dunno if this helps - from the RPI web site.....
A check list of common simple issues
.Being sure of TDC position with regard to crank-indicated timing mark is a must.
Plug gap needs to be 0.8mm - 0.9mm.
Don't use resistor plugs and suppressed leads together.
Std. spec. high street leads may not be able to handle the extra spark KVs.
Check fuel delivery pressure.
Check Carb float bowl height.
Check no blocked or restrictive fuel filter in line.
Do you have the fuel return hose (to the tank) connected? If so, it needs restricting.
Try an alternative coil even if yours is new?
Most importantly
You cannot trust the indicated timing marks on your engine's bottom pulley. We have found them to be up to 20 degrees out in the worst circumstances.
To check this, it is required to remove No 1 spark plug and rotate the engine (using some form of probe down the cylinder), to ascertain if No 1 piston and the indicated TDC timing marks do actually align as indicated TDC on your pulley.
Especially if your engine is other than the std. production one in the std. production vehicle it was originally fitted to.
If your indicated TDC pulley (reference) mark is wrong, then all you do and all we advise, will never stand a chance of achieving what's expected. This also applies to the information given above, so ignore this section at your peril.
There is a good check list for the distributors above and the following advice is also useful.
Its also worth noting that the best ignition timing in any given engine, is to achieve the most advance it can tolerate without pinking. ( Audible pre-ignition).
This is achieved by setting your V8 timing to about 4 deg. BTDC (assuming you've been through the distributor check list completely). Then tighten the distributor so that you can (with effort) still turn it by hand. ideally put a tip-ex mark or small scratch on the distributor body and engine block to record this spot.
Next road test the car and simulate high load by quickly shifting into a high gear or if Auto allow to change quickly up to 3rd or 4th Ideally you need to find a small hill or incline, now if you apply full throttle the engine should respond without pinking, find a safe place to pull over, open the bonnet and turn the distributor through a couple of degrees only, anticlockwise, this will add slightly more advance timing and if you do the same test, and repeat it until pinking is noticed you will be very close to your absolute best timing criteria
So now all you need to do is turn the distributor clockwise by the same amount by an amount to counteract the last adjust, retest for the absence of pinking and that the job done, you will have just achieved the best maximum timing position for your car
Having done this an ideal engine would run perfect in all areas and pull as you would expect from all load and rpm areas. you would also expect the final timing position to be somewhere close to 6-8 deg. btdc, (exceptions assumed) However if this is not the case and or your engine developers other strange habits then it is almost certainly pointing to another issue with your engine of which there can be many.
Fuel pump low pressure
Leaky older or high miles injectors
Poor or pretending plug wires
Flashy plugs that ar'nt so flashy after all
Throttle pot settings
Air flow meter settings
Coolant and fuel temp sensors
Lambda probe(s) if any
Distributor ability, both its output voltage and mechanical advance systems capability
to name but a few. !!!!!
