V8 Head Tightening

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Page created by T Mar 5th 2009: 

Head Bolt Holes 3 and 5 must not be torqued as high as the other Head Bolts or the Casting will fail as in this image. Photo by Johnny23Holden. Click to Enlargen.

V8 Head Tightening:

Broken Head Bolt Holes:

Ben Simpson has pointed out that there is a correct procedure for tensioning Holden V8 Head Bolts.Failure to observe it results in broken Head Bolt Holes as per the image.
308 V8 Block with Head Bolt Holes 3 and 5 still intact on both Banks. Photo by Rob Milne. Click to Enlargen.

253 Head Bolt Thread:

dont worry, if the rest of the engine is in re-usable condition, these bolt holes are not required. did you know the late model blocks do not have these holes at all??? these 2 are commonly broken as many people dont read the proper torque specs, and this is the result of them being torqued to the same as the main head bolts.
Drilling pin holes in the bottom of the Bolt Holes allows Oil to escape during tightening and prevents Hydraulic Cracking. Photo and info by MyEHHolden. Click to Enlargen.
Broken Head Stud Hole. Photo by Azzagts. Click to Enlargen.

Blind Inner 4 Head Bolt Holes:

The 4 inner head bolts are also "blind" holes, don't put any sealant or oil in them, the hydraulic pressure can be enough to crack the bosses of the block. Clean the threads properly and use some air to make sure they are dry before assembly. The EFI blocks didn't have them drilled, and I have seen opinions that you don't actually need to even fit them, but I don't think I would do that if I had a choice. But I do have a 253 with one of the bosses broken off, it has never blown a head gasket even though there is no bolt so that may be true but I don't think I'd use the block for an expensive build.End of submission by Another_HQSS.

Blind Exhaust Side Head Bolt Holes:

Of the five head bolt holes on the exhaust side (short bolts) numbers 2, 3, and 4 are also blind holes that require no sealant. Lightly oil these bolt threads and the underside of the bolt head before installing. JeffEnd of submission by HQJeff  



MyEH's Shed



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