Friday 17 January 2014

Throttle bodies & wiring

A new year brings with it a new approach again and some good progress. First the throttle bodies.

The plan to fully modify the existing carburetors to become permanent throttle bodies has been changed again and simplified. While putting the exact modifications required down on paper, I discovered that there is not enough wall clearance in the carbs to fully bore out the step in the casting that forms a small part of the venturi. That realisation then snowballed to simplifying all aspects of the modification.
  • Instead of interference fitting a block of aluminium into the slide orifice and machining out with the rest of the bore, I will now bond the original slides in place, fill them with high temperature epoxy resin and take them out to match the carb bore by hand. 
  • The main jet protrusion will be drilled out and smoothed out using epoxy.
  • The protruding float bowl pieces will be cut down to the level of the float bowl mating surface
  • New blanking caps will be made up to fit where the float bowls once fitted and an additional piece fixed towards the front of the carbs to allow for good injector seats. This will become clearer in photos.
  • Any imperfections and gaps between the carb body and the new blanking plates will be filled with temperature resistant JB Weld.
  • The only professional machining required will be to drill and bore the injector seats in the throttle bodies and the fuel rail.
The major advantage to the new (again) approach is that the majority of the work can be done using basic tools and so can be done quickly. Even better is the fact I am already pretty much ready to send off the carbs and fuel rail to machine the injector seats. Photo's of progress so far below.

Float bowl cut down to seat face

Mock up of float bowl blanking plates

Detail showing infill of gaps with JB Weld for injector seat

Slide filled with JB Weld

Rough filling of drilled out needle jet

I have also been tidying up the wiring somewhat to make it the entire setup more permanent. More to go and there's not a whole lot to see anyway but some idea of what the old CDI area currently looks like is below. Including resistors hard-wired inline into the VRIN wires.

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