TO30 Cylinder head studs

[Todd30]

Hello All, I am rebuilding a z129 engine and I keep stripping the head studs when I try to torque the nuts down (only 75 ft lbs). I found only one place that sells new ones but they"re $9 a piece. Has anyone had any luck using bolts? If so what lengths did you use? Thanks.
 

[mathman]

Where did you find the studs?
 

[Richard L]

Any auto parts store should have them.
 

[DrLoch]

Thats odd, I've never stripped the threads off a stud or out of the nut and I've built a number of different motors. Are these the factory studs or have you replaced them with something else? Are you using any sort of assembly lube on the studs? If not you should be regardless of what the manual says.

When torqueing something down, there are quite a few forces involved. There is a resistive force from the friction between the surface of the bolt or stud and the object it is in contact with (block, head, cover, etc). There is, also, a resistive force coming from the stud itself as it is literally stretched (the primarly cause of the preload). There is a resistive force between the stud threads and the nut being rotated.

If everything is dry, the friction forces can be quite high. These forces effect the amount of force being put on the stud. This can and often does result in an improper preload on the bolt.

There are two different lengths used, 1 7/8″ which is part number 353964X1 and 4 11/16″ which is part number 1035877M1. They are certainly pricie..... I would try using an ARP stud and nut, they will sell individual studs and nuts if you know the thread and pitch.
 

[Don Hooks]

Just a note on a similar experience: I was rebuilding some piece of equipment and the studs were good but I had beat up the nuts taking them off. I decided to replace them with the same grade nut from the hardware store and the same thing happened - they stripped! Turns out the new nuts were just a little larger than the originals. A case of USA studs and far eastern nuts.
 

[Todd30]

Thanks all for the quick replies. I believe these studs are original. Can you think of a downside to using regular bolts?

Dr. Loch - what is an ARP?

Mathman - Jacks Small Engines has the new ones.
 

[DrLoch]

I would use studs. When I rebuild my 23C this winter I'm going to replace the head bolts/studs with all ARP studs. Same with the rod bolts.

http://arp-bolts.com/ American Racing Products. Once you find the length and pitch you can call them to get a match. I've used there products for years in racing engines, wouldn't use anything else. Did you see the price for them @ Jack's? ARP's aren't necessarily cheap either, but you get what you pay for. They will also have the hardened nuts and washers to go with the studs.
 

[Steve@Advance]

I would not use regular bolts. Couple of problems, bolts don't give the full thread depth engagement that a stud does, and a stud with a fine thread nut pulls harder than a coarse thread bolt.

Most everyone knows to run a tap in the bolt holes when going back together with an engine, which is the proper thing to do. Some assume the same is true with a stud, to run a die over the threads, especially if they're rusty. Not true! Never run a die over a bolt or stud, it will under size it. The threads are rolled on prior to heat treating. Not saying you did this, but if you did...
 

[Jason S.]

[Todd30]

Thanks all for your advice. I decided to bite the bullet and buy all new studs.