TR2/3/3A Head bolt torque???

[Kleykamp]

Haynes manual says 45 ft lbs in one paragraph and then shows 100-105 ft lbs in tech data page. Does anybody really know what torque it is? I'm at 45 and seems like going 60 more would be near impossible. Not the first mistake I've run into in Haynes manual. Thanks for correct help.

 

[titanic]

You are not the first one to be bitten by that glitch, usually noticed after the rocker assembly is in place. 100-105 is correct. Why do you find 60 or more near impossible? Berry

 

[PKPoole]

Joe,
Be sure to lube the nuts before putting the torque wrench to it. You may also want to re-torque after the engine warms up. Glad to know you are going back together. Pat

 

[TR3driver]

I agree, 100-105 is correct. I believe (not certain) that is "dry" torque though. At least there is no mention in the factory manuals about the need to lube the threads. It does, however, specify to recheck torque with the engine cold.

If the problem is that you can't pull the wrench that hard, a longer torque wrench might help. I use one rated to 150 ftlb that is nearly 30" long instead of the more common 22".

 

[luke44]

I think the concern when you get up over 80 lbs or so is snapping a head stud or worse yet pulling one out of the block.

 

[Kleykamp]

All torqued to 105. I ran all nuts down to the bottom of the threads with no evidence of "hanging" prior to installing and torquing the head. I have a 22" wrench so it was a little strain to do 105 which just seemed like I was pulling pretty hard, but not impossible. Everything still going into place. Next step...timing.

 

[alanjohnturner]

We did all this recently on the UK TR-Register forum when one of our regulars found a pulled-thread in the block on one of the deepest holes.

We had to talk him through repair by Helicoil and we found that the standard Helicoil tap is too short for these deep holes.
So a standard stud winds up 1in too long.

Whilst this was going on I researched the recommended torque for bolts of this size. 110ftlbs is fine for 1/2in UNF but a head-stud is UNF on one end but UNC on the other.

110 ftlb is near the maximum for a top grade HT bolt with 1/2in UNC.
But these go in a cast-block! So if I were you I would regard 110 ftlbs as the absolute maximum.

One of our members, who races a 4, and has built a number on engines completly degreases the head studs and nuts.
Lubrication has the effect of generating more tension for a given applied torque thereby increasing the chance of a stripped block.

Another thing is to be sure your torque-wrech is accurate. A "click" type is more likely to go out of calibration and give excess torque than my favorite "bendy-bar" type.

 

[TR3driver]

Another thing is to be sure your torque-wrech is accurate. A "click" type is more likely to go out of calibration and give excess torque than my favorite "bendy-bar" type.

True enough. But none of them are perfectly accurate at every setting; which is why I always treat specifications like "100-105" as really meaning "102.5 +/- 2.5". In other words, you should torque to the middle of the range, and hope the error allowance is enough to cover the error in your torque wrench and/or your reading of it. (Dunno about you, but I find it almost impossible to pull to 102.5 ft lbs with my face directly above the scale; which is why I use a click-type wrench.)

 

[jimstr4]

I torqued mine with a click type one in 4 stages and to 90lbs as per Greg Solow.

 

[luke44]

...110 ftlb is near the maximum for a top grade HT bolt with 1/2in UNC.
But these go in a cast-block! So if I were you I would regard 110 ft lbs as the absolute maximum....

Some good insight in this posting. I was going by my gut after 40+ years of wrenching on these lbc's, over 100 lbs just plain feels like too much.