Re-Torque Head Bolts Procedure
Thread Starter
Pro
Joined: Oct 2004
Posts: 628
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Re-Torque Head Bolts Procedure
I just replaced the head gaskets on my supercharged LT-1 (installed Cometic MLS gaskets). The car has been through a heat cycle and I am ready to re-torque the head bolts (per Cometic guidance).
I am going to unbolt the front brackets (supercharger and power steering brackets), but should I drain the coolant and / or remove the intake? Any other procedures that people use?
Thanks, Andy.
I am going to unbolt the front brackets (supercharger and power steering brackets), but should I drain the coolant and / or remove the intake? Any other procedures that people use?
Thanks, Andy.
Racer
Joined: Oct 2007
Posts: 250
Likes: 1
No,
You don't need to do either. You probably should loosen the intake bolts some and retorque them after doing the heads, but you don't need to remove the intake.
You shouldn't have to drain the coolant. The gaskets SHOULD keep that sealed during the retorque. It would not hurt in the least to drain and then replace the coolant, though.
From the post I get the impression that you are familiar with your gasket manufacturers retorque directions. If not, a standard procedure is to break all the head bolts loose and then retorque to a low level first(following the torque seq. pattern), Torque a middle step(in pattern) and final torque to spec(by pattern). If single-use torque to yield bolts, I think you just retorque to spec(by pattern) without breaking loose. Then you can retorque the intake.
I hope this is helpful, Take Care and Be Safe, -John
You don't need to do either. You probably should loosen the intake bolts some and retorque them after doing the heads, but you don't need to remove the intake.
You shouldn't have to drain the coolant. The gaskets SHOULD keep that sealed during the retorque. It would not hurt in the least to drain and then replace the coolant, though.
From the post I get the impression that you are familiar with your gasket manufacturers retorque directions. If not, a standard procedure is to break all the head bolts loose and then retorque to a low level first(following the torque seq. pattern), Torque a middle step(in pattern) and final torque to spec(by pattern). If single-use torque to yield bolts, I think you just retorque to spec(by pattern) without breaking loose. Then you can retorque the intake.
I hope this is helpful, Take Care and Be Safe, -John
Drifting
Joined: Jun 2004
Posts: 1,477
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This is from their catalog for the MLS gaskets
"The composition of MLS will also withstand the shearing forces created by aluminum heads on cast iron blocks. No re-torque is necessary."
Are they suggesting that to you because of the supercharger?
"The composition of MLS will also withstand the shearing forces created by aluminum heads on cast iron blocks. No re-torque is necessary."
Are they suggesting that to you because of the supercharger?
Drifting
Joined: Jun 2004
Posts: 1,477
Likes: 87
Heel & Toe
Joined: Jun 2007
Posts: 22
Likes: 1
From: Los Angeles, CA
Hmm, this doesn't make sense to me. I am also using Cometic MLS on my 383 rebuild (with 11.4 C/R). I'm going to be fastening the heads in a day or two.
As for retorquing with MLS gaskets... I can't see why you would need to. The gaskets are steel shims, that's it! If you are using a fiber-based gasket (i.e. Felpro) then it would make sense to retorque after several heat cycles.
Looks like I'll be making a call to Cometic also...
-Justin
As for retorquing with MLS gaskets... I can't see why you would need to. The gaskets are steel shims, that's it! If you are using a fiber-based gasket (i.e. Felpro) then it would make sense to retorque after several heat cycles.
Looks like I'll be making a call to Cometic also...
-Justin
Thread Starter
Pro
Joined: Oct 2004
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I dont think its anything to do with the gasket, but everything to do with the bolts.
After a full (30 minute) heat cycle on Sunday, I spent the effort on Monday to re-torque the passenger side head bolts and on average it felt that it took only about 30 ft-lbs to break the bolts loose. I eyeballed a few bolts and they turned an extra 20-30 degrees further clockwise from the original Torqued position.
During the build I used new ARP bolts, ARP assembly lube on the tops of the bolts, ARP assembly lube on the threads of non-water jacket bolts and ARP thread sealant on the threads of the water jacket bolts.
May just be my build, but after this experience I may actually re-torque the bolts again after I have put about 500-1000 miles on the car (and before race season officially starts).
Comments welcome!
After a full (30 minute) heat cycle on Sunday, I spent the effort on Monday to re-torque the passenger side head bolts and on average it felt that it took only about 30 ft-lbs to break the bolts loose. I eyeballed a few bolts and they turned an extra 20-30 degrees further clockwise from the original Torqued position.
During the build I used new ARP bolts, ARP assembly lube on the tops of the bolts, ARP assembly lube on the threads of non-water jacket bolts and ARP thread sealant on the threads of the water jacket bolts.
May just be my build, but after this experience I may actually re-torque the bolts again after I have put about 500-1000 miles on the car (and before race season officially starts).
Comments welcome!
Last edited by djxib; Jan 16, 2008 at 03:08 PM.
