why bother building a mega inch SBC at all.

grumpyvette

grumpyvette

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Staff member
now admittedly IM writing this some what tongue in cheek, because Im well aware of the addicted, at times even RABBID SBC faction,
BUT as a dedicated BBC, and old school Pontiac, and mopar BIG BLOCK FAN, who likes building 454-540 bbc, 455-468 Pontiac, 440-500 MOPARS and 392 hemi,s, IM always amazed at the guys who want to stick with the sbc rather than upgrade,to a basic block config thats designed for the extra displacement. but I get guys in my shop all the time who want to build 427-454 SBC engines, for street strip use, and expect both decent street manors and 550-600 flywheel hp I build ocasional sbc engines of 406 (.030 over bore 400sbc engines)and 426 (4.185 bore/3.875 stroke sbc engines)displacement, but far more 383-396 simply due to the base 350 block being far more common, I build a good deal of 383s designed for nitrous us, that easily exceed 550-600hp on the giggle gas, but once you get over a 3.875" stroke things are getting pretty tight in the cam/connecting rod clearance so I try to steer them into a BBC combo if I can, for the simple reason that its a lot simpler to build a 482-489-496 BBC (4.25" stroke 454 with or without a slight over bore) and in most cases the final product cost per horsepower will be slightly in the bbc favor once you try to exceed 550-600hp N/A
yes I can hear the screams already!
but after you have a few brandys and think it thru, many guys find Im correct,If your goal is 550-600hp plus N/A, and you want both reasonable drive ability on the street and an occasional bonzi charge to impress your buddies with reasonable chances of taking the car out without maintenance issues, a big block makes more sense to me

OK ILL STEP BACK, YOU CAN START SCREAMING AND BURNING MY LIKENESS IN EFFIGY
 
GRUMPYVETTE?
Here is a simple, basic question: If I had a 427 SB and a 427 BB equivalent heads, headers, etc.. Which makes more power?

the problem here is that " equivalent heads" and other factors
the BBC can EASILY produce a GOOD DEAL MORE HP, Ive built easily a 100 plus BBC engines and well over 100 other engines of all types, and the problem with the comparison is that decent sbc heads usually flow in the 220cfm-300cfm range and at best have 2.05/1.6 valves while a decent set of BBC heads has 2.3"/190 valves and flows 280cfm-440cfm
its really not a contest

look heres one of the best STANDARD 23 deg SBC heads
http://www.airflowresearch.com/sbc-210cc-c-72_93.html
210ccRH.gif




heres a SMALL BBC HEAD
http://www.airflowresearch.com/bbc-315cc-c-1_99.html
315ccCNC.gif


srp400.png



now if you know what your doing the BBC can have a 4.5-4.6" bore that un-shrouds the larger valves, and install a 3.25 de-stroker and build a killer high rpm bbc
but even if the engines both displace identical 427 cubic inches the 427 BBC almost always has MORE THAN ENOUGH extra hp to MORE than compensate for the extra block weight.
theres been several magazine articles on that theme and if done fairly the BBC always pulls more hp

http://www.chevyhiperformance.com/techarticles/0707ch_small_block_vs_big_block/index.html


Small Block VS Big Block - A Game of Rat And Mouse

Small-Block Dyno Details
Headers 171/48 Headman headers
Fuel 91-octane unleaded
CARBURETOR Dual 750-cfm Holley carburetors
Jets Test 1: 71/80 Test 2: 72/77

TEST 1
Advance 37 degrees
Max torque 522 lb-ft at 4,700 rpm
Max power 526 hp at 5,900 rpm
Average torque 501.3 lb-ft
Average power 480.2 hp
Power 1.24 hp/ci
RPM lb-ft hp
4,100 510 398
4,200 511 409
4,300 514 421
4,400 517 433
4,500 519 445
4,600 521 457
4,700 522 467
4,800 521 476
4,900 518 484
5,000 515 490
5,100 510 496
5,200 506 501
5,300 500 505
5,400 494 508
5,500 487 510
5,600 482 514
5,700 478 519
5,800 474 523
5,900 468 526
6,000 460 525


BBC RESULTS BUILT FOR THE SAME MONEY
Block VS Big Block - A Game of Rat And Mouse

TEST 2
Advance 42 degrees
Max torque 543 lb-ft at 4,700 rpm
Max power 574 hp at 6,100 rpm
Average torque 518.8 lb-ft
Average power 515.8 hp
Power 1.36 hp/ci
Changed oil to Royal Purple
Lashed valves 0.020/0.032
RPM lb-ft hp
4,100 530 414
4,200 530 424
4,300 531 435
4,400 534 447
4,500 537 460
4,600 541 474
4,700 543 488
4,800 543 496
4,900 542 506
5,000 540 514
5,100 536 520
5,200 531 526
5,300 528 533
5,400 526 540
5,500 523 548
5,600 521 555
5,700 517 561
5,800 512 566
5,900 506 568
6,000 501 572
6,100 494 574
6,200 486 574
6,300 478 573
6,400 469 572
6,500 461 570



then you might want to keep in mind with a 4" stroke on both engines the SBC with a DART block and a 4.185 bore has a 440 displacement
the BBC with a DART block 4.60 bore has a 531 displacement, but a BBC can EASILY use a 4.25" stroke and with the correct block a 4.6" bore gives it 565 cubic inches of displacement, EVEN IF they both made the same 1.2 hp per cubic inch that results in a 529hp sbc and a 678hp bbc, and TRUST ME WHEN I TELL YOU its a whole lot easier to clearance a 4.25" stroker BBC than a 4" stroker SBC
 
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EVER wonder why the engine masters winning engines seems to be dominated with the 420 cubic inch and smaller engines?
especially when the BIG BLOCKS always seem to produce the best peak power and the high torque numbers?

ITS because of the TESTING PARAMETERS BEING USED, favor those engines and the RPM limits are set up to limit the effective use of larger port sizes at higher rpms and displacement parameters tend to favor the smaller engines,with the mid sized ports , you can get an engine set up to produce a wide torque curve over a mid rpm range and limited to 6500rpm to produce power well, but once you add the larger ports, and the larger bores the larger engines, have and the cam timing required to feed that larger displacement you kill off much of the off idle torque, and the testing parameters,its not like the big block won,t have much more torque or horsepower, its just that it won,t always dominate if the formula divides the results PER CUBIC INCH and limits the rpms,rules like that are set up to favor and measure that low rpm torque, as well as the peak hp, change the test parameters to measure the narrower 5000rpm-7500 power band and a 427-477 displacement starts to look better, keep in mind POWERS all about efficient air flow thru the cylinders , when your measuring horsepower PER CUBIC INCH of displacement the smaller engines tend to have a higher ratio of valve curtain area, to displacement making the engine breath easier and less air flow needed to effectively fill the cylinders, you can,t get a valve large enough into a 4.5" bore on a BBC to equal the flow per cubic inch that a 2.02 valve on a 327 SBC has, each sq inch of valve curtain in a 327 needs to feed only 12.6 cubic inches of displacement, a 2.25" valve on a 454 feeds about 16 cubic inches of displacement
if they only measured max torque and peak hp over the 3000rpm range the engine builder selected regardless of displacement , or only measured hp at the rear wheels, or how fast you can push a 3000 lb car, the big blocks would easily dominate
 
Grumpyvette said:
BBC almost always has MORE THAN ENOUGH extra hp to MORE than compensate for the extra block weight
Click to expand...

Yes, but its that extra weight(and fitment) that made me stick with a sbc on my car. Because a BBC is darn heavy on the front of the car/steering wich those car was not designed for(80 camaro). Did i say agility?

Now, a question. If you have the above 327 sbc and 327 bbc. Wich one will have the better MPG?
 
the smallest bbc engines the 366 , yes its possible to build a 316 with a 348 chevy crank and custom pistons, but the valves would still need to be the 366 heads size and I doubt the 316 bbc would have any advantage over the lighter 327 sbc
 
Oh, i meant 427 sorry about that.

I also feel the BBC is more reliable because of a better bore to stroke ratio, i am wrong?
 
the results would depend on the car weight and drive train gearing but Id select the 427 BBC almost every time even if it got a bit worse mileage, simply due to the fact I build and tune far more BBC engines every year and have far more spare parts, yet if I was overly much more concerned with both mileage and durability ID select a 5.7 LS crate engine
Chevy V8 bore & stroke chart
I saw this online and figured I would post it..I am going to add the popular lsx strokers soon
CID BORE STROKE
262 = 3.671" x 3.10" (Gen. I, 5.7" rod)
265 = 3.750" x 3.00" ('55-'57 Gen.I, 5.7" rod)
265 = 3.750" x 3.00" ('94-'96 Gen.II, 4.3 liter V-8 "L99", 5.94" rod)
267 = 3.500" x 3.48" (Gen.I, 5.7" rod)
283 = 3.875" x 3.00" (Gen.I, 5.7" rod)
293 = 3.779" x 3.27" ('99-later, Gen.III, "LR4" 4.8 Liter Vortec, 6.278" rod)
302 = 4.000" x 3.00" (Gen.I, 5.7" rod)
305 = 3.736" x 3.48" (Gen.I, 5.7" rod)
307 = 3.875" x 3.25" (Gen.I, 5.7" rod)
325 = 3.779" x 3.622" ('99-later, Gen.III, "LM7", "LS4 front wheel drive V-8" 5.3 Liter Vortec, 6.098" rod)
327 = 4.000" x 3.25" (Gen.I, 5.7" rod)
345 = 3.893" x 3.622" ('97-later, Gen.III, "LS1", 6.098" rod)
350 = 4.000" x 3.48" (Gen.I, 5.7" rod)
350 = 4.000" x 3.48" ('96-'01, Gen. I, Vortec, 5.7" rod)
350 = 3.900" x 3.66" ('89-'95, "LT5", in "ZR1" Corvette 32-valve DOHC, 5.74" rod)
364 = 4.000" x 3.622" ('99-later, Gen.III, "LS2", "LQ4" 6.0 Liter Vortec, 6.098" rod)
376 = 4.065" x 3.622" (2007-later, Gen. IV, "L92", Cadillac Escalade, GMC Yukon)
383 = 4.000" x 3.80" ('00, "HT 383", Gen.I truck crate motor, 5.7" rod)
400 = 4.125" x 3.75" (Gen.I, 5.565" rod)
427 = 4.125" x 4.00" (2006 Gen.IV, LS7 SBC, titanium rods)

Two common, non-factory smallblock combinations:

377 = 4.155" x 3.48" (5.7" or 6.00" rod)
400 block and a 350 crank with "spacer" main bearings
383 = 4.030" x 3.75" (5.565" or 5.7" or 6.0" rod)
350 block and a 400 crank, main bearing crank journals
cut to 350 size
http://garage.grumpysperformance.co...ng-piston-pin-height-compression-height.5064/

Specs
  • Comp Height 5.565" Rod - 1.561
  • Comp Height 5.7" Rod - 1.433
  • Comp Height 6.0" Rod - 1.13
  • Pin Diameter - 0.9272

if you change to much cheaper and much stronger 5.7" connecting rods the less common compression height pistons are not an issue
youll have dozens of choices in a 4.125-4.165 bore diam. with a 5.7" rod
keep in mind the old O.E.M. rods have already been through millions of stress cycles and they are a weak design
resizing, , refurbishing the original 400 connecting rods, and replacing
just the connecting rod bolts will cost far more than the SCAT 5.7" aftermarket rods that are at least TWICE as strong
.

http://www.scatcrankshafts.com/rods/

https://www.speedwaymotors.com/KB-Claimer-Chevy-400-Hypereutectic-Pistons-Flat-Top-57-Rod,33222.html


5.565 rods
http://www.herbertcams.com/espcrs5565b-3d-sb-chevy-5-565-4340-forged-h-beam-rods/

https://www.stevemorrisengines.com/...cks/sbc/sbc-4340-forged-h-beam-rods-5565.html


5.7" rods
https://www.speedwaymotors.com/Smal...el-I-Beam-Rods-5-7-Inch-Bushed-Pin,29376.html

https://www.speedwaymotors.com/Scat...340-I-Beam-Rods-5-7-Inch-Bushed-Pin,6608.html


piston for 5.7 rod
https://www.summitracing.com/parts/slp-h615cp


piston for 5.565 rods
https://www.summitracing.com/parts/slp-h400cp
ALL production big blocks used a 6.135" length rod.
CHEVY BIG BLOCK V-8 BORE AND STROKE


366T = 3.935" x 3.76"
396 = 4.096" x 3.76"
402 = 4.125" x 3.76"
427 = 4.250" x 3.76"
427T = 4.250" x 3.76"
454 = 4.250" x 4.00"
477= 4.5" bore x 3.76" stroke
496 = 4.250" x 4.37" (2001 Vortec 8100, 8.1 liter)
502 = 4.466" x 4.00"
557T= 4.5 bore 4.375" stroke
572T = 4.560" x 4.375" (2003 "ZZ572" crate motors)

T = Tall Deck

ALL production big blocks used a 6.135" length rod.
http://www.jegs.com/i/GM-Performance/80 ... tId=956504
 
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