Frequently Asked Questions
Small Block Ford Aluminum Cylinder Heads
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Answers
1) SPARK PLUGS:
Use 14mm x 3/4" reach gasketed, no tapered seat plugs. Street application
use Autolite 3924, for 205cc & 225cc race head use Autolite 3922, or
equivalent. Plug selection is of course dictated by many factors including
RPM level, compression ration and fuel type. Forced induction or nitrous
applications usually require 1 to 2 heat ranges colder. Spark plug gap should
be determined by the ignition manufacturer.
2) HEAD BOLT TORQUE:
Apply moly-oil mixture to washers, and area around head bolt to prevent
galling and improper torque readings. Torque to 70ft/lbs. for 7/16"
bolts or studs (289 or 302) or 100ft/lbs. for 1/2" bolts or studs (351W)
in three or four steps following the factory tightening sequence. Then tighten
the long (upper) head bolts or studs 80ft/lbs. (7/16") or 110 ft/lbs.
(1/2"). A re-torque is recommended after initial start-up and cool
down (allow 2-3 hours for cooling). Sealer should be applied to all head
bolts or studs that enter into the blocks water-jacketing system. Permatex
is a good general-purpose sealer.
TORQUING:
We suggest not using a Torque Wrench on intake and exhaust manifold bolts,
accessory bolts,or spark plugs, as inaccurate torque wrench values can easily
strip the smaller threads. Just snug up hand tight with a wrench only.
3) Valve Clearance:
Piston to valve clearance must be checked before assembly. AFR 185cc aluminum cylinder heads with 2.020 valves usually will not fit a
piston without valve notches having proper reliefs. Also AFR 205cc heads
with 2.080 valves might experience the same issues.
NOTE:
All stock pistons must be notched for clearance.
4) Rocker Arms:
Only part #1472 & 1492 with pedestol style rocker arm boss towers will
fit stock rocker arms. Stud mount style AFR heads require aftermarket rocker
arms.
5)Gaskets:
On SBF SVO blocks, Fel-Pro 1011-1 and 1011-2 cannot be used. Must use Fel-Pro 1022 (left side) and 1023 (right side).
6) Pushrods:
To find out the correct pushrod length for you, check out the Crane Cams pushrod tech page.
7) Purchasing AFR Heads:
You may purchase your AFR Aluminum Cylinder Heads directly from Air Flow Research or any one
of our authorized distributors.
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