Quote:
Originally Posted by David Barton
We have been cutting into the valve cover bolt holes forever and have been through teardown enough times to fill our wall full of records. And not once did I ever hear anything from anybody about valve cover bolt holes. If it was illegal you would think somebody in the last few decades would have said something.
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As far as I can tell it was illegal right up until the "EXCEPT AH" was recently added.
NHRA RULE AMMENDMENTS MADE FROM THE END OF THE 2012 SEASON TO THE BEGINNING OF THE 2013 SEASON
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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 sodium-filled 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. Valve cover bolt holes must remain unaltered and in their original location.
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, bronze-wall valve guides. Valve spring umbrellas optional. Cylinder head may have all of the seats replaced. Any valve job permitted,Oringing prohibited. Exhaust plates prohibited.