NHRA STOCK valve job

[PRH]

How do you interpret what’s legal in Stock for a valve job these days?

I’m sure Chad has the answer as far as NHRA is concerned.

SECTION 11A: STOCK, ENGINE: 1, CYLINDER HEADS (Page 3)

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 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; 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. External modifications prohibited. 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. Intake manifold bolt holes must remain unaltered 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, cylinder head studs. Valve spring umbrellas optional. Cylinder head may have all of the seats replaced. Any valve job permitted, O-ringing prohibited. Exhaust plates prohibited.

[DeezNutz]

You get to do lots of R&D to determine what valves and angles will yield the best results. Lots of flow bench testing to get results.

Basically no modification to the ports, no grinding, no sandblasting, no nothing...

Each head design is unique and wants different things.

What combination is it?

[PRH]

I’m having an argument on another forum about what is and isn’t legal with regards to the valve job itself.

My interpretation of “any valve job permitted” is anything goes.

In 2007 or 2008 they removed any wording about seat angles.
Their argument is the stock seat angle must be retained.

That isn’t how the rule is currently written.

[nhrastocker]

Stock angles do not need to be retained anymore. Just the OEM valve size and stem diameter must be retained.
As said earlier, every cylinder head likes its own angles and valve shape.
You can also post your question on the technical section of ClassRacer...just don't expect to get much technical details...

[PRH]

I’m not a member over on CR, but the topic had been brought up when the rule changed, with what looked like a fair amount of confusion within some of the answers.

Like I said, my interpretation was that any angles were legal...... and that the NHRA simply wanted to get away from having to check/police it.

[DeezNutz]

Yes, any angles are allowed. Also any valve style, tulip, nail head... etc... lots of testing... and different manufacturers valves will be better than others.... also keep an eye on the weight of the valve train components... every little bit pays off big in class racing

[Jeff Lee]

I’m not a member over on CR, but the topic had been brought up when the rule changed, with what looked like a fair amount of confusion within some of the answers.

Like I said, my interpretation was that any angles were legal...... and that the NHRA simply wanted to get away from having to check/police it.

You are correct in your understanding. You could run any angle you want. Some angles give more CFM here and less CFM there, one way my help performance, one way may hurt performance. There is also much to be gained from the angles on the backside of the valve head. Don’t forget they specify the bowl cut under the seat also. That has been liberalized from what the standard used to be. You can have undercut stem also.
I’m no expert. I write the checks to the experts!

[Walter R. Malik]

I’m having an argument on another forum about what is and isn’t legal with regards to the valve job itself.

My interpretation of “any valve job permitted” is anything goes.

In 2007 or 2008 they removed any wording about seat angles.
Their argument is the stock seat angle must be retained.

That isn’t how the rule is currently written.

There are certain things that even though they are deemed illegal, they never bother checking in tear-down ... One is valve seating angle as long as the entire valve job width meets the rule.

[mag2555]

If you do not have your own flow bench and a heck of a lot of time and different valves to test and heads to eat up, and or have your own way to install seats and then of course do valve jobs then you need to find and use a shop that has done this massive time consuming type of testing.

One thing that seems to be certain is that the fattest Intake flow numbers you can get @ .200" lift coupled with a high scavenging Exh system ( while the piston is parked at TDC ) during the overlap phase is a big key part of the puzzle for greater VE numbers!

[tenxal]

edit: info removed

[ClassAct]

The OP is asking if it is legal in NHRA Stock Eliminator to use other than factory valves seat angles. I think he understands not every valve job works on every head and what it takes to test them.

He just wants to know if his reading of the rule book is what is legal. And that is can you use other than the factory valve seat angle in Stock Eliminator or must you retain the factory valve seat angle, whatever that is.

[tenxal]

The OP is asking if it is legal in NHRA Stock Eliminator to use other than factory valves seat angles. I think he understands not every valve job works on every head and what it takes to test them.

He just wants to know if his reading of the rule book is what is legal. And that is can you use other than the factory valve seat angle in Stock Eliminator or must you retain the factory valve seat angle, whatever that is.

OK. Previous post edited to remove all info.

[PRH]

There are certain things that even though they are deemed illegal, they never bother checking in tear-down ... One is valve seating angle as long as the entire valve job width meets the rule.

The thing is...... there is no more rule.

As written, the rule states, “any valve job permitted”.
From what I can see, the only wording in that entire section pertaining to the valve job states that anything is legal.
All wording regarding total valve job widths, seat angles, etc was omitted from the head section years ago.

So, if you set a record and are in the tear down area and they’re looking over your heads....... and let’s say your heads originally had 45* seats and now they are 50*.......
A- are they even going to check, because there is no longer a valve job rule?
Or
B- if they check, do they care?(because there is no valve job rule)
Or
C- they check, and tell you the 50* seats aren’t legal.
If it’s C....... what rule are they going to point to in the rule book to show you the stock angle has to be retained?

[1972ho]

The only thing they did to my heads in 2016 was cc intake and exhaust runner and combustion chamber and measure the valve diameter and checked the casting number.

[1980RS]

I was told recently that the Line's competition valve jobs for legal cars start out at 1K.