Hi can any one help me I want to fit new mounting grommets (cbc1448) to a new fuel pump the old spacers are very crushed does any one know how long they should be?

 

They should be about level with the new grommets, or just slightly below.
This is so because when the pump is mounted, you want the spacers to take the load when the nuts are tightened up.
This allows the new grommets to take the weight of the pump with out being crushed and to absorb the sound of the pump.

 

See here: Fuel System ? Valve Chatter

Scroll down.

 

I would use rubber grease for the grommets, not Vaseline and boiling water.

 

Vaseline is just fine. It is just microfine wax & totally rubber compatible.

 

I found rubber grease to be more slippery.
Makes dealing with difficult rubber products that much easier.

 

Yes ~ depends what you are doing. e.g. Vaseline/Petrolatum is the preferred product for rubber seals (elastomers) used on Auto transmission valvebody assemblies (e.g. Allison)