Just wondering if anyone who has done heads on a 3.9/4.0 etc. Has seen a clear justification for using studs instead of TTY bolts. I have a bunch of years as an A&P mechanic, high performance automotive guy. So I know all the ussual reasons for using studs instead of bolts. Just trying to figure out if the added cost is worth it on a Rover. So if you used studs and can say, "wow sure glad I used studs becouse......" I would like to hear it.
ARP Head Studs
- Thread starter Leadvagas
- Start date
..also, ARP has a new kit (157-4301) to only be used with composite gaskets. The old kit (124-4003) that everyone used (myself included) is now specified for metal gaskets only, even though many used it with composite gaskets.
Differences I've noticed in the new kit:
10 studs per head (instead of 14)
12 point nuts
100 ft-lb torque spec (instead of 80)
Differences I've noticed in the new kit:
10 studs per head (instead of 14)
12 point nuts
100 ft-lb torque spec (instead of 80)
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"wow sure glad I used studs because......"
Becuase I know I fitted the best quality available engineered fastener system which (fro personal experience), demonstrated consistent torque / angle relationship across all the fasteners while going through the torquing sequence.
The one and only time I used bolts on my disco engine (before I replaced the block), for the final angle, I was applying almost double the torque to some fasteners than others - and in disassembly, torque was also all over the place.
I also believe that any "second-hand" thread must be assumed to be compromised. Once you remove the original bolts to do your first HG job, and wind in new bolts, the threads in the block can no longer be assumed to be as the factory intended, and any angle/torque relationship can't be guaranteed. So when Quality controls are in place at the factory, with the same (truly OE approved) fasteners being driven into virgin threads, that is as good as it'll ever be... And never again will it be controlled once that fastener is removed and replaced. The ARP stud puts prescision matching thread forms against each other, for well, as good of a solution as could be desired.
Finally; the engineer in me also doesn't like the "principle" of high-torqing fasteners into alloy; studs are the superior option. If the RV8 was an iron block, this factor be less of a issue to me, but still relevant all things considered.
I don't believe that TTY are totally superior, instead that they are merely "engineered to the lowest price to meet the requirements for the application". Anyone who doesn't believe this should actually perhaps listen to those who have experience working for OEM's and seeing the bean counters at work... 2c per fastener, with 16 fasteners per engine and 100K engines per year works out to a lot of coinage. ARP's don't quite fall into this "low cost" category.
THAT SAID,
The only thing I'd like to see differently in the ARP's, is to have the shank necked down, the necked section having the same length and diameter for all studs. This would provide an assured element of "stretch" to the fastener as it is torqued to the final stated torque value, deemed sufficient for the gasket, and allowing for the thermal change of the fastenened joint, while remaining functioning in the elastic region of the material, allowing the fastener to be re-used repeatedly. This would mean that both the long and short fasteners would then be assured of having the same applied tension for a given torque.
This is also something that the "supposed TTY" head bolts (interestingly often just marked as metric grade 10.9 on the head) could also benefit from... I just don't believe anyone makes a REAL TTY fastner for the RV8.
A REAL TTY bolt should / would have either a necked down section in the shank, or the whole shank is necked down and the thread OD is larger than the shank. Anything else, is just a pretender of the TTY concept, becuase the weakest point (and primary stretch initiated location) will be at the smallest diameter - ie the root of the fastner thread (or more likely just stripping the alloy thread out of the block as we know happens).
Becuase I know I fitted the best quality available engineered fastener system which (fro personal experience), demonstrated consistent torque / angle relationship across all the fasteners while going through the torquing sequence.
The one and only time I used bolts on my disco engine (before I replaced the block), for the final angle, I was applying almost double the torque to some fasteners than others - and in disassembly, torque was also all over the place.
I also believe that any "second-hand" thread must be assumed to be compromised. Once you remove the original bolts to do your first HG job, and wind in new bolts, the threads in the block can no longer be assumed to be as the factory intended, and any angle/torque relationship can't be guaranteed. So when Quality controls are in place at the factory, with the same (truly OE approved) fasteners being driven into virgin threads, that is as good as it'll ever be... And never again will it be controlled once that fastener is removed and replaced. The ARP stud puts prescision matching thread forms against each other, for well, as good of a solution as could be desired.
Finally; the engineer in me also doesn't like the "principle" of high-torqing fasteners into alloy; studs are the superior option. If the RV8 was an iron block, this factor be less of a issue to me, but still relevant all things considered.
I don't believe that TTY are totally superior, instead that they are merely "engineered to the lowest price to meet the requirements for the application". Anyone who doesn't believe this should actually perhaps listen to those who have experience working for OEM's and seeing the bean counters at work... 2c per fastener, with 16 fasteners per engine and 100K engines per year works out to a lot of coinage. ARP's don't quite fall into this "low cost" category.
THAT SAID,
The only thing I'd like to see differently in the ARP's, is to have the shank necked down, the necked section having the same length and diameter for all studs. This would provide an assured element of "stretch" to the fastener as it is torqued to the final stated torque value, deemed sufficient for the gasket, and allowing for the thermal change of the fastenened joint, while remaining functioning in the elastic region of the material, allowing the fastener to be re-used repeatedly. This would mean that both the long and short fasteners would then be assured of having the same applied tension for a given torque.
This is also something that the "supposed TTY" head bolts (interestingly often just marked as metric grade 10.9 on the head) could also benefit from... I just don't believe anyone makes a REAL TTY fastner for the RV8.
A REAL TTY bolt should / would have either a necked down section in the shank, or the whole shank is necked down and the thread OD is larger than the shank. Anything else, is just a pretender of the TTY concept, becuase the weakest point (and primary stretch initiated location) will be at the smallest diameter - ie the root of the fastner thread (or more likely just stripping the alloy thread out of the block as we know happens).
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BTW - I finally have a skidmore in my possesion, along with a set of spare ARP studs, and a spare block. If anyone has any odd spare un-used "supposed TTY" bolts for the RV8, I'll happily do a study of applied angle vs applied torque vs achieved clamp pressure, to add more information to the studs vs bolts debate....
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I never thought the tty was the problem, but the thread engagement and expansion differences in between the bolt and alum block were.
ptschram
Well-known member
This is another interesting post about the bolts showing "oem" from several vendors in comarison to ones removed from an actual engine.
http://www.discoweb.org/forums/showpost.php?p=225340&postcount=5
http://www.discoweb.org/forums/showpost.php?p=225340&postcount=5
Honestly the studs nor bolts matter, as long as you have discomike walk you through the install on the phone your Rover V8 is guaranteed to last forever.
I am much closer to dunce than expert mechanic.
I was able to torque the heads on ARPs without ripping any threads.
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