Head bolts

S

SC

New member
I have a friend who is about to install a high compression head (I don’t know the manufacture). He doesn’t want to use standard grade 8 studs and instead plans on using grade 8 bolts and washers. He reasons that the car is a daily driver so why not use bolts instead of studs. Plus he believes it would make it easier to get the head off in the future not having to remove the water pump by simply unbolting the head. It’s not the route I’d take but what is the argument in bolting VS using studs to attach the head? Thanks
 
I'm not an expert on bolts or bolt torque, but most HC heads require extra torque. 60 to 65 ft. lbs. vs 55 ft lbs. When you use head studs, you first screw them into the block so they are tight. Then when you torque the head nuts, it is the nuts and the upper threads on the studs that absorb the force.

If you torque bolts in tho the block it is the 80 year old threads in the block that absorb that force. Probably more so, because there is only the one set of threads per bolt as opposed to the two sets on a stud. It seems to me that you are more likely to damage the threads in the block using bolts then you are studs.

Someone will correct me if I am wrong.

If your friend is concerned about removing the water pump tell him to mount the pump with bolts instead of studs, or get some of the bolts made to look like studs. You take them out an the pump comes off.

Wish your friend luck,
Jon
 
JBR is on the right track. Additionally, notice the threads in the block are coarse, the threads for the nuts are fine. Fine threads hold up better to the twisting action under pressure. Coarse threads in cast iron do not hold up too well under those conditions.
 
I too feel the same way and have read the same reasoning from others. Besides why would you need to take the head on and off?
 
Another concern with bolts is they are coarse thread and the studs are fine thread. Coarse threads would require more torque.

I got my new engine from the rebuilder with bolts. I took them out and put in studs.
 
If you bottom a bolt in the block you will definitely strip the threads out. plus the fine thread on the stud is a leverage device to allow more even torque.

But then most everyone says it's his car so he should do what makes him happy.
 
SC said:
I have a friend who is about to install a high compression head (I don’t know the manufacture). He doesn’t want to use standard grade 8 studs and instead plans on using grade 8 bolts and washers. He reasons that the car is a daily driver so why not use bolts instead of studs. Plus he believes it would make it easier to get the head off in the future not having to remove the water pump by simply unbolting the head. It’s not the route I’d take but what is the argument in bolting VS using studs to attach the head? Thanks
Click to expand...

SC,
Your friend should do what he wants to do with his engine..as it's his !!
However, you ask for advice ('arguments'), so pay attn to what most here have said as it's good advice. I don't know much, but was informed in the beginning that: fine thread= strength ;use where higher torque (clamping force) may be necessary. Henry Ford and co. set the model a head stud system so that this fine thread 'strength' principle was employed -vs- coarse thread (holding power) in the block.
If you explain this to your friend and he chooses to ignore/test Fords' engineering...well, you've been a friend for trying:) !
You can lead a shadetree tinkerer to knowledge, but you can't make him drink(?):o
 
Model T Fords had coarse bolts. When changing to a high compression head most Many good T builders use model A head studs. Especially with high compression heads.
In order to get the same gasket crush as 50ft. lbs. you'd get with a fine thread you'd have to torque a coarse bolt to 72.
When you switch to fine thread you multiply the torque setting by .7
Example: in a T if we want to torque to 50 with coarse thread bolts we can use model A studs and nuts and torque to 35 to get the same gasket crush (50 X .7=35).
If you use coarse threaded bolts you'd have to torque to 72 to get the same gasket crush as you would with 50 on fine threads (72 X .7=50.4).
You may want to go tighter with a special high compression head.
Do you think those old threads can hold that?
 
pat in Santa Cruz said:
JBR is on the right track. Additionally, notice the threads in the block are coarse, the threads for the nuts are fine. Fine threads hold up better to the twisting action under pressure. Coarse threads in cast iron do not hold up too well under those conditions.
Click to expand...
Remember, ford went to bolts on the flathead V/8??????????????
 
My opinion is there is no point in "tightening" studs in the block. You do that to hold something together. Usually, it's not ruining the threads but cracks the bottom of the hole and does not allow for the set height of the stud so the nut has the proper amount of threads holding when all is said and done. As mentioned the final clamping torque is on the nut with hopefully a single thread of the stud showing.
 
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