The V8 Owners Forum -

Hello all.
Engine is fitted in my Capri & I have the MOT at 9am tomorrow - trust it to play up now!
Engine is an SD1 with twin SU carbs & K&N's fuelled by a Facet Red Top via a Filterking set at 7psi.
Problem:
Ticks over ok-ish but when I road test it I put the throttle down and get a waaaar noise but no increase in power, then it runs rough/cuts out. Restarts ok, then same again.
Questions:
1) What pressure should the Filterking be set at?
2) Any suggestions on getting it running properly once I'm moving?

Desperate now as the clock is ticking/daylight fading & I've ran out of ideas.

Cheers, Paul

Sounds like fuel starvation.

With an electronic fuel pump, fuel vapourisation is not usually a problem, so therefore I would suggest replacing your fuel filter and see if that makes a difference.

Best of luck,

Ron.

Hi,

Have you changed the needles in the carbs to suit the K + N filters ?

Normally 4 - 5 psi is enough fuel pressure to run these carbs.

Regards
Jim

Red Top, Filterking (& filter) are new items so I assume they are up to the job.
Carb/K&N setup is what came with the car when bought so I'm not sure what needle work will have been done.
Found many articles on Google which suggest that 2-4psi would be better? What do you people think?

Hello BudgieV8,

If the needles had not been changed to suit the K & N air filters, which will allow considerably more air into the engine, when compared to the OEM paper filters, then the engine will be running very lean indeed.

Lean mixtures will cause hesitation upon acceleration, and engine damage if really lean enough. Pistons with holes melted in them for starters!

SU float levels if too low, ie 20 thou or less can also add to lean running when under hard acceleration, as can air leaks from old seals in the carburettor bodies.

Have you just purchased the vehicle? Has it been running alright and now is not? or????

Ron.

I would set you fuel pressure to 4 PSI, 5 PSI absolute max. SU's can be a bit fusy about too much fuel pressure, If the last change was the fuel pump and it was working before then I would sugest your problem lies with the pump and fuel supply side. I suspect your carbs are on the edge of flooding and as a result it is running rich at idle, you floor it, the damper in the carbs richens the mixture further and it runs like a dog! set the fuel pressure a bit lower, check the filters in the fuel system then if it is unchanged, undo the dashpots on the carbs, if it picks up better on the throttle then it is too rich on transition, if it dies compleetly then it is too lean and you need to start hunting around for things like air leaks, collapsed floats (possable if you have been running with high fuel pressure) crud in the main jet drillings, float bowles full of crud etc.
Best of luck
Mike