[F-BIRD'88]

We know the 400's where never designed for high performance use.They where never intended for high compression use.I.E.:76cc heads

The 1970 400 SBC had a 10.25:1 compression ratio. I had one of these 1970 high compression ratio 400's.
it ran a 13 sec quarter mile back then in my chevelle. It was a high performance engine by any ones defination.


The 8.60 second 400 sbc we did we only had to use 1 block to do it right the first time. Stock GM block with blocked steam holes in the decks to strengthen the decks.

But gees it only ran 8.60's... Must have been something wrong with it..

The 406 street motor I have now...hummm 1 block... stock too. no steam holes in the heads. 5+ years.

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[1Gary]

For the record from Wiki:

400

The only 400 cubic inch size 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 cast siamesed, used a 2.65" 'large' main bearing journal, and oftentimes had one more core/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 full and mid-sized Chevrolet Passenger car, available in both A-Body and B-Body lines. While popular with circle-track racers and drag racers, the engine could be prone to cooling problems if cylinder heads without added steam holes were used.

And from E-question:

Engine HP Specs for 1970 to 1980 Chevy 400s
Written by moss strohem
Engine HP Specs for 1970 to 1980 Chevy 400s

The Chevrolet 400 CI small-block engine was introduced in 1970 and remained in production until 1980. It was an "in-between" engine option, fitting in the middle of the 350- and 454 CID Chevy engines.
Design and Applications

Based on the original SBC platform, the 400 engine used a crankshaft stroke of 3.75 inches (1/4 longer than the 350 SBC) and a 4.125-inch cylinder bore. It was -- as a large-displacement, small-sized engine -- used in Chevy full-size cars and light-duty pickup trucks. High horsepower was never the intention for the 400 SBC. Rather, the increased torque from the greater displacement made it suitable for heavy vehicles.

Standard Performance Output

The highest rated output for the 400 SBC occurred in 1970 -- 265 horsepower. Horsepower declined throughout the 1970s due to a combination of increased emissions requirements as well as measuring the output at the rear wheels (net) as opposed to at the engine flywheel (gross). At its lowest, output was rated at 150 to 180hp.

You can search any number of reliable sources,myself included,that advise drilling the steam holes.In my professional opinion drilling steam holes in non 400 heads has no relevance to the thin OEM 400 block decks.

[1Gary]

Curious as I always have been,I had to go search for the Turbo-Fire 1970's 400's spec.Honestly I didn't find the compression ratio,maybe it would be in a repair manual.Still,a two barrel 265hp engine in what would be at best a 3500lb car running 13 seconds in OEM trim,I am having a hard time wrapping my head around that.That is 43 yrs ago.

[F-BIRD'88]

The, my 1970 400 engine was stock other than headers and dual exhaust. Was in a 68 chevelle with 3.73's.
Some of us don't need to search on Wiki. Some of us were actual there and had these engines.
Factory rated at 330hp. These 1970 330hp 400's had flat top pistons and the 487x head 1.94x 1.60 factory valves. The cr was 10.25:1. With headers it had to have been 360hp. Made a ton of torque. I had a factory GM Qjet intake and a Qjet off my old 396, on it. It had th stock cam. 195-202-.390-.410 112. the "929" cam.

I took this 330 HP 400 SBC from a 1970 Impala.

I ran this for few years. Then, one winter the block cracked from not enough antifreeze.

this I did need to look up.: The 1970 330hp 400sbc engine RPO code was "LS3". The 1970 2 bbl 265hp 400 was a different low cr engine RPO code "LF6"

[F-BIRD'88]

I still have and use the old 14x3 GM high perf air cleaner and the th-350 transmission from that Chevelle, in my Firebird, today.

[1Gary]

The RPO code LS3 in a 1970 Chevelle was at 330 hp a BBC 402.

At this pointless post I just made,I refuse to waste anymore time on a topic having nothing to do with the O/P's question.Furthermore,I refuse to be the second party hi-jacking this thread.

[F-BIRD'88]

Originally Posted by 1Gary

The RPO code LS3 in a 1970 Chevelle was at 330 hp a BBC 402.

At this pointless post I just made,I refuse to waste anymore time on a topic having nothing to do with the O/P's question.Furthermore,I refuse to be the second party hi-jacking this thread.

Thats right but this engine was not from a chevelle.
It was a 400/330hp SBC from a 1970 Impala. And the RPO code was LS3.

There was actually three difference 1970 engines that year that had the same
RPO code LS3.

[gamedawg03]

Would lunant voodoo 60132 or 60133 be a good choice of cam

[1Gary]

Originally Posted by gamedawg03

I was looking at the lunati voodoo 60132 and 60133 cam i think they have complete kits to its going in a 87 monte carlo ss 7.5 10 bolt 4.10 gear but looking for ford 9in

Hope we didn't lose you.I left it off with a question about what your using for the bottom end of the engine??.

[gamedawg03]

Its a callies crank compstar h beam rods and mahle pistons its a complete rotating assembly im getting it internally balanced do i need a 350 damper and fly wheel since its internally balanced thanks for all the info

[techinspector1]

Originally Posted by gamedawg03

Im looking for a serious street and strip motor. This is my first serious motor being built, i have had all the machine work done to it i have been looking at rotating assemblies in cnc notorsports website. The one i looked at says its 11.6 cimpression with 64 cc heads .im getting my heads port matched and bowl blended and putting 2.05 valves in them my question is what would be the best way to go for cam for best power on street and strip a retrofit roller or solid roller

I'd like to help you, but I need to see what you're talking about. Can you post a link to the parts you're talking about?

[gamedawg03]

Yeah im trying to sorry about that but is on.cnc motorsports 406 rotating assembly 11.6 compression

[gearheadslife]

my motors manual list no 70 400 small block with 10.25 to 1 330hp
funny they do list a 402 big block. tho.. carry on

[gamedawg03]

Its part number cnc-3704 for rotating assembly on cnc motorsports

[1Gary]

Competition Lightweight Rotating Assembly Kit, 3.750 Callies Crank, 6.0 Compstar Rods, Mahle 11.6:1 Pistons, Chevy 400/406 | CNC Motorsports | Car Parts | Truck Parts | Competition Engines