Head retorque procedure U20

[SLOroadster]

Studs, depending on who you talk to, yes, and no. I will say that there have been some monster U20s built (like 250 hp, 9000 rpm) that used the stock bolts. There have been lesser U20s built with studs that leaked, and leaked more the more the stud was tightened due to the stud pulling up the areas in the block around them. If the guy who makes his living building hot Nissan engines (be it L series or U series) tells me to run the bolts, I'll run the bolts.

Even with studs, you will still need to retorque the head. How to do it? Make sure it's totally cold then reduce the torque on the bolts in reverse order ending with the two in the center. Then, torque to 25 lbs in the correct order, then 45, and last, pull to the full 65 lbs.

Yes, head bolts can be reused. I've been using the same ones for the past 15 years. Never had an issue. They were the ones that came on the car when I got it, so they are far from new. I did replace the rod bolts when I rebuild the engine in 2003, reused them when I rebuilt it in 2010. 13 years later and lots of time above 6000 rpm, still no problems. (ARP rod bolts)

Will

[nismou20]

That's what I like to hear. Would the same hold for Rod bolts? Purely stock block.

[Gregs672000]

There will be the time when one of them will break, whether it's a stud or a bolt, just because it can happen. It has always been my understanding (per Nissan material) that the head bolts were "true stretch bolts" and were intended to be torqued once and replaced. I too have reused bolts as well as retorqued them without problem, but I have also broken one, had the threads pull out on an L-series I did as a teen, and broken a head stud (incorrect torque number unlubed vs lubed) so...
I have observed some stretched head bolts before. It does suck when they break, as you have to pull the head off, tap out the broken bolt, etc. Lubrication on the threads makes a big difference in how much torque you put on them. Normally they remain dry after they are assembled, but I have pulled head bolts that came out wet with oil, so that is just an assumption. Regarding method, just break them free a little bit and retorque in proper sequence. I usually do a lighter pull (10lbs off max) and then a final, but that's just me...
I've never retorqued rod bolts, have reused them, also replaced them, never broke one.

[jamesw]

The reason the studs are better and easier to use is that the pitch on the threads at the top (where you tighten) is less. The big coarse thread on the stock head bolts make them really clunky. I feel much more comfortable torquing the stud nuts/bolts because the wrench turns smoothly and you see the torque coming up slowly.

I put studs in without taking the head off. You just pull one bolt, chase the threads, with a tap, use a wet q-tip to grab the gunk that comes out, then run in the stud.

HTH
James

[Linda]

Head bolt hole cleaning:
http://www.311s.org/phpBB3/viewtopic.ph ... d+bolt+tap

Linda

[sunbeam590]

Well all that makes interesting reading, we are all car nuts, some of us more or less experienced as mechanics we mostly all like to do our own engine work, I think in the end you troll though the different advice and have a go and at the end of the day what works for you, you keep, its called experience, some painful, but after fifty yrs of it Im glad I had a go, just my off topic thoughts. cheers.

[bakerjf]

Update: I performed the head retorque this morning. No broken bolts, no surprises or drama, took about 10 minutes to knock it out. Thanks to all for the advice and help. If and when I go through the engine again I will switch over to something else.

I did find some interesting stuff checking/resetting my valves - I shared that on another thread dealing with that subject.

[Linda]

So since you had no drama, what did you do specifically? Crack the bolts one at a time or all at once? What pattern for retorque? Several steps or all at once? Details, need details

Linda

[bakerjf]

So since you had no drama, what did you do specifically? Crack the bolts one at a time or all at once? What pattern for retorque? Several steps or all at once? Details, need details

Linda

I followed the tightening sequence specified in the manual (inside to outside). I used a breaker-bar to back each one off about 1/16th turn, then popped on my torque wrench and smoothly brought it back up to 65ft/lbs. I did each bolt like this, one at a time. After an initial valve check/adjustment, I fired it up and brought it up to temperature, then shut it off and performed a "hot" adjustment on the valves, popped the valve cover back on, put a timing light on it, and then took the car out for a 20 minute test drive. Checked for leaks when I got back - all good!