tdstuart
Well-Known Member
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Another member (@Mad1186) and I have had apex torque head stud failures! The headstuds are loosening over time, this is not due to power. If you have apex head studs please read this carefully!
Both were gen3 coyote head stud kits. Both were running gen3 shortblocks with gen 2 heads (the heads shouldn't really affect this but it is interesting).
My head stud kit was part of the batch shipped beginning of October 2022. Unsure of when the other person's was produced.
My car had them on for about 5k miles before the engine broke due to unrelated issues. During engine teardown, I discovered 2 loose bolts and one backed-out stud. Several studs/bolts I could tell were not close to torque spec, some were even just hand-tight.
Update (@Mad1186 info):
Mad1186 purchased his apex headstuds in February 2023. They had 8k miles on them when the failure occurred. Also had the same problem of several studs being in various stages of loose and tight. Seems like our failures are identical.
I sent the headstuds back to Apex to check out and they said they didn't see anything wrong with them. I held off on making a post because I thought there was a possibility I did something wrong, but with another failure, it is enough confirmation for me that there is a serious problem.
Technical Stuff:
I now have arp head studs, neither arp nor apex mentions retorquing head studs. As I understand some head studs require this but since the coyote ones are such a pain to access they are made so they shouldn't have to be retorqued.
Apex Torque Specs:
Step 1: 74 lb/ft
Step 2: 92 lb/ft
ARP Torque Specs:
Step 1: 40 lb/ft
Step 2: 80 lb/ft
Step 3: 125 lb/ft
ARP uses lube on the contacting washer and nut surface, as well as the nut threads.
Apex only uses lube on the contacting washer and nut surface.
Both headstuds are reusable, you can disassemble the motor, clean them up, and reuse them as they are not torque to yield.
ARP Part #: 256-4702
Apex Torque Part #: CM-HSK-12M
Apex Response on my Headstuds:
We didn’t see any apparent problems. The hardness was within our specifications for that generation of stud. We will send a replacement to the customer if we wants to proceed this way, or he can decide on a refund instead. We do not have any in stock. However, we can get him a set from the batch that becomes available in the next two weeks.
Apex Runnout Problem (from Travis Rosenbarger):
It seems super strange for that to happen, I don't think they would pull or stretch because the load is pretty low.
It could be a runout issue with the studs, the earlier versions sometimes had a slight runout to them, and that over time could allow the stud to work loose maybe. I haven't seen it before. I would not reuse them, I would turn them in for warranty just to be sure.
Other members (@Mad1186) post regarding his headstud and engine failure: https://www.mustang6g.com/forums/threads/engine-failure.189694/post-3813981
Both were gen3 coyote head stud kits. Both were running gen3 shortblocks with gen 2 heads (the heads shouldn't really affect this but it is interesting).
My head stud kit was part of the batch shipped beginning of October 2022. Unsure of when the other person's was produced.
My car had them on for about 5k miles before the engine broke due to unrelated issues. During engine teardown, I discovered 2 loose bolts and one backed-out stud. Several studs/bolts I could tell were not close to torque spec, some were even just hand-tight.
Update (@Mad1186 info):
Mad1186 purchased his apex headstuds in February 2023. They had 8k miles on them when the failure occurred. Also had the same problem of several studs being in various stages of loose and tight. Seems like our failures are identical.
I sent the headstuds back to Apex to check out and they said they didn't see anything wrong with them. I held off on making a post because I thought there was a possibility I did something wrong, but with another failure, it is enough confirmation for me that there is a serious problem.
Technical Stuff:
I now have arp head studs, neither arp nor apex mentions retorquing head studs. As I understand some head studs require this but since the coyote ones are such a pain to access they are made so they shouldn't have to be retorqued.
Apex Torque Specs:
Step 1: 74 lb/ft
Step 2: 92 lb/ft
ARP Torque Specs:
Step 1: 40 lb/ft
Step 2: 80 lb/ft
Step 3: 125 lb/ft
ARP uses lube on the contacting washer and nut surface, as well as the nut threads.
Apex only uses lube on the contacting washer and nut surface.
Both headstuds are reusable, you can disassemble the motor, clean them up, and reuse them as they are not torque to yield.
ARP Part #: 256-4702
Apex Torque Part #: CM-HSK-12M
Apex Response on my Headstuds:
We didn’t see any apparent problems. The hardness was within our specifications for that generation of stud. We will send a replacement to the customer if we wants to proceed this way, or he can decide on a refund instead. We do not have any in stock. However, we can get him a set from the batch that becomes available in the next two weeks.
Apex Runnout Problem (from Travis Rosenbarger):
It seems super strange for that to happen, I don't think they would pull or stretch because the load is pretty low.
It could be a runout issue with the studs, the earlier versions sometimes had a slight runout to them, and that over time could allow the stud to work loose maybe. I haven't seen it before. I would not reuse them, I would turn them in for warranty just to be sure.
Other members (@Mad1186) post regarding his headstud and engine failure: https://www.mustang6g.com/forums/threads/engine-failure.189694/post-3813981
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