Now going into the most mis-understood engine component. Small Block Chevy heads are very often mis-identified. When first looking at this component, it seams they're basically all the same. There are however major internal differences to each seperate casting. External casting marks on cylinder heads have caused confusion among a lot of people when they first glance at a set of heads. Bare in mind that every set of small block chevy heads will bolt into pretty much every small block engine built,that may be the extent of the bolt on though. Valve clearence issues,intake manifold bolt patterns and valve size all factor into the equation. Do not use external casting marks to make a positive identification of small block chevy heads. There are cylinder head that had the same casting marks but,very different valve sizes. The bottom line is,it's best to use the services of a professional engine builder to thuroughly check out and identify a set of heads you plan on buying or using before putting out some big bucks to get them done.
For the purposes of keeping things simple we'll discuss the major differences that will effect different applications.
Date codes are also located between valve spring seats but,read like this A246.A=month,24=day,6=year of the decade
Valve covers in the right of this picture feature the staggered fastening bolt design,the left feature the holes directly across from each other. This came about in 1959
The temperature send out unit's location as of 1968.Pre 68 cylinder heads had no provision for the threaded hole with the exception of the "291" casting.
These are small chamber cylinder heads featured on almost all high performance engines available during the 60's.
These are open chamber heads from a small block 400,note the steam holes and the difference in chamber size from the small chamber shown above.
The major difference noted between the average chamber design and the "Vortec" note how the edge of the inner chamber shrouds the valves creating a smaller quench area. This promotes a faster fuel mixture burn and greater efficiency.
For the purposes of keeping things simple we'll discuss the major differences that will effect different applications.
- From 1955-59 the valve covers had a staggered bolt pattern,late 59 is when this changed to bolts directly across from each other and the valve covers could be swapped end for end.
- In 1968 accessory bolt holes were added to some truck applications (casting number 3917293 sometimes called the "transition heads") And were available on all applications for the 1969 model year. The accessory bolt holes were either 3/8's or sometimes 7/16's in size.
- 1968 the the temperature sending unit was moved to the side of the cylinder head from the intake manifold
- In 1971 most small blocks started using the 5/8" tapered seat spark plug,prior to that the 13/16" plug with the copper washer was used.
- There are different combustion chamber sizes that usually take an engine builder to measure properly. most common size were the small chamber or closed 62 cc's and the large chamber or open 74-76 cc's. bare in mind that these are loose numbers,just like the rocker arm ratio. They advertise a 1.5 ratio but,accurately measure to anywhere from 1.44 to 1.49. This is a result of assembly line built engines and pretty much happen to every engine manufacturer.
- In 1970 the small block 400 came along and so did another casting of cylinder head specifically designed for it,these heads feature steam holes to assist with engine cooling.
- For the 1986,and the 1985 Corvette model year the cylinder head for the small block underwent a bit of a design change. The valve cover fastening bolts were re-located to the center of the valve cover,the manifold fastening holes were also re-designed. These heads feature the two center bolt holes on each side drilled at 73 degrees to the mating surface. The outer bolt holes remain the same as previous heads. The valve cover mating surface was also raised to accommodate a coolant passageway to assist in cooling the heads and reduce oil leaks.
- "Vortec" heads became standard on all truck applications in 1996,although they were featured on some of the 1995 model years. The Vortec featured a newly designed chamber that promoted a faster burn,these cylinder heads have the highest flow chart numbers of any small block Chevy head from the factory. With the devolopment of these heads it made almost all other stock factory head obsolete. However that doesn't mean you can't realize very good performance for other head castings.
Date codes are also located between valve spring seats but,read like this A246.A=month,24=day,6=year of the decade
Valve covers in the right of this picture feature the staggered fastening bolt design,the left feature the holes directly across from each other. This came about in 1959
The temperature send out unit's location as of 1968.Pre 68 cylinder heads had no provision for the threaded hole with the exception of the "291" casting.
These are small chamber cylinder heads featured on almost all high performance engines available during the 60's.
These are open chamber heads from a small block 400,note the steam holes and the difference in chamber size from the small chamber shown above.
The major difference noted between the average chamber design and the "Vortec" note how the edge of the inner chamber shrouds the valves creating a smaller quench area. This promotes a faster fuel mixture burn and greater efficiency.
| Casting | CID | Year | Model Aplication | Comments |
|---|---|---|---|---|
| 330545 | 307,350 | 73 | Pass,Camaro,Chevelle,Nova | med perf |
| 333882 | 350,400 | 73-76 | Passenger | |
| 333882 | 350 | 74-76 | Camaro,Z-28 | W/O Steam holes |
| 333882 | 400 | 74-76 | Chevelle,Monte Carlo | With Steam holes |
| 333882 | 350 | 74-79 | Truck | light duty |
| 333882 | 400 | 75-79 | Blazer | 4x4,with steam holes |
| 333882 | 400 | 76-80 | Truck | light duty,w/steam holes |
| 340292 | 350 | 70's | Replacement | hi perf "turbo" head |
| 354434 | 262 | 75-76 | Monza,Nova | light casting |
| 354434 | 305 | 76-79 | Truck | light casting |
| 354434 | 305 | 76-85 | Pass,Camaro | light casting |
| 358741 | 262 | 75-76 | Monza,Nova | |
| 376445 | 350 | 77-85 | Truck | Heavy Duty |
| 462624 | 350 | 71-79 | Camaro,Corvette | Hi Perf |
| 462624 | 400 | 75-80 | Truck | light duty |
| 462624 | 350 | 75-86 | Truck | light duty |
| 462624 | 350 | 80-85 | Truck | Heavy Duty |
| 462624 | 350 | 80-85 | Corvette | All |
| 468642 | 350 | 71-79 | Truck | Heavy Duty,small plugs |
| 468642 | 400 | 75-80 | Truck | Light Duty,small plug |
| 468642 | 350 | 80-85 | Corvette | Small Plugs |
| 468642 | 350 | 80-85 | Truck | Heavy Duty |
| 517513 | 267 | 79-82 | Pass,Malibu,Monte Carlo | |
| 3703523 | 265 | 55 | Corvette | 195 HP |
| 3703523 | 265 | 55 | Passenger | 4 BC |
| 3725306 | 265 | 56 | Corvette | 2 bolt ex man,225hp early 56 |
| 3731539 | 283 | 57 | Passenger | 4 BC |
| 3731539 | 283 | 57 | Corvette | 283 HP,F.I. |
| 3731539 | 283 | 57 | Truck | |
| 3731554 | 283 | 57 | Passenger | 2 BC |
| 3731762 | 265 | 56 | Passenger | 2x4 BC |
| 3731762 | 265 | 56 | Corvette | 3 bolt ex man,240 hp |
| 3731762 | 265 | 56 | Corvette | 3 bolt ex man,225hp,late 56 |
| 3740997 | 283 | 57 | Passenger | 2x4 BC & 250hp F.I. |
| 3740997 | 283 | 57 | Corvette | 220,245,250,270 HP |
| 3740997 | 283 | 57 | Truck | 4 BC |
| 3748770 | 283 | 58 | Corvette | X58 on side,staggered valve cover holes |
| 3748770 | 283 | 58-59 | Passenger | X58 on side,staggered valve cover holes |
| 3748872 | 283 | 58-59 | Truck | |
| 3748872 | 283 | 58-59 | Passenger | |
| 3755539 | 283 | 58-59 | Truck | Staggered Valve Cover Holes |
| 3755549 | 283 | 58-59 | Truck | |
| 3755550 | 283 | 59 | Corvette | Early 59,staggered Valve Cover Holes |
| 3755585 | 327 | 62-67 | Passenger | |
| 3767460 | 327 | 62-67 | Truck | |
| 3767460 | 283 | 63-67 | Truck | |
| 3767462 | 327 | 62-67 | Passenger | |
| 3767465 | 283 | 59 | Corvette | Late 59,inline valve cover holes |
| 3767792 | 283 | 60-67 | ||
| 3770126 | 327 | 69 | W/Accy Bolt Holes 2BC | |
| 3774682 | 283 | 60-65 | Passenger,Chevelle,Chevy II | |
| 3774682 | 327 | 62-63 | Passenger | |
| 3774682 | 327 | 62-67 | Truck | |
| 3774682 | 283 | 62-67 | Truck | |
| 3774684 | 283 | 58-62 | Truck | |
| 3774684 | 327 | 62-67 | Truck | Heavy Duty |
| 3774684 | 283 | 64-67 | Truck | |
| 3774692 | 283 | 60 | Corvette | All Engines |
| 3774692 | 283 | 60-67 | Pass,Nova,Chevelle | 2 & 4 bc |
| 3774692 | 283 | 61 | Corvette | 230,245,270 hp |
| 3782461 | 283 | 61 | Corvette | 275,315 hp,F.I. |
| 3782461 | 327 | 62 | Corvette | 300,340,360 hp |
| 3782461 | 327 | 62-66 | Passenger | Hi Perf |
| 3782461 | 327 | 62-67 | Truck | Light Duty |
| 3782461 | 327 | 63-66 | Corvette | All 327 engines |
| 3782461 | 327 | 64-66 | Chevelle | 4 BC,Hi Perf |
| 3782461 | 327 | 65-66 | Chevy II | 4 BC,Hi Perf |
| 3795896 | 327 | 62-64 | Corvette | 250 HP |
| 3795896 | 327 | 62-65 | Passenger | |
| 3795896 | 327 | 62-67 | Truck | |
| 3795896 | 283 | 63-67 | Truck | |
| 3795896 | 283 | 63-67 | Passenger | |
| 3795896 | 327 | 63-67 | ||
| 3814480 | 327 | 62-67 | Truck | |
| 3814480 | 283 | 63-67 | Truck | |
| 3814480 | 283 | 64-67 | Passenger | |
| 3814482 | 327 | 62-63 | Truck | |
| 3814482 | 283 | 63-67 | Truck | Light Duty |
| 3814482 | 283 | 64-67 | Passenger | |
| 3814482 | 350 | 67 | Camaro | |
| 3817681 | 327 | 66-67 | ||
| 3836842 | 283 | 62-67 | Passenger | 2 BC |
| 3836842 | 327 | 62-67 | Passenger | 2 BC |
| 3837064 | 265 | 56-57 | Truck | |
| 3837064 | 265 | 56-57 | Passenger | Standard Perf |
| 3876775 | 283 | 60-62 | Truck | W/accy bolt bosses one end |
| 3876775 | 327 | 62-67 | Truck | W/accy bolt bosses one end |
| 3876775 | 283 | 64-67 | Truck | W/accy bolt bosses one end |
| 3884520 | 283 | 60-67 | Truck | Light Duty |
| 3884520 | 327 | 62 | Corvette | 250 hp |
| 3884520 | 327 | 62-64 | Passenger | Standard Perf |
| 3884520 | 327 | 62-67 | Truck | Light Duty |
| 3884520 | 283 | 64-67 | Chevelle,Nova | 2 bc & 4 bc |
| 3890462 | 327 | 66-68 | Pass,Camaro,Nova,Chevelle | 4 BC,Q-Jet,275 hp |
| 3890462 | 327 | 67 | Corvette | 300,350 hp |
| 3890462 | 302 | 67 | Camaro,Z28 | Hi Perf |
| 3891462 | 327 | 62-67 | Truck | Light Duty |
| 3891462 | 327 | 64-67 | Passenger | Standard Perf |
| 3911032 | 307 | 68 | Truck | W/O Accy Bolt Holes |
| 3911032 | 307 | 68 | W/O Accy Bolt Holes | |
| 3911032 | 327 | 68 | W/O Accy Bolt Holes | |
| 3911032 | 327 | 68 | Truck | |
| 3917290 | 327 | 68 | Truck | Light Duty |
| 3917290 | 307 | 68 | Truck | W/O Accy Bolt Holes |
| 3917290 | 327 | 68 | Truck | Light Duty |
| 3917290 | 307 | 68 | Passenger | W/O Accy Bolt Holes |
| 3917290 | 307 | 68 | Camaro,Chevelle,Nova | 2BC,210,250 hp |
| 3917291 | 302,327,350 | 67-68 | Camaro,Z28,Nova,Chevelle | Special Hi Perf |
| 3917291 | 327 | 68 | Corvette | 300,350hp w/temp unit hole |
| 3917292 | 327 | 68 | Corvette | 350 hp |
| 3917293 | 327 | 68 | Truck | W/accy bolt bosses one end |
| 3917293 | 307 | 68 | Truck | W/accy bolt bosses one end |
| 3917185 | 327 | 69 | Pass,Camaro | w/accy bolt holes,2 bc |
| 3917185 | 350 | 69-72 | Pass,Camaro,Nova,Chevelle | w/accy bolt holes,2 bc |
| 3917185 | 307 | 69-73 | Camaro,Chevelle,Nova | w/accy bolt holes,2 bc |
| 3917185 | 307 | 69-73 | Truck | Light Duty,w/accy bolt holes |
| 3917185 | 350 | 69-76 | Truck | heavy Duty Small Valves |
| 3917185 | 350 | 69-76 | Truck | Light Duty Small Valves |
| 3927186 | 302 | 69 | Camaro,Z28 | Hi Perf,290 hp,Large Valves |
| 3927186 | 350 | 69 | Corvette | 300,350 hp,Large Valves |
| 3927186 | 350 | 69-70 | Nova SS | 4 bc,Hi Perf,Large Valves |
| 3927186 | 350 | 69-76 | Truck | Light Duty,Large Valves |
| 3927186 | 350 | 70 | Corvette | 300,350,370 hp,Large Valves |
| 3927186 | 350 | 70 | Camaro | Hi Perf,360 hp,Large Valves |
| 3927187 | 350 | 69-70 | Corvette | 350 hp |
| 3927187 | 350 | 69-70 | ||
| 3932441 | 350 | 69-74 | Pass,Camaro,Nova,Chevelle | w/accy bolt holes |
| 3932441 | 350 | 69-74 | Truck | Light Duty |
| 3932454 | 307 | 69-73 | ||
| 3932454 | 350 | 69-79 | Truck | Heavy Duty |
| 3946813 | 350 | 69-70 | ||
| 3947041 | 350 | 69 | Corvette | 300 hp |
| 3947041 | 350 | 69-70 | Pass,Camaro,Nova,Chevelle | 4 bc,Large Spark Plugs |
| 3970126 | 350 | 69-72 | Pass,Camaro,Nova,Chevelle | Big plugs 69-70,small 71-72 |
| 3970126 | 350 | 69-74 | Truck | Big plugs 69-70,small 71-72 |
| 3973414 | 350 | 70 | Corvette | 370 hp |
| 3973414 | 350 | 70 | Camaro Z28,Nova | Hi Perf |
| 3973487 | 350 | 71 | Corvette | 270,330 hp |
| 3973487 | 350 | 71-76 | Pass,Camaro,Chevelle,Nova,Monte Carlo | Small Plugs |
| 3973487 | 350 | 71-76 | Truck | Light Duty |
| 3973487 | 350 | 72 | Corvette | 200,255 hp |
| 3973493 | 400 | 73-76 | Pass,Chevelle,Monte Carlo | Small Plugs |
| 3986339 | 307 | 69-73 | Truck | w/send out hole,accy bolt holes both ends |
| 3986339 | 350 | 69-79 | Truck | Heavy Duty |
| 3986388 | 350 | 69-79 | Truck | Heavy Duty,accy holes |
| 3991492 | 350 | 73 | Camaro,Corvette | Hi Perf,Angled or old style plugs |
| 3998916 | 350 | 72 | Corvette | 255 hp |
| 3998991 | 307 | 69-73 | Truck | Light Duty w/accy bolt holes |
| 3998993 | 307 | 69-73 | Truck | Light Duty,w/accy bolt holes |
| 3998993 | 350 | 69-74 | Truck | Light Duty |
| 3998993 | 350 | 69-74 | Pass,Camaro,Chevelle,Nova | Single heat riser Tunnel |
| 3998993 | 307 | 69-74 | Camaro,Chevelle,Nova | w/accy bolt holes |
| 3998993 | 350 | 72 | Corvette | 200 hp |
| 7185392 | 327 | 69 | w/accy bolt holes | |
| 14010201 | 305 | 84 | ||
| 14011034 | 350 | Current | Replacement | Over the counter hi perf |
| 14011039 | 350 | Current | Replacement | Over the counter hi perf |
| 14014415 | 305 | 76-85 | ||
| 14014415 | 267 | 80-82 | ||
| 14014416 | 305 | 80-86 | Truck | |
| 14014416 | 305 | 86-87 | ||
| 14022301 | 305 | 80-87 | ||
| 14022301 | 305 | 86-87 | ||
| 14022601 | 305 | 76-85 | ||
| 14022601 | 267 | 80-82 | ||
| 14022601 | 305 | 86-87 | ||
| 14071114 | 350 | 80-85 | Corvette | |
| 14071114 | 350 | 86-87 | Flat Tappets,Carburetor | |
| 14079261 | 350 | 86 | Truck | |
| 14101081 | 305 | 87-88 | Camaro | Valve covers bolt through center |
| 14102187 | 305 | 87-88 | ||
| 14102187 | 305 | 87-88 | Truck | |
| 14102191 | 305,350 | 87-up | All | Center Valve Cover bolt holes |
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