ARP VS standard cylinder head bolts

Falcon20x

Registered User
The Ford manual says to torque the bolts to 70N-m ( 59 lb-ft) +/- 90 degrees turn. Most people recommend the ARP bolt to be torque at 90.

Why is there such a difference in torque between the two?
What is the advantage of the ARP over the standard bolts?
Thanks
 
Arp bolts and studs are not torque to yield bolts or tty for short. Meaning the tty bolts are designed to have higher elasticity. When the engine heats up and the heads expand the tty bolts stretch. The theory is they keep the clamping force even throughout expansion and contraction. The down side is that over time they loose this elasticity and begin to fail. The other down side is that since they are designed to stretch you can't get much torque out of them because as you crank down on them the bolt just stretches till it finally shears.

ARP studs and bolts don't stretch like a tty bolt. You can torque an arp bolt up to higher forces than a tty bolt giving greater clamping force. The be careful is that too much clamping force can actually cause distortion thus causing the gasket surfaces to warp. Our head bolts are only 11mm which isn't overly beefy.

I put up a nice post on here about a year ago about this exact issue. I'll see if I can dig it out.
 
Great post it is exactly what I was looking for. I did a search but I did not see this one.

I still have one question.

You said: "You don't measure a torque to yield bolt with a torque wrench as they are measured by torque angle."

The manual says in the last step : " in sequential order rotate bolts a additional 90 to 110 degrees".

I assume you mean torque the bolts to the ford published torque settings using a torque wrench, then use the torque angle tool to comply with the last step (additional 90 to 100 degrees)?
 
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