Cylinder Head Studs
 

Does anyone know exactly why they're prohibited in stock? I asked my father and he can't think of any reason why.

Dave Stinner

UNDER CYLINDER HEADS ON PAGE 54 & 55 OF THE 2007 NHRA RULE BOOK READS CYLINDER HEAD STUDS ARE PROHIBITED. I AGREE WITH YOUR DAD I DONT KNOW WHY.ABOUT EVERY THING ELSE IN LEGAL IN STOCK SO WHY NOT HEAD STUDS?

Allen Lambert

As far as he and I can tell, there's no performance advantage to using studs. They make it a little easier to attach the head to the block as opposed to using head bolts.

Dave Stinner

Don't know if it has anything to do with it since the tech official would simply tell the racer "That's your problem, deal with it.", but there are more than a few applications that would require removal of the master cylinder or have other obstructions if using head studs.

Locomotion Racing
http://www.geocities.com/locomotionracing

Ahh yes...many Fords; shock towers and head studs - not a happy marriage!

IHRA V/SA #3110

One argument I have heard is about tech inspections. Some body engine combinations require you to remove the engine or component body parts to remove a particular head or either head. The argument was that decisions of which head to remove would be a source of conflict (for example, big bocks in early Camaros and Novas) because of the extra effort imposed by the studs. Imagine four racers with the same engine type-body type in tech. Three get to pull the easy head, you have to pull the hard head. There are some people that would use such a situation to sue NHRA for discrimination.

If NHRA does not consider it to be out of the question to pull a piston and rod, what's the big deal about doing a little extra work to pull a head?

Because cylinder head studs offer more clamping pressure than bolts offer. If you have a high compression engine and the block is only 4 bolts per cylinder then you might have a problem with head gaskets. That problem could be fixed if allowed head studs. Under the old regime at NHRA, that's what they would tell you. Under the technically challenged new NHRA, they may allow it, not fully understanding the ramifications to fellow competitors.
Why do you want head studs if they offer no advantages?

Why? Some people have lots of money tied up in old blocks because there is no available legal replacement. Studs help keep from wearing out threads and this make blocks last longer.

As I mentioned in the carburetor thread, a prime example is the new ZL-1 block. GM sold the complete engines with head studs, and had them made by ARP. And ARP doesn't even make head bolts for the block at all, only studs.

If the factory has documented head studs then I would say it's legal. Present it to NHRA for clarification in your blueprint specs.