| AFR would like to congratulate you on your
purchase of the highest flowing and strongest castings currently offered
in a “production" style BB Chevrolet Cylinder Head. These heads, properly
installed and maintained, will generate impressive
power figures and provide you with years of trouble free service. The
following instructions and guidelines are meant to assist you in the proper
installation and set-up of your new cylinder heads. It is important that
you read through all of this information before attempting installation!!
Inspection:
Check all machined surfaces for nicks, burrs, etc., that might have occurred
during shipping or storage. If necessary, carefully dress
with a file, or sandpaper supported flat by a straightedge. This
is especially important on the head deck and intake manifold flange to have
an effective trouble-free gasket seal.
Valve Springs:
It is the customer’s responsibility to check and make sure that spring
pressures are correct for his/her camshaft application. We recommend a
minimum of .060” clearance from coil bind at full valve lift.
Valve Guide Clearance:
Our typical valve guide clearances are .0013-.0016. In some severe applications
with heavy nitrous, marine endurance racing, or blower usage, looser guides
might be required. Check with your engine builder.
Piston Dome Clearance:
Piston dome to combustion chamber clearance MUST be checked prior
to final engine assembly. This is especially important on pistons that
have a .700" + dome heights which are common on high compression
427-511 based engine configurations. Pay special attention to the crest
in the chamber directly across from the spark plug. Consider .040 minimum
clearance with 7000 rpm or less. Slightly more would be required for motors
that are turned higher.
ENGINE BUILDER'S TIP: While doing your "pre-assembly"
checks, install the cylinder head on the engine without the head gasket
and slowly attempt to turn the motor over. if it turns over freely and
you plan on running an .040 thick head gasket, then this simple test
would confirm that you have at least the thickness of the head gasket
as clearance. if you do feel resistance attempting to turn the engine
over, remove the head and carefully place modeling clay over the entire
piston dome (just a thin layer will do). reinstall the head and once
again turn the motor over slowly until you feel the clay compressing
and the engine beginning to bind....do not force it. remove the head
and check where the clay has been squeezed away. this is the area that
needs to be clearanced on the piston to achieve the necessary piston
dome to head acceptable tolerance. DO NOT GRIND ON THE CYLINDER HEAD
as this will certainly have an adverse effect on airflow as well as
power. Carefully clearance the pistons as required until you achieve
the proper tolerances. this may take quite a bit of time, as you should
slowly creep up on it. Attempt to remove as little material as possible
from the piston dome, always checking your progress along the way.
Piston to Valve Clearance:
It is your responsibility to check and make sure you have adequate piston
to valve clearance before final engine assembly. Don’t forget to check
radial (side) clearance as well.
Spark Plug Clearance:
In the event your engine has extremely tall piston domes, it might be
necessary to index the plug electrodes and/or slightly clearance your piston
domes to provide a minimum of .060” from piston dome to electode
tip. Do not use projected tip plugs with extremely tall dome design (unless
you are certain you have enough clearance).
Note: While on the subject of clearance, it is vital that you check
clearance of all moving parts due to the vast array of rocker arms, lifters,
cams, springs, etc. Don’t forget to check pushrod to head clearance as
well as any potential interference from your rocker arms and spring assemblies
prior to final engine assembly.
Rocker Studs:
AFR BB Chevy heads require two different length rocker studs. The (8)
shorter studs (referring to the coarse thread length that screws into the
head) should be installed on the intake side with a small amount of Teflon
or some other non-hardening thread sealer. Conventional bolt thread lubricant
can be used on the longer (8) exhaust studs. Never use a shorter stud on
the exhaust side.
Note: Torque Rocker Studs to 55-60 ft/lbs.
Valve Seats:
Both intake and exhaust valve seats are heat treated ductile iron and
are compatible with unleaded fuels.
Guide Plates:
Only AFR and CompCam guide plates will properly
fit our AFR Big Block Chevy cylinder heads. We carry them in stock under
AFR part #6109: The CompCams part # is 4806.
Pushrods:
All AFR cylinder heads will require pushrods that are longer than stock length.
The most common lengths are a +.200” to a +.250”, however, due to a large
number of variables (deck height, cam base circle, lifter height, etc.)
all pushrod lengths must be physically checked to achieve proper valve train
geometry.
Stud Girdle:
All of our BB Chevy Cylinder Heads have been designed with valve angles
rolled over two degrees from stock location to provide better flow characteristics.
Stud girdles produced for stock chevy castings
as well as other aftermarket pieces that have standard valve angles will
not fit properly. We stock a high quality girdle in a convenient two piece
design that will fit our heads correctly. (Most girdles that fit Dart Heads
will also fit due to their two degree roll-over design as well.)
Head Studs/Bolts:
AFR BB heads take one inch longer fasteners along the exhaust port (bottom)
side of the cylinder head. AFR stocks complete kits or partial kits (studs
or bolts) for the eight additional longer fasteners.
Note: We recommend the use of studs due to the higher clamping load
they place on the cylinder heads. Blown, turbo, or nitrous engines should
always use studs due to the much higher cylinder pressures they create.
Recommended Gaskets:
Head Gaskets or: Mark IV Block 4.540 Bore
Felpro 1017-1
Note: 1017-2 is .051 compressed
thickness
Mark IV Block 4.630
Bore Felpro 1057
Mark IV Block 4.625 Bore Felpro
1093
Note: O-ring perfectly round,
.051 thick, typical
“pro-stock” style gaskets.
Mark V-VI 4.540 Bore Felpro 1047 or 17048
Mark V-VI 4.630 Bore Felpro 17049
Note: All after market Merlin and Dart Big Blocks accept
"Mark IV" style head gaskets.
Intake Gaskets: (For best fit) AFR #6855
Felpro #1275
Mr Gasket #121
Note: Do Not port match your intake manifold to these manufacturer gaskets
or Fel-Pro Gaskets, as they do not exactly fit AFR headsOnly use AFR’s
#6855 for port matching. Most other gaskets have a slightly larger entrance.
You will see NO PERFORMANCE GAIN by opening your heads or intake
manifold to the larger gasket opening.
Exhaust Gasket: Felpro
#1412
Spark Plug Recommendation:
(Flat seat with gasket, .750 long reach, with a 5/8 hex head)
Autolite #3932
std. tip. race application
Champion #C59C Std. Tip. race application
Champion #R12YC Projected tip, Street
application
Note: Other spark plug manufactures
offer plugs that will also cross-reference and fit our AFR BBC castings.
Always consult with the manufacturer for heat range that best fits your
application.
Head Bolt Torque:
All AFR BB Chevy Cylinder Heads should be torqued to 75 ft/lbs. This should be done in the proper General
Motors sequence in 15lbs increments beginning at 30ft/lbs. Moly lube should be applied between fasteners, washers, and
area around head bold to prevent galling and improper torque valves. Sealer
should be applied to all thread areas of fasteners that enter into block
water jackets. Sealer is unnecessary with blocks that have “blind holes”
in the deck surface and do not go into water.
Valve Length:
Intake Valve 5.500” (+.250) Exhaust Valve 5.450” (+.100)
Important:
Apply anti-seize to all bolts and sparkplug threads to insure long thread
life.
Coolant:
It is important to maintain 50/50 mix of antifreeze in the cooling system
to prevent corrosion of aluminum heads. Do not use tap water, use distilled
water instead. Most supermarkets sell purified or distilled water. Check
labeling to verify purified through deionization.
Head Fastener Re-Torque:
All high compression, supercharged, turbo and nitrous motors should receive
a re-torque after the first running and complete cool-down. Be sure to
back off the fastener about 1/8 of a turn to eliminate false readings from
“break-away” torque. Always re-torque in the same general motors sequence
you initially tightened them with.
Valve Lash:
Be aware that an aluminum headed/iron block combination usually requires
approximately .006 tighter lash when it is cold.
An all aluminum engine could be as much as .010-.020 tighter when the motor
is cold. Every motor is different, but these guidelines should get you
in the ballpark.
If you require more assistance:
Please feel free to contact us here at AFR either by phone/fax/email,
and someone will be back to you shortly to answer any further questions
you might have.
Cleaning:
AFR thoroughly cleaned your cylinder heads prior to shipment. Your heads were washed
in water soluble chemical agitation tank and blown out with high pressure air
3 to 4 times before they were boxed. However during some machining operations
chips are packed and wedged into the water jacketing and occasionally come
loose in transit. Keep in mind one chip the size of a dime breaks into hundreds
of tiny chips and makes the situation appear much worse than it is in reality.
It is not usually if you blow high pressure air into the water jacketing to see
additional foreign debris, or chips finding their way out. AFR recommends that
you thoroughly blow out your heads prior to installation.
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