Cylinder Head Studs

Dwight Southerland · 06-25-2007, 12:57 PM

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?

RocketBlock · 06-25-2007, 05:50 PM

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?

Dwight Southerland · 06-25-2007, 08:09 PM

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.

Alan Roehrich · 06-25-2007, 08:42 PM

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.

RocketBlock · 06-26-2007, 12:36 AM

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

Alan Roehrich · 06-26-2007, 12:42 AM

Already done. Waiting on NHRA reply.

RocketBlock · 06-27-2007, 01:17 AM

ZL-1 parts would cross over to all BBC parts except cating numbers, etc. Just as you can use a BBC cast crank and rods from a low HP version on a 427-425 for a reduction in weight, then you should be able to run a ZL-1 specific bolt on a 396-325. Good call. So Ford racers, what head bolts were on the 427 SOHC engines? Been awhile since I had a HEMI apart but I think it had studs also.

06-25-2007, 12:57 PM	#1
Dwight Southerland VIP Member Join Date: Dec 2001 Location: Arkansas - In the middle of everything. Posts: 2,002 Likes: 64 Liked 783 Times in 195 Posts	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? __________________

06-26-2007, 12:42 AM	#6
Alan Roehrich Veteran Member Join Date: May 2006 Location: Murfreesboro TN Posts: 5,130 Likes: 1,589 Liked 1,897 Times in 425 Posts	Already done. Waiting on NHRA reply. __________________ Alan Roehrich 212A G/S

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06-25-2007, 05:50 PM	#2
RocketBlock Junior Member Join Date: Jan 2003 Posts: 57 Likes: 0 Liked 0 Times in 0 Posts	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?

06-25-2007, 08:09 PM	#3
Dwight Southerland VIP Member Join Date: Dec 2001 Location: Arkansas - In the middle of everything. Posts: 2,002 Likes: 64 Liked 783 Times in 195 Posts	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.

06-25-2007, 08:42 PM	#4
Alan Roehrich Veteran Member Join Date: May 2006 Location: Murfreesboro TN Posts: 5,130 Likes: 1,589 Liked 1,897 Times in 425 Posts	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.

06-26-2007, 12:36 AM	#5
RocketBlock Junior Member Join Date: Jan 2003 Posts: 57 Likes: 0 Liked 0 Times in 0 Posts	If the factory has documented head studs then I would say it's legal. Present it to NHRA for clarification in your blueprint specs.

06-27-2007, 01:17 AM	#7
RocketBlock Junior Member Join Date: Jan 2003 Posts: 57 Likes: 0 Liked 0 Times in 0 Posts	ZL-1 parts would cross over to all BBC parts except cating numbers, etc. Just as you can use a BBC cast crank and rods from a low HP version on a 427-425 for a reduction in weight, then you should be able to run a ZL-1 specific bolt on a 396-325. Good call. So Ford racers, what head bolts were on the 427 SOHC engines? Been awhile since I had a HEMI apart but I think it had studs also.