Going 100-120 ft/lbs on the Head Bolts.. Why not?
06-04-2002, 09:56 PM
#21
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Re: Going 100-120 ft/lbs on the Head Bolts.. Why not? Thanks. I guess I just don't get it.
If you TQ them at 110 ft/lbs 'til they stop turning do you think they are tightened more or less than the GM method?
Who knows which method really is stressing the bolt or tightening the heads down better. Not sure I trusts GM's voodoo is all. We've seen no problems at all. So, comparing these 2 techniques I wonder which works better. Under boost, etc.
We've never had an issue.
Guess I'll find out how 110 ft/lbs does under 8psi soon enuff.
If you TQ them at 110 ft/lbs 'til they stop turning do you think they are tightened more or less than the GM method?
Who knows which method really is stressing the bolt or tightening the heads down better. Not sure I trusts GM's voodoo is all. We've seen no problems at all. So, comparing these 2 techniques I wonder which works better. Under boost, etc.
We've never had an issue.
Guess I'll find out how 110 ft/lbs does under 8psi soon enuff.
06-04-2002, 10:19 PM
#22
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Re: Going 100-120 ft/lbs on the Head Bolts.. Why not? on the aluminum block and stock bolts forget about it, using hardended bolts with the soft threads in the block, better be careful over 90ft lbs. i have nightmares when i think about some of the things ive seen done to blocks with different bolts and torue specs. its either gm stock specs or studs.
06-05-2002, 12:05 AM
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Re: Going 100-120 ft/lbs on the Head Bolts.. Why not? </font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">
If you TQ them at 110 ft/lbs 'til they stop turning do you think they are tightened more or less than the GM method?
</font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">The GM method is ~70#/ft. I use ~75#/ft on the final run. People in your HP range (<600rwhp) blow head gaskets due to bad tuning, not running too little headbolt torque.
If you TQ them at 110 ft/lbs 'til they stop turning do you think they are tightened more or less than the GM method?
</font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">The GM method is ~70#/ft. I use ~75#/ft on the final run. People in your HP range (<600rwhp) blow head gaskets due to bad tuning, not running too little headbolt torque.
06-05-2002, 06:56 AM
#24
Re: Going 100-120 ft/lbs on the Head Bolts.. Why not? No reason to go to any more than the proper torque angle on the GM bolts as there will not be any better clamping force. They are stretching already with the TA method. They can weaken and break as mentioned above if done wrong.
The reason GM does the TA method is due to a more even clamping. Up to the 22ft/lbs, they do not stretch and then GM engineers know that after the 90*-90*/50* sequence they stretch properly at that point. Similar to the way rod bolts are torqued. ARP, Lunati, Manley and down the line prefer to check rod bolt stretch over the torque method for proper clamping force. This is due to, as mentioned above, the different lubes that can be used causing different stretch points with torque readings.
Bottom line in my opinion is follow GM guidelines with GM head bolts and ARP guideline with ARP studs and you will be fine. Like Terry said, most likely a gasket failure is a tuning problem, not torque reading related. As Al mentioned, the heads will come off easily on an F-body and also a C5 with the ARP studs in place.
Later,
Mike
The reason GM does the TA method is due to a more even clamping. Up to the 22ft/lbs, they do not stretch and then GM engineers know that after the 90*-90*/50* sequence they stretch properly at that point. Similar to the way rod bolts are torqued. ARP, Lunati, Manley and down the line prefer to check rod bolt stretch over the torque method for proper clamping force. This is due to, as mentioned above, the different lubes that can be used causing different stretch points with torque readings.
Bottom line in my opinion is follow GM guidelines with GM head bolts and ARP guideline with ARP studs and you will be fine. Like Terry said, most likely a gasket failure is a tuning problem, not torque reading related. As Al mentioned, the heads will come off easily on an F-body and also a C5 with the ARP studs in place.
Later,
Mike
