Torque the top head bolts more than the bottom?

[Zero Signal]

Most places say torque the heads 70 ft-lbs or so, but I got an AERA technical bulletin about how ford now torques the top bolt about 5 ft-lbs more than the bottom due to our intake manifold mounting style. It mentions that since our manifold bolts straight down, it has a tendency to wedge the heads outward near the top. It mentions that AERA members were reporting lots of blown head gaskets on the top side of the head. So their recommended torque is more like 70 on the bottom and 75 on the top. Has anyone heard of this?

On another note, does anyone know if it's safe to re-torque ARP head bolts? I know their torque value is for 75% yield, so it seems they should still be far enough into their elastic zone to be torque multiple times. I heard they say you can do it 3 times. Is that true? Obviously I would need to replace the head gaskets if I remove the heads, but I hate to buy all new bolts again.

 

[CManT1914]

I seem to remember hearing that. IIRC, I torqued my lowers to 75, and my uppers to 80.

 

[final5-0]

I seem to remember hearing that. IIRC, I torqued my lowers to 75, and my uppers to 80.

John

I called ARP and told them I was using their bolts on AFR heads and these were the specs the tech gave me

Using ARP sealant Lower 65 Upper 70

Using Locktite teflon sealant Lower 70 Upper 75

He then told me to use use sealant on all bolts for consistent results and be sure to lube the head/washer junction to prevent galling.

Grady

 

[CManT1914]

Grady, nice job quoting the wrong person!

Was it 70 lower 75 upper? Maybe that's what I torqued them to. Dang I hate having a bad memory.

 

[Zero Signal]

Well the ARP specs are assuming you use a sealant for the bottom and something else for the top, since they say to use sealant for the wet holes and something else for the 'blind' holes. I'm pretty sure those values are due to the variance in friction between compounds. So something that lubes really well will required less torque to achieve the same tension on the bolt.

 

[blksn955.o]

I have always heard to use the higher trq. setting method with non-trq. to yld. bolts.

 

[blk9450]

i torqued my arp studs 100 on top 90 on bottom. i dont want any blown gaskets

 

[Zero Signal]

Well it makes sense that it would all be the same with torque to yield bolts. Steel has this property where once it yields and you keep straining it, it doesn't actually pull more net tension (called plastic state). So the bolt will torque more and more untill it yields, then you might find that you hit a flatline where it doesn't seem to get tighter, but it will eventually strain-harden before it snaps. In theory you could actually re-use those bolts, but the problem is you have no idea how far they were strained in the first place so you don't know what stress-strain state the bolt is in the second time around. If its already nearing strain hardening, you can get your torque value initially, but get them really hot and the bolts will lose there tension and fail.

 

[Grn92LX]

Follow the arp instructions. They call for 60 ft/lbs for aluminum heads on ALL bolts using their lubrication.