Headbolt re-torque question
Thread Starter
Melting Slicks
Joined: Oct 2000
Posts: 3,010
Likes: 1
From: Sweden/Stockholm
Headbolt re-torque question
Hello.
The engine whas put together last spring. So i used last summer to do the break-in ( i put around 3100 miles on it ). Now the car is in the garage, so I decided to check everything out.
I re-torqued the headbolts. Used the factory manual spec for alu heads( 65ft/lbs for the "upper" and 60ft/lbs for the short ones near the exhaust ports ) just as I did during assmebly.
The "top" bolts where fine. But the shorter "lower" bolts needed between 0.11inch-0.19inch tightend before the Torque Wrenche klicked. So i whent ahead and re-torque them all..
Is this to be expected?
What does your experince tell you?
The engine runs fine, consume no oil or water...
Thanks
The engine whas put together last spring. So i used last summer to do the break-in ( i put around 3100 miles on it ). Now the car is in the garage, so I decided to check everything out.
I re-torqued the headbolts. Used the factory manual spec for alu heads( 65ft/lbs for the "upper" and 60ft/lbs for the short ones near the exhaust ports ) just as I did during assmebly.
The "top" bolts where fine. But the shorter "lower" bolts needed between 0.11inch-0.19inch tightend before the Torque Wrenche klicked. So i whent ahead and re-torque them all..
Is this to be expected?
What does your experince tell you?
The engine runs fine, consume no oil or water...
Thanks
Team Owner
Joined: Dec 1999
Posts: 34,873
Likes: 487
From: Lacey WA RVN 68-69
NCM Sinkhole Donor
If the cylinder head surfaces were true and clean, you used a good quality head gasket, and you torqued the head bolts in the proper sequence, you should not have to re-torque them at all.
The FSM for my 92 LT1 motor says that all head bolts should get a light coating of sealing compound, and the bolts are tightened to 65 ft-lbs (88 N-m) using three passes (20, 40 and 65 wil work) and tighten in a clockwise pattern from the center bolt outwards.
The 92 manual does not specify a lower torque value for the bolts above the exhaust manifold. The torque values could be different for the 96 motors but you should be able to tighten them all to the same value.
The FSM for my 92 LT1 motor says that all head bolts should get a light coating of sealing compound, and the bolts are tightened to 65 ft-lbs (88 N-m) using three passes (20, 40 and 65 wil work) and tighten in a clockwise pattern from the center bolt outwards.
The 92 manual does not specify a lower torque value for the bolts above the exhaust manifold. The torque values could be different for the 96 motors but you should be able to tighten them all to the same value.
Race Director
Joined: Sep 2003
Posts: 16,836
Likes: 337
From: Database Error Indiana
It does not suprise me. When I put on new heads I was amazed, how much they turned. With old heads they seem to hold torque better. I guess the new castings move around untill the alluminum has finished taking its shape, after a few heat cycles.
Drifting
Joined: Feb 2003
Posts: 1,976
Likes: 2
From: San Antonio Texas
You're probably fine. That's why some people re-torque the bolts, after running for a while. Some gasket companies say you don't have to, but I usually do for my own peace of mind.
Head bolts often have different TQ ratings for different locations; I would pay attention to what GM (FSM) says about yours. If you have aftermarket heads, you probably want to go with their suggestions. For instance, some motors have 3 different bolt lengths, and TQ rates.
Head bolts often have different TQ ratings for different locations; I would pay attention to what GM (FSM) says about yours. If you have aftermarket heads, you probably want to go with their suggestions. For instance, some motors have 3 different bolt lengths, and TQ rates.
Last edited by Curveit; Feb 14, 2008 at 08:20 PM.
Le Mans Master
Joined: Sep 2006
Posts: 6,050
Likes: 147
From: Phoenix AZ
2021 C4 of the Year - Modified Finalist
head bolts
I would not retorque them. if you put the sealant on the bolts, they might not stop water from migrating up the bolts and possibly weep antifreeze
Thread Starter
Melting Slicks
Joined: Oct 2000
Posts: 3,010
Likes: 1
From: Sweden/Stockholm
Thanks for the feedback.
coupeguy2001:
Yes, i thougt about that to. That re-torque them could "damage" the sealant, but I whent ahead and did it nevertheless. I guess i will se when i fire it up again. But I didnet whant to use the engine with the headbolts out of torque spec.
Curveit:
Yes I use canfield heads. No torque values where printed in the papers that came with the heads. So I used the factory manual specs.
cmcbunch:
I whas trying to use the proper pattern. But as the "longer" bolts where in spec, they never "moved". But the "lower" did, so basicly I did not use the proper pattern, if you understand what I mean.
Well, I guess time will tell. Thanks for the input
coupeguy2001:
Yes, i thougt about that to. That re-torque them could "damage" the sealant, but I whent ahead and did it nevertheless. I guess i will se when i fire it up again. But I didnet whant to use the engine with the headbolts out of torque spec.
Curveit:
Yes I use canfield heads. No torque values where printed in the papers that came with the heads. So I used the factory manual specs.
cmcbunch:
I whas trying to use the proper pattern. But as the "longer" bolts where in spec, they never "moved". But the "lower" did, so basicly I did not use the proper pattern, if you understand what I mean.
Well, I guess time will tell. Thanks for the input
Le Mans Master
Joined: Feb 2005
Posts: 5,146
Likes: 3
From: The Motor City
that would also depend on what type of sealant. If you used RTV (silicon) and re-torqued, the seal on the threads could change, if using something like permatex #2, then I 'd say no problem.
Last edited by mseven; Feb 15, 2008 at 06:25 AM.
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Thread Starter
Melting Slicks
Joined: Oct 2000
Posts: 3,010
Likes: 1
From: Sweden/Stockholm