Quote:
Originally Posted by Rawknees'Turbo
With non-turbo engines, steel were used on the intake sides and dilivar on the exhaust sides in an attempt to balance out the differing expansion rates of the intake-v-exhaust side of the cylinders & heads and maintain consistent clamping forces, but the dilivars have proven to be very failure prone.
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This has to be one of the worst detailed design decisions that could be made.
The notion that the forces created by differing levels of expansion can be balanced in this manner doesn't stand up to much scrutiny.
At the very best there may be one condition where this could occur but the chances of an engine running in this manner for the majority of its life are negligible.
Consider steel studs, even if the two sides of the cylinder ran at a temperature difference of 30 deg C across the cylinder, the difference in the expansion generated preload would be around 20% which is well within the elastic capability of the studs and probably within the scatter associated with torque tightening techniques.
If we then fit Dilavar on the exhaust side it is likely that the Dilavar studs will be more lightly loaded than the inlet side as soon as the difference in temperature exceed around 5 degC so in general why take the chance ? If there is only a 5 degree difference then the steel studs only see a load difference of 3%.
The engine will most likely run with unbalanced loads even when fitted with Dilavar on one side and if we make detailed measurement we are likely to find that the 'benefits' are insignificant.
Thermal Reactors may make this worse but these were used with Mag engines prior to the use of Dilavar so it all seems a bit moot.
I still wouldn't use Dilavar on an Aluminium Case as I believe that they aren't needed.