head bolts?

[TFaucette]

how many times can the stock head bolts be torqued before they should be replaced??

 

[DVolk]

Id say atleast once but id have to read the book , although it seams like everyone says replace bolts now days

 

[Bob4x4]

As long as they have not stretched they are fine to use

 

[TFaucette]

how can i measure if they are stretched? i have already reused them once and i am running more timing, boost, and fuel than stock so i want to make sure they will hold but don't want to drop 400 bucks on arp studs if not neccessary (head bolts held before just washed out number one cylinder)

 

[Ncostello]

Sometimes you have to just do what's right. In this case that means either new bolts or ARP studs. I prefer the ARP studs because you're not transfering the friction of the thread twist when torquing the bolts (to ultimately make them stretch to clamp) to the threads (or general area) in the block. Many cracks in blocks have been attributed to the use of bolts over studs... or at least assumed because no other reason could be found for the cracks. I prefer studs for those reasons. Otherwise you're gonna end up doing this job again. And you said you "wanna make sure they will hold".



You probably can't measure "stretch"... mainly because there isn't any permanent deformation. They come back to their original size assuming they weren't taken into the yield strength region of the material used. But the stretch that occured has caused "damage" to the original bolts. Furthermore the threads are different now (polished) and the torque you apply will actually result in further rotation under the same applied torque... which means more stretch than originally done.



If you really want it to hold... and you're doing all the extra power adds... you really better consider the $400 to keep it all together.



Bolt stretch is all that a bolt really does to do its job. Turning with a wrench and using threads is just a means to stretch the bolt (and highly variable at that). Some big bolt jobs have machines to stretch the bolt by actually pulling on it. Then the nut is just snugged down by hand and its all good. Then you know each bolt has the same clamp load. NASA doesn't talk much about torque for instance... . they talk in terms of clamp force. Even using a lube or the wrong lube on threads can ruin bolts from over torquing. Head bolts are critical.

 

[DVolk]

it pays to shop around on hardware there is always some place that will sell for less , and if you buy from a speed shop there wont be any deals on them

 

[Shadrach]

Cummins does make a "stretch gauge" for head bolts. P/N 3823921 is for B & C engines



From the Cummins Tool Catalogue:



These templates are designed especially to measure the free length (stretch) of the used cylinder head capscrews that have been used in the torque plus angle tightening method prior to installing in the cylinder head.



Part No. Description

3823546 Cylinder Head Capscrew Length Gauge (L10 and all NH)

3823921 Cylinder Head Capscrew Length Gauge (B and C Series)

3824955 Cylinder Head Capscrew Length Gauge (QSK19 Series)

3163162 Cylinder Head Capscrew Length Gauge (Signature 600/ISX)

3163328 Cylinder Head Capscrew Length Gauge (QSK45/60)

3823611 Cylinder Head Capscrew Length Gauge (“A” Series Engine)

3163760 Cylinder Head Capscrew Length Gauge (QST30)

3164057 Cylinder Head Capscrew Length Gauge (ISB 4 Cylinder, ISBe 4 and 6 Cylinder and F Series)

3164364 Cylinder Head Capscrew Length Gauge (M11/ISM)

3164435 Cylinder Head Capscrew Length Gauge (QSK23, QSK78)



Shad