Something the good Doc said in a previous thread got me thinking... someone else was chasing plug fouling issues and the Doc mentioned too much fuel pressure might be a cause.... my car also fouls plugs easily...

the fuel pump on my car sounds hardcore... no idea what it is except for it's loud and sounds like it pumps a lot of fuel...

seeing as the SU doesn't have a fuel return... should i be running a pressure regulator? How does the SU cope with having shirtloads of fuel pushed at it constantly?

Well if your using the right pump, it will only delivery 3 - 4 psi. The recommended pressure for an SU is 3.5 psi.

Your plug fouling problem is Unlikely to be fuel pressure. Either running to rich, bad plug leads / ignition problem or the incorrect heat range spark plugs.

If you have too high a fuel delivery pressure to an SU, it will flood but it will also piss out the fuel bowl vent, which is just under the fuel inlet pipe.

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thanks GT,

i'm trawling through the list of fouling issues... just trying to minimise possible causes...

is it BP5ES or 6ES Ngk plugs everyone uses? i always get confused with hotter/colder plugs,

which ones will help burn more fuel and hopefully help stop the fouling?

the car will be dynoed again once i've sorted it as much as i can at home... it was really good for months after is was dynoed last time, then all of a sudden. fouling. i think i caused the fouling by using the choke to help keep it idling.... going to get the carb rebuilt and make sure the linkages and return spring are all good so i can get it to idle of it's own accord without help from throttle stabbing or choke pulling...

A hotter-range plug (e.g. the NGK BP5ES) has a slightly longer centre electrode, which causes it to sink less heat into the surrounding ceramic. This means it physically runs hotter than another plug, which allows it to burn off more deposits.

That said, if you're fuelling the cylinder too much, I doubt any plug is going to help...

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Simon

The adventures of an owner builder in the Tallarook Ranges

i have been fiddling with 5 and 6 plugs this week. im considering going back to the 5's.

im in the desert, really bloody hard to tune the SU when its 5 degrees in the morning and then 35 in the daytime.

but, after putting the 6's had to make the fuel richer, and with the cold morning starts, i am starting to flood the chambers and its misfiring on cold start. (need to pull the choke right out in the mornings)

i have yet to work out with the richer fuel on the 6's whether i get better fuel economy with the 5's or the 6's.

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Aussie Leyland, Aussie Factory, Aussie Mini S.