Stocker Cylinder Heads.... - Page 10

Wade_Owens · 06-13-2012, 02:27 PM

The head rules arent what's in the rulebook. Several engine builders have been told 1 thing and the tech officials something else. Tech's interpretations of the gray areas can be different and judgement calls vary from division to division.

There is a big difference between a stock head and a Stock Eliminator legal head. The legal bowl cut drastically changes the appearance, and its not mentioned in the rules.

CYLINDER HEADS
Must be correct casting number for year and horsepower claimed,
per NHRA Technical Bulletins or NHRA accepted. Porting,
polishing, welding, epoxying and acid-porting prohibited.
Combustion-chamber modifications prohibited. Cylinder heads are
additionally restricted in that they must retain original-size valves at
original angles +/- 1 degree and must be able to hold original
cylinder-head volume per NHRA Specifications. Runner volumes
may not exceed the current Super Stock cylinder-head volumes as
listed on www.NHRARacer.com. Regardless of the poured volume
measurement, any modifications to intake or exhaust runners
prohibited. Any evidence of modifications from the original castings
will be grounds for disqualifications as determined by NHRA in
NHRA’s sole and absolute discretion. Any aftermarket steel valve
permitted, must retain stock head and stem diameters. Only
engines OEM-equipped with sodium-filled valves may use sodiumfilled
replacement valves. Titanium prohibited. Hardened keepers
permitted. Lash caps prohibited. Valve-diameter tolerance: +.005-
inch or -.015-inch from NHRA Specs. The following are prohibited:
spark-plug adapters; cylinder-head studs; any grinding in ports or
combustion chambers; removal of any flashings; sandblasting or
any other modification to cylinder head; any film coating of intake
and exhaust runners; any film coating of combustion chamber.
Runners and combustion chamber must retain OEM appearance.
Final acceptance as determined by NHRA in NHRA’s sole and
absolute discretion. Intake side of head may not be cut into any part
of valve cover bolt holes. Heat riser passage may be blocked from
intake manifold side of cylinder head. Blocking passage down in
valve pocket prohibited. The following are permitted: polylocks, jam
nuts, screw-in larger-diameter rocker studs or pinned studs, bronzewall
valve guides. Valve spring umbrellas optional. Cylinder head
may have all of the seats replaced. Any valve job permitted,Oringing
prohibited. Exhaust plates prohibited.

We need the rulebook updated and clarified, please.

Wade

06-13-2012, 02:27 PM	#1
Wade_Owens Senior Member Join Date: Jul 2007 Posts: 578 Likes: 0 Liked 3 Times in 1 Post	Stocker Cylinder Heads.... The head rules arent what's in the rulebook. Several engine builders have been told 1 thing and the tech officials something else. Tech's interpretations of the gray areas can be different and judgement calls vary from division to division. There is a big difference between a stock head and a Stock Eliminator legal head. The legal bowl cut drastically changes the appearance, and its not mentioned in the rules. CYLINDER HEADS Must be correct casting number for year and horsepower claimed, per NHRA Technical Bulletins or NHRA accepted. Porting, polishing, welding, epoxying and acid-porting prohibited. Combustion-chamber modifications prohibited. Cylinder heads are additionally restricted in that they must retain original-size valves at original angles +/- 1 degree and must be able to hold original cylinder-head volume per NHRA Specifications. Runner volumes may not exceed the current Super Stock cylinder-head volumes as listed on www.NHRARacer.com. Regardless of the poured volume measurement, any modifications to intake or exhaust runners prohibited. Any evidence of modifications from the original castings will be grounds for disqualifications as determined by NHRA in NHRA’s sole and absolute discretion. Any aftermarket steel valve permitted, must retain stock head and stem diameters. Only engines OEM-equipped with sodium-filled valves may use sodiumfilled replacement valves. Titanium prohibited. Hardened keepers permitted. Lash caps prohibited. Valve-diameter tolerance: +.005- inch or -.015-inch from NHRA Specs. The following are prohibited: spark-plug adapters; cylinder-head studs; any grinding in ports or combustion chambers; removal of any flashings; sandblasting or any other modification to cylinder head; any film coating of intake and exhaust runners; any film coating of combustion chamber. Runners and combustion chamber must retain OEM appearance. Final acceptance as determined by NHRA in NHRA’s sole and absolute discretion. Intake side of head may not be cut into any part of valve cover bolt holes. Heat riser passage may be blocked from intake manifold side of cylinder head. Blocking passage down in valve pocket prohibited. The following are permitted: polylocks, jam nuts, screw-in larger-diameter rocker studs or pinned studs, bronzewall valve guides. Valve spring umbrellas optional. Cylinder head may have all of the seats replaced. Any valve job permitted,Oringing prohibited. Exhaust plates prohibited. We need the rulebook updated and clarified, please. Wade