 400[402].

CSB 400, best set up?

Car1

DZAUTO

topdog

topdog

Attachments

Car1

topdog

bigblock261

mr55/56

DZAUTO

mr55/56

DZAUTO

mr55/56

Top Contributors this Month

Recommended Communities