top end rebuild

[Tosh]

just rebuilt,about to take it out for a small ride and then to return to torque all bolts down again,
is this ok without the cylinder cowl on

[Andy Pickering]

Wouldn`t go far Tosh but know why your doing this..quick heat cycle then nip down then after 100 miles re nip IMO..

[nelson pk]

Is it worth the risk? Not in my opinion. Your gonna need to do about 50 miles to make any difference, especially if your re-tourqing head nuts etc.
It doesn't take long to drop the shock, whip the exhaust and head cowl off.

[coaster]

I'd be interested to hear a convincing technical argument for re-torqueinh heads. The specified torque setting should allow for 'settling in" of gasgets etc it's not normal to return new vehicles for this either

[soosh]

I'd be interested to hear a convincing technical argument for re-torqueinh heads. The specified torque setting should allow for 'settling in" of gasgets etc it's not normal to return new vehicles for this either

Probably not. I've personally not done it.

[Tosh]

Thanks all for the reply`s,i decided to put the cowl on went for a ride turned out to be 65miles ish
returned to base undid engine bolt,took earth strap off,shocker,and plug and my cowl slipped off no need to touch exhaust checked bolts,all ready to go happy days

[nelson pk]

I'd be interested to hear a convincing technical argument for re-torqueinh heads. The specified torque setting should allow for 'settling in" of gasgets etc it's not normal to return new vehicles for this either

I use it as a belt and braces approach bearing. 90% of all engines that i've done, when it has come to retorque the nuts haven't moved at all and all has been nice and tight but 10% have so if you take the risk most of the time you will get away with it.

[warts]

I'd be interested to hear a convincing technical argument for re-torqueing heads. The specified torque setting should allow for 'settling in" of gasgets etc it's not normal to return new vehicles for this either

I think its all down to this modern technology stuff. Torque to yield bolts and multi-layer steel gaskets, combined with CNC production accuracy plus auto/semi auto assembly means everything is right every time.
Torque to yield bolt are tightened beyond the point where they will spring back to their original length(exceeding their elastic limit). The extra torque translated into higher clamping force and less likely to wind out but then they can't be re-used. They are also easier to productionise - they are machine tightened to a given torque then a further number of degrees.
Multi-layer gaskets don't compress being steel in the same way as aluminium or copper, but the thin layers allow a degree of conformity. There are composite gaskets too which I assume can work because the clamping forces, surfaces and tolerances are now so much more consistent.
Some of the car makers do conducted tours though I think you will have to go to Germany for that. Porsche and Benz in Stuttgart, Audi in Ingolstat, BMW in Munich all have done tours in the past. Rüsselsheim just outside Frankfurt (the nearest) still did up to last year- they seem to be undergoing perpetual "restructuring" after the "happy time" in the sixties and seventies. Anyway, you get to see modern production techniques, unfortunately not much in the way of technical explanation, but it is very interesting - even my technophobe big sis found it fascinating.

[coaster]

The thing with Lambtrettas though is the tensile strength of the cylinder studs is WAY beyond the torque required to stretch them. The torque specified is just sufficient to provide the required clamping force to seal the cylinder head without causing distorsion of the ally head/barrel. I suspect that if you used say 20lb if gaskets were not used and maybe 21 or 22lb where gasgets are used you would never find any need to re-torque. No harm if you want reassurance though. On the other hand, exhaust gaskets are VERY prone to squashing in use and would benefit from re-tightening.

[tavspeed]

i,ve never been in a car that vibrates like a lambretta,vibration means things come loose,break fall off,wasnt there a thread on recently about nordlock washers,google them ,these seem the answer to loose head nuts,anybody using them ?.