Northeast Street Car Association

Big Block Chevy Info

Popular BBC Bore and Stroke Combinations

Useful Links:

GM Perf Parts

Dart Heads

Brodix

Canfield

Edelbrock

Steve Schmidt

Alan Johnson

Steve Schmidt

World Products

Donovan Engineering

Keith Black

Chuck Nuytten Blocks

Arias

Big block chevys use the traditional 18436572 firing order unless the cam is specially ordered to swap 4 and 7 (becoming more popular these days). Most parts are interchangeable with SBCs like distributors, transmissions , torque converters and flywheels. Heads: For racing, most aftermarket heads will far surpass the potential airflow of any OEM installed heads. Dart, Brodix, Canfield, Edelbrock and many others produce heads in both "Chevy type" and "Big Chief" or "Olds" heads. Chevy type heads are designed around oem specifications (i.e. long and short intake ports using the traditional two pairs of intake ports per head). A typical Dart 360 head can flow 400 cfm with professional porting, enough to sustain 900 hp naturally aspirated. Aftermarket Pro Stock type heads use symmetrical ports that are spaced more evenly and use a more shallow intake valve angle ranging from 18* down to 10* (stock chevy is 26*). These heads require specific manifolds and shaft rocker arm systems (Jesel or T&D). Airflow figures can reach as high as 550 cfm, and can sustain 1,400+ hp naturally aspirated. A spec sheet for Dart 18* big chief heads is listed below for reference. Blocks :BBC Block Info GM factory blocks come in primarily 2 deck heights. 9.8" and 10.2" from crank centerline to cylinder deck. Some bowtie blocks came with 9.2" heights for pro-stock use only. All passenger car motors use the 9.8" height block with the 10.2" reserved for HD truck applications (366 and 427 cubic inches) from GM. Short deck blocks come in both 2 and 4 bolt main configurations. OEM bore spacing is 4.84", which limits bore sizes to 4.650 for most practical purposes. 4.625 is generally the largest bore possible before re-sleeving is necessary. 4.9" and 5.0" bore space blocks are available in the aftermarket for larger bores and better cylinder head flow.

BBC Motor total weight: Cast Iron Heads and Block    ---     640lbs Aluminum Hds Iron Block     ---     555lbs Aluminum Heads and Block   ---     425lbs note: short deck blocks

For reference a typical SBC motor is about 485lbs

Tech Specs:   Dart  18  Degree    Big  Chief  Aluminum Cylinder Head Part#                                   18000000                                I-038A                                     Material:                              355T6  alum alloy Comb Chambers:                 85cc as cast      (95cc  Tit,  100cc SS  w/CNC) Intake Valve Dia:                 2.400”  Intake Port volume:             395cc as cast,  SM-402cc,  FP-424cc Intake Port Dim:                  1.800” x 2.500” (as cast),  1.810” x 2.525”  (S/M),  1.890” x 2.530” (F/P) Int Port Location:                 Raised  1.500”   Spread ports Intake Gasket:                      Fel-Pro# 1298 Exh Valve Dia.:                     1.900” Exh Port volume:                  175cc (S/M),  185cc (F/P) Exhaust Port Dim:                (As cast & S/M)  2.000” x 1.680”,   (F/P) 2.100” x 1.800”                          Exh Port Location:                Raised  .900”     Std chevy bolt pattern Exhaust  Gasket:                  Mr Gasket 5914  Flow, Intake:                         (S/M) 444 cfm @ .800”,   (F/P)   492 cfm  @ .900” lift/28” Flow, Exhaust:                      (S/M) 301 cfm @ .800”,   (F/P)   343 cfm   @.900” lift/28”   Manifold:                               Dart  Big Chief   (opening - 1.750”x 2.350”)   8.00” tall Milling:                                 Min. 92cc / .020” max   (.006” = 1cc)    Flat mill only. Pistons:                                  Must use pistons for Big Chief. Spark Plug:                           .750” reach, gasketed.  Champion  C57C / C57YC   Spring Cups:                         1.625” - .035 cup  Spring Pockets                      1.740”  OD  for 1.625” cup  (.030” deeper max) Springs:                                 Our Assembly:     1.625D =  250# @ 2.000” /  .790” max    Vasco-Jet H-1                                              optional triple:      1.625T =  330# @ 2.100” /  .910” max    Comp  948      Valve Angles:                         Int - 18°,  Exh - 9°,    4° cant Valve Length:                        Int - 6.600”         Exh - 6.450”   Our assemblies w/ SS – 6.380” Valve Stem Dia:                   .3415”   -   11/32” Valve Train:                          Jesel  or  T&D  rocker system Valve Guides:                        1/2”  OD  Mag - bronze      Cut for .530” PC seals    (.002” press) Valve Guide length:             3.000”         Valve Guide clearance:        .0014” - .0021”   (with our .3415 dia. valve stem) Valve Guide Spacing:          Widened for use on min. 4.375” bore Valve Seats:                          Ductile Iron,   .006”  press     Valve Seat dim.                     Int. - 2.490” x 2.000” x .375”         Exh - 2.000” x 1.600” x .375” Valve Seat angles:                Int =  32° - 45° - 60° - 70°     Exh = 37° - 45°  - radius                     Studs, head:                         Must use Big Chief  stud kit    #66120015 Titanium Valves                   Must use lash caps Torque:                               Head Bolts = 70 ft/lb                                           Manifold =  35 ft/lb