Expanded Blueprint Specs:

  • The first thing you will notice is a whole lot more data than you get from the NHRA Tech Bulletins pages. That is why individual engines are shown rather than every available engine for the year-make.
  • The additional data that is not included on the NHRA Tech Bulletins pages is not authorized or approved by NHRA so do not assume that this has the same authority in those areas as the information on the official NHRA Technical Bulletins. The data from the NHRA web Technical Bulletins is included here and every effort is made to ensure that this data is the most up to date information published by NHRA.
  • An interesting tool is the link on the right side of the page to show all the cars that use the engine you have selected. You will find that information valuable in considering options for class placement for this engine.
  • You will find all the relavent information from NHRA for accepted replacement parts - pistons, rods, oil pans, etc. - is all located in this one page. You do not have to look anywhere else to find that information.

Engine Blueprint Specifications:  1973 Pontiac 250 HP 455 V8

PONT-73      Issued: 3/9/1973      Last Revised: 4/3/2012      Revisions: 7-21-78, 1-1-08 WR, 6-18-08 WR, 4/3/12 PC

Engine Family:   General Motors, Pont V8 Late         Advertised Comp Ratio:   8.80:1         Induction:   1-4 Bbl         Engine Type:   V8

Basic Specs:BoreStrokeMain Journal DiaRod Journal DiaMax BoreMax StrokeMax Displacement
 4.153"4.214"3.250"2.250"4.233"4.229"476.1 ci

Piston-Rod Specs:Piston WeightComp HeightPin WeightRingsRings WeightRod C/CMax Rod C/CRod WeightMin Assy Weight
 535 g1.470"90 g5/64, 1/16, 3/1654 g6.625"6.650"760 g1439 g

Compression:Deck HeightHead GasketPiston TypeDome/Dish VolDome/Dish HgtComb Chamber VolMax Compression
 .000".045"Flat w/notches0 cc0102.3 cc9.66:1

Valve Train:Int Rocker RatioExh Rocker RatioIntake ValveExhaust ValveLifter TypeSpring TypeLifter Dia.
 1.50:11.50:12.113"1.663"HydraulicOuter & inner0.842"

Camshaft:Intake LiftExhaust Lift 

Cylinder Heads:Casting No. Intake VolumeExhaust Volume  
 488541 156.0cc142.0ccNot official NHRA data, but from a reliable source.
 494341 156.0cc142.0ccNot official NHRA data, but from a reliable source.

Intake Manifolds:Casting No. 
 491244Cast Iron
 492744Cast Iron
 494282Cast Iron

Carburetors:NumberManufacturerTransTypePrimary ThrottleSecondary ThrottlePrimary VenturiSecondary Venturi 
 1901EdelbrockALL4-Bbl1.375"2.250"1.108".000"AV Secondary. Replacement for GM small venturi Quadrajets. NOTE: Venturi specs include .015" maximum allowable tolerance.
 7043262RochesterAuto4-Bbl1.375"2.250"1.093".000"Air valve secondary
 7043265RochesterSM4-Bbl1.375"2.250"1.093".000"Air valve secondary

Power Factors:Stock Man Stock Auto S/S Man S/S Auto GT Man GT Auto GTFwd Man GTFwd Auto 
Base Factors315 315 3105/30/023105/30/023105/30/023105/30/023105/30/023105/30/02
Exception: Firebird3067/15/113067/15/113103/7/183103/7/18        

Accepted Replacement Pistons for Stock Eliminator

   Effective 10/16/2018
Specs:     Comp Hgt-1.470"    Pin Dia-0.980"    Rings-5/64, 1/16, 3/16   
Distance to Top Ring-0.270"    Piston Min Weight-535g

Manufacturer Part Number
CP Pistons P3-CP
JE 146348
Ross 99600
Sealed Power 2365P
TRW L2359F
TRW L3088F
Venolia 455-435

Accepted Replacement Oil Pans for Stock Eliminator

Engine Group - Pont V8 Late           Effective 7/3/2019

Manufacturer Part Number
Milodon 30770
Moroso 20492

Accepted Aftermarket Crankshafts

Manufacturer Part Number
Eagle 4.45542E+11 Pontiac 455

Accepted Replacement Blocks

Manufacturer Part Number
K&M Performance MR-1
All Pontiac APSJB

Accepted Replacement Connecting Rods for Stock or S/S

    Effective 2/4/2020
Specs:     C/C Length- 6.625"    Min Weight- 760g    Journal Dia- 2.249"    Big End Dia- 2.375"    Pin Dia- 0.980"

Manufacturer Part Number C/C Length Wgt. Pin Dia.
Carrillo C427-76635S 6.625" 834g 0.990" Pontiac
Carrillo C427-A76635H 6.625" 787g 0.990" Pontiac
Carrillo P-455-SS 6.631" 760g NA SUPER STOCK ONLY
Carrillo P-455-SS (2) 6.625" 760g 0.000" Super Stock Only
Childs & Albert 389-12 6.625" NA 0.947" Pontiac
Crower F91059 6.625" NA 0.981" Pontiac
Crower ML93015B5 6.624" 773g NA SUPER STOCK ONLY
Crower SP93419 6.625" 830g 0.947" Pontiac
Eagle CRS-6625P3D 6.625" 760g 0.947" Pontiac
Eagle CRS6635 6.635" 830g 0.990" BB Chev
Manley 14168 6.635" 830g 0.990" BB Chev
Molnar Technologies PH6625WRB8-A 6.623" 769g 0.980"
Oliver ORPPONT6625 6.625" NA 0.981" Pontiac
Oliver P6225PONT 6.625" 790g 0.980" Pontiac
Oliver P6625PONTFR8 6.625" 819g 0.980" Pontiac

Note the calculations for actual displacement the maximum actual compression ratio.

Would you like to see a list of all the cars where this engine is used? Click here:

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