Blown 3mm head gasket
05-04-2009, 08:11 PM
#42
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Thread Starter
It's not my tool. Belongs to the PRB (Clubman) workshop where I rebuilt my engine.
Apparently they call it 'Diane' after a previous employees wife. I'm not sure of the whole story but you can guess pretty easily.
Apparently they call it 'Diane' after a previous employees wife. I'm not sure of the whole story but you can guess pretty easily.
05-04-2009, 08:31 PM
#43
From memory my arp stud package specified 86 ft/lb.
I make sure both ends, and both sides of the washers are covered in ARP lube. Then take them to 40 ft/lb, then 60 ft/lb then 86 ft/lb.
I then loosen them in reverse order approx 1/4 turn, the retorque in sequence to 86 ft/lb.
Repeat the loosen/retorque sequence 2 more times.
If at any time I get a creek noise or any shudder I remove the nut and relube both sides of the washer.
If you retorque after a few heat cycles, the process is the same, back of 1/4 turn and retorque.
I make sure both ends, and both sides of the washers are covered in ARP lube. Then take them to 40 ft/lb, then 60 ft/lb then 86 ft/lb.
I then loosen them in reverse order approx 1/4 turn, the retorque in sequence to 86 ft/lb.
Repeat the loosen/retorque sequence 2 more times.
If at any time I get a creek noise or any shudder I remove the nut and relube both sides of the washer.
If you retorque after a few heat cycles, the process is the same, back of 1/4 turn and retorque.
05-04-2009, 09:45 PM
#45
It would only be 200 ft/lb if the bolts didn't stretch.
The important thing is the clamping pressure on the bolts.
A yield to torque bolt is going to relax to a certain clamping load which is determined by the design and material. If the engine gets hot and the head expands more than the design allows, the bolt is going to stretch further resulting in lower than designed clamping pressure.
A conventional bolt, provided it isn't pushed into plastic deformation should maintain a consistent clamping pressure through hot/cold cycles. The only catch is if the gasket its clamping compresses with cycles. If that happens there will be a loss of clamping pressure. Most gaskets compress up in the first few heat cycles which is why retorquing is recommended.
Ideally, you want the bolts torque spec to allow for the relaxing of the gasket.
Bolts stretch a lot during installation. This is elastic stretching and the bolt will return to the same length once the load is off it. Generally for the size of bolts used in engines, its about 0.004" per inch of bolt. The longer a bolt/stud is the large the window is to maintain clamping load if a gasket compresses.
The important thing is the clamping pressure on the bolts.
A yield to torque bolt is going to relax to a certain clamping load which is determined by the design and material. If the engine gets hot and the head expands more than the design allows, the bolt is going to stretch further resulting in lower than designed clamping pressure.
A conventional bolt, provided it isn't pushed into plastic deformation should maintain a consistent clamping pressure through hot/cold cycles. The only catch is if the gasket its clamping compresses with cycles. If that happens there will be a loss of clamping pressure. Most gaskets compress up in the first few heat cycles which is why retorquing is recommended.
Ideally, you want the bolts torque spec to allow for the relaxing of the gasket.
Bolts stretch a lot during installation. This is elastic stretching and the bolt will return to the same length once the load is off it. Generally for the size of bolts used in engines, its about 0.004" per inch of bolt. The longer a bolt/stud is the large the window is to maintain clamping load if a gasket compresses.
05-05-2009, 07:42 PM
#46
Heatcycling would mean I have to do the torqueing sequence, put the engine back together all the way, then run it till the cooling fans kicked in (full operating temp).
Then I'd have to take it all apart down to studs to re-torque?
Then I'd have to take it all apart down to studs to re-torque?
