92Camaro305TBI

Is a small block up to 399 Ci


And a BB 400Ci and up??? Thanks

Scrams84Z

No, actually a 400 is a small block. The 396 was a destroked big block. It's most easily to tell the difference by the heads. A small block has in line valves, a Big Block will have offset valves.

------------------
'84 Z28 w/ T-tops, 420HP Stroked 383, Trick Flow aluminum heads, Tremec 5 speed, 3.73 posi rear, Edelbrock 750 cfm carb, Dual Snorkel air cleaner w/ K&N filter, Edelbrock headers & 3" exhaust, Edelbrock Strut Tower Brace, Hotchkis LCA's and Panhard Rod, there is much suspension work to come.

1979 Corvette - Black/Black - 350 CI L82 w/ MM4 close ratio 4 speed manual

"Smoke 'em if you got 'em"

RB83L69

The Chevy small block has one center-to-center bore spacing, and all of the "big blocks" have another, larger one. Consequently all small block cranks have the journals the same distance apart, the head gaskets are the same, the cam lobes have the same spacing, etc. Big blocks have different measurements for all of those things.

The distinction has nothing directly to do with cubic inches. There are big blocks down to 366 cu.in. from the factory, and small blocks up to 400 (401.6 actually) from the factory. The 396 wasn't "destroked", it was the original stroke which was 3.76", it came out in 1965. The 454 which came out in 1970 had a longer stroke. The 366, 396, 402, and 427 all have the 3.76" stroke.

------------------
"So many Mustangs, so little time..."
ICON Motorsports

Scrams84Z

You are correct. I apologize for that bit of mis-information.

AlkyIROC

The original chev big block was a 348. It was then upgraded to the famous 409. In 1965, chev redesigned the engine again using valve train designs of the first generation big block and the oiling system of the small block. What they produced was the first Mark IV big block of 396 CID. Since that date the big block remain unchanged in design until 1991 when they produced the Gen V engine.

------------------
Follow my racing progress on Stephen's racing page
and check out the race car

87 IROC-Z SuperPro ET Bracket Race Car
461 naturally aspirated Big Block

Best ET on a time slip: 11.242 altitude corrected to 10.89
Best MPH on a time slip: 121.52 altitude corrected to 125.89
Altitude corrected rear wheel HP: 497.9
Best 60 foot: 1.546

Racing at 3500 feet elevation but most race days it's over 5000 feet density altitude!
Member of the Calgary Drag Racing Association

87 IROC bracket car, 91 454SS daily driver, 95 Homebuilt Harley

jms

iTrader: (1)

The 409 led to the 427. No not the Mark IV 427 (used from 1966 to 1969), but a SUPER HIGH PERFORMANCE version of the 409 used for drag race only. RPO Z11, used in 1963, had a 13.5 to 1 compression with 2 four barrel carbs.

Then there was the Mark II 427. Called the Daytona Mystery engine. Used mostly in NASCAR in 1963 (and until the few supplied ran out into '64), this engine is a hybrid between the 409 version of the big-block and the Mark IV big block due in 1965.

The 348/409 crankshaft can be installed in Mark IV engines with a little machine work, if you want a super short stroke big-block.
3 1/4" stroke on the 348 and 3 1/2" on the 409.

In 1965, the 396 was the first Mark IV big block released in full-sized cars, 'Vettes and late in the model year-Chevelles.

The Chevelle 396 (201 made) was rated at 375 horsepower (with hydraulic lifters), but the same engine (with solid lifters) was rated 425 horsepower in the 'Vette.

The 427 became available in model year 1966 (through 1969) with later year versions factory rated up to 435 horsepower. Sure!!! Several L-88 427s were dynoed at 580 plus horsepower (at the crank) with the addition of just headers.

A few parts CAN interchange between big and small blocks (although not necessarily work very well). Distributors, carbuerators, starters, flywheels and lifters.
jms

AJ_92RS

I didn't know all that. Cool. I just always remember the easy way to tell. If you look under the hood and see the center exhaust ports touching, then it's a SB. If there's a gap between the center exhaust ports, then it's a BB. That's correct right?

I know the SB port sequence is EIIEEIIE, but is the BB (from front to rear) EIEIEIEI on one side and IEIEIEIE on the other, or are both sides the same?

Thanks in advance,
AJ

RB83L69

Well, since the heads are identical, they "read" the same from left to right, viewed from the side, which is front to rear on one side of the car and rear to front on the other side... so it's IEIEIEIE on one, and EIEIEIEI on the other.

Antoher quick way to tell at t glance is that small blocks have 4 bolts ont eh valve cover, 2 on the intake side and 2 on the exhaust side, or they have center bolts. Big block VCs have 7 bolts, 4 across the exhaust and 3 on the intake.

Stephen mentioned the old "W" block 348/409 engine; its valve covers aren't straight along the exhaust side, they have large "dents" to clear the spark plugs. If ou ever see the block disassembled, it has the extremely weird feature of the deck not being parallel to the top of the pistons.

The other 2 motor jms mentions are extremely rare and hardly matter except as a historical interest. They never came in production cars. Neither those nor the "W" block are what people are talking about when they say "big block" even though they are technically large blocks.

------------------
"So many Mustangs, so little time..."
ICON Motorsports

84 Z-28 350

the 409 and other early big blocks are "wedge" heads(hence them being called "W" blocks), the combuston chamber is not in the head but in the block itself. This is preformed by not cutting the piston bores perpendicular to head face unlike modern engins where they are perpendicular. this cauases a "wedge" shaped combustion chamber. hope I cleared some things up