ARP Head Bolts

[qkjuicedpony]

But it still does all come down to the tune as said before...plus knowing when to let out of it.


If he is planning on leaving the stock bottom end as is i would just throw bolts in it.

[coupe]

A stud is setup to have a better clamping force on the head than a bolt is

The only way a stud has more clamp is if you tighten it more...but it's not good to practice to overtighten a stud just becasue it's a stud. The torque value should be about equal for the stud and the bolt becasue they are both 7/16" diameter. And they're the same material.

Why do you think we run head STUDS in our diesels and not bolts...because at 40+psi of boost it wont lift the heads and it will with the bolts.

The 40psi is not what causes the problems. It's the 20:1 compression ratio combined with uncontrolled flame ignition, which yields in excess of 1000psi, that lifts the heads.

[qkjuicedpony]

well if bolts are just as good as studs....why the heck do they make both

[qkjuicedpony]

Here’s why. When you use bolts to secure the head, the fastener is actually being “twisted” while it’s being torqued to the proper reading. Accordingly, the bolt is reacting to two different forces simultaneously. A stud should be installed in a “relaxed” mode – never crank it in tightly using a jammed nut. If everything is right, the stud should be installed finger tight. Then, when applying torque to the nut, the stud will stretch only on the vertical axis. Remember, an undercut shorter stud will have a rate similar to a longer, standard shank stud. This provides a more even clamping force on the head. Because the head gasket will compress upon initial torquing, make sure studs and bolts are re-torqued after the engine has been run.




I copied this from another site....direct from an ARP engineer

[coupe]

Originally Posted by qkjuicedpony

well if bolts are just as good as studs....why the heck do they make both?

Bolts are not as good as studs. That's what I'm saying...Studs are better for the reasons the ARP engineer posted. The very shortcomings he mentions are the reason I prefer a studded cylinder head in any application other than a rebuild or freshen up of a stocker.

There is a common misconception that you can get away with a lot more torque on a stud than a bolt...and it's simply not true. I've heard people say you should tighten a regular 302 7/16" stud to 100 ft. lbs!
Although it can physically be done, it's not good for the 7/16 threads because the proof load is too high for the "fastening connection."

I think we're on the same page Brian.

[Craig K.]

baaah what is torque anyway, other than a rude method of trying to calculate clamp load which is what really matters.

[coupe]

True. But it's difficult to measure stretch in the bolt when one end is down in the block!

[LeeH]

Originally Posted by coupe

True. But it's difficult to measure stretch in the bolt when one end is down in the block!

A more accurate way of tightening a fastener if unable to check fastener stretch is by Tq turn, We Tq then pull however many degrees is require to achieve propper stretch then back them off and do it over again. This initial tq crushes the gasket so the very last tq is 90% fastener stretch, This method allows for a more even clamping force. There was a study done on this due to numerous head gasket failures on a certain series of engines, It was found that using a predetermined tq value vs tq turn to stretch the head bolts was not allowing for an even stretch(clamping load). The differences were quite alarming as in the variation from lowest to highest using a numerical tq value was 60-90% vs 80-95% using tq turn, It is all based on evening the frictional losses and torsional loads.

With that said it also depends highly upon the type lubricant used on the load bearing surfaces of the fastener.

[BAD INT]

I am sure most of you know that on a SBF the way the intake bolts down it tries to lift the upper side of the head so be totally aware of all things when building.Torque specs are to be followed but I have allways torqued upper and lower head bolts the same just because of the intake and I will double and tripple check when using lots of power adder.

[Wickd GT]

Speaking of these ARP studs. I bought these Iron GT 40s and they have the sleeve adapter to use the 7/16 stud, looks like these heads were on a 351eng which uses the 1/2" stud. My question is, do I need to put ARP washers when I'm ready to put these together or is these sleeve adapter for the heads at the top don't need a washer.

Edgar