What is the MAX compression ratio the factory 7/16 head bolt can take without risking blowing head gaskets?

Or is it always just better to drill and run 1/2 head bolts?

 

My $.02....

It is not compression that lifts the heads, it is cylinder pressure/horsepower.

This is also dependent on RA finish on the cylinder head and the block deck, how flat the deck and cylinder head surface is, what kind of 7/16 head bolt or stud you use (Stock OEM or ARP), and finally, how good the head gasket design is.

One of the shortcomings that we encountered on our build was that it had 7/16 ARP head bolts..... We were already far along on the assembly as I had assumed it had been drilled and tapped for 1/2 at the old Mondello shop. Unfortunately, It hadn't.

Needless to say, with 7/16 ARP head bolts, decent deck and excellent cylinder head surface finishes, and running cometic head gaskets (.027 thick), we didn't have any issues at 604hp naturally aspirated.

If we were running boost or Nitrous, who's to say how much power the 7/16 bolts will hold with the Cometic gaskets?

 

So if 7/16 are safe. Are head STUDS better than head BOLTS?

 

Studs (quality ones like ARP)offer more clamping force as compared to an ARP bolt of the same diameter.

Whatever fasteners you decide on, make sure and use those same fasteners when torque plate honing the block to ensure the same forces and bore distortions are present as if the engine was bolted together and running.

 

What do you torque the ARP head studs to?

 

Here is the link to the 7/16 455 ARP stud kit

https://arp-bolts.com/kits/arpkit-de...p?RecordID=680

looks like torqued in 3 steps to 80ft lbs is what I saw on the instructions

I "cylcle" both ARP studs and ARP head bolts at least 3 times (torquing up and then backing them off) in the 3 steps up to the max torque, as you will feel them stretch a good bit the first 2 times you torque them up to the spec torque.

Also, I use the ARP moly lube on the threads of the stud that the nut goes on, and not much ARP moly or just oil on the threads that go into the block, and only screwed in by hand into threads that have been cleaned out with a thread cleaner tap.
Use arp moly under and above the washer and a little on the threads of the nut for the stud.



On an ARP bolt, use the ARP moly lube on the threads, and make sure the threads in the block are clean and corrected with a thread cleaning tap. Use ARP moly on both sides of the washers, and make sure the chamfer is facing up towards the underside of the bolt head.

Many people don't use the proper lube or not enough and don't torque cycle the fasteners before calling it the final torque, therefore never achieving true fastener strength and clamping force.