differential main stud question

[sportinawoody]

if you switch to arp studs from the factory bolts for the differential bearing caps , do you have to have the 2 main caps align honed ? I mean an engine block has to be line bored due to the changing of the clamp loads when switching so am i far off here ? experience preferred but speculation is fine as long as you make it apparent​

 

[TexasBlownV8]

Is that different than putting the caps back on like they were, just with different bolts?
I always notch-mark them before removing them so they go back in the same location and orientation, but never have used arp's on them either.

 

[Scott]

In my build I went with a Moser Engineering Main Cap Stud kit, part number 7116. There is no need to align hone OEM caps with studs replacing OEM bolts. However if replacing OEM caps with billet ones align honing is of course required.

 

[AutoXRacer]

Nope, they are just bolts...

 

[sportinawoody]

Nope, they are just bolts...

stock yes, but im asking about switching to studs.


not arguing but just a thought,,, why must you line bore a block when changing from bolts to studs but not a rear end housing ? i mean changing torque load changes the radius in engine bearing caps so why not rear end caps also.

 

[01yellerCobra]

What about torquing the caps and checking roundness? If it's in spec you're good to go right?

 

[AutoXRacer]

stock yes, but im asking about switching to studs.


not arguing but just a thought,,, why must you line bore a block when changing from bolts to studs but not a rear end housing ? i mean changing torque load changes the radius in engine bearing caps so why not rear end caps also.

I did not know that. When my engine builder changed from OEM studs/bolts mains to ARP studs, he did not line bore the block (mains). There is a different torque spec for the ARP fasteners though.

When a shop replaced my rear end bolts to studs, they also did not line hone the rear end caps, they just torqued it to ARP specs and not OEM.

 

[sportinawoody]

sorry to get you worried but if your engine builder went from stock main bolts to arp studs in your mains and didnt line hone your block then i wouldn't expect to many miles out of your bottom end before it pukes bthe bearings up. the reasoning is the extra clamping force distorts the radius of the circle which the bearings rely on. thats the reason for line boring is to "true" up the holes and line them up perfectly with one another. that is just retarded for a builder to skip over on a built , blown engine.

back to the point though, it probably wouldnt change much in a rear since a steel race sits in the hole but i just wanted to ask. i cant get my bore gauge in there to check runout but many have done it so i will follow that path.

 

[AutoXRacer]

I don't agree with your statement...
ARP does not mention anything about line honing a block to install their main studs or any of their other bolts for that matter.

There is a torquing difference between OEM bolts and ARP studs/bolts...if they are torqued properly, then the final clamping forces are equal.

 

[blownGTvert]

I don't agree with your statement...
ARP does not mention anything about line honing a block to install their main studs or any of their other bolts for that matter.

There is a torquing difference between OEM bolts and ARP studs/bolts...if they are torqued properly, then the final clamping forces are equal.

However, align boring the main caps is generally done for a high performance builds. It's also standard practice on high mileage engines and engines that have failed due to lack of oil pressure. The fact your shop didn't align bore the mains raises some questions.

 

[AutoXRacer]

However, align boring the main caps is generally done for a high performance builds. It's also standard practice on high mileage engines and engines that have failed due to lack of oil pressure. The fact your shop didn't align bore the mains raises some questions.

Would you line bore a 10K mile motor that just needed a rehone and new rings due to a poor break-in?

 

[blownGTvert]

Would you line bore a 10K mile motor that just needed a rehone and new rings due to a poor break-in?

If it wasn't originally done, then yes. Again, it's typically always done in a high performance build. Similar in practice to using torque plates and balancing rotating assemblies.

You may or may not ever have an issue. I'm just suprised your shop didn't do it as standard practice. Especially given the issues you've had, and the application.

 

[sportinawoody]

the clamp force does change from bolts to studs because there is a roughly 15lb/ft change in torque from the bolts to the studs ( 30 lbs + 90 degrees w/ stock bolts vs 65 lbs with arp studs ) which causes the main distortion regardless of mileage. the same science applies to an egg if you want to try it. if you had the studs installed and line align honed before on your previous build you are fine but if you just switched on this go round then your builder is an idiot. im sorry if i sound like an ass, not my intention at all but dont take my word for it. Call any reputable engine builder and ask them if mains caps dont distort with that much difference in torque .
had to edit, had my numbers wrong

 

[AutoXRacer]

The point is...there should be no difference in final clamping forces.
If you torque the ARP bolts per OEM Ford torque specs, then you are introducing over clamping; over torquing your components.

Thats why there are different torque specs for OEM bolts and ARP studs and bolts.

Torque specs are dependent on the size and material of fastener.

But your final installed clamping forces onto the bearings and crank or whatever you are installing (heads, cams, bearing journals, etc) should be the same as with OEM fasteners.

So using ARP hardware vs OEM hardware is a moot point...clamping forces onto the journals should be equal.

Your typical engine build won't require a line bore unless some type of failure (crank, piston, rod, oil pressure, etc) occurred in the motor. As long as your builder verifies the roundness of the main bores, you should be fine. Remember, of course a machine shop will try to convince you to line bore your block, its one of the most expensive services they offer.

As long as you spec the block and everything is within specifications...you will be fine.