Re-torquing after cylinder rebuild

[AtLarge]

When checking the head bolts with a torque wrench should you loosen them first and then tighten to spec or just check them to make sure they are still at proper torque?   

[retaRD]

DO NOT LOOSEN.

Check at peak torque in a cross pattern, until stabilized.

[AtLarge]

Ok good.  I just finished the 2nd heat cycle.  Retested and they barely budged.

[retaRD]

Ok good.  I just finished the 2nd heat cycle.  Retested and they barely budged.

Remember to wait until the engine is fully cooled. 

[Czakky]

I've always cracked em all and then re-torqued. That's how I was taught on 4t anyway...
next time I'll do as retaRD says.

How important are the special washers on the head bolts for these air cooled Yamahas?

[Striker1423]

I've always cracked em all and then re-torqued. That's how I was taught on 4t anyway...
next time I'll do as retaRD says.

How important are the special washers on the head bolts for these air cooled Yamahas?

They help distribute the torque evenly. But a lot of people use the bolts alone and don't have any issues fwiw.

[Jspooner]

I've always cracked em all and then re-torqued. That's how I was taught on 4t anyway...
next time I'll do as retaRD says.

How important are the special washers on the head bolts for these air cooled Yamahas?

I've never heard of "cracking them loose" before re-torquing them on anything. The point of re-torquing is to make sure nothing came loose or that everything is still as tight as it should be.

[SoCal250]

I've always cracked em all and then re-torqued. That's how I was taught on 4t anyway...
next time I'll do as retaRD says.

How important are the special washers on the head bolts for these air cooled Yamahas?

I've never heard of "cracking them loose" before re-torquing them on anything. The point of re-torquing is to make sure nothing came loose or that everything is still as tight as it should be.

I've never heard of that either. (And that goes for 4T V8 engines too).  "Cracking them loose" is just going back to square one and starting all over. It doesn't even make sense (logically).

Follow retaRD's advice, he's spot on in his 2 posts above 

[~JM~]

In the V-8 world, many believe that you loosen, then re-torque one bolt/stud at a time while following the recommended tightening pattern. This is done after one or more heating cycles while the engine is cold.

Here's another question. Do you clean & re-apply the ARP type of molly lube prior to re-torque? I'm thinking probably.

[SoCal250]

Off-topic, but as I recall ARP stated NOT to use anything on threads because it would interfere with torque values. Also they did not instruct to loosen before retorque.

[Old Brit]

I've never heard of that either. (And that goes for 4T V8 engines too).  "Cracking them loose" is just going back to square one and starting all over. It doesn't even make sense (logically).
[/quote]
Exactly 

[murphywv]

I have seen the torque loosen retorque procedure and used it as per manufacturer recommendations (Caterpillar). This was used on torque to yield head bolts that were replaced when the head gasket was replaced. torque up in 3 stages, loosened in sequence and retorqued. It was a pain in the ass but if you didn't do it the gasket would fail.
Some big Cat engines you measured stud stretch with a dial indicator.

Lube (moly, oil, anti-seize) will impact the torque. I think the best thing is to do what works, either by your own experience or the experience of others.

On a small engine a good, even and progressive torque to spec is as good as anything in my experience.

[~JM~]

Off-topic, but as I recall ARP stated NOT to use anything on threads because it would interfere with torque values. Also they did not instruct to loosen before retorque.

https://arpinstructions.com/generaltorque.html

https://arp-bolts.com/p/technical.php

https://arp-bolts.com/p/FAQ.php

I've also read/heard somewhere that new fasteners should be torqued to value, loosened & then re-torqued several times to burnish the threads for a more accurate clamping force. I cannot locate that information at this time.

[m in sc]

when i was still working for CP/Desoutter, we had nut runner application in factories that would require tightening, loosening, then tightening with torque /angle to set the bolt stretch. this was on initial assembly in lots of different applications. this was on items like rod bolts for GE locomotive (power-train applications) and, Daimler, Hyundai,etc. the values were always set with fasteners oiled so it wouldn't gall. that being said, 40+ year old cylinder studs are pretty much already stretched as it is.  a double check of torque, as mentioned, after heat cycled a few times, and cooled down, is the best method for rds. my .02 I try to set mine to 18-20 on head bolts.

[SUPERTUNE]

OK, Here goes my opinion since a lot of comments are in my WHEEL HOUSE!
As some of you know I work in a automotive race engine machine shop now for the last 4 years and I have owned my racing automotive race engine machine shop my whole life with my dad until I burned out and closed the shop, sold off the shop automotive specific equipment in '98 and went 2 stroke jetski and motorcycles only.
The first post didn't even state what engine he has.
IMO, on a normal 2 stroke conventional setup I oil the threads upon assembly, never re-loosen, just check torque after a few heat cycles and again after I get a 100 miles or so.
In the automotive racing engines I build every day using ARP products with almost every race engine I build... I never need to retorque when using the ARP lube and torque spec's.

Chuck, at almost 60 years old doing engine building my whole life this is my take!