Heads Studs vs. Head Bolts

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siuauto

siuauto

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Putting together a small block stroker motor. I need to purchase fasteners for the heads. Going APR but curious if I should go studs or bolts. Is there any disadvantage to going with studs?
 
If you go studs you really should hone with a plate. Plus what was mentioned above.
 
The studs provide more consistent clamping force. Less variation between each fastener is another way to look at it.

This is what I do if space is tight for studs. Usually it is only some studs, not all of them. I put the offending studs in the heads with a cloths peg around the top of the stud to stop it hanging out the bottom of the head during installation.
 
Serious hardcore racing? High CR? use studs. Otherwise it’s just blowing money on unnecessary overkill and a placebo effect. Everything else bolts are more than adequate. ARP bolts with washers and using the lube as they advise correctly and then Tighten them in 10 ft/lb increments. Learned this 35 plus years ago from the 40+ year old Mopar Bible. Nothings changed as far as tightening head bolts correctly.

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I use studs on everything but it’s not for placebo. I do it because I want the screw load up at the nut and not in the threads in the block.
 
448Scamp said:
I use studs on everything but it’s not for placebo. I do it because I want the screw load up at the nut and not in the threads in the block.
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It’s not a blanket statement obviously (I should have been clearer :() but it does occur often, with everything in life. I’ll stand by my assertion that if racing, using higher CR studs are best, otherwise bolts are proven acceptable. End users discretion.
 
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448Scamp said:
I use studs on everything but it’s not for placebo. I do it because I want the screw load up at the nut and not in the threads in the block.
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"the screw load up at the nut and not in the threads in the block."
It just does not work that way, the load applied is going to be distributed equally across the length of the bolt shaft from the under head down to the threads whether using bolts or studs.
Think of a bolt as a rubber band, as the bolt is tightened it stretches along its shank. The pulling of the shaft longer provides the tension to make the clamp load that keeps the cylinder head compressed.
In comparing bolts and studs, think of a rubber band being stretched and twisted at the same time, that is how clamp load is developed in a head bolt. Now think of a rubber band being stretched as it is held so the lengths of the band are held parallel to each other. That is how clamp load is developed in a head stud.
The single action of only pulling and not twisting is easier on the bolt shaft, and develops a more repeatable clamp load when torque is applied.
Remember the head gasket that you are trying to keep in place never sees the torque that is applied to the head bolts or studs. The head gasket sees the clamp load that is generated by the stretch of the head bolt or stud that occurs when sufficient torque is applied. The more repeatable the stretch, the more repeatable the clamp load.
 
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my68barracuda said:
"the screw load up at the nut and not in the threads in the block."
It just does not work that way, the load applied is going to be distributed equally across the length of the bolt shaft from the under head down to the threads whether using bolts or studs.
Think of a bolt as a rubber band, as the bolt is tightened it stretches along its shank. The pulling of the shaft longer provides the tension to make the clamp load that keeps the cylinder head compressed.
In comparing bolts and studs, think of a rubber band being stretched and twisted at the same time, that is how clamp load is developed in a head bolt. Now think of a rubber band being stretched as it is held so the lengths of the band are held parallel to each other. That is how clamp load is developed in a head stud.
The single action of only pulling and not twisting is easier on the bolt shaft, and develops a more repeatable clamp load when torque is applied.
Remember the head gasket that you are trying to keep in place never sees the torque that is applied to the head bolts or studs. The head gasket sees the clamp load that is generated by the stretch of the head bolt or stud that occurs when sufficient torque is applied. The more repeatable the stretch, the more repeatable the clamp load.
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Ok, I’ll say it this way. With a bolt the threads in the block get a twisting force as well as a pull. With a stud, the threads in the block get a straight pull on them. So it is different. You can either put the screw load up in the nut or down in the block. It even changed bore distortion. So again, it is different. The cost difference is so minimal that I use studs. The factory uses bolts because they are cheap.
 
12many said:
Serious hardcore racing? High CR? use studs. Otherwise it’s just blowing money on unnecessary overkill and a placebo effect. Everything else bolts are more than adequate. ARP bolts with washers and using the lube as they advise correctly and then Tighten them in 10 ft/lb increments. Learned this 35 plus years ago from the 40+ year old Mopar Bible. Nothings changed as far as tightening head bolts correctly.

View attachment 1715784820

View attachment 1715784821
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Good post and advice. I have that book.
Cometic Mls and arp stud at 120 ft pounds is the way to go imho.
 
I don't know if I need them at 11.8 cr but I'm going with studs, I was advised
 
I think it is good insurance on an engine that really could use a 5th head bolt. They have a hex in the end of the stud. So when I remove a head I just run the studs out.
 
Thanks. I agree. ARP head studs and a quality gasket.
Big thumbs up!
The cam is small. It creates a lot of cylinder pressure. I figured it was a good area to step up in. Along with the TF heads and 1.6 rockers, the engine makes some good steam especially when the rpm’s clime.
 
siuauto said:
Putting together a small block stroker motor. I need to purchase fasteners for the heads. Going APR but curious if I should go studs or bolts. Is there any disadvantage to going with studs?
Click to expand...
I've always reused the original head bolts.
I save my money for rod bolts and main studs. Never blown a head gasket, ever.
After 2 builds on same heads, they checked flat within .001
Thats over an 8 year period.
Once you have your stuff milled flat, its good unless you overheat the heck outta it or need them smaller.
One thing that can be nice is the smaller 12 heads.
To your direct question...
bolts are my recommendation.
 
Careful with head studs on a B/RB. My ARP's hit the header flange I was using and I had to hit the stud end with a grinder. I stud about everything I can especially when the hole is wet (ex manifold ends, timing covers and stat housings, etc). Makes it a pain to remove the stuff with radiator installed but I know Im getting complete thread engagement and the stationary RTV'd ends wont leak.
 
MOPAROFFICIAL said:
I've always reused the original head bolts.
I save my money for rod bolts and main studs. Never blown a head gasket, ever.
After 2 builds on same heads, they checked flat within .001
Thats over an 8 year period.
Once you have your stuff milled flat, its good unless you overheat the heck outta it or need them smaller.
One thing that can be nice is the smaller 12 heads.
To your direct question...
bolts are my recommendation.
Click to expand...
What compression ratio ? Sbm are notorious for gasket issues at high ratios because of using only four bolts per cylinder.
 
Well lets hope my 14:1 410 stroker holds up with gaskets then. Glad to read some of this stuff.
 
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