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how to torque chromemoly head bolts for bbc

5K views 6 replies 3 participants last post by  Clint Cummins 
#1 ·
Hello!
I'm about to torque my heads on the chevy 454 with my new allstar performance chromemoly cylinder head bolts ALL87002 but there was no instruction included so I don't know how I should torque them.
I've searched on allstar performance webpage and for instruction on arp's webpage for torque spec for arp:s chromemoly head bolts but they were not listed.

I'm using arp:s "oil"/lubricant

should I just torque the after factory specs in same increments of 3?

I live in sweden so call them is a problem and it's weekend so...

thanks!
 
#2 ·
Torqueing head bolts...

Hello,
It's my understanding that you put something like liquid teflon on the threads.. especially the threads of bolts going into the water jackets.

Greg Colletti said to oil the underside of the head bolts with engine oil so there is no friction to give false torque readings.

I've seen it written elsewhere to use white lithium grease under the bolt heads to reduce friction.

Do the 3 step torque sequence.. 20, 40, 60 then with your most accurate click torque wrench bring them up to say 65 ft lbs on a small block chevy.

I'm not for certain if that 65 is the same on a big block chevy. That is important because if you over torque any of the bolts.. the bolts can stretch and or your block deck can distort.. no matter how slight.

Does this help any?
 
#3 ·
Clint Cummins said:
Hello,
It's my understanding that you put something like liquid teflon on the threads.. especially the threads of bolts going into the water jackets.

Greg Colletti said to oil the underside of the head bolts with engine oil so there is no friction to give false torque readings.

I've seen it written elsewhere to use white lithium grease under the bolt heads to reduce friction.

Do the 3 step torque sequence.. 20, 40, 60 then with your most accurate click torque wrench bring them up to say 65 ft lbs on a small block chevy.

I'm not for certain if that 65 is the same on a big block chevy. That is important because if you over torque any of the bolts.. the bolts can stretch and or your block deck can distort.. no matter how slight.

Does this help any?

Thanks for answering but I know how and where to use the the oil and how to torque them but not how much? There is no torque specs included.
 
#5 ·
Berres said:
Hello!
I'm about to torque my heads on the chevy 454 with my new allstar performance chromemoly cylinder head bolts ALL87002 but there was no instruction included so I don't know how I should torque them.
I've searched on allstar performance webpage and for instruction on arp's webpage for torque spec for arp:s chromemoly head bolts but they were not listed.

I'm using arp:s "oil"/lubricant

should I just torque the after factory specs in same increments of 3?

I live in sweden so call them is a problem and it's weekend so...

thanks!
If these are made from material other than what the factory uses then the torque values will be different. The torque specified is the result of testing how much torque applied to the bolt nets the needed amount of length stretch so that the operating loads can't stretch the bolt further.

The Rocket Science:
So the material the bolt is made from directly relates to the amount of torque that results in the needed amount of stretch to the rule above. Usually, but not always, aftermarket bolts require more torque to get the proper stretch but without further instruction there's no way of knowing what it should be. There's a lot of different chrome-moly alloys and add to that the stretch is also affected by details of the bolt's configuration regarding steps and reliefs leading to the threaded portion, the major and minor thread diameters, the shape of the root at the bottom of the thread all play with the stretch characteristic so one firms spec, lets say ARP, may not be the same as an-others.


The Reality:
Now for a dose of reality, this is their website it has no real technical information: http://www.allstarperformance.com/product.htm?prod=652&part=ALL87002&add=no

But it provides a hint, "ALL87002 OE-type grade 8 cylinder head bolts are sold in complete sets and are ideal for stock or budget performance rebuilds." Grade 8 OEM means same as Original Equipment Manufacturer, in other words equal to stock Chevy parts. Probably made by a Chinese wanna be bolt maker.

So based on this glowing piece of engineering data I'd say; use stock GM recommended torque values and hope the bolts don't break first. Remember if you have to push the wrench away from you, keep your fingers open so if the bolt busts the fingers don't get caught between the flying wrench and some hard place.

Bogie
 
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