Need a sanity check on arp head torque (wrench discrepancy)
 

I did the 65 ft-lbs with the arp lube in three stages as per instructions.

I have a kobalt 3/8 (150 ft-lb max) click torque wrench and an ac delco digital torque adapter.

at first I was using the kobalt wrench and I got to 65. I then thought for the hell of it I’d see what my digital wrench adapter says and it started moving the nuts at just over 40 ft lbs.

I did end up going to 65 with the ac delco and didn’t seem to crack the head. I was certainly paranoid and went slowly and to be honest it felt like a good bit of effort for 65 foot pounds, but I had the engine on a stand with wheels so I was fighting that as well as just don’t have a good feel for what that torque feels like with heavy lubrication like that.


so I guess my question is should I buy a third wrench to figure out if I over torqued, or should I just run it? Of the head wasn’t damaged at this stage do I run the risk of issues later on if they are over torqued?

Can't go back in time, but if you discovered you have a torque wrench discrepancy, better to fix that problem before torqueing the entire head down.

I'd fix it if it's over torqued. Thermal expansion as it warms up will put more stress on the studs than when cold.

Got to weigh those feet on a triple beam ;) Maybe you can verify your torque wrenches with a real beam torque wrench. I always use a real triple beam wrench on anything critical and I consider head fasteners critical. I have said it before.

The 65 ft-lb number is a hefty pull on a head bolt. It doesn't sound all that high, but most of the time when you're taking things that high it's a vertical swing rather than a horizontal one, so you're using different muscles. Think about lug nuts -- you're using your legs to pull up (or body weight to push down), rather than your arms to pull towards you.

Do you know anyone with a "beam" type torque wrench you can borrow? While those are a total PITA to use for real work, they tend to be pretty accurate and there really isn't anything in them that can drift in calibration. You can check a torque wrench with the right size 12 point socket by putting two of them back-to-back.

http://www.codrus.com/miata/fm2r/block-assemble5.jpg

--Ian

Exactly, a 1/2" 12 point or 8 point and verify your digital wrench.

Pretty sure the delco digital adapter is faulty. I hung a 40 pound cinder block (weighed on scale) one foot down the handle with the adapter clamped in the vice. It registered 27.5 foot lbs on the delco. I then did what I think is correct math for this procedure with my click wrench. Middle point of the grip is about 14.5 inches from apex point in the wrench. I took 14.5/12=1.2 and 1.2x40=48. Set the torque wrench to 48 and hung the 40 pound weight from the middle of the grip and it was almost dead on. Wouldn’t click at 50.

What did did you mean by “apex point”? The length should be measured from the middle of the 1/2” drive square.

Otherwise, Assuming your wrench was horizontal when you did your cinder block hang, then you did it correctly.

Yea that’s what I meant. Late night... couldn’t find my words. Wrench was perfectly horizontal.