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It's dependent on induction setup and fuel type - along with a host of other contributing factors.
There is no right or wrong.
multiple fuel types are always going to involve a compromise and perhaps this also means different vacuum sources are appropriate for each.
I'll probably end up with 2 black boxes as in the RRC thread, programmable and switchable for lpg and petrol.Quote:
Originally Posted by Mercguy
This does away with vac advance altogether.
My POS used to run better on lpg, on manifold vac, till I lost the points and went electronic.
Could only get a good idle using ported vac and nothing else had changed.
DL
Back in the old days we always ran ported vacuum for manual cars and manifold vacuum for automatic to help the engine idle smoothly with the torque converter.
LPG required a different ignition advance curve than petrol. forty odd years ago I had an MSD type ignition box fitted that had a different advance curve for when using different types of fuel. It worked well , i think it went out of production a long time ago but there is probably something similar available.
Getting your distributor recurved is always a good idea, though probably not many doing this service any more since computers took over.
Set your timing to what ever makes you happy and gives good economy without pinging.
Ian
Bittern