I'm having a coolant prolem at high boost only. It sprays out the overfill during high boost. Engine temps are normal.

I was just informed that some ARP 12mm head studs don't hold up as claimed, that they stretch and return to normal when engine cools down.

Anyone have this problem?

Can they be retorqued? Originally I torqued them as follows:

50lbs
90lbs
115lbs
128lbs

I am going to do a pressure test when the engine is cold. Then when hot.

If I don't lose pressure when it is cold but do lose pressure when it is hot, that should be a very clear explanation.

Any suggestions?

 

Yes, they will stretch. Do a re-torque on the studs. They should be re-torqued after install.

 

all fasteners stretch, that tension is what holds everything tight

one time to 128ftlbs w/ moly should be no problem, re-use and enjoy

 

Heat cycles affect creep...always retorque after several good heat cycles.

IMH (never blew a head gasket) O of course...

 

According to ARP, once the studs have been torqued properly (stretched and taken set) they will not move anymore. Problem is, how do you know when you've reached that perfect torque? Are you using the torque wrench properly? Is your wrench calibrated? I bought an expensive Snap-On digital just for that job. Wanna buy it?

 

If you really want to get the proper tightness you would put a dial indicator on the top of the stud and measure the stretch. The torque value that you use is very close to giving you the proper stretch amount if the fastener is torqued as recommended by manufacturer, I.E. proper lubrication and accurate torque wrench. A brand new, dry fastener will never be stretched the correct amount based on applying the proper amount of torque.

L8r,..........dogger

 

Don't know if you'd get that accurate of measurement that way. That is the way I measure when tightening connecting rod bolts, though.... the dial indicator is connected to both sides of the bolt/stud in that application.

 

How would you know the difference between the compression of the head gasket and stretch of the stud?

 

the first time i did a retorque i got almost 1/2 a turn more, a couple good heat cool cycles later, retorqued and got just over 1/4 turn more, a month later and a lot of wot passes later, i retorqued for the 3rd time, got just shy of 1/4 turn extra.....

the gasket only compresses a few thou of an inch. alot less than 1/8 of a turn.... fire rings on the other hand... alot!

 

The dial indicator could be setup on a magnetic base attached to the block not the head. Any stretch measured would only be of the stud not gasket compression. Easier way good torque wrench, and properly lubricated threads.

L8r,..........dogger

 

I will probably be putting studs in over the summer, (probably 625+ for peace of mind) and am looking for the best way to install. I see several different techniques discussed on the forum but first time I have seen this one. sounds like it might be the most accurate for stretch if the specs are provided for the studs. Probably need a real good stand and base though.

 

I've never heard of anyone measuring the stretch of a head stud. Those 625's get torqued to around 150lb/ft. So if you somehow do this, you'll need a really strong box end wrench with a persuader on it to give you the leverage required. Plus that dial indicator is only measuring stretch from the head up. What about the bottom of the stud? When using this tool on connecting rod bolts, it is attached to top and bottom to measure true stretch, so I don't know how accurate, if at all, this method would be. Like I said, I've built a few engines and never heard of this technique. I've been wrong before though....

 

Hello,

Never heard of anyone measuring head bolt stretch either. I cannot think of how it could be done. It is very common in higher end rod installations to measure stretch. It is the most accurate method.

Damon

Damon