That's odd, it should go right in.  Sometimes you need to tap them a little with a plastic hammer to get them fully seated, but if it won't go in at all it seems something's wrong.  Any way you can post a pic?

Here is a bearing picture. I can't push it anymore by hand. I'm a newbie when it comes to SBF engines, be nice. Is this the one that should go in the middle?

Last edited by StangStinson (10/22/2016 1:42 PM)

I've built a lot more Chevy motors than Fords over the years, so my tendency is also to put the thrust bearing on #5.  I though that might be your issue.  Glad it was an easy fix.

Be sure and check crankshaft end play, you may have sprung the bearing side thrust plates. If not enough end play clearance the bearing could seize, spin and wreck crank and block. Just make sure you have end play!!! 

a good indicator on any thrust bearing location, is the block side for the thrust, will be undercut to accept the thrust flange of the bearing half.  Jerry

Yes, always do a spin test after installing the crank.  If you can't spin it by just grabbing the snout and rotating is something is wrong.  FYI, if you install main studs in an engine you will likely have to have the line bore honed because the extra clamp load will distort the bores and pinch the bearings. 

Most studs have National Course threads in the block with SAE threads on the nut end.  SAE threads have a more shallow angle which provides better thread leverage.  For example, a 1/2" NC thread commonly seen on head bolts and main caps will have 13 threads per inch.  A 1/2" SAE thread, commonly seen on stud nuts will have 20 threads per inch.
Wikipedia has a pretty nice description of thread sizes;
https://en.wikipedia.org/wiki/Screw_thread
If anyone ever uses ARP rod bolts, they torque by bolt stretch instead of turning torque of the bolt head.

MS wrote:

TKOPerformance wrote:

Yes, always do a spin test after installing the crank.  If you can't spin it by just grabbing the snout and rotating is something is wrong.  FYI, if you install main studs in an engine you will likely have to have the line bore honed because the extra clamp load will distort the bores and pinch the bearings. 

 
Why does a stud torqued to the same value as a bolt create more clamping force?

As 66coupe said, the different thread pitch, and also because studs stretch the fastener instead of pulling on the threads in the block.  This also greatly reduces damage to the threads in the block, which is the other half of the reason why studs are always used in a race engine, because the threads in the block don't suffer from repeated teardowns. 
 

And I have had issues, which is why I bring it up.  My 347 had to be line bored to get proper bearing clearance.  In fairness, this is the only SBF I've ever put studs in the mains, and I've studded several SBCs and BBCs and never had an issue, but I also always check everything religiously, even if its been to the machine shop, so I spot a problem like that before the engine ever runs. 

Also remember that torque is deceptive.  When we measure torque with a torque wrench we are actually measuring resistance to turning.  Something as simple as applying lube to the fastener and what type of lube can make a dramatic difference in how much it should be torqued.  When you torque and ARP stud you are using ARP lube, but when you torque a normal main bolt its either dry of with engine oil (usually 30 weight), so that alone makes a big difference.  The goal is to achieve a specific fastener stretch, but that's impossible to read directly in a blind tapped hole, so the fastener's manufacturer has figured out that with a certain lube and at a certain measured resistance to turning, read in lbs/ft, the fastener has been sufficiently stretched.  If you read ARP's instructions though they specify using their lube because the studs produce higher friction and motor oil is inconsistent.  Even at the same torque value as read on a wrench the studs are producing a higher and more consistent clamp load, if for no reason other than the lube you use with them reduces friction considerably more than a dry fastener, or even one lubed with motor oil. 

Connecting rod bolts being replaced add distortion to the rods since they are either curved or knurled for an interference fit. That does require resising the rods.  That does not apply to a main stud.

Main studs are screwed into the block by hand and they do not distort the block any more or any less than a bolt once the nut is torqued.  I am not convinced the main caps are distorted more as a nut is tightened with fine threads vs coarse threads. Usually with ARP bolts or studs using the slippery ARP lubricants, a lower torque value is called out to provide the same stretch value as the original bolt.  A more accurate torque value is reached using studs with a nut, and the typical stud has more tensile strength than the typical bolt.