Cyl head on 2JZ --- has to be retorqued?

[JohnA]

When refitting the cyl head, a new head hasket is obviously used. Once the bolts are torqued at the right values, right sequence etc, does the engine have to run at operating temps for a while and then retorque them when it cools down?

 

I was chatting to a friend yesterday who used to work in a garage years ago, and he insisted that's how it's done (old fashioned way that is)

 

Is this true?

I haven't seen anything like this in the manuals...

[tonyhawk]

Isn't that dependant on the type of bolt used? I know the old non-stretch types often did, but the newer stetch types are tightened to a preset pressure, and then effectively "over-torqued" with a 90 degree (or what ever the ratring for that bolt is), so they're permanently pulling, and thus don't need to be re-torqued.

 

The only problem there is I'm not sure what type the orignial Supra head bolts are...

[bedlam]

John

 

Yes thats what you did.

 

Andy

[JohnA]

What I did? I've done nothing mate.

 

Are the std Toyota bolts stretch items then? It would be messy and inconvenient to start the engine for a couple of hours (what my friend said) then wait for it to cool, dismantle the top, retorque, then put it back together again.

Where are we, in the middle ages? lol....

[Digsy]

From an OEM mass production point of view, a hot test followed by a head bolt re-torque would be a production nightmare, and I'd be gobsmacked if Toyota did it on the 2JZ. I gues some people still do it after repairs and for very low production volumes, however.

 

Mind you, the instruments that do up the head bolts on the end of a production line are a far cry from the torque wrench in your garage or mine. They are precise, computer controlled affairs that can measure torque and angle turned, look for errors, trends, etc. You can assume thet the load applied by the head bolts from the factory is very consistent.

 

However, once you start using more run of the mill tools, things can go awry. Also, environmental factors can influence the final torque. It can veary a lot if you lube the threads, for example.

 

I would say that if you had new head bolts and a bloody accurate torque wrench and clean parts, then you could be fairly happy with a tighten-and-forget approach. You might want to use the torque and angle tightening method the Tony descirbed above (if you can find the proper torque and angle specs.) This is much better than pure torque tightening to get accurate bolt preloads, and is also much easier to do accurately in a workshop, using a normal range wrench and a breaker bar.

[absz]

auto data manual 2005 supra 2jz-gte

 

headbolts renew----NO

tighten 1 -----18nm

STAGE 2 -----34nm

stage 3 ------- 90 degrees

stage 4--------90 degrees.

[JohnA]

So that manual specifies to reuse the same bolts and no mention of warmup before the last stage eh?

[absz]

So that manual specifies to reuse the same bolts and no mention of warmup before the last stage eh?

 

nope

 

 

but i always replace the head bolts anyway. i think digsy mentioned this in his post about condition of bolts effects the tighting torque.

[Chris Wilson]

Doesn't need re torquing IF you use stock Toyota bolts and a stock multi layer steel shim headgasket. Bolts are torque to yeild type and should be renewed rather than reused. If you use none stock parts the above MAY not apply.