how much hp does a 400 come from the factory with [Archive] - Chevy Nova Forum

: how much hp does a 400 come from the factory with


speedfreak78
20th-December-2006, 11:02 AM
i would like to know how much hp a 400 has from the factory

Mike Goble
20th-December-2006, 11:22 AM
Depends on the year, some were rated at about 165, I think the most was in the mid-200's.

Philip
21st-December-2006, 07:35 PM
Actually until the rpm gets up into the 5k range horsepower is not what you are feeling, it is torque. The 400 torque numbers are higher than the other small blocks. When I first drove the Impala purchased for the 400 that was in it the engine was running poorly due to a stretched timing chain with a bad nylon gear and worn cam. It lit the tires up in first and broke them loose when the th350 hit second gear. In its poor condition running on about 6 1/2 cylinders it powered a 5300 lb Impala better than some good running 350 engines could. If you have the chance ride in a 400 powered car or if possible drive one. The big block that was originally planned to go into my car was sold and I have never regreted that decision.
Here are some numbers for you:
1970 400 2 bbl 9.0-1 compression 265 hp 400 ft lbs tq @2400 rpm
1970 350 4bbl 10.25-1 compression 300 hp 380 ft lbs tq @3200 rpm
1970 350 2bbl 9.0-1 compression 250 hp 345 ft lbs tq @2800 rpm
This comparision shows that with less compression and a 2bbl carb the 400 is equal if not superior to the 350 with a 4 bbl and lots more compression.

reo78rally
21st-December-2006, 11:58 PM
I'm glad someone asked this question, i was pretty close to making my own post.

I've been eye-balling the motor below for quite a while, and couldn't make up my mind.

1978 Chev 400ci engine out of 1978 motor home chassis. 2 bolt main block. 78000 miles, excellent running condition- I have it set up on a test stand, you can hear it run. For another $100 bucks, you can have the turbo 350 trans- newly rebuilt, although I do not have the paper work to confirm. I guess you would have to take your chances.


The guy wants $400 but is negotiable. I don't need the tranny, but I might get it anyway. He really didn't know for sure what it was, he said th350 in the ad. But after talking with him, he said it was a strange shape pan, and it being for a motorhome, I told him its a Th400.

Probably a very torquey motor, 78k miles, might just run it as is with a new intake and carb and maybe throw a cam at it while the intake is off, see what it does. Rebuild it when i get more money. How do you find specs on motors for motor homes? :D

Oh, and can you run any clutch package with a standard flywheel, or does it need to match the engine for balance?

Anyone else running a 400sbc?

StoveBolt
22nd-December-2006, 08:38 AM
Oh, and can you run any clutch package with a standard flywheel, or does it need to match the engine for balance?
No difference in clutch but 400s are external balanced, so you have to use a 400 flywheel and harmonic balancer.

edit: 400s are also Siamese bored and require a good cooling system, and if you ever change heads they have to have steam holes. (All no big deal though)

reo78rally
22nd-December-2006, 12:34 PM
No difference in clutch but 400s are external balanced, so you have to use a 400 flywheel and harmonic balancer.

edit: 400s are also Siamese bored and require a good cooling system, and if you ever change heads they have to have steam holes. (All no big deal though)

I knew about the harmonic balancer, but not the flywheel.

So, not every set of heads for sbc will work on 400's?

Bscman
22nd-December-2006, 12:48 PM
So, not every set of heads for sbc will work on 400's?

Have your local machine shop drill steam holes, and you'll be fine.

StoveBolt
22nd-December-2006, 02:28 PM
So, not every set of heads for sbc will work on 400's?
Yes they will, like Bscman said they have to be drilled and easy to do yourself, all small block head gaskets have the holes for steam holes, just lay the gasket on the head and mark, center punch and drill.. I did a couple sets on a drill press, just block up the head so the surface is fairly square and drill (you are just drilling into the water jacket maybe 1/8" thickness)

And you can always spot a 400 flywheel. it will have a long weight on one side of it.

Stock72Nova
22nd-December-2006, 02:54 PM
i would like to know how much hp a 400 has from the factory

What are the casting numbers I can get you the info. I have a SBC 400 with casting # 330817. Its a 2 bolt 1970-1980 block that made 150-180 HP stock.

1975ssnova
24th-December-2006, 06:18 PM
2 bolt 400's are better than 4 bolt this is backwards of other motors.

reo78rally
27th-December-2006, 05:50 PM
2 bolt 400's are better than 4 bolt this is backwards of other motors.

Can you explain a little more why? I've heard this before as well, but never had any evidence to support the claim.
Thanks

reo78rally
27th-December-2006, 05:51 PM
2 bolt 400's are better than 4 bolt this is backwards of other motors.

Can you explain a little more why? I've heard this before as well, but never heard any evidence to support the claim. 4bolt refers to how many bolts the main bearing caps have correct? Does the opinion have more to do with weight reduction? Or actual strength?
Thanks

1quik69
27th-December-2006, 06:24 PM
There is less material in the webs to support the crank caps with a 4 bolt 400. Although the 4 bolt 400 in our 72 was used as a race engine for over 20 years and it's still running fine.

Philip
27th-December-2006, 08:14 PM
The main webs are thinner to accomadate the larger cylinders. The outside bolt hole on the four bolt blocks is actually drilled thru part of the web and not fully contained like on the other small blocks. This is where the claim to being a weaker block comes from. Unless being built for high rpm usage it is not anything to worry about. 400's can make awesome power under 5000 rpms, if building a high rpm engine the holes can be filled and splayed caps installed to strengthen the block. The use of main studs also helps add a little strength.
Mine is a 4 bolt with studs and i am using stock length rods. A combination all say is not optimum. All my power is under 5000 rpm's and I am not worried a bit about pushing it.

mazer78
27th-December-2006, 10:03 PM
dont be put off by the low numbers that you see on the stock 400's. with a good cam and head package it will be night and day. as far as 2 bolt and 4 bolt go, i have a stock 2 bolt that i had splayed caps put on and i am pushing 648hp@7200rpm at the flywheel. i am not the least bit worried about it not holding up.

fast68chevy
21st-January-2007, 10:33 PM
plus these ratings are net, not gross


my TLS 400sb 509 casting in my 77 k-10 pickup is rated 175 horsies and 290 torque

but thats net, not gross

it has insane torque it will pull hard and will spin all four tires very easily and it is all original never been opened and doesnt have headers or anything else

good strong engines these old 400's are, low end power big time

im selling mine for 500 and if no one takes it then im putting it in my 82 trans am in which i already put a th350 in place of the thm200c

good luck

FunkyNova66
21st-January-2007, 10:44 PM
2 bolt 400's are better than 4 bolt this is backwards of other motors.Mine is a 2-bolt 400.:D

and yes...I love it.:D

Philip
21st-January-2007, 10:57 PM
While cleaning the garage today I ran across the radiator hold down plate from the Impala I took my 400 out of. I read the data and found some info I had missed or forgotten about. It had a factory requirement of 91 octane; given the low compression ratio that was surprising.

fast68chevy
7th-February-2007, 08:48 PM
car engines were typically more compression than truck ones

usually, but not always

again that depends on the year make and model and RPO code of the engine

it was probably closer to 9.0:1 CR in an impala
the specs could be found online if you did enough searching, would be at least one RPO code for the 400 engine in that year and model, if not 2 or 3


good luck

Philip
12th-February-2007, 11:10 AM
The 72 Impala 400 had 170 hp @3400 rpm and 325 ft lbs of torque @2000 rpm with 8.5:1 compression.
The numbers I posted earlier were from 1970 passenger cars and were the gross figures most of us are more familiar with. 1971 started the decline of compression, the retarding of cam timing and the end of the high horsepower era.

speedfreak78
12th-February-2007, 02:27 PM
now i just have to find one that doesnt cost alot of $$$$$
thanks guys

Stock72Nova
1st-March-2007, 04:40 PM
http://i146.photobucket.com/albums/r257/BrokeChevy/DSCF1525.jpg

Got this 400 one for $400. Actually I got a truck for $500 that had this engine in it pulled the engine and sold the truck for $100.